Comparative morphology of cerithioidean radula (Mollusca: Gastropoda) observed using scanning electron microscope.

Radula is the feeding organ of gastropods (Mollusca). This organ is a long ribbon shaped that rolls up inside the buccal cavity, and is composed of tens to hundreds of teeth arranged in a transverse row. Morphological characters of radula have been used in the classification of gastropods at all taxonomic levels as their characteristics reflect inter− and intraspecific variations. Detailed descriptions of radular characters among gastropod species, therefore, provides essential information to identification. In this study, the radula of six Cerithiodean species of the families Pachychilidae (i.e., Sulcospira testudinaria, S. kawaluensis and Tylomelania toradjarum) and Thiaridae (i.e., Melanoides tuberculata, Stenomelania plicaria and S. punctata) were compared. The radula was extracted enzymatically using Proteinase-K and were observed using a scanning electron microscope (SEM). The six species studied have the taenioglossate type of radula with the formula 2-1-R-1-2. The radular characteristics that distinguish members of Pachychilidae from those of Thiaridae include the ribbon length, the glabella shape, and the marginal teeth structure. The pachychilid species have a longer ribbon (x̅ = 14.11-19.48 mm) compared with the thiarid species (x̅ = 2.93−4.16 mm). Moreover, pachychilid species have a narrow glabella with a convex basal shape and short marginal teeth, whereas thiarid species have a broad glabella with a flat basal shape and long marginal teeth. Each species in the present study shows radular variations in the number of rows as well as the shapes of teeth. [ABSTRACT FROM AUTHOR]