Enhanced larval settlement of the hard clam Mercenaria mercenaria by the gem clam Gemma gemma
Marine Ecology Progress Series
The presence of dense assemblages of Gemrna gernma enhanced settlement of Mercenaria mercenaria larvae in laboratory experiments. There was a tendency toward increased settlement of hard clam larvae with increasing density of gem clams. Microscopic examination showed that increased settlement did not result from trapping or entanglement in sticky secretions from gem clams. Enhancedsettlement in the presence of gem clams was persistent in both gently aerated and recirculated waters, and in both
... aters, and in both sand and muddy sand, suggesting that M. rnercenaria larvae could recognize settlement cues associated with G. gemma in various habitats and hydrodynamic conditions. Preferential settlement in sediment previously exposed to gem clams indicates that gem clams alter sediment in some way to make it attractive for larval settlement. In addition, increased settlement in the presence of empty gem clam shells in sediment suggests that settlement cues are properties of the shell, although the nearly significant settlement with gravel particles suggests that physical cues, such as grain size and bottom roughness, may play a role. Thus, this study demonstrates dense assemblages of small suspension feeders can enhance larval settlement of another bivalve species.