A comparative survey of the mantles in Lithophaga lithophaga, Mytilus galloprovincialis and Petricola lithophaga with special reference to the boring habit

Abstract

Lithophaga lithophaga and Petricola lithophaga are two bivalve species in which the boring habit has been evolved. Mytilus galloprovincialis is another bivalve closely related to L.lithopaga, but which lacks this boring habit. Observations were made on live animals. A comparative gross morphological, histological and histochemical study was made on the mantle of the three bivalves. A spectrophotometric analysis of Ca concentration in the mantle of L.lithophaga and M.galloprovincialis was carried out. It was confirmed that M.galloprovincialis was carried out. It was confirmed that M.galloprovincialis lacks the compact pallial glands found in L.lithophaga and lacks also the extreme development of the middle marginal fold of L.lithophaga. In addition the pattern of distribution of secretory cells is different in the two. Evidence is produced for a much higher secretory activity in L.lithophaga. P.lithophaga differs considerably in the gross anatomy from the two mytilid species. Though the secretory activity of the mantle in P.lithophaga is considerable, probably more advanced than in L.lithophaga, the location, histology and histochemistry of the glands in the latter two species is quite different. It is concluded that the middle marginal fold is in all probability mainly responsible for boring in L.lithophaga, and that boring in P.lithophaga is achieved by a different mechanism, possibly being partly mechanical.