Apanthura koreaensis, Song, Ji-Hun & Min, Gi-Sik, 2015

Song, Ji-Hun & Min, Gi-Sik, 2015, Two new species, Caenanthura koreana sp. nov. and Apanthura koreaensis sp. nov. (Crustacea: Isopoda: Anthuridae) from South Korea, Zootaxa 3937 (2), pp. 362-376 : 368-374

Apanthura koreaensis sp. nov.

( Figs 5–7 )

Material examined. Holotype (NIBRIV0000307412): Non-ovigerous female ( Fig. 5 A), 7.8 mm in length, Boryeong-si (36°20´N, 126°31´E), Chungcheongnam-do, west coast of South Korea, muddy bottoms, depth 1.9 m, collected on 22 Feb 2004, coll. S. J. Song ( Fig. 1 ).

Paratypes (NIBRIV0000307413–0000307418): 6 females, same sampling location as the holotype. All collected on Feb 2004, coll. S. J. Song.

Diagnosis. Body elongate and slender, about 12.7 times longer than wide with no mid-dorsal pits. Eyes very small. Rostrum short, as long as anterolateral lobes. Pleon as long as pleotelson, and longer than pereonite 7. Pleonites 1–5 visible dorsolaterally. Antennular flagellum with 3 articles. Antennal flagellum with 5 articles. Maxillipedal palp with 3 articles (1–2 fused; 3 free; 4–5 fused). Pereopod 1 robust, propodus with palm not stepped or swollen. Uropodal endopod about 1.9 times longer than wide; exopod about 1.9 times longer than wide. Pleotelson 2.2 times longer than wide, with 2 basal statocysts.

2 palp

2 Pereonites

engimatica 10.8 2.8* (1–3 fuse Presence 2.5* Sub–equal

(Presence) 1, 4, 5, 6 4–5 fuse)

Measured by figures in the article.

A: Not available.

Description. Female holotype (NIBRIV0000307412): Body ( Fig. 5 A) length 7.8 mm, slender, about 12.7 times longer than wide; no setation or mid-dorsal pits. Eyes very small, black. Cephalon small, 1.3 times as long as wide; rostrum short, as long as anterolateral lobes. Pleon 1.3 times longer than wide, as long as pleotelson and pereonite 7. Pleonites 1–5 visible dorsolaterally.

Antennule ( Fig. 5 B) peduncle with 3 articles. Article 1 laterally with 1 plumose sensory seta; article 2 with 1 long simple seta and 2 plumose sensory setae; article 3 distally with 1 long simple seta. Flagellum with 3 articles. Article 3 with 4 simple setae and 2 aesthetascs.

Antenna ( Fig. 5 C) peduncle with 5 articles. Article 2 with 1 simple seta; article 3 with 1 simple seta; articles 4 and 5 distolaterally with 2 plumose sensory setae and 3–4 simple setae. Flagellum with 5 articles (last 4 articles minute) with numerous setae.

Maxilliped ( Fig. 5 D) palp with 3 articles (1–2 fused; 3 free; 4–5 fused). Article 3 with 5 simple setae; 4–5 fused articles smallest, triangular with 6 simple setae, not elongate.

Mandible ( Fig. 5 E) palp with 3 articles. Article 1 with 1 long seta distally; article 2 with 1 short seta and long seta; article 3 smallest with 3 apical setae. Incisor with 4 teeth.

Maxilla ( Fig. 5 F) with 6 stout distal teeth.

Pereopod 1 ( Fig. 6 A) robust; basis as long as ischium with 1 simple seta; ischium with 1 simple seta on ventral margin; merus with 1 simple seta on ventral margin, 2 simple setae on dorsal margin; carpus with 4 simple setae on ventral margin; propodus with palm not stepped or swollen, with 15 simple setae on ventral margin, 1 distal simple seta; unguis much longer than other pereopods.

Pereopod 2 ( Fig. 6 B) basis slightly longer than ischium; basis with 2 simple setae and plumose sensory setae; ischium with 2 simple setae on ventral margin, 1 simple seta on dorsal margin; merus with 5 simple setae on ventral margin, 2 simple setae on dorsal margin; carpus triangular, with 4 simple setae on ventral margin; propodus with 1 short robust spine and 7 simple setae on ventral margin, 1 distal simple seta and plumose sensory seta.

