SIPHONOPHORA (CNIDARIA) FROM THE COSTA-RICA DOME

The composition, general distribution and abundance of siphonophores at the Costa Rica Dome, in the eastern tropical Pacific (Nov. 1981), were sampled by surface hauls with a Bongo-type net, with a 0.5 mm-size mesh. A total of 29 species were identified; Eudoxoides mitra, Muggiaea atlantica and Abylopsis eschscholtzi were the most abundant. The highest total densities were related to the main upwelling zone. Chelophyes appendiculata and C. contorta, allopatric species, ocurred simultaneously. Muggiaea atlantica, a neritic species was also recorded. A. tetragona, an abundant species in the ecuatorial region was absent. Furthermore, high diversity and low dominance indexes, as well as chord distances, indicate that the local siphonophore community was greatly influenced by the mixture of water masses characteristic of the dome.