ABSTRACT
Forty species of unstalked crinoids (Order Comatulida) in 20 genera and five families were collected at 24 reef sites (maximum depth: 50 m) on the north coast of Papua New Guinea chiefly in the Nagada Harbor area north of Madang. Taxonomic revisions will probably reduce this figure to about 35 species. This is the first detailed SCUBA-based survey of crinoids within the East Indian Region, the area that supports the richest living crinoid fauna in the world. Given the limited sampling effort, faunal richness compares well with more intensively investigated assemblages on the Great Barrier Reef and at Palau. Nocturnal censusing (25-m2 transects) reveals mean densities of 3–23 crinoids m−2 on shallow reefs (1.5–4 m) with a maximum of 115 m−2. Several comasterid species exhibit parallel morphological variations apparently in response to a flow energy gradient; specimens in shallow (<4 m) habitats subject to strong surge/wave action tend to have shorter, more numerous arms. The range of within-species morphological variation exhibited by several taxa challenges the validity of several traditional taxonomic characteristics, and underlines the difficulties that exist in understanding what constitutes a crinoid species.
