Extended parental care in marine amphipods. I. Juvenile survival without parents

Abstract

Extended parental care is found among a variety of marine peracarid species including endobenthic and epibenthic amphipods. After hatching from the female's brood pouch, small juveniles enjoy parental care for time periods of several days up to several weeks. This study examined whether small juvenile amphipods can survive without parental care to determine if this reproductive strategy is obligate or facultative. Juveniles of the burrow-dwelling species Leptocheirus pinguis (Stimpson 1853) and Casco bigelowi (Blake 1929) survived well in predator-free trays, indicating that extended parental care in these species is a facultative reproductive strategy — juveniles can survive without their parents. Medium-sized juveniles of the epibenthic, suspension-feeding species Dyopedos monacanthus (Metzger 1875) survived relatively well in predator-free traps, but small juvenile D. monacanthus did not. This low survival rate of small D. monacanthus, even in predator-free trays, demonstrates that extended parental care is obligate for the survival of early juvenile stages in this epibenthic amphipod. When exposed to predators, juveniles of all three amphipod species were susceptible to predation, and reacted by emigration. Most juvenile L. pinguis and C. bigelowi emigrated or disappeared from sand shrimp Crangon septemspinosa treatments, but many remained in hermit crab Pagurus longicarpus treatments. Almost all juvenile D. monacanthus emigrated from both sand shrimp and hermit crab treatments, indicating that this epibenthic amphipod species is very susceptible to epibenthic predation. Survival of juvenile D. monacanthus was lower than that of L. pinguis and C. bigelowi both in predator-free and in predator trays. These results suggest that juveniles of this and other epibenthic peracarids depend on maternal care to a higher degree than juveniles of endobenthic burrow-dwelling species.