Observations on the reproductive biology of the hydrothermal vent tube worm Riftia pachyptila

Abstract

On the Hydronaut Expedition to 13N on the East Pacific Rise, we made some observations on the reproductive biology of Riftia pachyptila relevant to larval dispersal, symbiont acquisition, and sperm transfer. Two females spawned in a pressure chamber about 15 h after collection. During each 30 min spawning episode, the relatively small (105 pm), lipid-rich eggs were emitted in large numbers from the female gonopores and floated upward in still seawater at about 2 cm min-l. Therefore, it is likely that early development takes place in deep water well above the vent habitat of the adults. Two males spawned in non-pressurized aquaria about 45 min after reaching the deck of the ship. Semen issuing from the male gonopores contained sperm bundles, each composed of several hundred sperm wlth remarkable detached acrosomes. Each bundle swam vigorously through seawater by the beating of all its flagella In unison Motil~ty was not inhibited by hydrogen sulfide concentratlons greater than those at the vent habitat. After swimmlng for about 15 min, the bundles broke up into individual sperm that were relatively immotile. It is reasonable to assume that sperm bundles swim from the male to the female's tube or body where they adhere by their detached acrosomes before disintegrating into individual sperm that subsequently ferhhze the