Gutless Bivalves

Abstract

A new benthic species of the protobranch bivalve genus Solemya, from the northeastern Pacific Ocean, lacks a gut. It has no internal digestive enzymatic apparatus; nor is there any provision for the secretion of enzymes into the mantle cavity for extraorganismic digestion. The most likely nutritional mechanism for such an animal is the active absorption of dissolved organic molecules from the environment by the large ctenidial lamellae. These are well provided with blood, cleansed of sediment by cilia, and have phosphatases in their epithelial cells. Solemya borealis may also be gutless.