The genus Nereiphylla Blainville, 1828 is one of 18 genera in the family Phyllodocidae Örsted, 1843. The genus is widely distributed from intertidal to deep sea and it is known to inhabit both soft and rocky bottoms (Kato and Mawatari, 1999; Eklöf et al., 2007). To date, 11 valid species of this genus have been classified worldwide (WoRMS, 2019). Among them, three Nereiphylla species, N. castanea (Marenzeller, 1879), N. crassa Imajima, 2003, and N. hera Kato and Mawatari, 1999 have been recorded from the East Asia (Izuka, 1912; Imajima and Hartman, 1964; Paik, 1982, 1989; Kato and Mawatari, 1999; Imajima, 2003). Nereiphylla hera, originally described from Hokkaido in northern Japan, has been found in the eastern coast of South Korea (Choi et al., 2015). This species has been distinguished easily from its relatives through the following morphological features: the tentacular cirri are flat, spatulate with narrowly distinct tips that are broader than their cirrophores, the parapodia possess elongated dorsal cirri(Kato and Mawatari, 1999; Choi et al., 2015).
Recently, in the polychaete taxonomy, the cytochrome c oxidase subunit I (COI) DNA barcode has been in common use for the identification of the species and the revision of the traditional taxonomy based on the morphology (Carr et al., 2011; Choi et al., 2017; Park and Kim, 2017). Nevertheless, as of 16 July 2019, GenBank contained only three COI sequences of two Nereiphylla species, N. lutea (Malmgren, 1865) from Norway and N. castanea (Marenzeller, 1879) from Canada (Eklöf et al., 2007; Carr et al., 2011).
In this study, we determined the first COI sequences of N. hera and attempted to verify the effectiveness of the DNA barcoding for Nereiphylla in comparison with closely related species.
The specimens of N. hera were collected from Goseonggun (38°10ʹ17ʺN, 128°37ʹ40ʺE), South Korea. Their morphological characterization was carried out under a light microscope (Carl Zeiss Axioskop II, Göttingen, Germany) on the basis of Choi et al.(2015). Photographs of specimen were captured using an image system (LAS V4.7, Leica Microsystems, Heerbrugg, Switzerland) and presented in Fig 1. The voucher specimens were deposited in the National Marine Biodiversity Institute of Korea (MABIKNA00146571-00146572, 146575). Genomic DNA extraction and sequencing followed the methods of Maturana et al.(2011). The newly obtained sequences were deposited in GenBank under accession numbers MN126596-MN126598 and aligned with the congeners (N. lutea and N. castanea) using Geneious Pro v.9.1.8 (Biomatters, Auckland, New Zealand). The genetic distances calculated using the Kimura-2-parameter(K2P) model by MEGA X software (Kumar et al., 2018).
RESULTS AND DISCUSSION
The length of COI sequence alignment was 658 bp for three Nereiphylla species. The intra-specific variations of N. hera were 0-0.4% (Table 1). The inter-specific variations among Nereiphylla species ranged from 18.8 to 22.3%. Consequently, the gap between intra- and inter-species variations was consistent with those obtained in the previous study for Southern European Atlantic polychaetes(Lobo et al., 2016).
Table 1. Genetic distance (K2P) based on 658 bp size of COI sequence among three Nereiphylla species
In this study, we reported the first COI barcodes for N. hera with the morphological diagnosis and the photographs. These results would be helpful to understand taxonomy of phyllodicd polychaetes, although further analysis of undetermined taxa is considered for the COI DNA barcoding and its application.
Order Phyllodocida Örsted, 1843
Family Phyllodocidae Örsted, 1843
Genus Nereiphylla Blainville, 1828
Nereiphylla hera Kato & Mawatari, 1999 (Fig. 1)
Nereiphylla hera Kato and Mawatari, 1999: 353, figs. 1-3; Choi et al., 2015: 279, fig. 1.
Fig. 1. Photographs of Nereiphylla hera Kato & Mawatari, 1999 in the eastern coast of South Korea, lateral view (A) and anterior region (B). Scale bars: A=1.0 mm, B=0.5 mm.
Diagnosis. Prostomium with 4 antennae and paired eye and median antenna absent. Proboscis with numerous minute papillae irregularly distributed. Nuchal papilla absent. Tentacular cirri flattened, 4 pairs, with narrowly distinct tip. Tentacular formula: (1+S1/1)+S1/N. Segments 1 and 2 fused dorsally. Segment 2 without neuropodia and with setae only. Parapodia uniramous, with neuropodia and well developed dorsal and ventral cirri. Dorsal cirri heart-shaped, elongated, partially covered dorsum. Ventral cirri expanded, boarder than neuropodia. Chaetae composite with rostrum of chaetal shaft with distal crown bearing numerous teeth. Pygidium with two cirri slightly flattened.
This work was supported by the grants of National Marine Biodiversity Institute of Korea (2019M00100).