MICROSCOPY RESEARCH AND TECHNIQUE 77:619–630 (2014)
Fine Structure of Delia platura (Meigen) (Diptera: Anthomyiidae) Revealed by Scanning Electron Microscopy QI-KE WANG,1 YAN-ZHI YANG,1 MEI-QIN LIU,2 AND DONG ZHANG1* 1 2
Department of Zoology, College of Nature Conservation, Beijing Forestry University, Beijing, 100083, China Analysis and Testing Center, Beijing Forestry University, Beijing, 100083, China
KEY WORDS
Delia platura; morphology; scanning electron microscopy
ABSTRACT Delia platura (Meigen) is a phytophagous fly that can cause significant crop losses. To obtain a better understanding of the external morphology of this species, adult D. platura is studied using scanning electron microscopy. Organs or structures that are important for taxonomy, such as the compound eyes, spiracles, pulvilli, wings, and genitalia are highlighted to complement previous description based on light microscope. Mesothoracic and metathoracic spiracles of D. platura that provide efficiency in preventing entrance of fine materials or dust into the tracheal system are morphologically different. In addition, the elongate-oval pulvillus is densely covered with tenent setae with spoon-like tip, which can increase the number of contact points for attachment to a surface. Four types of sensilla are observed on the male genitalia of D. platura including: trichoid sensilla, chaetic sensilla, three subtypes of campaniform sensilla, and basiconic sensilla. Long bristles and microtrichiae are observed on the female genitalia of D. platura. The possible function of sensilla located in the genitalia of D. platura is discussed. Microsc. Res. Tech. 77:619–630, 2014. V 2014 Wiley Periodicals, Inc. C
INTRODUCTION Delia platura (Meigen), known as bean seed fly species, is an important phytophagous pest that is distributed worldwide in agricultural systems. There are reports of significant crop losses that caused by D. platura (Chaudhary et al., 1987; Finch, 1989; Gratwick, 1992). The maggots mine the roots of various beans, cereals, tubers, and tobacco seedlings (Griffiths, 1991), making which particularly vulnerable to stem rot organisms. Antennae and other organs, such as ommatidia, spiracles, pulvilli, and genitalia, are of different functions and play an important role in various behaviors during adult life (Nalbach, 1993; Dickinson, 1999; Sherman and Dickinson, 2004; Sukontason et al., 2005; Sukontason et al., 2006a; Sukontason et al., 2008). Ross (1992) described and compared antennal sensilla of several species in this genus, while there is a lack of study of body parts in this genus, as well as in the Diptera. The body parts included in this study have been widely used as taxonomic characteristics, and usually observed under light microscope. On the other hand, the potential for biomimetic applications of fly body parts have been reported in many studies (Drechsler and Federle, 2006; Sukontason et al., 2008). Taking into account the limited data of these important structures, this paper provides details of the ultrastructures that can easily be neglected in D. platura, and clarifies vagueness in previous descriptions. MATERIAL AND METHODS The adult males and females of D. platura used in this study were captured during summer of 2011 in SongShan, Beijing, China. Specimens were killed by C V
2014 WILEY PERIODICALS, INC.
placing in a freezer for 30 min before they were processed for this study involving scanning electron microscopy (SEM). To prepare for observation with the SEM (Electron source: secondary electron; Acceleration voltage: 5000 Volt), flies were rinsed by shaking in normal saline solution to remove surface artifacts. Specimens were fixed with a 2.5% glutaraldehyde mixture in phosphatebuffered saline (PBS), pH 7.4, at 48 C for 24 h. For the detailed examination of the external surface, antennae, palpi, legs were excised from the flies. In addition, the samples were then rinsed twice with PBS and dehydrated with ethanol. The dehydration process involved the specimens being sequentially subjected to the following increasing ethanol concentrations: 30, 50, 70, 80, 90, 95, and 100%. Specimens remained in each concentration of ethanol for 12 h during each step of the dehydration process. Finally, the specimens were subjected to critical point drying using a HCP-2 critical point dryer (Hitachi Corp., Tokyo, Japan), attached to double-stick tape on aluminum stubs in the correct orientation, coated with gold in a E-1010 ion sputter (Hitachi Corp.,
*Correspondence to: Dr. Dong Zhang, College of Nature Conservation, Beijing Forestry University, Qinghua East Road No. 35, Mailbox 162, Beijing 100083, China. E-mail: [email protected] Received 18 February 2014; accepted in revised form 1 May 2014 REVIEW EDITOR: Prof. Alberto Diaspro Qi-Ke Wang and Yan-Zhi Yang contributed equally to this work. Contract grant sponsor: Fundamental Research Funds for the Central Universities; Contract grant number: YX2013-08; Contract grant sponsor: National Nature Science Foundation of China; Contract grant number: 31201741; Contract grant sponsor: New Century Excellent Talents in University; Contract grant number: NCET-12-0783. DOI 10.1002/jemt.22380 Published online 22 May 2014 in Wiley Online Library (wileyonlinelibrary.com).
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Fig. 1. SEM micrographs of adult male Delia platura. A: Top view of head displaying the compound eye, antenna, palpi, and labellum. B: Magnification of the narrow frons showing rows of setae on each side, and the middle of the frons with density microtrichia. C: Domeshaped ommatidia with sparse, short ommatrichia (arrow). D: Higher
magnification of ommatidia showing densely postulate appearance of corneal lens. E: The right side of the gena, with several setae emanating from their sockets. F: Enlarged view of the gena showing concave facial scales. a, antenna; c, compound eye; p, paplus; lbl, labellum.
Tokyo, Japan), and observed using a Hitachi S34Q SEM (Hitachi Corp., Tokyo, Japan) at the Microscopy Core Facility, Biological Technology Centre, Beijing Forestry University (Beijing, China). The terminology and nomenclature used to describe fly morphology presented by McAlpine (1981) and antennal morphology and classification of sensilla types in this study follow those used by Zacharuk (1985), Hunter and Adserballe (1996), Shanbhag et al. (1999), and Setzu et al. (2011).
RESULTS Head The body of an adult D. platura can be divided into three regions: head, thorax, and abdomen, as in other flies. Prominent organs of the head include a pair of large compound eyes, three ocelli which form an inverted triangle antero-dorsally, antennae beneath the frontal suture, palpi and a sponging mouthpart (Figs. 1A and 1B). The compound eyes of male D. platura are located dorso-laterally and composed of Microscopy Research and Technique
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Fig. 2. SEM micrographs of antenna of adult male Delia platura. A: Anterodorsal surface of the whole antenna. B: Enlarged view of anterodorsal surface of the antennal scape and pedicel. C: Magnification of the setiferous plaques on the antennal pedicel. D: The distal articular surface of pedicel of antenna of adult male D. platura showing the location of pedicellar button (arrow); Magnification of pedicellar button is in the box. E: Magnification of trichoid sensilla on the
antennal funiculus. F: Magnification of large basiconic sensilla (arrow); Higher magnification showing the pore clearly is in the box. G: Magnification of small basiconic sensilla (arrow). H: Magnification of clavate sensilla (arrow). I: Magnification of coeloconic sensilla (arrows). Sc, scape; Pd, pedicel; Ar, arista; Fn, funiculus. [(D) scale bar 4lm in the box, (F) scale bar 1.5lm in the box].
numerous ommatidia with short ommatrichia infrequently present between the adjacent dome-shaped ommatidia (Fig. 1C). A rough cobbled surface, which could be described as densely postulate, appeared in the compound eyes of D. platura (Fig. 1D). Moreover, the face is decorated with concave scales with tapering ending (Figs. 1E and 1F). Similar to other higher dipterans, the antenna of D. platura comprise of three segments: a proximal scape (Sc), pedicel (Pd), and a distal flagellum, the latter is composed of an arista and a funiculus (Fn) (Fig. 2A). The surface of antenna is covered by microtrichia. The scape and pedicel both bear bristles with sockets at the base (Fig. 2B). Four setiferous plaques, which contain a bulbous seta, are observed on the pedicel (Fig. 2C). One pedicellar button is found on the distal articular surface of pedicel of antenna (Fig. 2D), which is domeshaped and surrounded by thick walls. The arista, a
bristle-like appendage or “hair,” is located proximally near the base of funiculus and is covered with numerous microtrichia (Fig. 2A). The funiculus is the most prominent part of the fly antennae. Based on SEM observations, we recorded five types of sensilla: trichoid sensilla, two types of basiconic sensilla, clavate sensilla and coeloconic sensilla. Trichoid sensilla are the most abundant type of sensilla on the funiculus. They are elongated, hair-shaped structures extending above microtrichia, ending with a rather pointed tip (Fig. 2E). Two types of multiporous basiconic sensilla, a large and a small one, can be distinguished according to shape and size (Figs. 2F and 2G). Clavate sensilla with club-like shapes are characterized by a distal swelling (Fig. 2H). Coeloconic sensilla are the shortest of the various types of sensilla and characterized by distinct longitudinal ridges on their walls (Fig. 2I).
