Medusan (Cnidaria) Assemblages off the Caribbean Coast of Mexico

Abstract

The species composition, distribution and abundance of medusae collected off the Mexican coast of the Caribbean Sea was analyzed from samples gathered from oblique plankton tows (0- 50 m) during five months (February, March, May, August and November, 1991). The highest mean medusan abundance was observed during March (2.354 org./1000 m³) while lowest values occurred in August (102 org./1000 m³). Twenty-four species and 4 genera were identified. Linuche unguiculata, Liriope tetraphylla, Clytia meerady and Aglaura hemistoma were the most abundant. They represented more than 96% of the total medusan numbers. Cluster analysis and the known ecological affinities of the species revealed two oceanic (primary and secondary) and one neritic assemblage whose distribution showed month to month variations, apparently related to the prevailing wind regimes. Intergradation of these assemblages and the presence of oceanic and even deep-living species very near the coast was attributed to the narrowness of the continental shelf.