New record of commensal scale worms, Arctonoe vittata (Grube, 1855) and Hyperhalosydna striata (Kinberg, 1856) (Polychaeta: Polynoidae) from Korean waters

Abstract

IntRoductIon Most polychaete annelids are free­living, crawling, tube­dwelling and burrowing. However, some poly­ chaetes are closely related with other invertebrates. Polychaete worms and other invertebrates in a commen­ sal relationship have been studied comprehensively by Paris (1955), Clark (1956), Britayev (1989), Martin and Britayev (1998), and Tokaji et al. (2014). More than 292 species are known commensal poly­ chaetes, of which >55% are polynoid scale worms. These scale worms are closely related with gastropods, echinoids, asteroids, holothuroids, cnidarians, decapods, and even in tube of other polychaetes (Martin and Brita­ yev, 1998). Two commensal polynoid scale worms, Arctonoe vittata (Grube, 1855) and Hyperhalosydna striata (Kinberg, 1856) were collected for the first time in Korean waters from the East Sea and Jeju­do Island, respectively. Arctonoe vittata has a symbiotic relationship with asteroids, holo­ thuroids, and gastropods. In this study, we identified sym­ biotic relationship with nudibranchs for the first time. Hyperhalosydna striata is known as both free­living or associated with eunicid polychaetes (Hanley and Bruke, 1991). Four specimens were collected under the rocks in free living conditions but one specimen was collected in a tube of eunicid polychaete. We provided descriptions, detailed illustrations and ecological photographs of two species based on Korean materials. MateRIals and Methods Specimens of present study were collected by SCUBA diving from subtidal zones in the East Sea and Jeju­do Island, Korea. Worms were fixed in 80% ethanol imme­ diately and then transferred to 80% ethanol in the lab­ oratory. Specimen observation was carried out using a Nikon SMZ 1500 stereomicroscope and a Nikon Eclipse 80i compound microscope with differential interference contrast (DIC) optics. Measurements and sketches were Two scale worms of the family Polynoidae, Arctonoe vittata (Grube, 1855) and Hyperhalosydna striata (Kingberg, 1856) were found for the first time from Korea by SCUBA diving survey. The two species are free­living organisms or associated commensally with a wide variety of other invertebrates. Specimens of A. vittata were collected from the East Sea and were closely associated with asteroids, holothuroids, gastropods and nudibranchs species. Specimens of H. striata were collected from Jeju­do Island, and of these, one specimen was collected in a tube of eunicid species. The two species can be easily distinguished from their congeners by distinct morphological characteristics as follows: (1) A. vittata has pigmented band near segment eight and two kinds of neurochaetae; (2) H. striata has reddish­brown longitudinal striped elytra. The morphological key characteristics of both species agreed well with their original descriptions and redescriptions. In this study, the descriptions, detailed illustrations and ecological photographs of two species based on Korean materials were provided.