Spatial variation in the body mass of the stout razor clam Tagelus plebeius: Does the density of burrowing crabs Chasmagnathus granulata matter?

JORGE LUIS CEFERINO GUTIERREZ; IRIBARNE, O. O.

JOURNAL OF SHELLFISH RESEARCH

Año: 2003 vol. 22 p. 69 - 73

0730-8000

A series of functional-group hypotheses proposed for marine soft-sediment systems predict that either deposit-feeders or highly mobile bioturbators exclude low-mobile supension feeders because of their sediment reworking activity. However, a low-mobile suspension-feeder -the stout razor clam Tagelus plebeius- coexists with highly mobile deposit-feeding burrowing crabs, Chasmagnathus granulata, in several Southwestern Atlantic estuaries. In this study, we compared the body mass (as relationship between shell length and dry weight of flesh) of the stout razor clam between replicated patches showing contrasting densities of burrowing crabs. Spatial variation was observed in the slope of the relationship between shell length and dry weight of flesh of T. plebeius in the three samplings dates (July 1999, January 2000, and April 2000). However, the pattern of spatial variation in the slope of this relationship was not consistent with the pattern of spatial variation in crab density. In addition, the pattern of spatial variation in the slope of the relationship between shell length and dry weight of flesh of the stout razor clams was not consistent between the three sampling dates. These results suggest either that (1) body mass of the stout razor clam is affected by habitat features other than crab density, or (2) effects of burrowing crabs on body mass of the stout razor clam are masked by spatial variation in other habitat features that affect body mass of stout razor clams or the extent to which crabs are able to affect clams.