Medusan (Cnidaria) assemblages off the Caribbean coast of Mexico

The species composition, distribution and abundance of medusae collected of f the Mexican coast of the Caribbean Sea was analyzed from samples gathered from oblique plankton tows (0-50 m) during five months (February, March, M ay, August and November, 1991). The highest mean medusan abundance was obse rved during March (2,354 org./1000 m(3)) while lowest values occurred in Au gust (102 org./1000 m(3)). Twenty-four species and 4 genera were identified . Linuche unguiculata, Liriope tetraphylla, Clytia mccrady and Aglaura hemi stoma were the mast abundant. They represented more than 96% of the total m edusan numbers. Cluster analysis and the known ecological affinities of the species revealed two oceanic (primary and secondary) and one neritic assem blage whose distribution showed month to month variations, apparently relat ed to the prevailing wind regimes. Intergradation of these assemblages and the presence of oceanic and even deep-living species very near the coast wa s attributed to the narrowness of the continental shelf.