Abstract

Squat lobsters frequently inhabit low-oxygen waters, facing particular physiological challenges. Pleuroncodes monodon inhabits one of the most extreme oxygen minimum zones in the world's oceans at low temperatures, but avoids high temperature hypoxic waters. The present study aimed to determine whether the maternally dependent reproductive outcome is compromised under realistic oxygen/temperature conditions (normoxia and 0.7 mg l(-1) at 11 and 15 degrees C) and to evaluate some potential metabolic bases. Females incubated for a significantly longer time at low as compared to high temperatures, but reproductive success was only compromised under hypoxic conditions. Brood viability and synchrony were affected by temperature and its interaction with oxygen concentration (especially under hypoxic conditions and 15 degrees C). Non-viable larvae were hatched at hypoxia-15 degrees C, and larvae hatched in hypoxia-11 degrees C did not survive until moulting. Under normoxic conditions, ventilation of the brood mass decreased with advancing embryo development, but remained high or increased under hypoxic conditions, especially at high temperatures. After releasing their broods, females from all treatments had developing oocytes in their ovaries, but the proportion of oocytes in secondary vitellogenesis was larger at 15 degrees C. The diameter of oocytes in secondary vitellogenesis was significantly smaller in hypoxia treatments. Oxygen consumption of ovigerous P. monodon was generally higher at 15 degrees C, especially at normoxia, and their critical point was significantly larger at 15 degrees C. Under hypoxic conditions, ovigerous females compensated their energetic requirements using anaerobic pathways (increase of pyruvate kinase:citrate synthase ratio and lactate). This suggests that this and other species living in hypoxic waters might suffer severe challenges in a warming ocean.