Effects of environmental stressors on blood-glucose levels in sea hares, Aplysia dactylomela

Abstract

Effects of natural stressors such as tidepool strandings, air exposure, and low salinity on blood-glucose levels were investigated in the sea hare Aplysia dactylomela from shallow areas of Discovery Bay, Jamaica. All treatments produced large and significant elevations in blood-glucose titre, 1.5-to 2.3-fold above baseline levels of 25 to 35 μg glucose ml-1. Response times were variable, with significant elevations being manifested within 30 to 120 min from initiation of the stressor. Recovery was swift, within an hour or two of restoration to pretreatment conditions, and often involved an undershoot to levels below control values. In two experiments involving tidepool strandings and associated high body-temperatures, excessively low blood-glucose titres were followed by death of all test individuals. When sea hares were exposed to 75 and 50% seawater (100%=33‰S) for 1 h, maximum elevation in blood-glucose concentrations occurred 1 to 2 h from onset of exposure, coincidental with maximum dilution of the body fluids of test individuals. The responsiveness of blood-glucose titres to relatively small temperature or salinity changes, or to short-duration air exposures, suggests that monitoring this physiological parameter may be a useful and sensitive means of diagnosing a wide variety of stressors in marine gastropods.