Shell polymorphisms in the bathyal mediterranean top Snail Clelandella Myriamae Gofas, 2005

Differences in shell morphology in the gastropod Clelandella myriamae Gofas, 2005 were investigated. Observations on a total of 341 empty shells supplemented the original description and allowed the distinction of two morphotypes differing in shell size, shape and wall thickness. The existence of shell variations was also demonstrated by statistical morphometrics. Size-frequency distributions of major parameters are slightly bimodal, suggesting a disruptive selection, which tends to encourage the extreme shell forms. The achievement of larger sizes and the construction of thicker shells was interpreted as a capability of the species to withstand predatory attack, testified by several drills and scars on most shells. The occurrence of the species and the shell size variation were put in relation with other possible environmental causes such as food availability represented in the area by abundant decaying vegetal detritus. The record of C. myriamae from the epibathyal of the Gioia Basin is quite far from the first finding in the bathyal Eastern Mediterranean, thus extending bathymetrical and geographical range of the species.