Gonadal structure of the Grouper, Cephalopholis taeniops and of the Blackspot picarel, Spicara melanurus
Author: Marcia Perazzo Valadares Costa (Currículo Lattes)
Supervisor: Dr João Carlos Brahm Cousin
Abstract
Cape Verde is an archipelago located in the Atlantic Ocean close to the African continent, whose main natural resources are marine. Fishing is the main responsible for food support (animal protein), and the quantity of fish caught have declined in recent years. Mariculture is a promising alternative to Cape Verde, and may be designed to target species for export or local consumption. Two fishes were chosen to begin preliminary studies of the biological basis: the grouper Cephalopholis taeniops and the blackspot picarel Spicara melanurus. The objective of this study was evaluating the reproductive biology of these two species, focusing on reproductive seasonality, gonadal development and sex change. Gonadal samples were fixed in buffered formalin and Bouin's solution, dehydrated in ascending gradient of ethanol (70%, 80%, 95% and 100%), cleared in xylene, stained with hematoxylin and eosin, and sectioned into a thickness of 3 to 7 μm. Cephalopholis taeniops presents multiple spawning during April to October. These fish are diandric protogynous hermaphrodites with primary and secondary male. Ovotestes were detected in individuals between 280 to 450 mm. The length of the smallest mature female and male were 220 and 210 mm, respectively. No histological difference between primary and secondary males was observed, both with ovarian cavity, lamellar structure and sperm ducts located within the ovary wall. S. melanurus presents multiple spawns practically throughout the year. These fish are protogynous hermaphrodites. Smaller and larger individuals are mostly males. Males present compact testes, organized into lobules containing spermatogenic cysts. The smallest mature female was 183 mm fork length. Hermaphrodites (250 mm) can be identified both macroscopically and microscopically. Ovotestes contain testicular and ovarian tissues, with abundant oocyte atresia, suggesting ovarian regression.
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