Regeneration of the proboscis of muricid gastropods after amputation, with emphasis on the radula and cartilages.

Abstract

1. All individuals of Urosalpinx cinerea, Urosalpinx cinerea follyensis, and Eupleura caudata etterae from which the proboscis was removed, recovered, and fully regenerated the proboscis. By the 4th day after proboscisectomy a blastema of loose tissue bound the amputated ends of the esophagus, buccal artery, ducts of the salivary glands, and the other tissues to the stump of the proboscis. Between the 8th and 12th days after the operation, snails had formed minute proboscides and radulae. Onset of boring of shell by regenerating snails varied from 11 to 34 days, and took place only after the radula and associated structures were developed and functional. The radula is thus an essential component of the mechanism of shell penetration. Formation of a given length of radula did not trigger penetration; other unexplained factors appear to be responsible.2. Although earliest regenerating rachidian and marginal teeth were small and misshapen, increase in size and normalization of form was rapid. In time regeneration of proboscides was complete, and they resembled normal proboscides anatomically, histologically, and functionally. Earliest teeth were worn by abrasion, indicating that snails began rasping soon after the teeth and odontophore were formed. Boreholes excavated by snails with small newly regenerating radulae generally corresponded in form and size to those bored by normal snails; this is evidence that the shape and size of the borehole are the products of chemical activity of the accessory boring organ rather than the radula.3. Histologically the organization of the regenerating odontophoral cartilages and associated musculature and other tissues was similar to that seen in regenerating vertebrate limbs. In both cases the regenerative process is dependent upon a unique cell aggregate (the blastema of vertebrates, and its analogue in muricid snails), a cap of cells organized at the regenerating tip of the amputated structure.4. The boring habit and rapid regeneration of the proboscis are distinct assets in procurement of food, and perhaps account in part for the biological success of Urosalpinx cinerea and Eupleura caudata and their significance as major predators of commercial oysters.