GENERAL
AND
COMPARATIVE
Stimulation
ENDOCRINOLOGY
38, 457-460 (1979)
of Parturition in a Viviparous Lizard (Sceloporus jarrowi) by Arginine Vasotocin LOUISJ. GUILLETTE,
Laborneory
of Comparative Reproduction. Biology, University
Department of Colorado.
JR.
of Environmental, Boulder, Colorado
Population 80309
and Organismic
Accepted April 26, 1979 Pregnant, adult female Sceloporus jurrovi were randomly partitioned into three groups. The control subjects received a single intraperitoneal injection (0.1 ml) of 0.75% physiological saline (N = 4), whereas the experimental animals received 0.02 pg AVT/O. 1 ml saline (N = 5) or 2.0 pg AV’lYO.1 ml saline (N = 5). Several dependent measures of parturition were obtained, including (1) initial contraction latency, measured as the duration from injection to first effective contraction, (2) parturition latency, or the time lapse between injection and first birth, and (3) interbirth duration, representing the period of time between individual births. Neither oviductal contractions nor parturition were observed in saline-treated females, whereas both concentrations of AVT induced parturition in all experimental subjects. No significant differences were indicated between the two AVT groups for initial contraction latency and parturition latency. Mean duration between individual births for the 2.0 and 0.02 Fg AVT groups did not differ and were found to be similar to those reported for natural births.
Parturition or oviposition can be induced in gravid female lizards by injecting neurohypophysial factors (see LaPointe, 1377). Clausen (1940) induced parturition in viviparous colubrid snakes with small amounts of snake posterior lobe extract. Bxytocin was used by Panigel (1956) to induce parturition in a viviparous lizard Lacerta (=Zootoca) vivipava, by LaPointe (1964) to initiate oviposition in the lizard Sceloporus occidentalis, and by Ewert and Legler (1978) to induce oviposition in 36 turtle species. Munsick er al. (1960) and LaPointe (1969), using the turtle Chrysemyspicru and the viviparous lizard Xantusiu (=Klauberim) riversiana, respectively, have shown that the neurohypophysial hormones oxytocin and arginine vasotocin (AVT) cause oviductal contractions in an in vitro bioassay. It was also observed that the oviductal tissue in their respective assay systems was IO-fold more sensitive to AVT than to oxytocin. LaPointe (1977) reported that isolated oviducts of the viviparous lizard SWioporus jarrovi respond to small doses of
AVT and that maximal sensitivity occurs near the preferred body temperature (34”) of this species. Acher et al. (1972) isolated only AVT and mesotocin from the posterior pituitary gland of Zg~ana iguana. Considering the above findings demonstrating the sensitivity of reptilian oviducts to AVT and the fact that AVT, not oxytotin, has been isolated in lizards, the present experiment was undertaken to determine the effects of AVT on parturition, birth rate, and related behavioral events in the viviparous lizard S. jarrovi. To date, there are no reports of AVT induction of parturition in a viviparous reptile. MATERIALS
AND METHODS
Female S. jarrovi were collected in the Graham Mountains of Arizona and transported to the University of Colorado, Boulder, where they were kept for 6 to 8 weeks in a large communal cage until the last 2 weeks of pregnancy. The degne of pregnancy was estimated from the female’s swollen appearance, which is indicative of the stage of pRgnancy (Ciuillette, unpublished observations). Animals were mainmined prior to the experiment on a photoperiod consisting of a 12-hr photophase and 12-hr scotophase. Animals were fed crickets and mealworms. Water was
LOUIS J. GUILLETTE,
458
available ad /i&rum. The cage was supplied with heat and ultraviolet lamps, which produced a temperature gradient from 2.5 to 45”. Fourteen mature females were selected for this study based on an anticipated parturition date of 1-2 weeks. Snout-vent lengths were 69.4 + 2.09 mm (i ? SE). These subjects were randomly partitioned into three groups. The control subjects (Group I) received a single intraperitoneal injection of 0.1 ml of 0.75% physiological saline, whereas the experimental animals received 0.02 pg AVT/O. 1 ml saline (Group II) or 2.0 pg AVT/O.l ml saline (Group III). Arginine vasotocin was obtained from the laboratory of V. Hruby, University of Arizona, Tucson, (Batch No. SPIII-15 (57-65)) and was assayed on rat uterus by J. LaPointe, New Mexico State University, Las Cruces, at 104 unitsimg against Sandoz synthetic oxytocin, Batch 64004, nominal potency = 507 III/ml. Subsequent to injections, all animals were placed in a single 75-liter glass aquarium, the floor of which was covered with San-i-tel. Ambient temperature existed in a gradient from 26 to 45” within the test aquarium at any given time. Water was available ad libitum during the test period. Several dependent measures of parturition were obtained, including (1) initial contraction latency, measured as the time duration from injection to first effective contraction, (2) parturition latency, or the time lapse between injection and first birth, and (3) interbirth duration, representing the period of time between individual births. Maximal experimental duration was 360 min subsequent to injections. Hence, females that did not deliver pups received parturition latency scores of 360 min. The body weights and condition of neonates, as well as some behavioral responses of the mothers and pups, were also observed.
