IngentaConnect Feeding Behavior and Functional Morphology of the Epiproboscis of...

Abstract:

The epiproboscis of Mitra idae Melvill is an extensible, J-shaped muscular rod passing beneath the buccal mass, and terminating within the buccal cavity. A muscular external sheath encloses that portion of the epiproboscis lying within the proboscis haemocoel. An invaginated internal sheath covers the ventral arm of the epiproboscis. The dorsal arm of the epiproboscis consists primarily of longitudinal muscle; the ventral arm of the epiproboscis consists of circular muscle surrounding a core of longitudinal muscle. Specialized postural muscles are present along the surface of, and within the circular muscle of, the ventral arm of the epiproboscis. The epiproboscis (1) locates prey during attachment of the proboscis to the prey, (2) retrieves prey viscera, (3) provides leverage and physical support for the buccal mass, and (4) assists in maintaining a hold on the prey as the proboscis attempts to retract. Both hydraulic and hydrostatic mechanisms probably serve to move the epiproboscis. Contraction of the external sheath forces haemolymph between the internal sheath and the surface of the epiproboscis, and thereby protracts the epiproboscis. Contraction of the circumferential muscle, and relaxation of the longitudinal muscle, of the ventral arm of the epiproboscis would also protract the epiproboscis. The intrinsic musculature of the epiproboscis provides postural control and assists in retraction of the epiproboscis. M. idae feeds on sipunculans, as do all other species of mitrids studied. The mitrid epiproboscis appears to be an adaptation for feeding on soft-bodied reclusive prey which occupy some form of protective confinement. This report is the first account of the functions and functional morphology of the mitrid epiproboscis.

Feeding Behavior and Functional Morphology of the Epiproboscis of Mitra Idae (Mollusca: Gastropoda; Mitridae)