Influence of water temperature on the larval development of Neoverruca sp. and Ashinkailepas seepiophila—Implications for larval dispersal and settlement in the vent and seep environments

Deep-sea hydrothermal vents and cold seeps are scattered and limited habitats, and species that are confined to these benthic habitats often have a planktonic larval stage in their life history to maintain dispersal and gene flow among discrete populations. We have reared the larvae of Ashinkailepas seepiophila, inhabiting inactive vents and active cold seeps, through their entire larval development under atmospheric pressure. Using two temperatures (4 °C, 10 °C) we examined whether larval development resembles other vent species in being affected by thermal stimulation. Under laboratory conditions, A. seepiophila completed larval development in 65 days at 4 °C. This is considerably shorter than the 100 days previously reported to be required at the same temperature by Neoverruca sp., a species confined to inhabiting active vents. Also in contrast to Neoverruca sp., A. seepiophila did not drastically shorten the developmental period from nauplius VI to cyprid when exposed to temperature of 10 °C. We conclude that there is no need for late naupliar stages of A. seepiophila to develop into cyprids more quickly at elevated temperatures because this species does not inhabit active vents. The difference in response to water temperature during larval development may contribute to the separated distribution of the two species at active vents (Neoverruca sp.) and inactive vents and cold seep (A. seepiophila) environments.