RESULTS
Data obtained in this study are presented in Table 1. Neither oviductal contractions nor parturition were observed in salinetreated females, whereas both concentrations of AVT induced parturition in all experimental subjects. Specifically, a oneway ANOVA (Keppel, 1973) indicated that initial contraction latency and parturition latency were not randomly distributed (F = 1120.61, a” = 11, P < 0.001 and F = 441.99, df = 11, P < 0.001, respectively). Duncan’s multiple range tests (Keppel, 1973) indicated no significant differences between the two AVT groups for the above parameters, but did denote a significant difference between the saline-treated group and the AVT-treatment groups. All saline-
JR.
VASOTOCIN
AND
PARTURITION
treated females gave birth naturally 2- 10 days following completion of the experiment. Injection of AVT also induced behavioral effects similar to those described by LaPointe (1964) for S. occident&s. All AVTtreated females closed their eyes, lowered the rostra1 portion of their bodies, and performed an open mouth pant only a few minutes subsequent to AVT injections and before the onset of the initial rhythmic contraction. Young were born both slightly premature (presence of yolk in the yolk sac) or fully developed, depending on the state of pregnancy of the individual mother. Complete litters were born by all AVT-treated females. Live young had a mean weight of 0.87 + 0.08 g, slightly higher than reported by Carpenter (1960) for a natural birth. An average of 5.6 + 1.66 young were born per female (range = I- 12). Mean duration between individual births for the two AVT groups were found to be 11 min, 35 set ? 2 min, 5 set (N = 24) and 15 min, 30 set ? 3 min, 6 set (N = 22). A Student’s independent t test indicated no significant difference between the two AVT-treated groups for duration between birth times.
IN
LIZARD
459
hances the amplitude of AVT-induced oviduct contractions in vitro in the turtle C. pi&a, whereas progesterone has no effect on contraction amplitude but does reduce the duration of the contractions and the rest period between contractions (Callard and Hirsch, 1976). Lemus et al. (1970) also observed that oviducts from gravid females (Liolaemus gravenhorti and L. tenuis) respond to oxytocin with greater amplitude and also show greater spontaneous contractility than do those from non-gravid females identically treated. It was also observed that oviducts obtained during late gestation exhibited the greatest oxytocin sensitivity. However, LaPointe (1969) found that steriods did not influence in vitro AVT-induced oviductal contractions in the viviparous lizard X. riversiana. In the present experiment, females were in the last 2 weeks of pregnancy. All gave birth when induced with AVT, indicating that the oviducts are sensitive to AVT during this period. Whether ovarian steriods influence AVT-induced parturition in S. jarrovi is not presently known. Lastly, Carpenter (1960) reported a mean interbirth duration of 9 min for natural births. The similarity of this value with those reported in this study indicates that DISCUSSION there was no difference between the natural This is the first report of AVT being used and AVT-induced birth rates. It also apto induce birth in a viviparous lizard. These pears that the differing dosages of AVT had findings are consistent with results of pre- no effect on the interbirth deviation. These vious in vitro experiments on S. jarrovi data suggest