Morphology and chemical composition relation of Rapana thomasiana shell sampled from the Romanian Coast of the Black Sea

• Age classification was performed by using Bhattacharya method.
• A chemical analysis was conducted for each age-group of rapana shells.
• Differences in shell morphology according to the biotope were recorded.
• The degree of mineralization is higher for younger age-classes of rapana shells.
• The organic content is quite the same for each sample and age-group.

Rapana thomasiana is a predatory gastropod and a successful invader, which is found in abundance in the Black Sea. The aim of this study is to determine whether there is a relationship between morphology and chemical composition of rapana shell and therefore if the maturation of R. thomasiana shells, quantified by morphological parameters, has influence on their mineralization level, assessed by chemical composition analysis. For this purpose, integer individuals of R. thomasiana were collected from Limanu, Midia Cape and Vadu-Corbu beaches and morphological parameters of shells, such as length (L), mass (m), thickness (th) were investigated using specific mathematical statistic methods. Characteristic features of rapana whelk were found according to the corresponding marine substrate. Age classification was done using Bhattacharya method which has divided R. thomasiana population within three to four age-groups. In order to determine if there are significant differences between age classes in terms of chemical composition, for each determined age-group a chemical analysis was conducted. In this respect, the mineral content and total organic carbon (TOC) determined, showed in general, statistically significant differences (p<0.025 and p>0.975) among Ca, Mg and organic C values for almost all age-classes. The statistical trend suggests a slight growth of the organic matter and a drop of mineral composition with age.