Solemya pervernicosa Lives in Sediment underneath Submerged Whale Carcasses: Its Biological Significance

Abstract

Solemya pervernicosa, which had previously been regarded as a bathyal species restricted to northeastern Japan, occurred in the sediment underneath whale carcasses submerged experimentally on the shelf off Cape Noma-misaki, Satsuma Peninsula, southwestern Japan, at depths of 219–254 m. This occurrence represents a significant range extension. Transmission electron microscopic observations of the gill tissue revealed dense bacteria in the epithelial cells. A molecular phylogenetic analysis strongly indicated that these bacteria are thioautotrophs closely related to the thioautotrophic symbionts associated with Solemya reidi and Acharax johnsoni. Analysis of carbon and sulfur isotopes of soft tissues of S. pervernicosa proved that this bivalve depends nutritionally on thioautotrophic symbionts. However, it is not clear at present whether the symbiont is transmitted vertically, as with some other chemosynthetic bivalves, or environmentally.