the hypothesis that the ovi(LaPointe, 1977) and other reptilian species duct possesses an intrinsic frequency of (X. riversiana: LaPointe, 1969; C. picta: contractility, the strength of which may be Munsick et al., 1960; Callard and Hirsch, influenced by the hormonal conditions pres1976), and suggest that AVT may play an ent at this stage of pregnancy. Testing of active role in reptilian oviposition or par- this hypothesis will require studies of (1) turition. Arginine vasotocin and mesotothe birth frequency and contraction tin, but not oxytocin, have been isolated in strength and duration using a threshold I. iguana by Acher er al. (1972), but it is AVT dosage and (2) the influence of steroid not presently known if S. jarrovi secretes hormones on AVT-induced oviductal conAVT. traction in S. jarrovi. Heller (1972) has suggested that the sensitivity of the reptilian oviduct to neuroACKNOWLEDGMENTS hypophysial hormones is dependent on the I am indebted to Steve Wylie for collecting the anphysiological state of tissue. Estradiol en- imals and to Dr. J. L. LaPointe for supplying the AVT
LOUIS
460
J. GUILLETTE,
used in this experiment. Thanks are due to Gary Flater, Kevin Fitzgerald, Dr. Hobart M. Smith, and Dr. David 0. Norris for their help during this study and critique of this manuscript. Special thanks are due to David Duvall and Dr. Richard E. Jones for help with experimental design and statistics concerning this project.
REFERENCES Acher, R., Chauvet, J., and Chauvet, M. T. (1972). Reptilian neurohypophyseal hormones: The active peptides of a saurian, Iguana @ana. GUI. Camp. Endocrinol. 19, 345-348. Callard, I. P., and Hirsch, M. (1976). The influence of oestradial-17P and progesterone on the contractility of the oviduct of the turtle, Chrysemys picta, in vifro. J. Endocrinol. 68, 147- 152. Carpenter, C. C. (1960). Parturition and behavior at birth of Yarrow’s spiny lizard (Sceloporus jarrovi). Herpetologica 16, 137- 138. Clausen, H. J. (1940). Studies on the effect of ovariotomy and hypophysectomy on gestation in snakes. Endocrinology 27, 700-704. Ewert, M. A., and Legler, J. M. (1978). Hormonal induction of oviposition in turtles. Herpefologica 34(3), 314-318. Heller, H. (1972). The effect of neurohypophyseal hormones on the female reproductive tract of low-
JR.
er vertebrates. Gen. Camp. Endocrinol. Suppl. 3,703-714. Keppel, G. (1973). “Design and Analysis: A Researcher’s Handbook.“ Prentice-Hall, Inc., Englewood Cliffs, N.J. LaPointe, J. L. (1964). Induction of oviposition in lizards with the hormone oxytocin. Copeia. 451452. LaPointe, J. L. (1969). Effect of ovarian steroids and neurohypophyseal hormones on the oviduct of the viviparous lizard, Klauberina riversiana. J. Endocrinol.
43,
197-205.
LaPointe, J. L. (1977). Comparative physiology of neurohypophysial hormone action on the vertebrate oviduct-uterus. Amer. Zool. 17, 763-773. Lemus, D., Zurich, L., Paz de la Vega-Lemus, Y., and Wacyk, J. (1970). Actividad espontanea y effect0 de oxitocina en el utero aislado de Lio/armus gravenhorti y Liolaemus tenuis T. Arch. Biol. Med. Exp. 7, 11-13. Munsick, R. A., Sawyer, W. H., and Van Dyke, H. B. (1960). Avian neurohypophysial hormones: Pharmacological properties and tentative identification. Endocrinology 66, 860-871. Panigel, M. (1956). Contribution a l’itude de la ovoviviparite ches les reptiles: gestation et parturition chez le lezard vivipare, Zootoca vivipara. Ann.
Sot.
Nat.
(Zoo/.)
Paris
18, 569-668.
