Alterations in serum steroid concentrations in the clearnose skate, Raja eglanteria: Correlations with season and reproductive status

Serum steroid hormones in the peripheral circulation of the clearnose skate , Raja eglanteria, were measured at the time of capture and at various time s throughout the year while the animals were maintained as a captive breedi ng population. These analyses demonstrate interesting correlations between changes in hormone concentrations and annual reproductive events. Animals w ere sampled once (78 females, 20 males) or multiple times (15 females). For both groups of females, 17 beta-estradiol was detected throughout the year with significant elevations occurring during October and November when ova rian follicles begin to mature (as determined through necropsy examinations ), and January and February when maximum mating activity is observed and eg g laying begins. Testosterone and dihydrotestosterone concentrations were s ignificantly elevated in females only during January and February. Testoste rone elevations were synchronous with longer-term elevations in 17 beta-est radiol in females sampled either once or repetitively. Testosterone concent rations in males were significantly elevated during times of maximum breedi ng activity compared to periods of sexual inactivity. Data from females sam pled during five stages of the egg laying process, as defined by the positi on of palpable egg capsules within the reproductive tract, revealed that 17 beta-estradiol was highest when egg capsules were forming in the nidamenta l gland (stage 2) or uterus (stage 3); testosterone and dihydrotestosterone were maximal when eggs were in the uterus (stage 3) or cloaca (stage 4); a nd progesterone was significantly elevated immediately after oviposition (s tage 5), suggesting a possible role for progesterone in the regulation of s equential laying of egg pairs. (C) 1999 Wiley-Liss, Inc.