THE INFLUENCE OF BODY CONDITION ON 17-BETA ESTRADIOL LEVELS IN RELATION TO VITELLOGENESIS IN FEMALE VIPERA-ASPIS (REPTILIA, VIPERIDAE)

Seventy-six wild Vipera aspis females were caught over 3 years and pla ced in outdoor enclosures; 39 reproduced and 37 did not. Almost all th e reproductive females had a body condition index (BCI) greater than 0 .70 when vitellogenesis began. Monthly blood samples were taken by car diac puncture. The main plasma parameters of vitellogenesis were measu red by spectrophotometry: total plasma calcium, phosphorus, phospholip ids, cholesterol, triglycerides, proteins, and albumin. Plasma 17-beta estradiol levels were determined by RIA. Vitellogenesis started soon after hibernation in reproductive females with very high 17-beta estra diol concentrations (average of 4.00 ng/ml) and there was a marked mob ilization of maternal reserves (fat bodies, liver, and vertebral bone) associated with very high values of plasma calcium, phosphorus, phosp holipids, cholesterol, triglycerides, and proteins. The kinetics of th e main plasma components were described throughout the vitellogenesis period (from March to early June), when all plasma parameters differed markedly between reproductive and nonreproductive females. After ovul ation, the differences between the two groups of females disappeared e xcept in the case of albumin, which remained at a very low level in re productive females for 6 months. All nonreproductive females had low 1 7-beta estradiol plasma levels during vitellogenesis (average of 0.08 ng/ml) and there was no suggestion of mobilization of maternal reserve s. After vitellogenesis plasma concentrations of estradiol were low in reproductive (an average of 0.08 ng/ml) and in nonreproductive animal s (0.06 ng/ml). Five nonreproductive females kept in the laboratory we re estrogenized by 17-beta estradiol silastic implants. The 17-beta es tradiol concentrations were close to those measured in reproductive fe males during vitellogenesis. Maternal reserves were mobilized, with al most all metabolic parameters exhibiting the vitellogenic pattern. Whe n the silastic implants were removed, 17-beta estradiol concentrations dropped sharply to a basal level, but the other components were maint ained near the vitellogenic values for several months. In contrast to previous studies on viviparous snakes, these results suggest that in V . aspis 17-beta estradiol levels are linked strictly to vitellogenesis . (C) 1994 Academic Press, Inc.