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.
