Experimental evidence suggesting temperature-driven dormancy in the planktotrophic larvae of the sea cucumber Isostichopus fuscus

ABSTRACT While larval ecology is central to the population dynamics of marine benthic species with multiphasic life histories, the adaptations of larvae to environmental variability remain incompletely understood in many species. Using the holothuroid echinoderm (sea cucumber) Isostichopus fuscus, we examined how a planktotrophic species can use pre-competency plasticity to withstand suboptimal conditions of temperature over extended periods. Five cohorts of propagules (embryos/larvae) were exposed to temperature treatments (28–29, 24–25 and 20–22°C) in standardized culture settings. Under the coldest temperatures (typical of offshore upwelling areas), development mirrored that obtained under warmer temperatures until the early auricularia stage, where development was arrested for ~5 months in a manner consistent with quiescence. When temperature was increased again, larvae quickly resumed development and settled; no lasting negative impact was noted. The findings suggest that the larvae can use a form of dormancy to withstand suboptimal oceanic conditions for indefinite periods of time until successful delivery to appropriate inshore locations, the habitat were I. fuscus is exclusively found.