Estudo morfofisiológico da estratégia reprodutiva em duas espécies de rhizoprionodon sp capturados na costa do Brasil

Abstract

Reproduction and morphophysiology of the elasmobranch reproductive organs became better understood in the last years of the past century. Still little is known about the reproduction morphology of several species. The objective of this study was to determine the reproductive strategy of Rhizoprionodon porosus and Rhizoprionodon lalandii species from the coast of Brazil. The captured specimen was morphometrically characterized, where Total Length (CT) and Pre-Caudal length (PC) were measured in cm along with their weights. The animals were sorted and viscerated, the testicles were obtained to determine their weight, length and width. For the histological analyses these organs were fixed in 10% formaldehyde for 48 hours, however, they were cleaved within the first 24 hours and then returned to the fixative solution. Subsequently, they were transferred to 70% ethanol and then submitted to the processing protocol for histological analysis. The macroscopic description classified the reproductive stage of each specimen according to the ICES 2013 reference. Of the 46 capture males, 15 was classified as immature, 5 in development, 6 capable of reproducing, 20 active and regressing males were not observed. This species has the diametric type testicles, the immature individual, was characterized by the presence of thin testicles with a width ranging from 0.3 to 1.6 cm and flexible clasper. Histologically, type I spermatogonia and spermatocytes were present. For the specimens labelled as “in development”, the testes were developed, although they did not fill the entire surface of the epigonal organ, the width ranged from 0.5 to 1.2cm. The clasper of these animals was partially calcified. The well-defined germinative zone was observed, with spermatozoa growing from one wall to the other, with spermatogonia, spermatocytes I and II and spermatids present. The males that were capable of breeding, had fully calcified claspers which in length had already passed the pelvic fin. The developed and well-irrigated testis had variations of 0.5 to 0.8 cm in width. Microscopically the testis at this stage had a good amount of seminiferous cysts along with the presence of spermatozoa whose head was facing the periphery and tails facing the lumen.