The morphofunctional characterization and ploidy levels of the digestive gland cells in prosobranch gastropod mollusks (Prosobranchia: Gastropoda) with special reference to somatic polyploidy

Resumo

The histological organization and ploidy levels of the digestive gland cells in 34 species of prosobranch gastropod mollusks that belong to the subclasses Patellogastropoda, Vetigastropoda, and Caenogastropoda (orders Littorinimorpha and Neogastropoda) were investigated using histochemical methods and cytophotometry of nuclear DNA. Two general types of differentiated cells, viz., digestive and basophilic (secretory-calcium), were identified in the epithelium of the digestive tubules. In Vetigastropoda and Neogastropoda species, all the cells are mostly diploid. In representatives of Patellogastropoda and Littorinimorpha, the digestive cells are diploid as well, but basophilic cells of many species reach polyploidy levels of 4–8c and in some species, even 4–8–16c. Cases of somatic polyploidy in basophilic cells are considered as adaptive modifications of histogenesis associated with the peculiarities of the environment (intensified metabolism in osmotically tolerant Littorina and Lottia species), the duration of ontogenesis (the short life cycle in Lacunida species), and a specific diet.