Fecal adrenal hormone patterns during ovulatory and non-ovulatory reproductive cycles in female veiled chameleons (Chamaeleo calyptratus).

The relationship between the reproductive (hypothalamic-pituitary-gonadal; HPG) and adrenal (hypothalamic-pituitary-adrenal; HPA) hormone axes is complex and can vary depending on the species and environmental factors affecting an individual. In an effort to understand this relationship in female veiled chameleons (Chamaeleo calyptratus), the patterns of fecal metabolites of corticosterone (C), estradiol (E), testosterone (T), and progesterone (P) were analyzed by enzyme immunoassay (EIA) during ovulatory (OC; eggs laid) and non-ovulatory cycles (NOC; no eggs laid). Glucocorticoid (GC) metabolites in the fecal extracts were characterized by HPLC and corticosterone EIA performance was assessed by parallelism, accuracy and precision tests. The results indicated that the assay chosen reliably measured the hormone metabolites present in the fecal extracts. Regular, cyclical hormone metabolite patterns consisting of an E peak followed by peaks of T, P and C in close succession were observed during both ovulatory and non-ovulatory cycles; relative levels of P and C, however, were higher during ovulatory cycles. Corticosterone metabolite levels, in particular, increased throughout vitellogenesis and peaked in late vitellogenesis (in non-ovulatory cycles) or around the time of ovulation, and remained elevated throughout the gravid period, falling just prior to oviposition. The results provide evidence of variation in glucocorticoid production throughout different stages of the reproductive cycle, including a role in the ovulatory process; the physiology, however, remains unclear.

Assessment of the reproductive status of female veiled chameleons (Chamaeleo calyptratus) using hormonal, behavioural and physical traits.

Egg binding is a common reproductive disorder in captive female reptiles leading to premature loss of breeding potential, or in severe cases death. It can result from failure to ovulate (and reabsorb) follicles; follicular stasis, or failure to lay eggs; dystocia. Reproductive status of female veiled chameleons (Chamaeleo calyptratus) in a research colony was assessed using enzyme immunoassay (EIA) of fecal reproductive hormones (estradiol; E2, progesterone; P, and testosterone; T) and their metabolites, ultrasound imaging of the reproductive tract, and receptivity to conspecific males. Periods of follicular growth (vitellogenesis) corresponded with increasing levels of E2, and following ovulation, a distinct change in morphology from round (follicles) to oval (eggs) structures, which was accompanied by a surge in P (>20-fold above baseline). P levels remained elevated throughout the gravid phase until just prior to oviposition. Length/width ratios of follicles and eggs were statistically different, but distinguishing a follicle from an egg based on the ratio was unreliable due to a large overlap in values. In animals that failed to ovulate on their first cycle, follicles began to recede but were not fully reabsorbed and could be distinguished from a second batch of follicles based on their echogenicity. Female receptivity to conspecific males was not related to cycle stage (i.e., previtellogenesis, vitellogenesis, or gravid) or reproductive hormone levels. This study demonstrates the use of ultrasonography and reproductive hormone analysis to assess phase of the reproductive cycle (pre- or post-ovulatory), or confirm ongoing follicular stasis.