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Fig. 3. SEM micrographs of mouthpart features of adult male Delia platura. A: Top view of mouthpart. B: Enlarged view of the mouthpart surface revealing dense covering of sharp-tipped microtrichia and chaetic sensilla emanating from their sockets. C: Lateral view of
the mouthpart. D: Higher magnification of the labellum. E: Front view of the mouthpart. F: Enlarged view of bifurcated prestomal teeth.
The mouthparts of this species form a tubular sucking organ called the proboscis, which terminates in a large, sponging structure known as the labellum (Figs. 3A23C). Bifurcated tips of the prestomal teeth project from the cleft between the labellar lobes. The prominent grooves of the pseudotracheae radiate from the food canal and prestomal teeth (Figs. 3D23F). Upon higher magnification observation, the palpus of D. platura is club-shaped, elongated, gradually enlarged to a rounded end distally, and attached rostrally to the proximal part of the proboscis (Fig. 4A). The whole surface of the palpus is exposed to the environment dur-
ing probing and feeding. Microtrichia, bristles and basiconic sensilla are observed on the palpus (Figs. 4B and 4C). The bristles are inserted into a cuticular socket and had longitudinal grooves evident in its hair-like shaft. The basiconic sensilla are small and similar to those observed on the antennal funiculus in morphology (Fig. 4D). Thorax The thorax of adult D. platura is composed of three segments: prothorax, mesothorax, and metathorax. In Microscopy Research and Technique
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Fig. 4. SEM micrographs of palpus features of adult male Delia platura. A: The front view of palpus. B: The lateral view of the palpi, with numerous short microtrichia and several long chaetic sensilla. C: Magnification of the palpus, showing the distribution of basiconic sensilla (arrows). D: Higher magnification of basiconic sensilla. Ba, basiconic sensilla.
flies, the mesothorax is enlarged and is covered with dense microtrichia. The mesonotum that consists of the entire dorsum of the mesothorax is covered with microtrichia (Figs. 5A and 5B). Sensilla, which emanated from swollen, dome-shaped sockets in the scutum and amongst numerous short microtrichia, are straight and sharp-tipped with prominent longitudinal grooved (Fig. 5C). The anterior spiracles (mesothoracic) are located near the junction of the pronotum and the mesonotum and appear as elliptical structures, with their upper portions partially open. The setae surrounding the mesothoracic spiracle are arranged in a single line along the rim of each spiracle (Fig. 5D). The posterior spiracles (metathoracic) with two clusters of long setae distributed on its rim are shaped as a rounded isosceles triangle (Fig. 5E). Beneath the two clusters of setae, a latticed membrane is observed (Fig. 5F). The wing membrane integument and the whole calypter are densely covered with microtrichia (Figs. 6B26D). Moreover, strong chaetic sensilla are implanted in the costal vein on the anterior margin of the wing and periphery of the upper and lower calypters (Figs. 6A and 6D). The haltere of D. platura is a small dumbbell-shaped organ, which consists of three main portions: base, stem, and end knob (Fig. 7A). A close-up view of the lateral portion of the base revealed that a set of campaniMicroscopy Research and Technique
form sensilla is apparent (Figs. 7B and 7C). These rows of campaniform sensilla are perpendicular to the longitudinal axis of the haltere. The terminal end of the knob possesses a sporadic group of sensilla (Fig. 7D). Legs are composed of a coxa, trochanter, femur, tibia, and five tarsal segments. The distal part of the terminal tarsomere is a tube bearing the tendon of the claw flexor muscle and articulated with the pretarsus. Pulvillus is connected to the tarsus by an elastic part containing resilin-like cuticle. It is structure adapted for attachment to a variety of surfaces and elongateoval in shape, but their anterior end tapering (Fig. 8A). The ventral surface of a pulvillus is densely covered by the tenent setae of spoon-like tip (Fig. 8). Abdomen Compared with the head and thorax, the abdomen of most insects typically has a highly reduced number of appendages. An examination of abdomen of male D. platura reveals abundant microtrichia and a good deal of long setae curved toward the apex of the body (Figs. 9A29C). Long setae appear as stout hair shafts bearing longitudinal grooves and inserted into cuticular socket (Figs. 9D and 9E). A lateral view of the male genitalia of D. platura shows the prominent features of the phallus, pregonite, postgonite, and cercus (Fig. 10A). The phallus
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Fig. 5. SEM micrographs of thorax features of adult male Delia platura. A: Lateral view of mesonotum showing dense microtrichia and long chaetic sensilla projecting posteriorly. B: Enlarged view of mesonotum showing microtrichia. C: Lateral view of scutellum showing several sensilla. Higher magnification of these sensilla is in the box.
D: Enlarged view of the anterior (mesothoracic) spiracle. E: Posterior (metathoracic) spiracle, with two clusters of setae distributed on its rim. F: Enlarged view of the inside of the posterior spiracle, showing the latticed membrane.
locates medially on a pair of pregonites, and its surface is slightly corrugated (Fig. 10B). Several setae are observed on the pregonite (Fig. 10A). The postgonite situated underneath the pregonite and is terminally curved inward. Several short sensilla are found on the basal region (Fig. 10C). The surstyli are large and swollen at the base, gradually decreasing terminally, slightly curving inwardly, and more or less rounded at the apical end (Fig. 10D). The external portion of the surstyli are greatly endowed along the lower half region with long bristles, which are morphologically similar to the triochoid sensilla. In addition, chaetic sensilla existed at the proximal region (Figs. 10D, 10I, and 10J). Three types of campaniform sensilla are observed all over the upper half region (Figs.
10E210G), and basiconic sensilla with subapical peg are present at the apical end (Fig. 10H). As for the ventral view of the female genitalia, the elongated ovipositor can be observed (Fig. 11A). The cerci, which are equipped with many long bristles, are more or less sclerotized and epiproct is lying between them (Fig. 11B). Lots of bristles and microtrichia are observed on the ovipositor (Figs. 11C and 11D). DISCUSSION Flies are equipped with a number of different receptors, which help them acquire information from the environment. The compound eyes are the most important visual organs, and the number of ommatidia varies depending on the biology of the insect (Elzinga, Microscopy Research and Technique
Fig. 6. SEM micrographs of mesonotal wing and calypter of adult male Delia platura. A: Anterior margin of costal vein implanted with stout chaotic sensilla. B: Microtrichiae on dorsal surface of wing membrane integument; part of the vein is showed in the box. C: The
margin of the wing on the dorsal surface; higher magnification of long and slightly bend setae is showed in the box. D: Dorsal view of the whole calypter.
Fig. 7. SEM micrographs of haltere of adult male Delia platura. A: Lateral view of the metathorax identifying upper calypter and lower calypter. Arrow indicates a set of campaniform sensilla. B: Set of campaniform sensilla presented as several rows perpendicular to longitudinal axis of haltere. C: Enlarged view of the campaniform sensilla. D: Terminal end of knob with several sensilla.
Fig. 8. SEM micrographs of pretarsus features of adult male Delia platura. A: Pulvilli of midleg showing numerous tenent setae covering on the surface. B: Enlarged view of pulvilli. C: Higher magnification of pulvilli showing the distribution of tenent setae with spoon-like tips. D: Extreme magnification of the tenent setae with a spoon-like tip.
Fig. 9. SEM micrographs of abdomen features of adult male Delia platura. A: Lateral view of the abdomen, with abundant microtrichiae and a number of long grooved setae. B: Enlarged view of part of the tergite VI showing numerous microtrichiae on the surface and
several long setae with longitudinal grooves. C: Higher magnification of microtrichiae. D: Lateral view of one row of long setae on the rump. E: Higher magnification of these long setae showing longitudinal grooves.
