New molluscan larval form: brooding and development in a hydrothermal vent gastropod, Ifremeria nautilei...

Despite extreme differences between some shallow and deep-sea habitats, the developmental modes and larval forms of deep-sea animals are typically similar to those of their shallow-water relatives. Here we report one of the first documented exceptions to this general rule. The hydrothermal vent snail Ifremeria nautilei displays two novel life-history traits: (1) an unusual uniformly ciliated larva that we here name Warén's larva, and (2) internal brood protection in a modified metapodial pedal gland. Warén's larva emerges from the internal brood pouch as a fully ciliated lecithotrophic larva with a unique external cuticle. The larvae swim with their posterior end forward and metamorphose into typical veliger larvae after 15 days at room temperature. Warén's larva is the only known example of a free-swimming pre-veliger larval stage in the higher gastropods and is the first new gastropod larval form to be described in more than 100 years.