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Abstract

POLYCLAD FLATWORM DIVERSITY OF THE WIDER CARIBBEAN

D.M.Bolaños¹, S.Y.Quiroga¹, K. A. Rawlinson², M.K.Litvaitis^1
1 University of New Hampshire
² Smithsonian Marine Station at Fort Pierce
Bio

A distinct polyclad fauna exists in the tropical waters of the western Atlantic. To corroborate and update past literature, an inventory of the polyclad fauna of the wider Caribbean was carried out between March 2004 and September 2006. Eight coastal regions were sampled, resulting in 77 species distributed in 31 genera and 17 families. Five new species of cotylean flatworms belonging to the genera Pseudoceros Lang, 1884, Thysanozoon Grube, 1840, Pseudobiceros Faubel, 1984 and Maritigrella, Newman & Cannon, 2000, were described. Specific determinations of the new species were based primarily on color and color pattern. Diagrammatic reconstructions of the reproductive systems derived from serial histological sections and whole mounts are presented. In addition, a re-description of Pseudoceros pardalis Verrill, 1900 resulted in the new combination, Pseudobiceros pardalis. The new pseudocerotid and euryleptid species described here are generally found in subtidal habitats, which were not sampled in earlier studies. Polyclads are mobile predators and possibly represent an important functional component of hard substrate marine environments globally. To understand natural patterns of spatial differences, polyclad assemblages were quantitatively sampled at seven of the coastal regions. Only Melloplana ferruginea and Pseudoceros bicolor were found in all surveyed regions. Conversely, 41 species were restricted to one or two sites, and 34 species were represented by one or two individuals. The distribution and abundance of species varied between the two suborders. Cotylea were most species rich and had a higher number of species of restricted range, whereas Acotylea showed a higher proportion of rare species. In most habitats polyclads were rare, but in some intertidal habitats Styloplanocera fasciata and Boninia divae were highly abundant, comprising over half of the individuals counted. In fact, they represented the dominant members of the benthic epifauna in these locales. Overall assemblages from the 7 regions were similar, revealing faunal homogeneity across the wider region. Reef assemblages were distinct from other habitats and were dominated by species of the Cotylea.