Laboratory and in situ flotation rates of lecithotrophic eggs from the bathyal echinoid phormosoma placenta
Young, C.M.; Cameron, J.L.
Deep-Sea Research Part A Oceanographic Research Papers 34(9): 1629-1640
ISSN/ISBN: 0198-0149 DOI: 10.1016/0198-0149(87)90112-9
The large, lecithotrophic eggs of the bathyal echinothurid echinoid Phormosoma placenta are positively buoyant both in vitro and in situ to depths of at least 608 m. Eggs attain terminal velocity in less than 5 cm. At constant salinity, flotation rate is related linearly to temperature; eggs move more slowly at lower temperatures. This effect is attributed to increased water viscosity at lower temperatures, not differential changes in egg and water density. Based on an average flotation velocity of 0.42 cm s-1, it is predicted that eggs produced at bathyal depths will reach the surface in approximately 2 days.