AND
COMPARATIVE
Stimulation
ENDOCRINOLOGY
38, 457-460 (1979)
of Parturition in a Viviparous Lizard (Sceloporus jarrowi) by Arginine Vasotocin LOUISJ. GUILLETTE,
Laborneory
of Comparative Reproduction. Biology, University
Department of Colorado.
JR.
of Environmental, Boulder, Colorado
Population 80309
and Organismic
Accepted April 26, 1979 Pregnant, adult female Sceloporus jurrovi were randomly partitioned into three groups. The control subjects received a single intraperitoneal injection (0.1 ml) of 0.75% physiological saline (N = 4), whereas the experimental animals received 0.02 pg AVT/O. 1 ml saline (N = 5) or 2.0 pg AV’lYO.1 ml saline (N = 5). Several dependent measures of parturition were obtained, including (1) initial contraction latency, measured as the duration from injection to first effective contraction, (2) parturition latency, or the time lapse between injection and first birth, and (3) interbirth duration, representing the period of time between individual births. Neither oviductal contractions nor parturition were observed in saline-treated females, whereas both concentrations of AVT induced parturition in all experimental subjects. No significant differences were indicated between the two AVT groups for initial contraction latency and parturition latency. Mean duration between individual births for the 2.0 and 0.02 Fg AVT groups did not differ and were found to be similar to those reported for natural births.
Parturition or oviposition can be induced in gravid female lizards by injecting neurohypophysial factors (see LaPointe, 1377). Clausen (1940) induced parturition in viviparous colubrid snakes with small amounts of snake posterior lobe extract. Bxytocin was used by Panigel (1956) to induce parturition in a viviparous lizard Lacerta (=Zootoca) vivipava, by LaPointe (1964) to initiate oviposition in the lizard Sceloporus occidentalis, and by Ewert and Legler (1978) to induce oviposition in 36 turtle species. Munsick er al. (1960) and LaPointe (1969), using the turtle Chrysemyspicru and the viviparous lizard Xantusiu (=Klauberim) riversiana, respectively, have shown that the neurohypophysial hormones oxytocin and arginine vasotocin (AVT) cause oviductal contractions in an in vitro bioassay. It was also observed that the oviductal tissue in their respective assay systems was IO-fold more sensitive to AVT than to oxytocin. LaPointe (1977) reported that isolated oviducts of the viviparous lizard SWioporus jarrovi respond to small doses of
AVT and that maximal sensitivity occurs near the preferred body temperature (34”) of this species. Acher et al. (1972) isolated only AVT and mesotocin from the posterior pituitary gland of Zg~ana iguana. Considering the above findings demonstrating the sensitivity of reptilian oviducts to AVT and the fact that AVT, not oxytotin, has been isolated in lizards, the present experiment was undertaken to determine the effects of AVT on parturition, birth rate, and related behavioral events in the viviparous lizard S. jarrovi. To date, there are no reports of AVT induction of parturition in a viviparous reptile. MATERIALS
AND METHODS
Female S. jarrovi were collected in the Graham Mountains of Arizona and transported to the University of Colorado, Boulder, where they were kept for 6 to 8 weeks in a large communal cage until the last 2 weeks of pregnancy. The degne of pregnancy was estimated from the female’s swollen appearance, which is indicative of the stage of pRgnancy (Ciuillette, unpublished observations). Animals were mainmined prior to the experiment on a photoperiod consisting of a 12-hr photophase and 12-hr scotophase. Animals were fed crickets and mealworms. Water was
LOUIS J. GUILLETTE,
458
available ad /i&rum. The cage was supplied with heat and ultraviolet lamps, which produced a temperature gradient from 2.5 to 45”. Fourteen mature females were selected for this study based on an anticipated parturition date of 1-2 weeks. Snout-vent lengths were 69.4 + 2.09 mm (i ? SE). These subjects were randomly partitioned into three groups. The control subjects (Group I) received a single intraperitoneal injection of 0.1 ml of 0.75% physiological saline, whereas the experimental animals received 0.02 pg AVT/O. 1 ml saline (Group II) or 2.0 pg AVT/O.l ml saline (Group III). Arginine vasotocin was obtained from the laboratory of V. Hruby, University of Arizona, Tucson, (Batch No. SPIII-15 (57-65)) and was assayed on rat uterus by J. LaPointe, New Mexico State University, Las Cruces, at 104 unitsimg against Sandoz synthetic oxytocin, Batch 64004, nominal potency = 507 III/ml. Subsequent to injections, all animals were placed in a single 75-liter glass aquarium, the floor of which was covered with San-i-tel. Ambient temperature existed in a gradient from 26 to 45” within the test aquarium at any given time. Water was available ad libitum during the test period. Several dependent measures of parturition were obtained, including (1) initial contraction latency, measured as the time duration from injection to first effective contraction, (2) parturition latency, or the time lapse between injection and first birth, and (3) interbirth duration, representing the period of time between individual births. Maximal experimental duration was 360 min subsequent to injections. Hence, females that did not deliver pups received parturition latency scores of 360 min. The body weights and condition of neonates, as well as some behavioral responses of the mothers and pups, were also observed.
