Morphology of the pedal circulatory system of the marine gastropod Busycon contrarium and its role in locomotion (Gastropoda, Buccinacea)

Summary

Dissections, injections, and histological preparations of the foot of Busycon contrarium show that the “open” circulatory system of the snail foot consists of discrete arteries and veins that anastomose throughout the foot in a pattern similar to the “closed” circulatory system of annelids and vertebrates. As the major arteries penetrate the foot, their diameter decreases and the thickness of their muscular walls diminishes. Near the ventral surface of the foot, the blood is channeled through the venous sinus, a fine network of discrete spaces delimited by the muscle and connective tissue of the sole. Small nuclei at the edges of some of these vessels indicate that they may have an incomplete endothelial lining. From the venous sinus, blood is channeled into two major veins on either side of the foot that join and return the blood to the kidney.

While probably important for expanding the sole region and for maintaining turgor once the foot has expanded, the circulatory system is not isolated from the pedal musculature, but rather forms a continuum with the pedal muscles and the surrounding connective tissue. It is therefore unlikely that the blood functions as the mechanical antagonist to the muscular contractions of locomotion. The results indicate that the role of the pedal circulation in Busycon is intermediate between the fluids in the hydrostatic skeleton of many worm-like animals and the muscular-hydrostat of cephalopod arms and tentacles.