EFFECTS OF ENVIRONMENTAL STRESSORS ON BLOOD-GLUCOSE LEVELS IN SEA HARES, APLYSIA-DACTYLOMELA

Effects of natural stressors such as tidepool strandings, air exposure , and low salinity on blood-glucose levels were investigated in the se a hare Aplysia dactylomela from shallow areas of Discovery Bay, Jamaic a. All treatments produced large and significant elevations in blood-g lucose titre, 1.5- to 2.3-fold above baseline levels of 25 to 35 mug g lucose 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 pretreat ment conditions, and often involved an undershoot to levels below cont rol values. In two experiments involving tidepool strandings and assoc iated high body-temperatures, excessively low blood-glucose titres wer e followed by death of all test individuals. When sea hares were expos ed to 75 and 50% seawater (100% = 33 parts per thousand S) for 1 h, ma ximum elevation in blood-glucose concentrations occurred 1 to 2 h from onset of exposure, coincidental with maximum dilution of the body flu ids of test individuals. The responsiveness of blood-glucose titres to relatively small temperature or salinity changes, or to short-duratio n air exposures, suggests that monitoring this physiological parameter may be a useful and sensitive means of diagnosing a wide variety of s tressors in marine gastropods.