RESULTS
Data obtained in this study are presented in Table 1. Neither oviductal contractions nor parturition were observed in salinetreated females, whereas both concentrations of AVT induced parturition in all experimental subjects. Specifically, a oneway ANOVA (Keppel, 1973) indicated that initial contraction latency and parturition latency were not randomly distributed (F = 1120.61, a” = 11, P < 0.001 and F = 441.99, df = 11, P < 0.001, respectively). Duncan’s multiple range tests (Keppel, 1973) indicated no significant differences between the two AVT groups for the above parameters, but did denote a significant difference between the saline-treated group and the AVT-treatment groups. All saline-
JR.
VASOTOCIN
AND
PARTURITION
treated females gave birth naturally 2- 10 days following completion of the experiment. Injection of AVT also induced behavioral effects similar to those described by LaPointe (1964) for S. occident&s. All AVTtreated females closed their eyes, lowered the rostra1 portion of their bodies, and performed an open mouth pant only a few minutes subsequent to AVT injections and before the onset of the initial rhythmic contraction. Young were born both slightly premature (presence of yolk in the yolk sac) or fully developed, depending on the state of pregnancy of the individual mother. Complete litters were born by all AVT-treated females. Live young had a mean weight of 0.87 + 0.08 g, slightly higher than reported by Carpenter (1960) for a natural birth. An average of 5.6 + 1.66 young were born per female (range = I- 12). Mean duration between individual births for the two AVT groups were found to be 11 min, 35 set ? 2 min, 5 set (N = 24) and 15 min, 30 set ? 3 min, 6 set (N = 22). A Student’s independent t test indicated no significant difference between the two AVT-treated groups for duration between birth times.
IN
LIZARD
459
hances the amplitude of AVT-induced oviduct contractions in vitro in the turtle C. pi&a, whereas progesterone has no effect on contraction amplitude but does reduce the duration of the contractions and the rest period between contractions (Callard and Hirsch, 1976). Lemus et al. (1970) also observed that oviducts from gravid females (Liolaemus gravenhorti and L. tenuis) respond to oxytocin with greater amplitude and also show greater spontaneous contractility than do those from non-gravid females identically treated. It was also observed that oviducts obtained during late gestation exhibited the greatest oxytocin sensitivity. However, LaPointe (1969) found that steriods did not influence in vitro AVT-induced oviductal contractions in the viviparous lizard X. riversiana. In the present experiment, females were in the last 2 weeks of pregnancy. All gave birth when induced with AVT, indicating that the oviducts are sensitive to AVT during this period. Whether ovarian steriods influence AVT-induced parturition in S. jarrovi is not presently known. Lastly, Carpenter (1960) reported a mean interbirth duration of 9 min for natural births. The similarity of this value with those reported in this study indicates that DISCUSSION there was no difference between the natural This is the first report of AVT being used and AVT-induced birth rates. It also apto induce birth in a viviparous lizard. These pears that the differing dosages of AVT had findings are consistent with results of pre- no effect on the interbirth deviation. These vious in vitro experiments on S. jarrovi data suggest