SULIKOWSKI, J.A.; TSANG, P.C. ; HOWELL, W.H. ; University of New Hampshire; University of New Hampshire; University of New Hampshire: Morphological, Histological and Steroidal Examination of the Reproductive Cycle in the Winter Skate, Leucoraja ocellata

Elasmobranch fish display a wide range of diverse and complex reproductive modes. These strategies include such attributes as internal fertilization, sperm storage, low fecundity and both morphological and physiological specializations for either oviparous or viviparous reproduction. Unfortunately, reproductive information has been collected for only a small number of inshore elasmobranchs and for sharks which have been the subject of commercial fisheries. Reproductive data for other elasmobranchs tends to be fragmented or incomplete. Populations of winter skate, Leucoraja ocellata, in the waters of the Gulf of Maine are of particular interest because they represent an elasmobranch reproductive mode (oviparity) that has gone largely unstudied on the organismal level. In order to evaluate the seasonal reproductive cycle of this species, we collected adult specimens over a continuous 30 month time period and evaluated reproductive parameters along with serum levels of steroid hormones. In females, increasing ovary and shell gland weight along with increasing follicle size, suggest a well defined annual cycle beginning in May and peaking in September. Preliminary studies of serum 17β-estradiol levels corroborate these findings. In males, histological analyses of spermatogenetic activity revealed spermatogenesis present in all months. To correlate specific stages of spermatogenesis with steroid production and associate relative steroid levels with specific phases of the winter skate�s reproductive cycle, serum levels of 17β-estradiol, progesterone and testosterone are currently being analyzed in males while the latter two are currently being analyzed in females.