Journal of Herpetology · 1982 · 57 citations · 11 references
Life SciencesAnimal SciencesPhysiologyHerpetologyParturitionReproductive PhysiologyEndocrine Regulation Of DevelopmentNeuroendocrine RegulationOvarian FunctionOviduct FunctionOviposition BehaviorSpecies Differences In ParturitionIn Vivo StudiesIntraperitoneal AdministrationNeuroendocrine Regulation Of EcdysisOviductal MotilityOviductal SecretionParturition In CarnivoresStress Physiology During MoltingSurgical Removal Experiments
-A single, intraperitoneal injection of 0.02 ig arginine vasotocin (AVT) caused oviposition and associated behaviors in the lizards Sceloporus aeneus aeneus, Hemidactylus frenatus, and Lepidodactylus lugubris. In addition, AVT induced parturition in Sceloporus aeneus bicanthalis, a viviparous lizard. These results, along with previous reports that oviposition or parturition are correlated with regression or surgical removal of corpora lutea, suggest that luteal regression induces AVT secretion. Neither 0.02 ig nor 2.0 ig AVT stimulated oviposition in Anolis carolinensis, whether the were kept in a dry or moist substrate. Since previous work showed that the oviducts of these contract in response to AVT in vitro, it is hypothesized that there is a stress-induced neural inhibition of AVT-induced oviduct contraction in vivo. The neurohypophysis of lizards secretes two octapeptide hormones, arginine vasotocin (AVT) and mesotocin (Sawyer, 1977). Although AVT has been shown to induce rhythmic oviductal (uterine) contractions in vitro in several lizard species (LaPointe, 1969, 1977; Guillette and Jones, 1980), an in vivo effect of AVT on oviductal contractions has been reported in only one species, the viviparous lizard Sceloporus jarrovi (Guillette, 1979). To date, there are no studies concerning the effects of AVT on gravid, oviparous lizards. We report here that administration of a single injection of a low dosage of AVT induces oviposition in gravid lizards: Hemidactylus frenatus, Lepidodactylus lugubris, and Sceloporus aeneus aeneus, as well as parturition in the viviparous lizard Sceloporus aeneus bicanthalis. We also discuss the curious finding that AVT failed to induce oviposition in the oviparous lizard, Anolis carolinensis. MATERIALS AND METHODS Sceloporus aeneus.-Female S. aeneus of both subspecies (S. a. aeneus and S. a. Present address: Department of Biological Sciences, Wichita State University, Wichita, Kansas 67208, USA. bicanthalis) were collected from two locations in Mexico. Gravid S. a. bicanthalis were obtained from the Parque Nacional de Zoquiapan, Mexico, Mexico, whereas gravid S. a. aeneus were obt ined near El Capulin, Volcan Ajusco, Distrito Federal, Mexico. Specimens were obtained during May 1979. Both collecting sites were at 3200 meters. It should be noted that S. aeneus is reproductively bimodal; that is, the taxon S. a. aeneus is oviparous, whereas the subspecies S. a. bicanthalis is viviparous (Guillette, 1981a). Ten gravid, female S. a. aeneus and six pregnant S. a. bicanthalis were randomly partitioned into equal treatment groups. The control subjects (N = 5 S. a. aeneus and 3 S. a. bicanthalis) received a single intraperitoneal injection (0.05 ml) of 0.75% physiological saline, whereas the experimental (N = 5 S. a. aeneus and 3 S. a. bicanthalis) received 0.02 fig AVT/0.05 ml saline. Arginine vasotocin was obtained from Sigma Chemical Company (Lot #28C-0359). Subsequent to injection, all were placed in a soil-filled, 95-liter glass aquarium. The ambient temperature within the test aquarium during the experiment existed in a gradient from 25?C to 35?C. Water was available ad libitum during This content downloaded from 157.55.39.231 on Wed, 05 Oct 2016 04:22:55 UTC All use subject to http://about.jstor.org/terms INDUCED OVIPOSITION IN LIZARDS the test period. Several dependent measures of parturition or oviposition were obtained, including (1) initial contraction latency, measured as the duration from injection to first total body contraction, (2) birth latency, or the time lapse