INTRODUCTION

The genus PentiasRichardson, 1904 is one of 22 genera belonging to the family Idoteidae Samouelle, 1819 that currently comprises four species (Poore and Schotte 2015). The genus Pentias is reported for the first time in South Korea.

We provide detailed descriptions of the diagnostic characteristics, illustrations and partial sequences of the mitochondrial cytochrome c oxidase subunit 1 (CO1) of the two species: Pentias hayiRichardson, 1904 and Pentias thompsoni Collinge, 1916. Additionally, a key to the worldwide species of Pentias is provided.

MATERIALS AND METHODS

1.Sample collection

The specimens of Pentias hayi and P. thompsoni were collected with light traps from Heuksan-do Island and Ulleung- do Island in South Korea, respectively. They were preserved directly in 95% ethyl alcohol after collection. All examined specimens were deposited in the National Institute of Biological Resources (NIBR) and Inha University, South Korea.

2.Morphological analysis

Specimens were observed and dissected under a stereomicroscope (Model SZX-7; Olympus, Tokyo, Japan). Illustrations of appendages were made with a drawing tube connected to a light microscope (Model DM 2500; Leica, X50- 630, Wetzlar, Germany). Drawings of whole bodies were made using a drawing tube attached to a stereomicroscope (Olympus SZX-12). Measurements of appendages and whole body lengths were taken using a stage micrometer (Leica, Germany) and an ocular micrometer.

3.DNA sequencing

The CO1 sequences were determined according to the method used in the paper by Song and Min (2015) with two primers: jgLCO1490 5′- TITCIACIAAYCAYAARGAYATT GG-3′ and jgHCO2198 5′-TAIACYTCIGGRTGICC RAA RAAYCA-3′(Geller et al. 2013).

RESULTS AND DISCUSSION

Order Isopoda Latreille, 1817 등각목

Suborder Valvifera Sars, 1882 유변아목

Family Idoteidae Samouelle, 1819 주걱벌레과

Genus PentiasRichardson, 1904

거친다리주걱벌레속 (신칭)

1.Pentias hayiRichardson, 1904 길쭉거친다리주걱벌레 (신칭) (Fig. 2)

Synonyms: Pentias hayiRichardson, 1904: 47, figs. 24, 25.

Material examined: Korea: 1 female (NIBRIV00003077 57), Heuksan-do Island, Sinan-gun, Jeollanam-do, 34°40′N, 125°26′E, Apr 3 2012, depth 3~4 m, collected with light traps by Song JH (Fig. 2).

Diagnosis: Body elongated, about 5 times longer than wide, 17.1 mm; coxae 6~7 occupy whole lateral margin. Maxillipedal palp with five articles. Pleotelson very long, with 3 incomplete sutures, almost equal in length to last five pereonites (3~7). All pereopods robust and short, with distinct bi-unguiculate dactylus. Coxal plates well visible dorsally on pereonites 2~7.

Remarks: In general, the material of Pentias hayi collected from South Korea is well agreed with the original description of Richardson (1904). Pentias hayi is very similar to P. namikawaiNunomura (2006) in external features. However, P. hayi differs from P. namikawai in the ratio between length and width in body; coxal plates on pereonites 2~7. Body almost 5 times longer than wide; coxal plates well visible dorsally on pereonites 2~7 in P. hayi. But, body almost 7.8 times longer than wide; coxal plates hardly visible dorsally on pereonites 2~7 in P. namikawai.

Habitat: This species collected from the South Korea on sandy and gravel bottom with some algae at 3~4 m depth.

World distribution: Japan (Richardson 1904), Korea.

Deposition: NIBR No. NIBRIV0000307757.

Molecular characteristic: GenBank accession number: KR261927.

Identifiers: Ji-Hun Song, Gi-Sik Min.

2.P entias thompsoni Collinge, 1916 넓적거친다리주걱벌레 (신칭) (Fig. 3)

Synonyms: Pentias thompsoni Collinge, 1916: 1, pl. 3, figs. 1-10. Fig. 2-3

Material examined: Korea: 1 female (NIBRIV00003144 09), Ulleung-do Island, Ulleung-gun, Gyeongsangbuk-do, 37°28′N, 130°54′E, Jul 20 2013, depth 3~4 m, collected with light traps by Song JH (Fig. 1).

Diagnosis: Body oblong ovate, about 3.5 times longer than wide, convex dorsally, 9.3 mm. Pleotelson narrower than pereonites 2~7, with 1 complete suture and 2 incomplete sutures. All pereopods robust and short, with distinct bi-unguiculate dactylus. Pleotelson have 1 complete suture and 2 incomplete sutures.

Remarks: In general, the material of Pentias thompsoni collected from South Korea is well agreed with the original description by Collinge (1916). Pentias thompsoni is distinctly different from all other species of Pentias: (1) pleotelson have 1 complete suture and 2 incomplete sutures (other species have 3 incomplete sutures) and (2) relative wider body, about 3.5 times longer than wide (more than 5 times longer than wide in other species).

Habitat: This species collected from the South Korea on sandy and gravel bottom with some algae at 3~4 m depth.

World distribution: Japan (Collinge 1916), Korea.

Deposition: NIBR No. NIBRIV0000314409.

Molecular characteristic: GenBank accession number: KR261928.

Identifiers: Ji-Hun Song, Gi-Sik Min.

3.Pentias arimotoiRafi, 1973 Synonyms: Pentias arimotoiRafi, 1973: 1041, figs. 1, 2.

4.Pentias namikawaiNunomura, 2006 Synonyms: Pentias namikawaiNunomura, 2006: 27, fig. 9.

Key to the worldwide species of the genus Pentias

1.The pleotelson with 1 complete suture and 2 incomplete

sutures (1+2)················································P. thompsoni - The pleotelson with 3 incomplete sutures (0+3)·············2

2. Pereonites 5~7 with dorsally invisible coxal plates·········· ··········································································P. arimotoi - Pereonites 5~7 with dorsally visible coxal plates···········3

3. Body almost 5 times longer than greatest width; coxal plates well visible dorsally on pereonites 2~7·······P. hayi - Body almost 7.7 times longer than greatest width; coxal plates hardly visible dorsally on pereonites 2~7··············· ······································································P. namikawai