J. Insect Physiol.. 1978, Vol. 24. pp. 97 to 99. Pergamon Press. Printed in Great Britain.

EFFECT OF HYDROCORTISONE ON THE GROWTH AND DEVELOPMENT OF LARVAE TENEBRZO MOLITOR GRZEG~RZ

ROWSKI, LEXAW PILC and LUDWIK OBUCHOWICZ

Department of Animal Physiology. Institute of Biology, Adam Mickiewicz University. Fredry 10, 61-701 Poznali, Poland (Receioed 24 June 1977)

Abstract-Hydrocortisone

administered

with the food causes inhibition of growth in larvae Tenehrio

molitor. Hydrocortisone together with the reduction in the rate of growth retards the moulting cycle in larvae T. molitor. The action of hydrocortisone does not influence greatly the number of larvae

moulting cycles.

75 + 5%. The animals were selected on the basis of weight and this made it possible to obtain an experiMORDUE (1967) showed that hydrocortisone causes mental population in the same stage of development. inhibition of the growth in insects. The influence of During the whole cycle of experiments, the larvae this hormone on some metabolic transformations in ‘were kept individually in tubes of 30 x 50 mm, insects (MORDUE,1967) confirms the generally known divided into two groups-the control one and expericharacter of its action in mammals (KAPLANand SHI- -mental one. Each of these groups contained at least MIZU, 1963; RYANand CARVER,1963) and birds (BEL- 12 larvae. Both groups got the same quantity of food LAMYand LEONARD,1965). Hydrocortisone, known that is of meal bran which was exchanged for the as a hormone of catabolic influence on protein transfresh one in weekly intervals. formations in vertebrates (BELLAMYand LEONARD, Hydrocortisone was administered to the group of 1965; KAPLANand SHIMIZU,1963; RYANand CARVER, experimental larvae with the food. Meal bran was 1963), also stimulates these processes in tissues of insaturated with a 50% ethanol solution of the hormone sects, causing the reduction in the synthesis of protein and dried at WC. The proportion of the hormone and increasing simultaneously the level of the free for 1 g of meal bran are given in the diagrams and amino acids, as well as bringing about the production Table 1. In the first experiments the group of control of larger amounts of uric acid (MORDUE,1967). larvae was fed with dried meal bran, which had been r It is a matter of common knowledge that the saturated with 500/, ethanol. Because, however, no ingrowth and development of the insect is controlled fluence of ethanol had been stated, the control aniby the neurosecretory system (SEHNAL,1971; GILBERT mals received food in the form of meal bran without and KING, 1973; GILBERT, 1974). Hormonal subsaturating it with ethanol. Both groups of larvae were stances, produced by the neurosecretory system, conweighed with a precision up to + 1 mg in equal time trol as well physiological processes connected with intervals. Each experiment was repeated not less than the growth (SEHNAL,1971; MILLER, 197% as metathree times. The hormone in the form of hydrocortibolic transformations (L’HELIAS,1970). sonum hemisuccinatum was of “Polfa” make-The aim of the paper was to investigate the inPoland. fluence of hydrocortisone on the growth and development, as well as on the moulting cycle of larvae Tenebrio m&or. RESULTS AND DISCUSSION INTRODUCTION

MATERIAL

Hydrocortisone administered to larvae of 7’. mohtor with food causes a decrease in weight. The greatest inhibition of growth was observed in young larvae of 3 mg at a constant dose of hydrocortisone

AND METHODS

The larvae Tenebrio molitor, were reared in optimum conditions of temperature 27 &-0.5”C and r.h.

Table 1. Mean duration of instars in larvae maintained on food with the addition of 0.2 mg of hydrocortisone

for

one gram meal bran

Culture Control With hydrocortisone

Number of larvae 60 120

1 g*1 11 +- 1

2 9+1 14 +_2

3

Following instars 4 5

I

a

Duration of instars in days +_S.D. 11 _+ 1 11 f 1 13 & 2 14 + 2

16 + 2

19 + 2

15 f 1

13 +_ 1

15 * 1

16 +_2 97

20 * 1

19 +_ 1

6

GRZEG~RZ ROSI~~SKI. LESLAW PILC AND LUDWIK OBUCHOWICZ

98

0

20

40

60 Days

of

80

I00

120

rearing

Fig. 1. Inhibition of the growth by hydrocortisone (OJmg/g of food) during the development of larvae of initial weight of 3 (A); 4.5 (B): 10 (C) and 25 (D) mg.

(0.2 mg/g) of meal bran (Fig. 1. curve A). The hormone administered to older larvae exerts considerably less influence during their grotih and development (Fig. 1, curves B, C, D). The results show that the influence of hydrocortisone depends on the age of the larvae in which the administration of the hormone was begun. In larvae of 3 mg, the inhibition of growth occurs during the period of about 60 days and reaches 68% in relation to the weight of control larvae. Then the inhibiting action of the hydrocortisone diminishes (Fig. I, curve A). As hydrocortisone was administered to the larvae getting older and older its inhibiting action not only diminished but was also shortened in time (Fig. I, curves B, C, D). This indicates that older larvae are less sensitive to the action of this hormone. SIEGRIST et al. (1966). while investigating the influence of hydrocortisone on the growth of chickens and BELLAMY (1964), while investigating the influence of this hormone on the growth of rats. obtained similar results.

