Enigmatic Story of Embryonic Diapause behind the Scaly Armor: Non-Invasive Assessment of Reproductive Cycle in Free Ranging Chinese Pangolin (Manispentadactyla) using Fecal Steroid Metabolites
Pangolins are the sole representative of order Pholidota. These myrmecophagous mammals are attributed by fossorial, solitary and nocturnal behaviour which engenders several challenges to unveil intricacies of its biology. Currently, several captive records have shown a significant variation in the gestation period of the Chinese pangolin(Manispentadactyla) ranging from 100-150 days to 90-240 days and 318-372 days. This study is a foremost attempt to generate endocrinological profile of wild Formosan pangolin (M. p. pentadactyla) to address this issue. The profile generated was from 40 fecal samples procured from 14 radio-tracked females from the Coastal Mountain Range of Taitung, southeastern Taiwan from 2010 to 2016. Fecal reproductive metabolites were measured using EIA for estradiol-17β and Pregnanediol-3-Glucuronide (PDG). Sample size for each month ranged from 1 to 6. The study augmented that there is a significant decrease in the levels of PDG with significant elevation in the levels of estradiol-17β around December, which corresponds to its birth season advocated by observations of peak births during the same time period. At the same time, increases in levels of estradiol-17β, indicated that fertilization may occur shortly after giving birth. Furthermore, the levels of both estradiol-17β and PDG were found lower during the months of February to April suggesting that Formosan Pangolin might exhibit phenomena of embryonic diapause (delayed implantation). Whilst, subsequent elevation in the levels of estradiol-17β and PDG was witnessed from the month of May suggested the implantation of blastocyst might commence during this time of the year. Similar hormonal profiles are discernible in wallabies. Moreover, lactation was observed between December and May and weaning was observed in May in one wild Formosan pangolin. Further investigations on the same subject to recognize the major fecal steroid metabolites can increase the accuracy in predicting pregnancy by using several consecutive samples because of variability of fecal metabolites concentration in different individual.Lastly, measuring metabolites can help to detect estrus phase since reliable assessment of the estrus can aid in breeding management and will unlock new doors of fragmented knowledge about its reproductive biology.
Keywords - Endocrinological Profile, Delayed Implantation, Estradiol-17β, PDG, Lactation, Non-Invasive Method.