BRODIE, R J; University of South Carolina: Life on the wedge: survival of low salinity conditions in larvae of the fiddler crab Uca minax

Newly hatched larvae of the fiddler crab, Uca minax, ride nocturnal ebb currents away from low salinity adult habitats towards high salinity coastal marine environments where they complete development. We investigated the low salinity tolerance of zoeae in the laboratory to determine how this physiological trait impacts larval survival en-route to the sea. To do this, we compared the survivorship of fifty larvae reared at 27 �C and 5 � to fifty control larvae from the same brood reared at 25 �. We found an average L:D 50 of 13�1 SD days (range= 12-14.5 days; N=5 broods) at 5�, with all larvae dead after an average of 16�1 SD days (range= 14-17 days). Survival of controls throughout the experimental period ranged between 90-96%. At 5�, larvae did not progress past the second or third zoeal stage, while larvae reared at 25 � (the controls) progressed normally to the postlarval stage. Preliminary work using the same experimental protocol on larvae reared at 0� shows that larvae are able to survive 2-3 days in freshwater. These salinity tolerance data combined with measurements of current velocities in tidal creeks and rivers and our understanding of larval swimming behaviors will be used to construct a model to predict the time needed to travel to the sea and the probability of surviving this journey from any release point along the inland population range of U. minax.