| Abstract |
The aim of this study was to investigate the development of the land snail shell as well as to account for environmental effects on its shape. In order to achieve this goal, specimens of land snails from nine sites were examined. Sampling areas were selected in order of latitude namely lowlands (0-100 m.), highlands (1.000 m.) and peaks (2.000 m.), in each of the three major massifs of the island of Crete. The model applied was based on the research of Lovtrup, S. & Lovtrup, M., (1988), Cortie (1989), Prusinkiewicz (1994), Meinhardt & Prusinkiewicz (1995), who have suggested a theoretical model that describes the development of land snails' shell. The innovative element of the present study lies on the method used, in order to confirm the model's predictions and its application on real shells. This method enables the objective comparison of trajectories that shells of different species follow, as well as shells of the same species at different locations. Besides the method, that defines the parameters of the model, four new parameters in gastropod morphometry are defined and measured. The methodology used to acquire raw data such as cut shell sections, illustration of the sections by a scanner, morphometric measurements by specific software, are applied for the first time and permit us to obtain new morphometric parameters. These parameters, according to the statistical analysis of the data, in combination with the application of the model shows that they can be used as diagnostic indices for the environmental influences in shell morphology. The Multivariate Analysis of Variance indicates that in some species the vertical differentiation that appears to exist in the morphometric characteristics of the shell is statistically significant. In addition for some species a horizontal axis of differentiation on the island in an East-West direction also emerged. The same method points out that the growth ratio of the spiral is smaller on the peaks of the mountains than at lower altitudes. Moreover it seems that in ecosystems at mountain peaks flattened forms prevail compared to those in lower altitudes. The distribution of endemic species of the genus Albinaria and Metafruticicola, points out that specific mechanism which reduce dehydration have been developed, by adjusting the aperture area. It is suggested that change in the growth ratio of spiral, intraspecific, is related to the prevailing environmental conditions during the growth of the organism.
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Διερεύννηση του μοντέλου ανάπτυξης που ακολουθεί το κέλυφος των χερσαίων γαστερόποδων και η διαφοροποίηση τους με το υψόμετρο
