Non-invasive endocrine monitoring: a unique method for studying the reproductive physiology of the critically endangered chinchilla (Chinchilla lanigera)

PONZIO M.F. RUIZ R R.D. CATALDI NNII AND FIOL DE CUNEO MM

Cincinati

Congreso; First Annual Conference of the International Society of Wildlife Endocrinologists.; 2010

The chinchilla, a South American hystricomorph rodent, possesses one of the most valuable pelts in the world. Intensive hunting for fur placed the species at the brink of extinction and today it is considered critically endangered by the IUCN and is included in Appendix I of CITES. Although native chinchilla are extremely rare, a hybrid produced by cross-breeding the two chinchilla taxa has been domesticated and selected for superior fur production for more than 80 years.  Therefore, knowledge gathered using the domestic stock as a model likely can be applied to its endangered counterparts. Despite its biological and economic importance, little scientific information is available about this species’ basic reproductive physiology, a key aspect for the implementation of assisted reproductive techniques and captive breeding programs.  Physiological measures of reproduction have typically relied upon the evaluation of steroid hormones in serum or plasma. However, attempts to obtain repeated blood samples from chinchilla were unsuccessful because of small vein size and their stress-susceptible nature. Non-invasive techniques provided a unique opportunity, allowing long-term endocrine monitoring while avoiding the stress-evoking stimuli of restraint and repeated venipuncture. With this in mind, the objectives of our studies were to demonstrate the validity and accuracy of urinary steroid metabolites quantifications for studying different aspects of the chinchilla reproductive biology. Hormones assessed in 24 h longitudinal urine samples included creatinine (colorimetric assay kit, Wiener Lab, Argentina), progesterone and estradiol metabolites (I125 RIA kits, Coat-A-Count, Siemens), LH and FSH (NIDDK-anti rat LH-RIA-S118rabbit AFPC697071P; NIDDK-anti rat FSH-RIA-11 AFP-C0972881, National Hormone & Peptide Program, Harbor-UCLA Medical Center, CA, USA). We were able to establish, among others, the endocrine profile of female pregnancy (111 d gestation length) and post-partum estrus (48 hs after pups birth), sexual maturity and responses to exogenous activation of the hypothalamic-hypophysis-gonadal axis (hormonal peak 4 d after eCG injection, vaginal opening at day 7). An improved understanding of these aspects will undoubtedly help animal managers to develop more effective captive breeding programs for both domestic and wild chinchillas.