A comparative gametogenesis and biochemical differentiation of goatfish (Family: Mullidae) from the Red Sea

Abstract

Comparative study between few species of goatfishes (Mullidae), locally called Sultan Ibrahim, has been investigated from Jeddah coast. The present study compares gonad structure, oogenesis and spermatogenesis in three species of goatfish. The various stages are similar in the different species, but differ in time of spawning. The reproductive biology of three goatfishes, Mulloidichthys flavolineatus (1 black blotch), Mulloidichthys flavolineatus (3 black blotches), Mulloidichthys vanicolensis, were examined. A macroscopic and histological examination of the gonads demonstrated that all the three species are typically gonochoristic. Species-specific reproductive parameters including male stages, changes in gonado-somatic index (GSI), classification of oocyte stages were analyzed for each of the three targeted species. All three species have asynchronous ovary. The spawning season for the three studied species differ from one species to another i.e., the spawning season for M. vanicolensis females and males from April to July; M. flavolineatus, (1 black blotches) for both sexes from May until December; for M. flavolineatus (3 black blotches) showed a peak in May to early October for both sexes. Ultrastructurally the mature spermatozoon’s head shape appears like a computermouse, the tiny mid-piece consist two mitochondria and a flagellum. The chromatin, within the nucleus is electron-dense and homogenous in M. flavolineatus (with one black blotch), while the chromatin is granular in (M. vanicolensis and M. flavolineatus (3 black blotches)). The posterior region of the nucleus is deeply penetrated by the nuclear fossa which contains, the basal part of flagellum and centriolar complex. The ultrastructure of the eggs of the three Mullidae species is circular in shape and contains a simple, circular micropyle. The ovarian follicular epithelium of the three Mullidae species consists of two layers, an outer theca layer and an inner granulosa layer with zona radiata under them. Zona radiata consists of 2 layer-interna and externa. Zona radiata interna is thicker than zona radiata externa. Differences in protein patterns of muscles and gonads were observed in the present study.