Steroid Profiles of Wild Terror Green (Andinoacara rivulatus) Associated with Gonadal Histology in the Baba River, Ecuador

Abstract

Native cichlids in Ecuador are represented by Andionoacara rivulatus and Cichlasoma festae mainly. These aquatic species are a fundamental part of the food chain of rural communities in the western subtropical region of Ecuador. For the first time, a detailed study on the gonadal development in A. rivulatus males and females was carried out, and the characterization of sex hormones present in their blood plasma from May 2019 to January 2020. Fish samples were captured in the multipurpose Baba River dam upstream of the Guayas River, Ecuador. Gonad and blood samples were collected for histological analysis and assaying of steroidal hormones such as 17β-estradiol and 11-ketotestosterone. The sex steroids were quantified by enzyme immunoassay (ELISA). As a result, the fish samples have asynchronous characteristics and show all development stages in testes and ovaries. The serological fluctuations show statistical differences (p <0.05) between the development stages, with low concentrations of estradiol and 11-KT. These results are somewhat related to the hydrological period of capture, where the temperature, luminosity, and rainfall play a fundamental role in the oogenesis and spermatogenesis in the captured fishes. The highest concentration of E2 is detected in female vitellogenesis stages and the highest concentration of 11-KT in the male spermatogenesis stage. These results confirm the fundamental role of these hormones in the key periods of gonadal development. In future studies, it is important to monitor the maturational hormone 17α, 20β-DHP, and the vitellogenin concentrations and thus understand the reproductive physiology of A. rivulatus.