A New Record of the Genus Pista (Polychaeta: Terebellidae) from Korea: The Validity and Redescription of Pista shizugawaensis

Abstract

A terebellid polychaete identified as Pista shizugawaensis Nishi and Tanaka, 2006, whose species validity has been doubted, is newly reported from the southwest coast of Korea. Korean materials of the present study have several characteristics that agree well with the original description of P. shizugawaensis as follows: two pairs of branchiae on the 2nd and 3rd segments have tufts composed of many dichotomously branched filaments; the nephridial papillae are present on the 6th and 7th segments; the uncini on the anterior and middle thoracic segments possess only long-handled shafts while those on the posterior ones have additional short-handled shafts or lacking shafts; the notosetae are broadly or narrowly winged capillary. The authors examined the taxonomic value of the presence of lateral lobes on the 5th and 6th segments, which has been known as a key characteristic feature of P. shizugawaensis in the classification of Pista species. In the present study, several characteristics such as the shape of notosetae, uncinial shafts in the thoracic segments, and the presence of thin narrow lateral lobes on the 4th segment are suggested as the specific characteristics that help to distinguish P. shizugawaensis from its congeners. A key to Pista species from Korean waters is also provided.

Review of genera within theAxionice/Pistacomplex (Polychaeta, Terebellidae), with discussion of the taxonomic definition of other Terebellidae with large lateral lobes

“…The differences described by Choi et al . (2015) in the notochaetae between their specimens and ours is no more than the difference seen through the compound microscope used by them and seen in the SEM used by us. Uncini without a manubrium in Axionice are normally present as a stage of development (see above), so the uncini without a manubrium reported by Choi et al .…”

“…Choi et al . (2015) did not agree and wrote: ‘ P. shizugawaensis differs from P. brevibranchiata referred by Leontovich and Jirkov (2011) in terms of the detailed shape of notosetae. P. shizugawaensis has broadly or narrowly winged capillary notosetae, while P. brevibranchiata has capillary notosetae bearing only small denticles on the surface.…”

“…Uncini without a manubrium in Axionice are normally present as a stage of development (see above), so the uncini without a manubrium reported by Choi et al . (2015) are either juvenile uncini or, more probably, uncini with broken manubria (it happens often and is not easily distinguishable). So we propose that Pista shizugawaensis should be accepted as a junior synonym of A. brevibranchiata or, more correctly, of A. agassizi (Hilbig, 2000), as A. brevibranchiata has never been described as required by the Code (see Hilbig, 2000 for taxonomic discussion). 2.…”