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Fig. 10. SEM micrographs of genitalia of adult male Delia platura. A: Lateral view of the entire genitalia illustrating the prominent features of the phallus, pregonite, postgonite, surstylus, and cercus. B: Enlarged view of phallus; higher magnification of part of phallus showing slight corrugation. C: Enlarged view of distal region of postgonite showing the distribution of short sensilla; higher magnification of short sensilla. D: Anterior view of a pair of surstyli; higher
magnification of lower half region of surstyli showing the distribution of sensilla. E: Magnification of campaniform sensilla type I. F: Magnification of campaniform sensilla type II. G: Magnification of campaniform sensilla type III. H: Magnification of basiconic sensilla with subapical peg. I: Magnification of trichoid sensilla. J: Magnification of chaetic sensilla. Ph, phallus; Prg, pregonite; Pog, postgonite; Sur, surstylus; Cerc, circus.
2004). Regarding the external surface of the corneal lens of the ommatidia, whose role is antireflection (Dey and Dkhar, 1992), a detail observation through SEM in this study has revealed the densely postulate appearance in the compound eyes of D. platura. This characteristic is in accordance with those observed in Chrysomya megacephala Fabricius (Sukontason et al., 2008) and in contrast with the sinuous sculpture pattern in the compound eyes of Lucilia cuprina Wiedemann (Sukontason et al., 2008). Shanbhag et al. (1999) suggested that the third antennal segment and palpus are the main and acces-
sory olfactory sense organs, respectively. Morphology and function of five types of surface sensilla and one type of pit sensilla that found on the antennae of D. platura have been discussed by Ross (1992). In addition to the sensilla that have been reported previously, pedicellar button are also found on the distal articular surface of pedicel of antennae of adult male D. platura in this study. The pedicellar button are cuticular component of a chordotonal organ, which may act as baroreceptor (McAlpine, 2011). Bascionic sensilla and bristles, which function as olfactory receptors and mechanoreceptors respectively, are found on the
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Fig. 11. SEM micrographs of genitalia of adult female Delia platura. A: Dorsal view showing extended ovipositor. B: Detail of the dorsal view displaying a pair of sclerotized cerci and the epiproct between them. C: Higher magnification of bristle on the genitalia of adult female D. platura. D: Long microtrichiae on the ovipositor. Epiprct, epiproct; Cerc, circus.
maxillary palpi. This result corresponds with that of Calliphora vicina Robineau-Desvoidy (Vander Starre and Tempelaar, 1976), Drosophila melanogaster Fallen (Singh and Nayak, 1985), Hydrotaea irritans Fallen (Been et al., 1988), and Musca domestica Linnaeus (Smallegange et al., 2008). Both sides of the wings of D. platura are densely covered with microtrichiae. A closer observation showed that all the microtrichiae are parallel to the adjacent veins. No significant morphological differences were observed between the microtrichiae on both sides of the wings. Previous research has discussed that microtrichiae could serve as a hydrophobic structure that prevents the wings from wetting in various insects (Wagner et al., 1996; Gorb et al., 2000; Cong et al., 2004; Parker and Townley, 2007; Watson et al., 2010). Nonwetting property of insect wings is crucial for the survival of insects in wet environments, as insects could be permanently trapped by water or wet surface. Super-hydrophobic or self-clean property of insect
wings could lead to next generation of contamination resistant or self-cleaning materials (Watson et al., 2010). The stout chaetic sensilla on the anterior edge of the wings are structurally similar to the ones found on scape and pedicle. The specialized basal structure indicates mechanosensory function. However, odorantbinding and chemosensory proteins were discovered in Drosophila wings (Shanbhag et al., 2001), as well as other insects (Jina et al., 2005), suggesting that wings could be chemosensory organs (Shanbhag et al., 2001). In flies, respiration is mediated by the multibranched tracheal system, which has cuticular openings called “spiracles” located at the thorax and abdomen (Sukontason et al., 2006a). Interestingly, mesothoracic and metathoracic spiracles of D. platura are morphologically different, which is corresponding with those of M. domestica (Sukontason et al., 2006a) and Hydrotaea chalcogaster Wiedemann (Sukontason et al., 2006a). The long, consistently arranged inward setae covering the finely porous opening of Microscopy Research and Technique
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mesothoracic spiracles are comparable with those previously reported in the bot fly, Dermatobia hominis Linnaeus (Fernandes et al., 2004). It has been suggested that these setae act as protection from entering the dust or fine particles in the tracheal system (Chapman, 1998). In regard to metathoracic spiracles, two clusters of setae observed in D. platura exhibited a different form from the relatively dense setae in H. chalcogaster (Sukontason et al., 2006a). Moreover, our detailed view of metathoracic spiracles clearly demonstrated the latticed membrane, which acts as protection apparatus, differed markedly from that of Manduca sexta Linnaeus (Wasserthal, 2001). Sukontason et al. (2008) have proposed that all of these different structural modifications provide various levels of efficiency in preventing entrance of fine materials or dust into the tracheal system. Pulvilli are structures adapted for attachment to a variety of surfaces (Gorb, 1998; Niederegger et al., 2002; Niederegger and Gorb, 2003; Gaume et al., 2004; Sukontason et al., 2006b). The ventral surface of pulvilli of D. platura is covered by tenent setae with a spoon-like tip, similar to the blow fly, Chrysomya villeneuvi Patton (Sukontason et al., 2006b). Moreover, tenent setae with a spatula-like tip and a pointed-like tip are also found on the ventral surface of pulvilli (Sukontason et al., 2006b). However, either the bearing spatula-like or spoon-like tip of the tenent setae increase the number of contact points for attachment to a surface (Gorb and Gorb, 2004). Morphological features of the male genitalia, especially the cerci, differed markedly between species, and thus are often used to identify flies and other insects (Senior-White et al., 1940; Sugiyama et al., 1988a, 1988b; Leite, 1995; Kurahashi, 2002; Dahlem and Naczi, 2006). In our study, several short sensilla are found on postgonite, which are similar to that of Agria mihalyii Rohdendorf and Verves (Zhang et al., 2013). In addition, six types of sensilla that include trichoid sensilla, chaetic sensilla, three types of campaniform sensilla (Ca), and basiconic sensilla are found on the surstyli. The Ca is thought to monitor general pressure in the cuticle, possibly through some directional sensitivity but it is certainly not as specific as other types of mechanoreceptive sensilla (Bromley et al., 1980). However, the mechanosensory function of these sensilla located in the male genitalia for aiding copulation in insects has been proposed in many studies (Rossignol and McIver, 1977; Spiegel et al., 2000; Gaino and Rebora, 2002; Acebes et al., 2003). In conclusion, the ultrastructural study of several organs of D. platura in this study allows us to understand the functional-morphological view point of these structures and helps to understand biological behavior of this economically important species. ACKNOWLEDGMENT The authors are grateful to Dr Jun-na Shi (Beijing Forestry University, Beijing, China) for her invaluable help with this study. REFERENCES Acebes A, Cobb M, Ferveur JF. 2003. Species-specific effects of single sensillum ablation on mating position in Drosophila. J Exp Biol 206:3095–3100.
