The Physiological Basis For Growth Differences Between Two Clam Species (genus Ruditapes): Allometric Size-scaling Relationships | 41841
Journal of Ecosystem & Ecography
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Clams (genus Ruditapes) constitute one important component of infaunal macrobenthic communities in coastal areas. Coexistence
of two species–the native clam (R. decussatus) and the Manila clam (R. philippinarum) introduced some decades ago for
commercial purposes in the intertidal zone along the Atlantic coast, poses the question of resource partitioning among populations
of both species since these clams share a common filter – feeding mechanism. In this study, two main physiological components of
the individual energy balance–filtration and metabolic rates were determined in these clams in order to ascertain whether differences
in physiological behavior accounted for higher rates of growth reported in the introduced species (FAO reports). To cover growth
trajectories, measurements were performed for a wide size-range of clams and physiological rate determinations formalized through
allometric size-scaling relationships. Comparisons of allometric equations using ANCOVA showed lack of significant inter-specific
differences in size exponents for either filtration or metabolic rates. Concerning the intercepts, differences were found no-significant
for metabolic rates while intercept for filtration rates was significantly higher in R. decussatus. Thus, results do not support the
expectation of higher filtration in the introduced species as inferred from their higher rates of growth reported. However, present
filtration rates were based on active filtering individuals and complementary information concerning cycles of activity in both species
is needed in order to achieve environmentally realistic assessments of energy acquisition.
Amaia Autor has recently finished her MSc in Zoology at Complutense University of Madrid. She is giving the first step toward research by trying to publish a work about extra-pair paternity in blue tits (directed by Santiago Merino and Elisa Perez of MNCN-CSIC) and by the work presented here about the inter-specific differences between two species of clams.