Gametogenesis in Paralonchurus brasiliensis (Pisces, Sciaenidae) from the Penha Region, Santa Catarina, Brazil N. A. Nalon, M. C. Sedrez, E. N. Fragoso-Moura, J. O. Branco, J. R. Verani

Abstract

Paralonchurus brasiliensis is a non-target species, frequent and abundant in the ichthyofauna associated with seven-beard shrimp ( Xiphopenaeus kroyeri ) fishing, however, studies on its reproduction are still scarce. The present work aimed to study the gametogenesis of P. brasiliensis caught in the seven-beard shrimp fishery on the coast of Penha/SC. The fish were collected in 30-minute trawls, in the 10, 20 and 30m isobaths, between the spring of 2013 and the winter of 2014. Total weight (g), total length (cm), sex, gonad weight (g) and macroscopic classification of gonadal maturation stages was carried out by characterizing the gonads in terms of color, vascularization, volume and size in relation to the coelomic cavity. The gonads were fixed in 10% neutral buffered formalin for 7 days, washed in water and stored in 70% alcohol. Standard histological processing was carried out to create permanent histological slides, including inclusion in histological paraffin, staining with Hematoxylin-Eosin and sections with a thickness of 5 to 7 micrometers. Of a total of 717 specimens captured, 391 were histologically analyzed, of which 169 were females, 95 were males and 127 were indeterminate. In the histological analysis of the gonads under light microscopy, the ovaries and testes showed germ cells at different stages of development. In the ovuligerous lamellae of the ovaries, oogenesis occurs and oocytes were seen in phases I, II, III, IV, V and VI, in addition to atretic oocytes, which will undergo involution and post-ovulatory follicles, the presence of which indicates spawning. Spermatogenesis develops in cysts in the walls of the lobules, where spermatocytes and spermatids are found, in addition to spermatozoa in the lumen of the lobules. According to the macro and microscopic analyzes of the gonads and the Gonadosomatic Index (IGS) values, five stages of gonadal maturation were defined: Immature, Maturing, Reproducing, Exhausted (males only) and Resting (females only). The frequency of gonadal maturation stages, in addition to the high seasonal average values ​​of IGS, defined the reproductive period as being in autumn and early winter. The histological investigation was fundamental in confirming and/or identifying the sex and maturation stages, as well as the reproductive study, contributing with new knowledge regarding the impact of trawling the seven-beard shrimp on P. brasiliensis .