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Been TH, Schomaker CH, Thomas G. 1988. Olfactory sensilla on the antenna and maxillary palp of the sheep head fly, Hydrotaea irritans (Fall en) (Diptera: Muscidae). Int J Insect Morphol Embryol 17:121–133. Bromley AK, Dunn JA, Anderson M. 1980. Ultrastructure of the antennal sensilla of aphids II. Trichoid, chordotonal and campaniform sensilla. Cell Tissue Res 205:493–511. Chapman RF. 1998. The insects structure and function, 4th ed. UK: Cambridge University Press. 770 p. Chaudhary RN, Kanaujia KR, Sharma VK. 1987. A note on the incidence of seed corn maggot, Delia platura Meigen (Anthomyiidae: Diptera) in spring sown maize. Bull Entomol (New Delhi) 28:159–161. Cong Q, Chen GH, Fang Y, Ren LQ. 2004. Study on the superhydrophobic characteristic of butterfly wing surface. J Bionics Eng 1:249–255. Dahlem GA, Naczi RFC. 2006. Flesh flies (Diptera: Sarcophagidae) associated with North American pitcher plants (Sarraceniaceae), with descriptions of three new species. Ann Entomol Soc Am 99: 218–240. Dey S, Dkhar B. 1992. An unusual type of corneal nipple in the earwig Forficula sp., with a possible anti-reflection role. Micron Microsc Acta 2:337–339. Dickinson MH. 1999. Haltere-mediated equilibrium reflexes of the fruit fly, Drosophila melanogaster. Phil Trans R Soc Lond B 354: 903–916. Drechsler P, Federle W. 2006. Biomechanics of smooth adhesive pads in insects: Influence of tarsal secretion on attachment performance. J Comp Physiol A 192:1213–1222. Elzinga RJ. 2004. Fundamentals of entomology, 6th ed. New Jersey: Pearson Education. 512 p. Fernandes FF, Chiarini-Garcia H, Linardi PM. 2004. Scanning electron microscopy studies of sensilla and other structures of adult Dermatobia hominis (Diptera: Cuterebridae). J Med Entomol 41: 552–560. Finch S. 1989. Ecological considerations in the management of Delia pest species in vegetable crops. Annu Rev Entomol 34:117–137. Gaino E, Rebora M. 2002. Sensory receptors on the forceps of the male imago and subimago of Echyonurus venosus (Ephemeroptera: Heptageniidae). Ann Entomol Soc Am 95:244–249. Gaume L, Perret P, Gorb E, Gorb S, Labat JJ, Rowe N. 2004. How do plant waxes cause flies to slide? Experimental tests of wax-based trapping mechanisms in three pitfall carnivorous plants. Arthropod Struct Dev 33:103–111. Gorb SN. 1998. The design of the fly adhesive pad: Distal tenent setae are adapted to the delivery of an adhesive secretion. Proc R Soc Lond B 265:747–752. Gorb SN, Gorb EV. 2004. Ontogenesis of the attachment ability in the bug Coreus marginatus (Heteroptera, Insecta). J Exp Biol 207: 2917–2924. Gorb SN, Kesel A, Berger J. 2000. Microsculpture of the Wing Surface in Odonata: Evidence for Cuticular Wax Covering. Arthropod Struct Dev 29:129–135. Gratwick M. 1992. Crop Pests in the UK. Collected Edition of MAFF Leaflets. London: Chapman & Hall. 490 p. Griffiths GCD. 1991. Anthomyiidae. In: Flies of the Nearctic Region. Griffiths GCD, editor. E. Schweizerbart’sche Verlagsbuchhandlung: Stuttgart. pp. 969–984. Hunter FF, Adserballe CF. 1996. Cuticular structures on the antennae of Hypoderma bovis De Geer (Diptera: Oestridae) females. Int J Insect Morphol Embryol 25:173–181. Jina X, Brandazza A, Navarrini A, Ban L, Zhang S, Steinbrecht RA, Zhang L, Pelosi P. 2005. Expression and immunolocalisation of odorant-binding and chemosensory proteins in locusts CMLS. Cell Mol Life Sci 62:1156–1166. Kurahashi H. 2002. Key to the Sarcophagidae of the Oriental region. In: Greenberg B, Kunich JC, editors. Entomology and the law: Flies as forensic indicators. United Kingdom: Cambridge University Press. pp. 138–142. Leite ACR. 1995. Ultrastructure of the male terminalia of Cochliomyia hominivorax and C. macellaria. Mem Inst Oswaldo Cruz 90: 475–481. McAlpine DK. 2011. Observations on Antennal Morphology in Diptera, with Particular Reference to the Articular Surfaces between Segments 2 and 3 in the Cyclorrhapha. Records Australian Museum 63:113–166. McAlpine JF. 1981. Morphology and terminology—Adults. In: McAlpine JF, Peterson BV, Shewell GE, Teskey HJ, Vockeroth JR, Wood DM, editors. Manual of Nearctic Diptera. Agriculture Canada: Ottawa. pp. 9–63. Nalbach G. 1993. The halteres of the blowfly Calliphora. I. Kinematics and dynamics. J Comp Physiol A 173:293–300.
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Niederegger S, Gorb S. 2003. Tarsal movements in flies during leg attachment and detachment on a smooth substrate. J Insect Physiol 49:611–620. Niederegger S, Gorb S, Jiao Y. 2002. Contact behaviour of tenent setae in attachment pads of the blowfly Calliphora vicina (Diptera, Calliphoridae). J Comp Physiol A 187:961–970. Parker AR, Townley HE. 2007. Biomimetics of photonic nanostructures. Nat Nanotechnol 2:347–353. Ross KTA. 1992. Comparative study of the antennal sensilla of five species of root maggots: Delia radicum L., D. floralis F., D. antique Mg., D. platura Mg. (Diptera: Anthomyiidae), and Psila rosae F. (Diptera: Psilidae). Int J Insect Morphol Embryol 21:175–197. Rossignol PA, McIver SB. 1977. Fine structure and role in behavior of sensilla on the terminalia of Aedes aegypti (L.) (Diptera: Culicidae). J Morphol 151:419–438. Senior-White R, Aubertin D, Smart J. 1940. Diptera. Family Calliphoridae. In: Sewell RBS, editor. The fauna of British India, including the remainder of the oriental region. London: Taylor & Francis. pp. 27–134. Setzu MD, Poddighe S, Angioy AM. 2011. Sensilla on the antennal funiculus of the blow fly, Protophormia terraenovae (Diptera: Calliphoridae). Micron 42:471–477. Shanbhag SR, M€ uller B, Steinbrecht RA. 1999. Atlas of olfactory organs of Drosophila melanogaster: Types, external organization, innervation and distribution of olfactory sensilla. Int J Insect Morphol Embryol 28:377–397. Shanbhag SR, Park SK, Pikielny CW, Steinbrecht RA. 2001. Gustatory organs of Drosophila melanogaster: fine structure and expression of the putative odorant-binding protein PBPRP2. Cell Tissue Res 304:423–437. Sherman A, Dickinson MH. 2004. Summation of visual and mechanosensory feedback in Drosophila flight control. J Exp Biol 207:133– 142. Singh RN, Nayak SV. 1985. Fine structure and primary sensory projections of sensilla on the maxillary palp of Drosophila melanogaster Meigen (Diptera: Drosophilidae). Int J Insect Morphol Embryol 15:291–306. Smallegange RC, Kelling RJ, Den Otter CJ. 2008. Types and numbers of sensilla on antennae and maxillary palps of small and large houseflies, Musca domestica (Diptera, Muscidae). Microsc Res Tech 71:880–886.
Spiegel CN, Brazil RP, Soares MJ. 2000. Sensilla on the terminalia of Lutzomyia spp. (Diptera: Psychodidae) sand flies. J Med Entomol 37:860–863. Sugiyama E, Shinonaga S, Kano R. 1988a. Sarcophagine flies from Nepal with the description of a new species (Diptera: Sarcophagidae). Jpn J Sanit Zool 39:355–362. Sugiyam E, Shinonaga S, Kano R. 1988b. The tribe sarcophagini from New Guinea with the description of a new species (Diptera: Sarcophagidae). Jpn J Sanit Zool 39:283–292. Sukontason K, Methanitikorn R, Kurahashi H, Vogtsberger RC, Sukontason KL. 2008. External morphology of Chrysomya pinguis (Walker) (Diptera: Calliphoridae) revealed by scanning electron microscopy. Micron 39:190–197. Sukontason KL, Methanitikorn R, Boonsriwong W, Piangjai S, Kurahashi H, Vogtsberger RC, Sukontason K. 2006a. Ultrastructure of spiracles of Musca domestica and Hydrotaea chalcogaster (Diptera: Muscidae). Parasitol Res 100:19–23. Sukontason KL, Bunchu N, Methanitikorn R, Chaiwong T, Kuntalue B, Sukontason K. 2006b. Ultrastructure of adhesive device in fly in families calliphoridae, muscidae and sarcophagidae, and their implication as mechanical carriers of pathogens. Parasitol Res 98:477–481. Sukontason KL, Methanitikorn R, Kurahashi H, Piangjai S, Sukontason K. 2005. Surface ultrastructure of prestomal teeth of some flies in the families Calliphoridae, Muscidae and Sarcophagidae. Parasitol Res 96:410–412. Vander Starre H, Tempelaar MJ. 1976. Structural and functional aspects of sense organs on the maxillary palps of Calliphora vicina. J Insect Physiol 22:855–863. Wagner T, Neinhuis C, Barthlott W. 1996. Wettability and contaminability of insect wings as a function of their surface sculptures. Acta Zoologica 77:213–225. Wasserthal LT. 2001. Flight-motor-driven respiratory air flow in the hawkmoth Manduca sexta. J Exp Biol 204:2209–2220. Watson GS, Cribb BW, Watson JA. 2010. How micro/nanoarchitecture facilitates anti-wetting: An elegant hierarchical design on the termite wing. ACS Nano 4:129–136. Zacharuk RY. 1985. Antennal sensilla. In: Kerku GA, Gilbert LI, editors. Comparative Insect Physiology, Biochemistry and Pharmacology. Oxford: Pergamon Press. pp. 1–69. Zhang M, Chen YO, Thomas P, Zhang D. 2013. Review of the genus Agria (Diptera, Sarcophagidae) from China. ZooKeys 310:41–55.
