Impact of short-term salinity stress on larval development of the marine gastropod Crepipatella fecunda (Calyptraeidae)

Abstract

Shallow-water coastal environments suffer frequent reductions in salinity due to heavy rains. This creates stressful conditions for the organisms found there, particularly for the early stages of development, including pelagic larvae. Freshly hatched larvae of the gastropod Crepipatella fecunda were exposed to different levels of salinity stress (32 (control), 25, 20 and 15) for a single 6h period. Subsequently, all veligers were maintained at normal control salinity (32) through metamorphosis. Periodic measurements were made of mortality, larval growth, and larval behavior. In particular, we measured changes in velar surface area, swimming velocity, clearance rate, oxygen consumption rate, shell growth rate, larval mortality, time to metamorphosis, and size at metamorphosis. The short exposure to salinity stress decreased subsequent mean growth rates at normal salinity and mean size at metamorphosis, but increased the duration of the planktonic period and the extent of larval mortality. It also reduced the rate at which the velar surface area increased relative to shell growth, and reduced mean larval swimming velocity. Mean oxygen consumption rates and clearance rates were also significantly lower for larvae that had been stressed early in larval life, compared with values obtained for control individuals. Exposure to low salinity for even a short time early in larval life can clearly have a substantial impact on the rest of larval development.