Gonadal architecture and fecundity in two populations of Fissurellidea megatrema (Vetigastropoda: Fissurellidae)

Abstract

Habitat selection is pivotal regarding reproduction and development in marine species. We describe the gonadal morphology in Fissurellidea megatrema d’Orbigny, 1839 in two populations from the southwestern Atlantic Ocean and tested whether these populations presented differences in reproductive parameters. Specimens were collected in two sampling sites: Mar del Tuyú (MDT) (36° 35'S; 54° 54'W) and Bahía San Blas (BSB) (40° 32'S; 61° 40'W). Components and morphology of the ovary and testes were characterized through histological techniques and reproductive parameters were defined in females. We determine that the trabeculae are made up of connective tissue (female and male gonads) while the jelly coats present glycosaminoglycans and proteoglycans, in the ovary. Both structures stain positively for neutral glycosaminoglycans. The analysis of fecundity showed significant differences in the comparison between localities (Tukey test, p < 0.001) and an increased fecundity for the population with lower temperature (MDT). The area of vitellogenic oocytes in MDT was bigger than BSB. Our results suggested that temperature can be associated with a control in oocyte size following the Rass's rule which describes a trend of increase in oocyte size in environments with lower temperature, and could be regarded as a habitat dependent pattern. We conclude that temperature could be influencing reproductive parameters in these populations and consider future studies related to energy storage to complement the analysis.