Reproductive aspects and energy allocation compromise to aerial exposure in the intertidal mussel Brachidontes rodriguezii. A case study at two tidal levels

Abstract

Histological and energetic parameters were evaluated seasonally between bivalves from two tidal levels. Results suggest different reproductive patterns between individuals from two contrasting intertidal zones, having also different spawning timing. Females of the lower level spawned in Spring and Autumn while females of the upper level did in Summer with a lower number of oocytes, possibly due to differential food availability between the two intertidal zones. The lipids content in the oocytes did not vary between seasons but varied in the digestive gland, being higher in Autumn – Winter, and suggesting that the digestive gland is a lipid reservoir. The energy density of females was similar throughout the seasons and levels, while in males it varied seasonally. Additionally, energy condition index is proposed as a proxy of stressful conditions, as air exposure time (therefore, to the food availability), mussels from the lower level reached a greater energy condition index than those from the upper level.