Effects of water temperature on glochidium viability of Unio crassus and Sinanodonta woodiana: Implications for conservation, management and captive breeding

The global decline of freshwater bivalves (Unionida) has prompted many programmes for their conservation and augmentation, which often include a captive breeding component. One key point to such programmes is the collection, maintenance and use of mussel glochidium larvae, which require attachment to a fish host in a sensitive parasitic stage of their life cycle. Understanding the thermal limits of glochidia can increase knowledge of mussel larval survival and ultimately aid in the development of conservation programmes. Glochidia of the endangered thick-shelled river mussel Unio crassus and the non-native Chinese pond mussel Sinanodonta woodiana were observed for active clamping ability at 5, 15, 17, 20 and 25 °C over the course of a 7-d period. The results from this study confirm that an inverse relationship between water temperature and larval viability can be observed in both species. Additionally, the significantly higher thermal tolerance of S. woodiana indicates that the species exhibits competitive invasive behaviour beginning from the larval stage. These findings also suggest that the collection and transportation of glochidia from genetically important yet distant populations is feasible if the larvae can be maintained at temperatures between 5 and 15 °C.