Microscopy Research and Technique
Fine Structure of Delia platura (Meigen) (Diptera: Anthomyiidae) Revealed by Scanning Electron Microscopy QI-KE WANG,1 YAN-ZHI YANG,1 MEI-QIN LIU,2 AND DONG ZHANG1* 1 2
Department of Zoology, College of Nature Conservation, Beijing Forestry University, Beijing, 100083, China Analysis and Testing Center, Beijing Forestry University, Beijing, 100083, China
KEY WORDS
Delia platura; morphology; scanning electron microscopy
ABSTRACT Delia platura (Meigen) is a phytophagous fly that can cause significant crop losses. To obtain a better understanding of the external morphology of this species, adult D. platura is studied using scanning electron microscopy. Organs or structures that are important for taxonomy, such as the compound eyes, spiracles, pulvilli, wings, and genitalia are highlighted to complement previous description based on light microscope. Mesothoracic and metathoracic spiracles of D. platura that provide efficiency in preventing entrance of fine materials or dust into the tracheal system are morphologically different. In addition, the elongate-oval pulvillus is densely covered with tenent setae with spoon-like tip, which can increase the number of contact points for attachment to a surface. Four types of sensilla are observed on the male genitalia of D. platura including: trichoid sensilla, chaetic sensilla, three subtypes of campaniform sensilla, and basiconic sensilla. Long bristles and microtrichiae are observed on the female genitalia of D. platura. The possible function of sensilla located in the genitalia of D. platura is discussed. Microsc. Res. Tech. 77:619–630, 2014. V 2014 Wiley Periodicals, Inc. C
INTRODUCTION Delia platura (Meigen), known as bean seed fly species, is an important phytophagous pest that is distributed worldwide in agricultural systems. There are reports of significant crop losses that caused by D. platura (Chaudhary et al., 1987; Finch, 1989; Gratwick, 1992). The maggots mine the roots of various beans, cereals, tubers, and tobacco seedlings (Griffiths, 1991), making which particularly vulnerable to stem rot organisms. Antennae and other organs, such as ommatidia, spiracles, pulvilli, and genitalia, are of different functions and play an important role in various behaviors during adult life (Nalbach, 1993; Dickinson, 1999; Sherman and Dickinson, 2004; Sukontason et al., 2005; Sukontason et al., 2006a; Sukontason et al., 2008). Ross (1992) described and compared antennal sensilla of several species in this genus, while there is a lack of study of body parts in this genus, as well as in the Diptera. The body parts included in this study have been widely used as taxonomic characteristics, and usually observed under light microscope. On the other hand, the potential for biomimetic applications of fly body parts have been reported in many studies (Drechsler and Federle, 2006; Sukontason et al., 2008). Taking into account the limited data of these important structures, this paper provides details of the ultrastructures that can easily be neglected in D. platura, and clarifies vagueness in previous descriptions. MATERIAL AND METHODS The adult males and females of D. platura used in this study were captured during summer of 2011 in SongShan, Beijing, China. Specimens were killed by C V
2014 WILEY PERIODICALS, INC.
placing in a freezer for 30 min before they were processed for this study involving scanning electron microscopy (SEM). To prepare for observation with the SEM (Electron source: secondary electron; Acceleration voltage: 5000 Volt), flies were rinsed by shaking in normal saline solution to remove surface artifacts. Specimens were fixed with a 2.5% glutaraldehyde mixture in phosphatebuffered saline (PBS), pH 7.4, at 48 C for 24 h. For the detailed examination of the external surface, antennae, palpi, legs were excised from the flies. In addition, the samples were then rinsed twice with PBS and dehydrated with ethanol. The dehydration process involved the specimens being sequentially subjected to the following increasing ethanol concentrations: 30, 50, 70, 80, 90, 95, and 100%. Specimens remained in each concentration of ethanol for 12 h during each step of the dehydration process. Finally, the specimens were subjected to critical point drying using a HCP-2 critical point dryer (Hitachi Corp., Tokyo, Japan), attached to double-stick tape on aluminum stubs in the correct orientation, coated with gold in a E-1010 ion sputter (Hitachi Corp.,
*Correspondence to: Dr. Dong Zhang, College of Nature Conservation, Beijing Forestry University, Qinghua East Road No. 35, Mailbox 162, Beijing 100083, China. E-mail: [email protected] Received 18 February 2014; accepted in revised form 1 May 2014 REVIEW EDITOR: Prof. Alberto Diaspro Qi-Ke Wang and Yan-Zhi Yang contributed equally to this work. Contract grant sponsor: Fundamental Research Funds for the Central Universities; Contract grant number: YX2013-08; Contract grant sponsor: National Nature Science Foundation of China; Contract grant number: 31201741; Contract grant sponsor: New Century Excellent Talents in University; Contract grant number: NCET-12-0783. DOI 10.1002/jemt.22380 Published online 22 May 2014 in Wiley Online Library (wileyonlinelibrary.com).
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Fig. 1. SEM micrographs of adult male Delia platura. A: Top view of head displaying the compound eye, antenna, palpi, and labellum. B: Magnification of the narrow frons showing rows of setae on each side, and the middle of the frons with density microtrichia. C: Domeshaped ommatidia with sparse, short ommatrichia (arrow). D: Higher
magnification of ommatidia showing densely postulate appearance of corneal lens. E: The right side of the gena, with several setae emanating from their sockets. F: Enlarged view of the gena showing concave facial scales. a, antenna; c, compound eye; p, paplus; lbl, labellum.
Tokyo, Japan), and observed using a Hitachi S34Q SEM (Hitachi Corp., Tokyo, Japan) at the Microscopy Core Facility, Biological Technology Centre, Beijing Forestry University (Beijing, China). The terminology and nomenclature used to describe fly morphology presented by McAlpine (1981) and antennal morphology and classification of sensilla types in this study follow those used by Zacharuk (1985), Hunter and Adserballe (1996), Shanbhag et al. (1999), and Setzu et al. (2011).
RESULTS Head The body of an adult D. platura can be divided into three regions: head, thorax, and abdomen, as in other flies. Prominent organs of the head include a pair of large compound eyes, three ocelli which form an inverted triangle antero-dorsally, antennae beneath the frontal suture, palpi and a sponging mouthpart (Figs. 1A and 1B). The compound eyes of male D. platura are located dorso-laterally and composed of Microscopy Research and Technique
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Fig. 2. SEM micrographs of antenna of adult male Delia platura. A: Anterodorsal surface of the whole antenna. B: Enlarged view of anterodorsal surface of the antennal scape and pedicel. C: Magnification of the setiferous plaques on the antennal pedicel. D: The distal articular surface of pedicel of antenna of adult male D. platura showing the location of pedicellar button (arrow); Magnification of pedicellar button is in the box. E: Magnification of trichoid sensilla on the
antennal funiculus. F: Magnification of large basiconic sensilla (arrow); Higher magnification showing the pore clearly is in the box. G: Magnification of small basiconic sensilla (arrow). H: Magnification of clavate sensilla (arrow). I: Magnification of coeloconic sensilla (arrows). Sc, scape; Pd, pedicel; Ar, arista; Fn, funiculus. [(D) scale bar 4lm in the box, (F) scale bar 1.5lm in the box].
numerous ommatidia with short ommatrichia infrequently present between the adjacent dome-shaped ommatidia (Fig. 1C). A rough cobbled surface, which could be described as densely postulate, appeared in the compound eyes of D. platura (Fig. 1D). Moreover, the face is decorated with concave scales with tapering ending (Figs. 1E and 1F). Similar to other higher dipterans, the antenna of D. platura comprise of three segments: a proximal scape (Sc), pedicel (Pd), and a distal flagellum, the latter is composed of an arista and a funiculus (Fn) (Fig. 2A). The surface of antenna is covered by microtrichia. The scape and pedicel both bear bristles with sockets at the base (Fig. 2B). Four setiferous plaques, which contain a bulbous seta, are observed on the pedicel (Fig. 2C). One pedicellar button is found on the distal articular surface of pedicel of antenna (Fig. 2D), which is domeshaped and surrounded by thick walls. The arista, a
bristle-like appendage or “hair,” is located proximally near the base of funiculus and is covered with numerous microtrichia (Fig. 2A). The funiculus is the most prominent part of the fly antennae. Based on SEM observations, we recorded five types of sensilla: trichoid sensilla, two types of basiconic sensilla, clavate sensilla and coeloconic sensilla. Trichoid sensilla are the most abundant type of sensilla on the funiculus. They are elongated, hair-shaped structures extending above microtrichia, ending with a rather pointed tip (Fig. 2E). Two types of multiporous basiconic sensilla, a large and a small one, can be distinguished according to shape and size (Figs. 2F and 2G). Clavate sensilla with club-like shapes are characterized by a distal swelling (Fig. 2H). Coeloconic sensilla are the shortest of the various types of sensilla and characterized by distinct longitudinal ridges on their walls (Fig. 2I).
