First Application of Morphometrics in a Study of Variations in Uncinial Shape Present within the Terebellidae (Polychaeta)

75 *To whom correspondence and reprint requests should be addressed. E-mail: [email protected] The Terebelliformia (sensu Rouse and Pleijel 2001) is a group of sedentary polychaetes comprising the families Terebellidae, Ampharetidae, Alvinellidae, and Pectiinaridae. Within the taxon Terebelliformia, the family Terebellidae contains more than 400 species grouped in approximately 60 genera within 4 subfamil ies: Polycirrinae, Thelepodinae, Trichobranchinae (Rouse and Pleijel 2001, Garraffoni and Lana 2004), and Terebellinae (Holthe 1986, Hutchings 2000, Rouse and Pleijel 2001). The Terebellidae is characterized by anterior grooved buccal tentacles, which are used to transport fine surface particles to the mouth (Fauchald and Jumars 1979, Hutchings 2000, Rouse and Pleijel 2001), and neurochaetae modified as uncini which have an anchor-like function (Hutchings 2000, Rouse and Pleijel 2001), allowing them to anchor their soft body within tubes in order to avoid the risk of predation (Holthe 1986, Woodin and Merz 1987). Exceptions are found in the genera Hauchiella Hartman, 1959; Enoplobranchus Webster, 1879; and Lysilla Malmgren, 1866, which lack neurochaetae, and the genus Amaeana Levinsen, 1893, which has neurochaetal spines rather than uncini. These 4 genera are included within the terebellid subfamily Polycirrinae. Analyses of neuropodial uncini in the families Terebellidae, Ampharetidae, Alvinellidae, and Pectiinaridae have shown that most morphological variation occurs in suprageneric taxa (Holthe 1986). In spite of these differences observed in each family, however, it is possible to find some common patterns. All uncini of the Terebelliformia have a main fang, an upper part or capitium (with numerous secondary teeth arranged in different positions), and a lower part, where a subrostral process can be present or absent (and a base called a manubrium) (Holthe 1986, Bartolomaeus 1995, Garraffoni and Lana 2004). Morphometrics allow rigorous quantitative analysis of variations in organism size from shape First Application of Morphometrics in a Study of Variations in Uncinial Shape Present within the Terebellidae (Polychaeta)