Spatial variability of larval parasites harboured by two crab species in an estuarine environment in Argentina

Abstract

Soft bottom intertidals of the Atlantic SW are dominated by the semi-terrestrial crabNeohelice granulataand the grapsid crabCyrtograpsus angulatus. They are similar in size butC. angulatusis mainly a subtidal species, whileN. granulatainhabits the intertidal zones, thus the two species overlap only during high tides in this area. Since these distribution differences between crab species across the Mar Chiquita Coastal lagoon may affect digenean infection success, the objective of this work is to describe the spatial differences in parasite infection levels and their selectivity on the host. To determine possible spatial differences in parasitism levels between sites and crab species across the lagoon, three areas dominated byN. granulatawere selected and adult crabs ofN. granulataandC. angulatuswere collected. Both crab species harboured metacercariae of the digeneansMicrophallus szidatiandMaritrema bonaerensis(Microphallidae), and cystacanths of the acanthocephalanProfilicollis chasmagnathi(Profilicollidae). Digenean species showed preferences between the two crabs.Maritrema bonaerensismean intensity was higher inN. granulatathan inC. angulatus, while the opposite trend was found forM. szidatiand could indicate some level of specificity. These results, nevertheless, depended on the study site. ForP. chasmagnathithe highest values of mean intensity depended more on the site than on the crab species. The values found here, compared with previous works from both crab species, suggest that besides the spatial heterogeneity, interspecific competition between parasites could explain the differences observed.