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Fig. 3. SEM micrographs of mouthpart features of adult male Delia platura. A: Top view of mouthpart. B: Enlarged view of the mouthpart surface revealing dense covering of sharp-tipped microtrichia and chaetic sensilla emanating from their sockets. C: Lateral view of
the mouthpart. D: Higher magnification of the labellum. E: Front view of the mouthpart. F: Enlarged view of bifurcated prestomal teeth.
The mouthparts of this species form a tubular sucking organ called the proboscis, which terminates in a large, sponging structure known as the labellum (Figs. 3A23C). Bifurcated tips of the prestomal teeth project from the cleft between the labellar lobes. The prominent grooves of the pseudotracheae radiate from the food canal and prestomal teeth (Figs. 3D23F). Upon higher magnification observation, the palpus of D. platura is club-shaped, elongated, gradually enlarged to a rounded end distally, and attached rostrally to the proximal part of the proboscis (Fig. 4A). The whole surface of the palpus is exposed to the environment dur-
ing probing and feeding. Microtrichia, bristles and basiconic sensilla are observed on the palpus (Figs. 4B and 4C). The bristles are inserted into a cuticular socket and had longitudinal grooves evident in its hair-like shaft. The basiconic sensilla are small and similar to those observed on the antennal funiculus in morphology (Fig. 4D). Thorax The thorax of adult D. platura is composed of three segments: prothorax, mesothorax, and metathorax. In Microscopy Research and Technique
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Fig. 4. SEM micrographs of palpus features of adult male Delia platura. A: The front view of palpus. B: The lateral view of the palpi, with numerous short microtrichia and several long chaetic sensilla. C: Magnification of the palpus, showing the distribution of basiconic sensilla (arrows). D: Higher magnification of basiconic sensilla. Ba, basiconic sensilla.
flies, the mesothorax is enlarged and is covered with dense microtrichia. The mesonotum that consists of the entire dorsum of the mesothorax is covered with microtrichia (Figs. 5A and 5B). Sensilla, which emanated from swollen, dome-shaped sockets in the scutum and amongst numerous short microtrichia, are straight and sharp-tipped with prominent longitudinal grooved (Fig. 5C). The anterior spiracles (mesothoracic) are located near the junction of the pronotum and the mesonotum and appear as elliptical structures, with their upper portions partially open. The setae surrounding the mesothoracic spiracle are arranged in a single line along the rim of each spiracle (Fig. 5D). The posterior spiracles (metathoracic) with two clusters of long setae distributed on its rim are shaped as a rounded isosceles triangle (Fig. 5E). Beneath the two clusters of setae, a latticed membrane is observed (Fig. 5F). The wing membrane integument and the whole calypter are densely covered with microtrichia (Figs. 6B26D). Moreover, strong chaetic sensilla are implanted in the costal vein on the anterior margin of the wing and periphery of the upper and lower calypters (Figs. 6A and 6D). The haltere of D. platura is a small dumbbell-shaped organ, which consists of three main portions: base, stem, and end knob (Fig. 7A). A close-up view of the lateral portion of the base revealed that a set of campaniMicroscopy Research and Technique
form sensilla is apparent (Figs. 7B and 7C). These rows of campaniform sensilla are perpendicular to the longitudinal axis of the haltere. The terminal end of the knob possesses a sporadic group of sensilla (Fig. 7D). Legs are composed of a coxa, trochanter, femur, tibia, and five tarsal segments. The distal part of the terminal tarsomere is a tube bearing the tendon of the claw flexor muscle and articulated with the pretarsus. Pulvillus is connected to the tarsus by an elastic part containing resilin-like cuticle. It is structure adapted for attachment to a variety of surfaces and elongateoval in shape, but their anterior end tapering (Fig. 8A). The ventral surface of a pulvillus is densely covered by the tenent setae of spoon-like tip (Fig. 8). Abdomen Compared with the head and thorax, the abdomen of most insects typically has a highly reduced number of appendages. An examination of abdomen of male D. platura reveals abundant microtrichia and a good deal of long setae curved toward the apex of the body (Figs. 9A29C). Long setae appear as stout hair shafts bearing longitudinal grooves and inserted into cuticular socket (Figs. 9D and 9E). A lateral view of the male genitalia of D. platura shows the prominent features of the phallus, pregonite, postgonite, and cercus (Fig. 10A). The phallus
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Fig. 5. SEM micrographs of thorax features of adult male Delia platura. A: Lateral view of mesonotum showing dense microtrichia and long chaetic sensilla projecting posteriorly. B: Enlarged view of mesonotum showing microtrichia. C: Lateral view of scutellum showing several sensilla. Higher magnification of these sensilla is in the box.
D: Enlarged view of the anterior (mesothoracic) spiracle. E: Posterior (metathoracic) spiracle, with two clusters of setae distributed on its rim. F: Enlarged view of the inside of the posterior spiracle, showing the latticed membrane.
locates medially on a pair of pregonites, and its surface is slightly corrugated (Fig. 10B). Several setae are observed on the pregonite (Fig. 10A). The postgonite situated underneath the pregonite and is terminally curved inward. Several short sensilla are found on the basal region (Fig. 10C). The surstyli are large and swollen at the base, gradually decreasing terminally, slightly curving inwardly, and more or less rounded at the apical end (Fig. 10D). The external portion of the surstyli are greatly endowed along the lower half region with long bristles, which are morphologically similar to the triochoid sensilla. In addition, chaetic sensilla existed at the proximal region (Figs. 10D, 10I, and 10J). Three types of campaniform sensilla are observed all over the upper half region (Figs.
10E210G), and basiconic sensilla with subapical peg are present at the apical end (Fig. 10H). As for the ventral view of the female genitalia, the elongated ovipositor can be observed (Fig. 11A). The cerci, which are equipped with many long bristles, are more or less sclerotized and epiproct is lying between them (Fig. 11B). Lots of bristles and microtrichia are observed on the ovipositor (Figs. 11C and 11D). DISCUSSION Flies are equipped with a number of different receptors, which help them acquire information from the environment. The compound eyes are the most important visual organs, and the number of ommatidia varies depending on the biology of the insect (Elzinga, Microscopy Research and Technique
Fig. 6. SEM micrographs of mesonotal wing and calypter of adult male Delia platura. A: Anterior margin of costal vein implanted with stout chaotic sensilla. B: Microtrichiae on dorsal surface of wing membrane integument; part of the vein is showed in the box. C: The
margin of the wing on the dorsal surface; higher magnification of long and slightly bend setae is showed in the box. D: Dorsal view of the whole calypter.
Fig. 7. SEM micrographs of haltere of adult male Delia platura. A: Lateral view of the metathorax identifying upper calypter and lower calypter. Arrow indicates a set of campaniform sensilla. B: Set of campaniform sensilla presented as several rows perpendicular to longitudinal axis of haltere. C: Enlarged view of the campaniform sensilla. D: Terminal end of knob with several sensilla.
Fig. 8. SEM micrographs of pretarsus features of adult male Delia platura. A: Pulvilli of midleg showing numerous tenent setae covering on the surface. B: Enlarged view of pulvilli. C: Higher magnification of pulvilli showing the distribution of tenent setae with spoon-like tips. D: Extreme magnification of the tenent setae with a spoon-like tip.
Fig. 9. SEM micrographs of abdomen features of adult male Delia platura. A: Lateral view of the abdomen, with abundant microtrichiae and a number of long grooved setae. B: Enlarged view of part of the tergite VI showing numerous microtrichiae on the surface and
several long setae with longitudinal grooves. C: Higher magnification of microtrichiae. D: Lateral view of one row of long setae on the rump. E: Higher magnification of these long setae showing longitudinal grooves.
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Fig. 10. SEM micrographs of genitalia of adult male Delia platura. A: Lateral view of the entire genitalia illustrating the prominent features of the phallus, pregonite, postgonite, surstylus, and cercus. B: Enlarged view of phallus; higher magnification of part of phallus showing slight corrugation. C: Enlarged view of distal region of postgonite showing the distribution of short sensilla; higher magnification of short sensilla. D: Anterior view of a pair of surstyli; higher
magnification of lower half region of surstyli showing the distribution of sensilla. E: Magnification of campaniform sensilla type I. F: Magnification of campaniform sensilla type II. G: Magnification of campaniform sensilla type III. H: Magnification of basiconic sensilla with subapical peg. I: Magnification of trichoid sensilla. J: Magnification of chaetic sensilla. Ph, phallus; Prg, pregonite; Pog, postgonite; Sur, surstylus; Cerc, circus.
