Ciclo reprodutivo da esponja Amphimedon viridis (Demospongiae, Haplosclerida) em uma região entre-marés do Atlântico tropical

Abstract

This study analyzed the reproductive cycle of Amphimedon viridis in an intertidal region of the tropical Atlantic between April 2023 and August 2024. We also investigated how the environmental factors could explain the reproductive dynamics of the species. Reproduction was continuous, with asynchronous development of reproductive elements. The species exhibited low reproductive effort, with only a small percentage of the population involved in reproduction throughout the study. It was observed that A. viridis is viviparous, and over the 17 months of research, only one larva (parenchymella) was recorded. During the analyzed period, oocytes were identified in 14 months, spermatic cysts in 5 months, and embryos in 10 months. Although oocytes were more frequent, their density was lower (0.01 ± 0.01 oocytes.mm⁻²) compared to spermatic cysts (0.51 ± 1.14 spermatic cysts.mm⁻²). No significant difference was found among the months of the study for the size of oocytes and spermatic cysts; however, embryos were larger during the dry season months. Among the environmental factors analyzed, air temperature (current month and one-month lag), low tide (current month), chlorophyll-a, and precipitation (current month and with one to two-month lags) significantly influenced the reproduction of A. viridis, mainly affecting oocyte density. The average individual size of the population was 195.64 ± 230.60 cm², showing significant variations among months but no difference of size between reproductive and nonreproductive individuals. Additionally, both air temperature and seawater temperature negatively impacted the surface area of the species, especially during periods with lower tides when individuals were larger. These results indicate that climatic and oceanographic factors play a fundamental role in the reproductive cycle of A. viridis, influencing both reproductive effort and morphological development.