the hypothesis that the ovi(LaPointe, 1977) and other reptilian species duct possesses an intrinsic frequency of (X. riversiana: LaPointe, 1969; C. picta: contractility, the strength of which may be Munsick et al., 1960; Callard and Hirsch, influenced by the hormonal conditions pres1976), and suggest that AVT may play an ent at this stage of pregnancy. Testing of active role in reptilian oviposition or par- this hypothesis will require studies of (1) turition. Arginine vasotocin and mesotothe birth frequency and contraction tin, but not oxytocin, have been isolated in strength and duration using a threshold I. iguana by Acher er al. (1972), but it is AVT dosage and (2) the influence of steroid not presently known if S. jarrovi secretes hormones on AVT-induced oviductal conAVT. traction in S. jarrovi. Heller (1972) has suggested that the sensitivity of the reptilian oviduct to neuroACKNOWLEDGMENTS hypophysial hormones is dependent on the I am indebted to Steve Wylie for collecting the anphysiological state of tissue. Estradiol en- imals and to Dr. J. L. LaPointe for supplying the AVT
LOUIS
460
J. GUILLETTE,
used in this experiment. Thanks are due to Gary Flater, Kevin Fitzgerald, Dr. Hobart M. Smith, and Dr. David 0. Norris for their help during this study and critique of this manuscript. Special thanks are due to David Duvall and Dr. Richard E. Jones for help with experimental design and statistics concerning this project.
REFERENCES Acher, R., Chauvet, J., and Chauvet, M. T. (1972). Reptilian neurohypophyseal hormones: The active peptides of a saurian, Iguana @ana. GUI. Camp. Endocrinol. 19, 345-348. Callard, I. P., and Hirsch, M. (1976). The influence of oestradial-17P and progesterone on the contractility of the oviduct of the turtle, Chrysemys picta, in vifro. J. Endocrinol. 68, 147- 152. Carpenter, C. C. (1960). Parturition and behavior at birth of Yarrow’s spiny lizard (Sceloporus jarrovi). Herpetologica 16, 137- 138. Clausen, H. J. (1940). Studies on the effect of ovariotomy and hypophysectomy on gestation in snakes. Endocrinology 27, 700-704. Ewert, M. A., and Legler, J. M. (1978). Hormonal induction of oviposition in turtles. Herpefologica 34(3), 314-318. Heller, H. (1972). The effect of neurohypophyseal hormones on the female reproductive tract of low-
JR.
er vertebrates. Gen. Camp. Endocrinol. Suppl. 3,703-714. Keppel, G. (1973). “Design and Analysis: A Researcher’s Handbook.“ Prentice-Hall, Inc., Englewood Cliffs, N.J. LaPointe, J. L. (1964). Induction of oviposition in lizards with the hormone oxytocin. Copeia. 451452. LaPointe, J. L. (1969). Effect of ovarian steroids and neurohypophyseal hormones on the oviduct of the viviparous lizard, Klauberina riversiana. J. Endocrinol.
43,
197-205.
LaPointe, J. L. (1977). Comparative physiology of neurohypophysial hormone action on the vertebrate oviduct-uterus. Amer. Zool. 17, 763-773. Lemus, D., Zurich, L., Paz de la Vega-Lemus, Y., and Wacyk, J. (1970). Actividad espontanea y effect0 de oxitocina en el utero aislado de Lio/armus gravenhorti y Liolaemus tenuis T. Arch. Biol. Med. Exp. 7, 11-13. Munsick, R. A., Sawyer, W. H., and Van Dyke, H. B. (1960). Avian neurohypophysial hormones: Pharmacological properties and tentative identification. Endocrinology 66, 860-871. Panigel, M. (1956). Contribution a l’itude de la ovoviviparite ches les reptiles: gestation et parturition chez le lezard vivipare, Zootoca vivipara. Ann.
Sot.
Nat.
(Zoo/.)
Paris
18, 569-668.
