Host-parasite relationships between the mussel, Mytilus edulis L., and the pea crab, Tumidotheres maculatus (Say), in the south-western Atlantic

TABLADO, A.; LÓPEZ GAPPA, J.

JOURNAL OF SHELLFISH RESEARCH

The National Shellfisheries Association

Año: 1995 vol. 14 p. 417 - 423

0730-8000

Incidence and effects of the pea crab Tumidotheres maculatus (Say) on a population of the mussel, Mytilus edulis L., were studied at an offshore bank near Quequén, Argentina (38º50’S, 58º55’W). Seven samples were obtained randomly, April to October 1990, among benthic invertebrates usually discarded by the benthic-demersal fishery. Infestation by pea crabs varied from 54.3 to 72.6% (average 63.6%), which is considerably higher than the incidence recorded at the same bank in 1970. The null hypothesis of random pea crab distribution among mussels was tested by fitting the data to a Poisson distribution. Male crabs were randomly distributed in their hosts. Significantly more Stage IV-V female crabs were single occupants of a mussel than expected. On the contrary, pre-hard crabs had a clumped distribution in their hosts. Correlation between mussel length and pea crab size was low but significant for Stage IV-V female crabs, absent for male crabs. Mussel length was significantly lower when parasitized by mature females (P < 0.001) but not when harbouring other pea crabs stages (P > 0.05). Mussels of a given length had significantly lower meat dry weight when parasitized by Stage IV-V female crabs (P < 0.01). Weight differences between mussels harboring other pea crab stages and uninfested mussels were not significant (P > 0.05). Our results confirm adverse effects of female T. maculatus on M. edulis.