2004). Regarding the external surface of the corneal lens of the ommatidia, whose role is antireflection (Dey and Dkhar, 1992), a detail observation through SEM in this study has revealed the densely postulate appearance in the compound eyes of D. platura. This characteristic is in accordance with those observed in Chrysomya megacephala Fabricius (Sukontason et al., 2008) and in contrast with the sinuous sculpture pattern in the compound eyes of Lucilia cuprina Wiedemann (Sukontason et al., 2008). Shanbhag et al. (1999) suggested that the third antennal segment and palpus are the main and acces-
sory olfactory sense organs, respectively. Morphology and function of five types of surface sensilla and one type of pit sensilla that found on the antennae of D. platura have been discussed by Ross (1992). In addition to the sensilla that have been reported previously, pedicellar button are also found on the distal articular surface of pedicel of antennae of adult male D. platura in this study. The pedicellar button are cuticular component of a chordotonal organ, which may act as baroreceptor (McAlpine, 2011). Bascionic sensilla and bristles, which function as olfactory receptors and mechanoreceptors respectively, are found on the
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Fig. 11. SEM micrographs of genitalia of adult female Delia platura. A: Dorsal view showing extended ovipositor. B: Detail of the dorsal view displaying a pair of sclerotized cerci and the epiproct between them. C: Higher magnification of bristle on the genitalia of adult female D. platura. D: Long microtrichiae on the ovipositor. Epiprct, epiproct; Cerc, circus.
maxillary palpi. This result corresponds with that of Calliphora vicina Robineau-Desvoidy (Vander Starre and Tempelaar, 1976), Drosophila melanogaster Fallen (Singh and Nayak, 1985), Hydrotaea irritans Fallen (Been et al., 1988), and Musca domestica Linnaeus (Smallegange et al., 2008). Both sides of the wings of D. platura are densely covered with microtrichiae. A closer observation showed that all the microtrichiae are parallel to the adjacent veins. No significant morphological differences were observed between the microtrichiae on both sides of the wings. Previous research has discussed that microtrichiae could serve as a hydrophobic structure that prevents the wings from wetting in various insects (Wagner et al., 1996; Gorb et al., 2000; Cong et al., 2004; Parker and Townley, 2007; Watson et al., 2010). Nonwetting property of insect wings is crucial for the survival of insects in wet environments, as insects could be permanently trapped by water or wet surface. Super-hydrophobic or self-clean property of insect
wings could lead to next generation of contamination resistant or self-cleaning materials (Watson et al., 2010). The stout chaetic sensilla on the anterior edge of the wings are structurally similar to the ones found on scape and pedicle. The specialized basal structure indicates mechanosensory function. However, odorantbinding and chemosensory proteins were discovered in Drosophila wings (Shanbhag et al., 2001), as well as other insects (Jina et al., 2005), suggesting that wings could be chemosensory organs (Shanbhag et al., 2001). In flies, respiration is mediated by the multibranched tracheal system, which has cuticular openings called “spiracles” located at the thorax and abdomen (Sukontason et al., 2006a). Interestingly, mesothoracic and metathoracic spiracles of D. platura are morphologically different, which is corresponding with those of M. domestica (Sukontason et al., 2006a) and Hydrotaea chalcogaster Wiedemann (Sukontason et al., 2006a). The long, consistently arranged inward setae covering the finely porous opening of Microscopy Research and Technique
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mesothoracic spiracles are comparable with those previously reported in the bot fly, Dermatobia hominis Linnaeus (Fernandes et al., 2004). It has been suggested that these setae act as protection from entering the dust or fine particles in the tracheal system (Chapman, 1998). In regard to metathoracic spiracles, two clusters of setae observed in D. platura exhibited a different form from the relatively dense setae in H. chalcogaster (Sukontason et al., 2006a). Moreover, our detailed view of metathoracic spiracles clearly demonstrated the latticed membrane, which acts as protection apparatus, differed markedly from that of Manduca sexta Linnaeus (Wasserthal, 2001). Sukontason et al. (2008) have proposed that all of these different structural modifications provide various levels of efficiency in preventing entrance of fine materials or dust into the tracheal system. Pulvilli are structures adapted for attachment to a variety of surfaces (Gorb, 1998; Niederegger et al., 2002; Niederegger and Gorb, 2003; Gaume et al., 2004; Sukontason et al., 2006b). The ventral surface of pulvilli of D. platura is covered by tenent setae with a spoon-like tip, similar to the blow fly, Chrysomya villeneuvi Patton (Sukontason et al., 2006b). Moreover, tenent setae with a spatula-like tip and a pointed-like tip are also found on the ventral surface of pulvilli (Sukontason et al., 2006b). However, either the bearing spatula-like or spoon-like tip of the tenent setae increase the number of contact points for attachment to a surface (Gorb and Gorb, 2004). Morphological features of the male genitalia, especially the cerci, differed markedly between species, and thus are often used to identify flies and other insects (Senior-White et al., 1940; Sugiyama et al., 1988a, 1988b; Leite, 1995; Kurahashi, 2002; Dahlem and Naczi, 2006). In our study, several short sensilla are found on postgonite, which are similar to that of Agria mihalyii Rohdendorf and Verves (Zhang et al., 2013). In addition, six types of sensilla that include trichoid sensilla, chaetic sensilla, three types of campaniform sensilla (Ca), and basiconic sensilla are found on the surstyli. The Ca is thought to monitor general pressure in the cuticle, possibly through some directional sensitivity but it is certainly not as specific as other types of mechanoreceptive sensilla (Bromley et al., 1980). However, the mechanosensory function of these sensilla located in the male genitalia for aiding copulation in insects has been proposed in many studies (Rossignol and McIver, 1977; Spiegel et al., 2000; Gaino and Rebora, 2002; Acebes et al., 2003). In conclusion, the ultrastructural study of several organs of D. platura in this study allows us to understand the functional-morphological view point of these structures and helps to understand biological behavior of this economically important species. ACKNOWLEDGMENT The authors are grateful to Dr Jun-na Shi (Beijing Forestry University, Beijing, China) for her invaluable help with this study. REFERENCES Acebes A, Cobb M, Ferveur JF. 2003. Species-specific effects of single sensillum ablation on mating position in Drosophila. J Exp Biol 206:3095–3100.
