The occurrence of juveniles of the grapsid crab Chasmagnathus granulata in siphon holes of the stout razor clam Tagelus plebeius.

JORGE LUIS CEFERINO GUTIERREZ; IRIBARNE, O. O.

JOURNAL OF SHELLFISH RESEARCH

Año: 1998 vol. 17 p. 925 - 929

0730-8000

Previous samplings for megalopae and juvenile instars of the southwestern Atlantic burrowing crab Chasmagnathus granulata showed that they occur at high densities in adult crab burrows. Nevertheless, this study documents the occurrence of juveniles of this species in siphon holes of the stout razor clam Tagelus plebeius after a settlement event. Carapace width of the crabs collected ranged between 1.9 mm and 4.5 mm (2nd to 8th instar). A significantly higher proportion of crabs were found inhabiting inhalant instead of exhalant siphon holes. The siphon holes occupied by crabs showed a significantly larger diameter than those not occupied by them, and a significant positive correlation was found between siphon hole diameter and crab carapace width. A lateral chamber connected to the inhalant siphon gallery was observed in siphon holes inhabited by larger crabs. No correlation was found between the density of pairs of siphon holes and the proportion of pairs of siphon holes inhabited by crabs. However, the proportion of pairs of siphon holes occupied by crabs was higher in a site with low density of adult burrows in relation to adjacent sites with high density of adult burrows. We propose that the presence of clam siphon holes allows crab larvae to colonize poorly structured habitats where adult crab burrows are absent or at low densities, making possible the growth of areas inhabited by crabs.