Gonadal development in hybrids of Mediterranean sparids: Sparus aurata (female) x Pagrus pagrus (male).

摘要

This study was conducted to determine whether hybrids produced by protandrous gilthead sea bream (Sparus aurata, Sa) [Pagrus aurata] and protogynous Mediterranean red porgy (P. pagrus, Pp) display sterile gonadal development. Hybrids were produced by artificial fertilization of Sa eggs with Pp milt. 133 hybrids (22 months old) were sampled monthly for 1 year. Histological analysis of the gonads, calculation of the gonadosomatic index (GSI) and determination of phenotypic sex and sexual maturity were conducted. It was shown that most of the hybrids (113, 86.9%) had undifferentiated or partly differentiated gonads. However, 17 (13%) of the hybrids had fully differentiated gonads similar to the ovotestes of the parental species. Most of the ovotestes fish were females (12) and only a few were males (5). Only oogonia and previtellogenic oocytes were present in female ovotestes, while all spermatogenic stages were found in 4 male ovotestes. Mean GSI did not significantly change during the sampling period. Further research is required to determine the reproductive traits of these hybrids and to determine their ability to produce functional gametes and viable embryos..