Isopod assemblages in the Straits of Magellan: structural and functional aspects

Abstract

Isopod crustaceans were found to constitute a substantial fraction of the zoobenthos collected in the course of a survey carried on in the Straits of Magellan during austral summer 1991. Twenty-four species and 637 individuals were found. The highest abundance and diversity within the taxocoene were recorded from the eastern areas of the straits. An analysis of population and trophic characteristics was conducted, in particular on a conspicuous sample from a site dominated by a mollusc thanatocoenosis. At this site, parameters such as size range of individuals and number of ovigerous females were estimated as indicative of a well-established population. Trophic structure was dominated by functional plant- and plant detritus-feeders. Cryptic requirements and trophic habits of most species appeared to be satisfied under conditions of enhanced habitat complexity and/or spatial patchiness. It is hypothesized that spatial heterogeneity acts on isopod distribution at different scales. The role of hydrodynamism is briefly discussed.