Symbiotic polychaetes from Papua New Guinea associated with echinoderms, with descriptions of three new species

Six species of symbiotic polychaetes, three of them new to Science, were found in association with echinoderms collected in Papua New Guinea. More than 500 echinoderms were sampled, on (or in) which occurred ca.185 polychaetes. About 25% of the echinoderms were infested. The number of polychaetes per host infested was from one to four. Crinoids were the most infested, then ophiuroids, asteroids, and holothuroids. No polychaetes were observed on echinoids. The polynoid scaleworm Gastrolepidia clavigera, a well known symbiont with a wide Indo-Pacific distribution, was found on four species of holothurians. The polynoid Hololepidella millari sp. nov. infested species of two asteroids and one crinoid; the polynoids Paradyte crinoidicola and Hololepidella laingensis sp. nov. both occurred on 24 species of crinoids. Hololepidella nigropunctata and the phyllodocid Eumida ophiuricola sp. nov. were associated with two ophiuroid species. E. ophiuricola was found in the ophiuroid bursae while the five former species were ectosymbionts. E. ophiuricola is the second registered symbiotic species among the phyllodocids. The polychaetes are described and notes on their taxonomy and ecology are given, together with a list of the host species.