It has been demonstrated that the molluscan integument can act as a site for the active exchange of ions and metabolites [2]. Endocytosis processes have also been described in the foot epithelium of a terrestrial gastropod [37] and in the foot of the limpet [38]. Nevertheless, despite presenting prominent microvilli, no evidence for endocytosis through the apical edge Sunitinib in Haliotis tuberculata epithelial cells has been found in this study. However the presence of mitochondria mainly distributed at the epithelial cell’s surface could suggest high metabolic activity.The sole foot epithelium of Haliotis tuberculata (present results) and of other aquatic gastropods [see [28] for review] is characterized by the abundance of ciliated cells that are probable used to distribute the mucus for mucus gliding locomotion [21].

Some similar scattered cells have been found in the side foot, but the significance of their function is not well understood in this part of the body. In Haliotis, sensory and water flux recirculation functions were described for the ciliated cells of the tentacles [6, 28]. Other feature of the sole foot is the presence of a more prominent mucus layer than in the side foot, which is also important in locomotion and adhesion to the substrate.4.2. Epithelial Secretory Cells and Subepithelial GlandsHistochemical studies have revealed the presence of epithelial secretory and subepithelial glandular cells in the gastropod foot, but their number and chemical composition varied greatly among the different species studied [28].

This is probably due to the considerable variety of habitats they occupy and to their different modes of life. It has been proposed that limpets can secrete different forms of mucus for mobility or adhesion to rocks [23] in response to their tidal activity cycles. However, we cannot expect the same for Haliotis who lives in the infralittoral area never exposed to tide cycles [39].Concerning the foot of Haliotis tuberculata, present results corroborate the occurrence of neutral and acidic (mostly sulphated) glycoconjugates that we have previously described [29]; in addition, in this work the presence and distribution of sugar residues in the oligosaccharide side chains of glycoconjugates in its pedal epithelium were investigated by using specific lectins.Following Dacomitinib classical carbohydrate histochemical techniques, most epithelial secretory cells along the foot of Haliotis are rich in acidic sulphated glycoconjugates (present results), which is in neatly agreement with previous studies describing that sulphate is a major component of the gastropod mucus [14, 15, 18, 40].