Thermal tolerance traits of the undulated surf clam Paphia undulata based on heart rate and physiological energetics

Abstract

Thermal tolerance traits are important factors that affect the ability of an aquaculture species to survive, grow, and reproduce in new habitats. Paphia undulata, a species of saltwater clam, has been farmed in China for over thirty years. Despite this, the ecophysiology of P. undulata and its effects on the aquaculture of this species are poorly understood. To investigate the thermal tolerance of P. undulata, the semi-lethal temperature, cardiac activity, and scope for growth (SFG) of the organisms were measured under different thermal stresses in a laboratory-simulated muddy habitat condition. Our results showed that the cardiac activity, feeding behaviors, and respiration rates of P. undulata were positively correlated with temperature changes from 10 °C to 32 °C. The upper incipient lethal temperature (192-h UILT50) and Arrhenius break temperature (ABT) of this species were 33.49 ± 0.02 °C and 35.64 ± 0.77 °C, respectively. SFG trend had negative values at temperatures between 10 °C and 16 °C and positive values at temperatures between 18 °C to 32 °C. These data suggest that the suitable thermal window that provided the energy required for the efficient growth and reproduction of P. undulata in the Dongshan Bay was approximately nine months out of the year. Taken together, these results indicate that P. undulata is proficient at adapting to thermal stress in the subtidal zone. Moreover, our results may also provide information that assists in both the management of wild populations of P. undulata and the improvement of P. undulata aquaculture.