Sperm masses and sperm transfer in a vestimentiferan, Ridgeia piscesae Jones, 1985 (Pogonophora: Obturata)

Discrete sperm masses, of irregular outline, 2–5 mm in their maximum dimension, were found on males and females of Ridgeia piscesae Jones, 1985 (Pogonophora: Obturata), hydrothermal vent tube worms from the Juan de Fuca and Explorer Ridges in the eastern North Pacific Ocean. Masses were found in tentacular and vestimental locations, often near the gonopores. The fine structure and size of spermatozoa from inside males are the same as in the masses and are distinctly different from described spermatozoa of perviate pogonophores. Maturation of the spermatozoa appears to be completed within the external sperm mass, after spawning. The sperm masses produced by males may be actively transferred to adjacent females of the densely aggregated animals found at the vent sites. In the females, these masses come to rest near the gonopores where fertilization may occur, just internal or external to the pores.