The Biological Bulletin, Vol 178, Issue 1 25-32, Copyright © 1990 by Marine Biological Laboratory

ECOLOGY AND EVOLUTION

Correlation of Abnormal Radular Secretion with Tissue Degrowth During Stress Periods in Helisoma trivolvis (Pulmonata, Basommatophora)

D. A. Smith and W. D. Russell-Hunter
Wabash College, Department of Biology, Crawfordsville, Indiana 47933

Laboratory experiments on starvation stress in Helisoma trivolvis elucidate a relationship between modifications of radular secretion and tissue degrowth resulting from stress. Tissue losses in starved adults ranged from 4.5% at 40 days to 27.7% at 160 days, with negligible mortality (<2%). Modifications in radular secretion that paralleled tissue loss involved not only abnormal secretion of individual teeth and of tooth rows, but especially an increased "packing" of radular rows per unit ribbon length. Radular length remained constant during experimental trials, however the mean number of tooth rows increased by almost 47% after 120 days of food deprivation. Radular patterns reflecting degrowth observed in these experiments were paralleled in radulae taken from overwintered animals sampled from natural populations. Rates of radular turnover averaged between 2.3% new growth per day (43 days to turnover) and 4.0% new growth per day (25 days to turnover). Radular samples could provide for post hoc detection of recent periods of tissue degrowth in snails, just as evidence of longer periods of tissue degrowth can be detected in the shells of long-lived bivalves.