PROGESTERONE ROLE IN THE REGULATION OF THE FEMALE REPRODUCTIVE CYCLE IN CAPTIVE ROYAL PYTHON (P. REGIUS): PRELIMINARY STUDY

Current studies support an important role for progesterone in the reproduction activity of reptiles [1]. Although detection of hormone levels in serum or plasma is the most direct method, blood sampling is quite invasive and therefore not easily repeatable on healthy animal for monitoring purposes, mostly in non-conventional and wild animals, particularly susceptible to stress. Noninvasive monitoring using feces has been successfully applied to many species and correlations between serum hormone levels and fecal metabolites have been demonstrated. So far very few studies regarding the monitoring of fecal steroid hormones metabolites in reptiles are reported in literature [2]. Royal python (P. regius) is one of the snake species most bred in captivity. However, studies regarding the evaluation of sex steroid hormones in the P. regius female reproductive cycle are not currently reported. The aim of the present study was to evaluate the variations of progesterone levels during the female reproductive cycle of captive bred Royal python, through faecal progesterone metabolites measurement. A total of 86 adult female were studied between January 2016 and January 2017. All animals were captive born, fed a diet of commercially raised rats and individually housed in rack at 28°C under a 12:12 h L/D cycle. Faecal samples were monthly collected and classified according to reproductive stages, identified by ultrasound scans of ovaries, follicles and eggs [3]. The samples were then processed by enzyme-linked immunosorbent assay using a species-independent kit (Progesterone Enzyme Immunoassay Kit K025-H5, Arbor Assays DetectX®, Ann Arbor, Michigan, USA) and mean fecal progesterone level (ng/g) for each phase of the reproductive cycle was calculated. Progesterone faecal metabolites reveal an increasing trend during the reproductive cycle. Metabolites concentrations corresponding to the reproductive quiescence (anovulatory phase) and the next stage in which restarts the ovarian activity (transition) are lower than those detected during the later stages of follicular and eggs development (folliculogenesis and embryogenesis) until deposition, with statistically significant difference (P<0.01). The high levels of progesterone highlighted during gestation, with a sharp decrease in correspondence to egg laying, recall the plasma progesterone trend evidenced during the reproductive cycle in some species of viviparous snakes [1]. From the results of this study, it can be supposed that progesterone plays a role in in the maintenance of pregnancy in captive Royal python. [1] Taylor EN, DeNardo DF, Jennings DH. 2004. Seasonal steroid hormone levels and their relation to reproduction in the Western Diamond-backed Rattlesnake, Crotalus atrox (Serpentes:Viperidae). Gen Comp Endocrinol, 136:328–337 [2] Kummrow MS, Gilman C, Mackie P, Smith DA, Mastromonaco GF. 2011. Noninvasive Analysis of Fecal Reproductive Hormone Metabolites in Female Veiled Chameleons (Chamaeleo calyptratus) by Enzyme Immunoassay. Zoo Biol, 30:95-115 [3] Bertocchi M, Di Ianni F, Bresciani C, Volta A, Bigliardi E, de Cesaris V, Ponzio P, Macchi E, Parmigiani E. Ultrasound monitoring of female reproductive cycle in captive Royal pythons (Python regius): preliminary observations. Short communication paper. Atti LXX Convegno SISVet-XIV Convegno SIRA 13-16 giugno 2016, p237. Palermo, Italy