A new species of Decamastus Hartman, 1963 (Polychaeta: Capitellidae) from the Gulf of California, with remarks on its habitat

Abstract

This is the first report of Decamastus Hartman, 1963 in the Tropical Eastern Pacific, since two previous records were misidentified. Based on individuals from the continental shelf of the Gulf of California, Decamastus okuilin sp. n. is described, illustrated, and compared with the other species of the genus. The new species can be distinguished by the presence of a palpode in the anterior end of the prostomium, the first chaetiger bearing only notopodia, abdominal hooded hooks with more than 20 small teeth arranged in at least four rows above the main fang, and a methyl green staining pattern characterized by a uniformly light green staining in chaetigers 7–10 and dark speckles encircling segments in chaetigers 11 and 12. Its habitat is characterized by variations in dissolved oxygen, depth (44 to 94 m), and sandy bottoms. The methyl green staining pattern of D. gracilis Hartman, 1963, the other species found in the Pacific, is also described and illustrated.