Etude Biométrique Comparative De Deux Espèces De Gastéropodes Marins (siphonaria Pectinata) (linnaeus, 1758) Et (patella Rustica) (linnaeus, 1758) Issues De Deux Sites Contrastés De La Côte Mostaganémoise

Résumé: The interest in gastropod molluscs is linked to the importance of their relations with the marine phytobenthos being very frequent on all the rocky coasts of western Algeria thus exposing complex ecological and behavioral traits which vary from one environment to another depending on the degree of pollution. Our study covers two parts. The first, which consists of the biometric analysis of the two bio-indicators chosen, namely the false limpet Siphonaria pectinata (Linné, 1758) and the patella Patella rustica inhabiting two rocky sites, namely Stidia (STD) and the port of Mostaganem (PM). The main objective of this study is the evaluation of the resistance of the latter, also to decide on their profile, they remain until then little known because apart from the similar studies carried out in previous years at the level of the university of Mostaganem, no other study has been devoted to them. But also to conduct an evolutionary comparison of its two species distributed in the rock to try to understand their development strategy. The work consists of a series of biometric measurements carried out on 240 individuals of these Gastropod Molluscs namely: the height of the shell (H), the length (L) the width (La), anterior vertex (Sa), posterior vertex (Sp) as well as the total fresh weight (Pt) are carried out for all the populations of S.pectinata, and P.rustica. The correlation of the different measurements (length-height, length-width, length-total weight, height-total weight, width-total weight, posterior vertex-anterior vertex) was processed and analyzed following the linear curves and powers of the form: y = ax + b and y = axb respectively and following the test of STUDENT “t”. The results obtained reveal prominent and major allometric relationships between the various biological parameters. It has been observed that the rustic limpet favors the development of its shell in height followed by the width and the length and finally the increase in the total fresh weight. On the other hand, for the Siphonaria it is the width which finds itself in the first position of development. The anterior vertex grows more slowly than the posterior vertex. This is indeed an adaptive response to the physical and ecological conditions of the environment. This study showed that there is no significant difference (p <0.05) between the morphometric characteristics of the two studied species sampled from the selected stations. This approach represents a good means of environmental assessment that could be used in biomonitoring programs.

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