between injection and first birth (oviposition), and (3) interbirth duration, representing the period of time between individual births (ovipositions). Maximal experimental duration was 360 minutes subsequent to injection. Thus, females that did not deliver young or eggs were assessed birth latency scores of 360 minutes. Student's t-tests, for non-paired samples were used to determine significance between the control and experimental groups. In addition, a two-way ANOVA was performed on the data obtained from the two subspecies of S. aeneus to determine any differences in response to AVT between these two closely related organisms. Hemidactylus frenatus.-Gravid house geckoes were collected from the island of Oahu, Hawaii on 20-28 December 1980. The were transported to Boulder, Colorado, housed in an aquarium in a greenhouse, and exposed to a 12L:12D photoperiod with a temperature of 33-25?C during the photophase and 18-25?C during the scotophase. Lizards were fed mealworms and provided water ad libitum. On 6 January 1981, six gravid females were given a single intraperitoneal injection of 0.02 tg AVT in 0.05 ml saline. Five additional gravid females received an injection of 0.05 ml saline alone. It should be noted that this test began after the onset of the scotophase, due to the fact that these are nocturnal (it is not known if oviposition occurs at night). The geckoes then were observed for six hours. Data collected were similar to those obtained for S. aeneus and were analyzed in a similar fashion. Lepidodactylus lugubris.-Collection, housing and testing of the parthenogenetic mourning gecko were as for H. frenatus. Anolis carolinensis.-This is an oviparous lizard that alternates ovulation of one egg from each ovary approximately every 14 days (Hamlett, 1952). An egg remains in one of the two oviducts for 18 or 19 days, after which it is oviposited. T ere is, as a result, a 4 or 5 day period when an old, shelled egg is in one oviduct (the egg that soon will be laid) while a new, unshelled egg is in the contralateral oviduct. We tested the effect of AVT in female Anolis with either one or two eggs in the oviducts. In the first experiment with Anolis (Exp. 1), reproductively active females purchased from a supplier were used (arrived on 23 May 1980). Animals were exposed to an environment of 14L(32?C):10D(20?C) and high humidity, and were fed mealworms and watered ad libitum, before the experiment. Animals were partitioned into six experimental groups (N = 10 for each group) on 27 May 1980. These were: (1) females with one oviductal egg that received a single, intraperitoneal injection of 2.0 Ag AVT in 0.05 ml saline; (2) one-egg females, 0.02 ,g AVT; (3) oneegg females, 0.05 ml saline alone; (4) fem les with two eggs in the oviducts that received 2.0 jig AVT in 0.05 ml salin ; (5) females, 0.02 ,g AVT; and (6) females, 0.05 ml saline alone. Intraperitoneal injections were made during the second hour of the photophase (mean body temperature of experimental subjects was approximately 32?C). After injections, were housed in a clear plastic box at 32?C and observed for 24 hours. In the second experiment with Anolis (Exp. 2), gravid females (received on 14 August 1980) were housed as in the first experiment. Only two-egg animals were used in this experiment. These females were given a single, intraperitoneal injection of either 2.0 ,g AVT in 0.05 ml saline (N = 10) or 0.05 ml saline alone (N = 10). In addition, half of each treatment group (N = 5) were kept in dry, plastic cages at 32?C after injection, whereas the other half (N = 5) were 141 This content downloaded from 157.55.39.231 on Wed, 05 Oct 2016 04:22:55 UTC All use subject to http://about.jstor.org/terms L. J. GUILLETTE, JR. AND R. E. JONES TABLE 1. Events related to oviposition or parturition in salineor AVT-treated female lizards.'
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Notes on Breeding and Reproduction in the Lizard Anolis carolinensis
G. W. D. Hamlett · Copeia · 1952 · 86 citations
Life Sciences, Biology, Zoology +12