Distribution of hyperiid amphipods (Crustacea) of the southern Gulf of Mexico, summer and winter, 1991

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The distribution and abundance of the hyperiid amphipods of the southern Gulf of Mexico was analyzed from zooplankton samples collected during summer and winter 1991. We evaluated the effect of the local hydrographic conditions, characterized by mesoscale eddies, on the hyperiid community. We explored the presumed correlation of hyperiids with siphonophores, one of the groups of gelatinous zooplankton to which they are symbionts. It was expected that hyperiids were more abundant in areas related to cyclonic eddies and less abundant in the anticyclonic eddies than in the surrounding waters, but most differences were not significant. Both our data set and previous observations are not conclusive because they are based on low resolution sampling grids. Hyperiids were significantly more abundant at night. Of the 57 species of hyperiids recorded, Lestrigonus bengalensis was widely dominant in both seasons. It was significantly correlated (Spearman r) with the siphonophore Muggiaea kochi during the winter and with Diphyes dispar in the summer, when this siphonophore was most abundant. It is suggested that the association takes place and is detectable when and where both species are highly abundant. There are other significant siphonophore/amphipod correlations; most are not likely to represent symbiotic associations. Variations of the gulf hyperiid community are related to: (i) the dominance of L. bengalensis, (ii) the seasonal abundance of the siphonophore D. dispar, mainly in relation to L. bengalensis, (iii) the anomalous occurrence of deep-living forms and (iv) day/night variations. The presumed influence of mesoscale eddies on the gulf hyperiid community deserves further study. eng

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