Days

of

As the quantity of hydrocortisone was increased from 0.2 to 6.4 mg/g of food, we observed greater and greater changes in the process of growth in young larvae of 3 mg (Fig. 2). Larvae maintained on lower doses of hormone (0.2-1.6mg/g of food), show a greater rate of growth, in the further stages of development after strong inhibition which occurs during 60 to 70 days. A distinct retarding in the growth of larvae can be seen at the dose of 1.6 mg of hydrocortisone for a gram of food. The larvae reached the weight of 10mg in the control group after 30 days of rearing. Whereas. in the group reared with the addition of 1.6 mg of hydrocortisone/g of food. the larvae reached the weight of IO mg only after 80 days (Fig. 2). The further growth of this group was however considerably faster but distinctly retarded, as well in relation to the control group as to the groups of larvae reared on lower doses of hormone. The weight of larvae reared with the addition of 3.2 and 6.4mg of hydrocortisone for a gram of food. hardly changes during development. Larvae, reared with the largest quantity of hormone (6.4mg/g of food), live about 100 days without increasing their weight and then die. MORDUE (1967) stated in his investigations that inhibition of the growth of larvae T. molitor, caused by hydrocortisone. is not connected with whatever changes in feeding. Hydrocortisone, administered to the chickens in increasing quantities by way of injections or in the diet, causes a greater and greater decrease in the weight of their body (BURNET and WARNER, 1960; BELLAMY and LEONARD, 1965; SIEGRIST et al.. 1966). The analysis of the moulting cycle was carried out simultaneously with the observations of the growth of larvae T. molitor of 3 mg. The number of larval moulting cycles in the animals maintained on food with the addition of 0.2 mg of hormone for one gram of meal bran, was not subiected to any change. The larvae ecdysed on an average nine times in both groups.

rearing

Fig. 2. Curves of the growth of larvae of initial weight of 3 mg. reared on food without the hormone (M) and with the hormone in dose 0.2 (M ); 0.4 (A--A); 0.8 (A--A); 1.6 (O----o); 3.2 (m-m) and 6.4 ( x x ) mg/g of food.

Effect of hydrocortisone Whereas during the development of young larvae, changes in the duration of instars occurred, as well in the group of control animals, and those maintained ‘on food with the addition of hydrocortisone (Table 1). The shortest instars are in control larvae in the initial stages of their development. As the animals grow. the following larval ecdyses occur more and more rarely. The situation is inversed in larvae maintained on food with the addition of 0.2 mg of hydrocortisone for one gram of food. The hormone brings about a marked prolongation of the instars in the initial stages of development of young larvae, and only from the sixth ecdysis. do the instars begin to become shorter (Table 1). The prolongation of the instars in these animals is distinctly co-ordinated with a weak increase in the weight of the body which takes place in this period. The investigations of MORDUE (1967), carried out on insects as well as the results obtained from the experiments performed on vertebrates (KAPLAN and SHIMIZU, 1963; RYAN and CARVER, 1963; FALUDI et al., 1964: BELLAMY and LEONARD. 1965) show that hydrocortisone acts directly on the growth of young animals. At the same time, the observed changes in the moulting cycle of larvae suggest that this hormone can act on the neurosecretory system of insects. As well the inhibition of the growth by hydrocortisone. the changes in the moulting cycle of larvae of T. molitor connected with it, are probably the result of the complex influence of this hormone on the insect. REFERENCES BELLAMYD. (1964) Effect of cortisol on growth and food intake in rats. J. Endow. 31, 83-84.

on the growth of T. molitor

99

BELLAMYD. and LEONARDR. A. (1965) Effect of cortisol on the growth of chicks. Gen. camp. Endocr. 5. 402-410. BURNEYF. M. and WARNERN. L. (1960) Assay of corticosteroids in the chick embryo. Nature. Loud. 187, 938-939. FALUDIG.. MILLS L. C.. and CHAYESZ. W. (1964) Effecect of steroids on muscle. Acta endow. 45. 68-78. GILBERT L. 1. (1974) Endocrine action during insect growth. Recent frog. Harm. Res. 30. 347-390. GILBERTL. I. and KING D. S. (1973) Physiology of growth and development: Endocrine aspects. In the Physiology of Insecta (Ed. by ROCKSTEINM.) I. 25%368. Academic Press, New York. KAPLANS. A. and SH~MIZUC. S. N. (1963) Effects of cortisol on amino acids in skeletal muscle and plasma. Endocrinology 72, 267-272. L’HELIASC. (1970) Chemical aspects of growth and development in insects. In Chemical Zoology; Arthropodo. (Ed. by FL~RKINM. and SCHEERB. T.) part A. 343-393. Academic Press. New York. MILLER T. A. (1975) Neurosecretion visceral organs in insects. A. Reo.

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Acta