Reproductive traits on the intertidal mussel <i>Mytilus platensis</i> in the South western Atlantic Ocean

Reproductive aspects were studied in the blue mussel Mytilus platensis d'Orbigny, 1846 in response to environmental variables. We hypothesize correlation between the reproductive parameters and the annual cycle of temperature and photoperiod. Mussels were collected at Villa Gesell (37°15′S: 56°57′W), Buenos Aires Province, Argentina, from January to December 2019 and March 2021. We measured each specimen and analyzed the gonadal tissue by histological procedure evaluating the gonadal development stages for females and males, as well as the area and number of vitellogenic oocytes for females. Females presented a main spawning event during austral winter (August–October) and a residual spawning in summer (February), while males presented several spawning events in austral fall, winter, and spring. Oocyte number quantification also concluded that the main spawning event happened in October. Environmental factors contributed to the reproductive cycle; the ripe stage was associated with a decrease in temperature and photoperiod reached minimum values, while the main spawning point was associated with an increase in both factors. The developing stage was represented in both sexes all along the year, while the post-spawning stage was most evident in the austral summer, with the increase in temperature. Reproductive effort in the intertidal zones involves numerous processes triggered by environmental factors (temperature and food availability) and energy compartmentalization.