ECOLOGICAL AND EVOLUTIONARY SIGNIFICANCE OF RESTING EGGS IN MARINE COPEPODS - PAST, PRESENT, AND FUTURE STUDIES

The occurrence of a resting egg phase in the life cycle of marine and freshwater planktonic copepods is well documented and receiving increa sing attention by investigators. The species generally occur in coasta l marine waters, freshwater ponds and lakes in areas that undergo stro ng seasonal fluctuations, though examples have been reported for tropi cal and sub-tropical areas not subject to such extreme fluctuations. T ypically such species disappear from the water column for portions of the year, but remain in the region as benthic resting eggs. Studies to date have focused on the conditions that promote the occurrence of re sting eggs, the factors that affect their survival and hatching from s ediments, the existence of egg banks in sediments, and the impact of r esting eggs on plankton community structure. Benthic resting eggs of c opepods include diapause eggs as well as subitaneous (non-diapause) eg gs that are quiescent due to conditions in the sediments. As with othe r groups of organisms the resting egg phase is viewed as being critica l for the perpetuation of species year after year, especially those th at disappear from the water column for portions of the year. Some data indicate that eggs can survive for many years in sediments which woul d expand their influence to evolutionary time scales. This paper summa rizes our understanding of embryonic dormancy in marine copepods.