Meeting Abstract
Coastal fresh-water habitats may experience rapid change in salinity. For the aquatic salamander, Amphiuma tridactylum, fluctuations in the concentration of environmental solutes offer challenges of osmotic stress, as they have limited options for avoidance and escape from their obligate habitat. A portion of the range for A. tridactylum is periodically subject to increased salinity due to salt-water intrusion (ca. 17 ppt salinity during storm surges) and drought (6.5 ppt salinity during natural drawdowns of water). Thus, it is probable that populations of A. tridactylum are euryhaline in their tolerance to salinity, particularly those populations within coastal and estuarine regions of its distribution. We investigated the threshold salinity that elicits behavioral avoidance by A. tridactylum and found that salamanders do not actively avoid increasing water salinity until concentrations reach 10 ppt. Such a level of environmental salinity is considerably more hyperosmotic than the normal blood plasma osmolality (250 mOsmol/kg) of A. tridactylum. Here we compare the typical physiological responses of amphibians to increased environmental salinity and outline the responses observed in A. tridactylum. We also introduce some preliminary findings on this species physiological and behavioral responses to evaporative water loss and dehydration.
