Ecological and evolutionary significance of resting eggs in marine copepods: past, present, and future studies

Abstract

The occurrence of a resting egg phase in the life cycle of marine and freshwater planktonic copepods is well documented and receiving increasing attention by investigators. The species generally occur in coastal marine waters, freshwater ponds and lakes in areas that undergo strong seasonal fluctuations, though examples have been reported for tropical and sub-tropical areas not subject to such extreme fluctuations. Typically 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 resting eggs, the factors that affect their survival and hatching from sediments, the existence of egg banks in sediments, and the impact of resting eggs on plankton community structure. Benthic resting eggs of copepods include diapause eggs as well as subitaneous (non-diapause) eggs that are quiescent due to conditions in the sediments. As with other groups of organisms the resting egg phase is viewed as being critical for the perpetuation of species year after year, especially those that disappear from the water column for portions of the year. Some data indicate that eggs can survive for many years in sediments which would expand their influence to evolutionary time scales. This paper summarizes our understanding of embryonic dormancy in marine copepods.