PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON 115(2):323-332. 2002. Asclerocheilus tropicus Blake, 1981 (Polychaeta: Scalibregmatidae): redescription based on Brazilian specimens Joao Miguel de Matos Nogueira Departamento de Zoologia, Institute de Biociencias, Universidade de Sao Paulo (USP), Rua do Matao, travessa 14, n. 101, Cidade Universitaria, 05508-900, Sao Paulo, SP, Brazil. E-mail:
[email protected] Abstract. — Asclerocheilus tropicus Blake, 1981 is redescribed, based on Bra-zilian specimens found in living colonies of a stony coral around islands off the coast of the State of Sao Paulo, Southeastern Brazil. This species, previously known from one specimen collected in Ecuador, shows considerable variation of characters considered very important for the taxonomy of the genus, such as the shape of prostoraium and eyes. Variable features within this species and size-dependent characters are discussed. This study improves the knowledge not only of this particular taxon but also about the possibility of variation in related taxa. Scalibregmatids are a small family of polychaetes, including 15 genera, and are known mostly from deep-sea bottoms, al-though several species live in shallow water (Blake 2000). The group has been studied mainly by Ash worth (1901), Chamberlin (1919), Fauvel (1927), Day (1967), and, more recently, by Kudenov & Blake (1978), Blake (1981, 2000), and Kudenov (1984, 1985). The most important taxonom-ic characters are: the shape of the prosto-mium, usually with two anterior horns; the presence and shape of eyes; the presence of anterior acicular spines and the number of setigers with those setae; the shape of para-podia and the presence or absence of dorsal and ventral cirri; in branchiate taxa, the shape of branchiae and the number of seg-ments bearing them; and the ratio between the tynes of lyrate setae (see Blake 1981, 2000; Kudenov 1984). In Brazil, the only records for the family come from Hartman (1965), Bolivar (1990), and Attolini (1997). Hartman (1965) iden-tified Asclerocheilus intermedius (Saint-Jo-seph, 1894) from the Brazilian slope, at depths of 780 m, while the other authors recorded the presence of Scalibregma infla-tum Rathke, 1843 in the states of Sao Paulo and Rio de Janeiro, respectively, in sandy and muddy sediments, from 12—197 m in depth. Asclerocheilus tropicus Blake, 1981 was described from a single specimen collected in Ecuador at a depth of 8-9 m. Due to the lack of material, Blake (1981) could not note the variation this species presents in features considered important for the tax-onomy of the family, such as the shape of prostomium and eyes. Thirty-two specimens of this species were found in living colonies of the mas-sive stony coral Mussismilia hispida (Ver-rill, 1868) in shallow water, around islands of the state of Sao Paulo. Due to the meth-odology utilized, it is not possible to locate precisely the place occupied by the worms in the corals or the relationship between them and the hosts, if any exists at all. In this paper, Asclerocheilus tropicus is redescribed based on the analysis of these Brazilian specimens, and an evaluation of variable and size-dependent features is giv-en. Materials and Methods Twelve colonies of Mussismilia hispida were collected at Laje de Santos (24°19'S,
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