Etude morpho-géométrique par la technique des points homologues de l’oursin Paracentrotus lividus (Lamarck, 1816) au niveau de quelques stations de la côte de Mostaganem

Abstract

This work is a morpho-geometric study based on landmarks of the livid sea urchin Paracentrotus lividus (Lamark, 1816). We sampled 162 individuals from four stations of the coast of Mostaganem: Stidia, Salamandre, Sidi Medjdoub and Sidi Lakhder by sampling at the two different floors (mediolittoral and infralittoral). Individuals were measured by considering the length (L) and the height (H) of the sea urchin test. The gibbosity parameter (H/L) was calculated to study the "floor" and the "stations" effect on P. lividus individuals sampled by the t-test and the ANOVA test respectively. Each individual was photographed in dorsal view in order to perform the morpho-geometric study based on 20 landmarcks analyzed by a CVA (Canonical Variances Analysis). The results showed that there was a "stations" effect on H/L and the landmarcks method showed that there was a significant difference between the individuals at the Sidi Lakhder station and the other individuals of Mostaganem region (Stidia, Salamandre and Sidi Medjdoub) may be due to an allopatric speciation created by geographical isolation between the two regions (Sidi Lakhder and Mostaganem). These morphogeometric techniques are not very expensive and could give results close to fastidious and very expensive phylogenetic studies.