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Been TH, Schomaker CH, Thomas G. 1988. Olfactory sensilla on the antenna and maxillary palp of the sheep head fly, Hydrotaea irritans (Fall en) (Diptera: Muscidae). Int J Insect Morphol Embryol 17:121–133. Bromley AK, Dunn JA, Anderson M. 1980. Ultrastructure of the antennal sensilla of aphids II. Trichoid, chordotonal and campaniform sensilla. Cell Tissue Res 205:493–511. Chapman RF. 1998. The insects structure and function, 4th ed. UK: Cambridge University Press. 770 p. Chaudhary RN, Kanaujia KR, Sharma VK. 1987. A note on the incidence of seed corn maggot, Delia platura Meigen (Anthomyiidae: Diptera) in spring sown maize. Bull Entomol (New Delhi) 28:159–161. Cong Q, Chen GH, Fang Y, Ren LQ. 2004. Study on the superhydrophobic characteristic of butterfly wing surface. J Bionics Eng 1:249–255. Dahlem GA, Naczi RFC. 2006. Flesh flies (Diptera: Sarcophagidae) associated with North American pitcher plants (Sarraceniaceae), with descriptions of three new species. Ann Entomol Soc Am 99: 218–240. Dey S, Dkhar B. 1992. An unusual type of corneal nipple in the earwig Forficula sp., with a possible anti-reflection role. Micron Microsc Acta 2:337–339. Dickinson MH. 1999. Haltere-mediated equilibrium reflexes of the fruit fly, Drosophila melanogaster. Phil Trans R Soc Lond B 354: 903–916. Drechsler P, Federle W. 2006. Biomechanics of smooth adhesive pads in insects: Influence of tarsal secretion on attachment performance. J Comp Physiol A 192:1213–1222. Elzinga RJ. 2004. Fundamentals of entomology, 6th ed. New Jersey: Pearson Education. 512 p. Fernandes FF, Chiarini-Garcia H, Linardi PM. 2004. Scanning electron microscopy studies of sensilla and other structures of adult Dermatobia hominis (Diptera: Cuterebridae). J Med Entomol 41: 552–560. Finch S. 1989. Ecological considerations in the management of Delia pest species in vegetable crops. Annu Rev Entomol 34:117–137. Gaino E, Rebora M. 2002. Sensory receptors on the forceps of the male imago and subimago of Echyonurus venosus (Ephemeroptera: Heptageniidae). Ann Entomol Soc Am 95:244–249. Gaume L, Perret P, Gorb E, Gorb S, Labat JJ, Rowe N. 2004. How do plant waxes cause flies to slide? Experimental tests of wax-based trapping mechanisms in three pitfall carnivorous plants. Arthropod Struct Dev 33:103–111. Gorb SN. 1998. The design of the fly adhesive pad: Distal tenent setae are adapted to the delivery of an adhesive secretion. Proc R Soc Lond B 265:747–752. Gorb SN, Gorb EV. 2004. Ontogenesis of the attachment ability in the bug Coreus marginatus (Heteroptera, Insecta). J Exp Biol 207: 2917–2924. Gorb SN, Kesel A, Berger J. 2000. Microsculpture of the Wing Surface in Odonata: Evidence for Cuticular Wax Covering. Arthropod Struct Dev 29:129–135. Gratwick M. 1992. Crop Pests in the UK. Collected Edition of MAFF Leaflets. London: Chapman & Hall. 490 p. Griffiths GCD. 1991. Anthomyiidae. In: Flies of the Nearctic Region. Griffiths GCD, editor. E. Schweizerbart’sche Verlagsbuchhandlung: Stuttgart. pp. 969–984. Hunter FF, Adserballe CF. 1996. Cuticular structures on the antennae of Hypoderma bovis De Geer (Diptera: Oestridae) females. Int J Insect Morphol Embryol 25:173–181. Jina X, Brandazza A, Navarrini A, Ban L, Zhang S, Steinbrecht RA, Zhang L, Pelosi P. 2005. Expression and immunolocalisation of odorant-binding and chemosensory proteins in locusts CMLS. Cell Mol Life Sci 62:1156–1166. Kurahashi H. 2002. Key to the Sarcophagidae of the Oriental region. In: Greenberg B, Kunich JC, editors. Entomology and the law: Flies as forensic indicators. United Kingdom: Cambridge University Press. pp. 138–142. Leite ACR. 1995. Ultrastructure of the male terminalia of Cochliomyia hominivorax and C. macellaria. Mem Inst Oswaldo Cruz 90: 475–481. McAlpine DK. 2011. Observations on Antennal Morphology in Diptera, with Particular Reference to the Articular Surfaces between Segments 2 and 3 in the Cyclorrhapha. Records Australian Museum 63:113–166. McAlpine JF. 1981. Morphology and terminology—Adults. In: McAlpine JF, Peterson BV, Shewell GE, Teskey HJ, Vockeroth JR, Wood DM, editors. Manual of Nearctic Diptera. Agriculture Canada: Ottawa. pp. 9–63. Nalbach G. 1993. The halteres of the blowfly Calliphora. I. Kinematics and dynamics. J Comp Physiol A 173:293–300.
630
Q.-K. WANG ET AL.
Niederegger S, Gorb S. 2003. Tarsal movements in flies during leg attachment and detachment on a smooth substrate. J Insect Physiol 49:611–620. Niederegger S, Gorb S, Jiao Y. 2002. Contact behaviour of tenent setae in attachment pads of the blowfly Calliphora vicina (Diptera, Calliphoridae). J Comp Physiol A 187:961–970. Parker AR, Townley HE. 2007. Biomimetics of photonic nanostructures. Nat Nanotechnol 2:347–353. Ross KTA. 1992. Comparative study of the antennal sensilla of five species of root maggots: Delia radicum L., D. floralis F., D. antique Mg., D. platura Mg. (Diptera: Anthomyiidae), and Psila rosae F. (Diptera: Psilidae). Int J Insect Morphol Embryol 21:175–197. Rossignol PA, McIver SB. 1977. Fine structure and role in behavior of sensilla on the terminalia of Aedes aegypti (L.) (Diptera: Culicidae). J Morphol 151:419–438. Senior-White R, Aubertin D, Smart J. 1940. Diptera. Family Calliphoridae. In: Sewell RBS, editor. The fauna of British India, including the remainder of the oriental region. London: Taylor & Francis. pp. 27–134. Setzu MD, Poddighe S, Angioy AM. 2011. Sensilla on the antennal funiculus of the blow fly, Protophormia terraenovae (Diptera: Calliphoridae). Micron 42:471–477. Shanbhag SR, M€ uller B, Steinbrecht RA. 1999. Atlas of olfactory organs of Drosophila melanogaster: Types, external organization, innervation and distribution of olfactory sensilla. Int J Insect Morphol Embryol 28:377–397. Shanbhag SR, Park SK, Pikielny CW, Steinbrecht RA. 2001. Gustatory organs of Drosophila melanogaster: fine structure and expression of the putative odorant-binding protein PBPRP2. Cell Tissue Res 304:423–437. Sherman A, Dickinson MH. 2004. Summation of visual and mechanosensory feedback in Drosophila flight control. J Exp Biol 207:133– 142. Singh RN, Nayak SV. 1985. Fine structure and primary sensory projections of sensilla on the maxillary palp of Drosophila melanogaster Meigen (Diptera: Drosophilidae). Int J Insect Morphol Embryol 15:291–306. Smallegange RC, Kelling RJ, Den Otter CJ. 2008. Types and numbers of sensilla on antennae and maxillary palps of small and large houseflies, Musca domestica (Diptera, Muscidae). Microsc Res Tech 71:880–886.
Spiegel CN, Brazil RP, Soares MJ. 2000. Sensilla on the terminalia of Lutzomyia spp. (Diptera: Psychodidae) sand flies. J Med Entomol 37:860–863. Sugiyama E, Shinonaga S, Kano R. 1988a. Sarcophagine flies from Nepal with the description of a new species (Diptera: Sarcophagidae). Jpn J Sanit Zool 39:355–362. Sugiyam E, Shinonaga S, Kano R. 1988b. The tribe sarcophagini from New Guinea with the description of a new species (Diptera: Sarcophagidae). Jpn J Sanit Zool 39:283–292. Sukontason K, Methanitikorn R, Kurahashi H, Vogtsberger RC, Sukontason KL. 2008. External morphology of Chrysomya pinguis (Walker) (Diptera: Calliphoridae) revealed by scanning electron microscopy. Micron 39:190–197. Sukontason KL, Methanitikorn R, Boonsriwong W, Piangjai S, Kurahashi H, Vogtsberger RC, Sukontason K. 2006a. Ultrastructure of spiracles of Musca domestica and Hydrotaea chalcogaster (Diptera: Muscidae). Parasitol Res 100:19–23. Sukontason KL, Bunchu N, Methanitikorn R, Chaiwong T, Kuntalue B, Sukontason K. 2006b. Ultrastructure of adhesive device in fly in families calliphoridae, muscidae and sarcophagidae, and their implication as mechanical carriers of pathogens. Parasitol Res 98:477–481. Sukontason KL, Methanitikorn R, Kurahashi H, Piangjai S, Sukontason K. 2005. Surface ultrastructure of prestomal teeth of some flies in the families Calliphoridae, Muscidae and Sarcophagidae. Parasitol Res 96:410–412. Vander Starre H, Tempelaar MJ. 1976. Structural and functional aspects of sense organs on the maxillary palps of Calliphora vicina. J Insect Physiol 22:855–863. Wagner T, Neinhuis C, Barthlott W. 1996. Wettability and contaminability of insect wings as a function of their surface sculptures. Acta Zoologica 77:213–225. Wasserthal LT. 2001. Flight-motor-driven respiratory air flow in the hawkmoth Manduca sexta. J Exp Biol 204:2209–2220. Watson GS, Cribb BW, Watson JA. 2010. How micro/nanoarchitecture facilitates anti-wetting: An elegant hierarchical design on the termite wing. ACS Nano 4:129–136. Zacharuk RY. 1985. Antennal sensilla. In: Kerku GA, Gilbert LI, editors. Comparative Insect Physiology, Biochemistry and Pharmacology. Oxford: Pergamon Press. pp. 1–69. Zhang M, Chen YO, Thomas P, Zhang D. 2013. Review of the genus Agria (Diptera, Sarcophagidae) from China. ZooKeys 310:41–55.
Microscopy Research and Technique