Pereopod 3 ( Fig. 6 C) generally similar to pereopod 2.

Pereopods 4 to 7 ( Fig. 6 D–G) similar, carpus with 1 thick spine and 3–4 simple setae on ventral margin. Dactylus of pereopod 7 margin by spinules. Unguis of pereopod 2 to 7 small.

Pleopod 1 ( Fig. 7 A) sympod with 3 retinaculae. Exopod 2.3 times longer than wide, surrounded distally and laterally by 24 plumose setae; endopod much more slender about one third of exopod width and slightly shorter than exopod, surrounded distally 5 plumose setae.

Pleopods 2 to 4 ( Fig. 7 B–D) similar, exopod surrounded distally by 13–14 plumose setae, 2 short plumose setae on lateral margin; endopod surrounded by 7–8 plumose setae.

Pleopod 5 ( Fig. 7 E) different shape, exopod widened distally with 15 plumose setae, 2 short plumose setae on lateral margin; endopod fringed with 6 setae.

Uropodal sympod ( Fig. 7 F) 1.6 times longer than wide, as long as endopod, laterally with 15 plumose setae.

Uropodal endopod ( Fig. 7 F) about 1.9 times longer than wide, distally and laterally about 26 simple setae; medially 3 plumose sensory setae. Endopod extends beyond apex of pleotelson.

Uropodal exopod ( Fig. 7 G, H) 1.9 times longer than wide, surrounded by about 46 plumose setae and 8 long simple setae.

Pleotelson ( Fig. 7 I) 2.2 times longer than wide, with 2 basal statocysts; apex with 4 setae; dorsally with 7 long simple setae and 6 short simple setae.

Molecular data. A 633 base pairs of CO1 sequence (GenBank accession number: KP225161 ) was obtained from one individual of A. koreaensis sp. nov. (NIBRIV0000307412). Sequence alignment did not contain any insertion or deletion. No stop codon was found during amino acid translation with invertebrate mitochondrial code.

Distribution. Apanthura koreaensis sp. nov. is known only from the western coast of the Korean Peninsula.

Etymology. The specific name ‘ koreaensis ’ is derived from the name of the nation from which the specimens were collected.

Remarks. The genus Apanthura contained many species distinguished only by slight morphological differences. For instance, some diagnostic characteristics are used to identify species in this genus: (1) the number of apical setae of article 3 on the mandibular palp; (2) the relative length between dorsal lobe and ventral lobe on the uropodal exopod ( Kensley 1979; Poore & Lew Ton 1985; Negoescu 1997). Apanthura koreaensis sp. nov. differs from previously reported species of Apanthura by having following unique combination of diagnostic characteristics: Propodus of pereopod 1 with palm not stepped; article 3 with three apical setae on the mandibular palp; uropodal exopod dorsal lobe not reaching as far posteriorly as the ventral lobe. Apanthura koreaensis sp. nov. is similar to A. trioculata Nunomura, 1993 with regard to features related to external appearance. These two species are similar in the following characteristics: (1) the general shape of the antennula and antenna; (2) the general shape of the pereopods; and (3) very small eyes. The new species, however, differs from A. trioculata in (1) the presence of lobes on the uropodal exopod; (2) the number of setae and shape on the mandibular palp; and (3) the shape of the cephalon. In A. trioculata , the shape of the uropodal exopod is elliptical, and not having any lobes; the mandibular palp is slender, article 1–2 with no setae and article 3 with two apical setae; the shape of the cephalon is inverted-triangular. In comparison, in the new species, the dorsal lobe is not reaching as far posteriorly as the ventral lobe on the uropodal exopod; the mandibular palp is plump, article 1 with one seta, article 2 with two setae, and article 3 with three apical setae; the shape of the cephalon is rectangular ( Table 2 ).

* Measured by figures in the article.

Figures

FIGURE 1. The type locality of two new species on the present study. 1, Caenanthura koreana sp. nov.; 2, Apanthura koreaensis sp. nov.

FIGURE 5. Apanthura koreaensis sp. nov., female. A, Body, dorsal view; B, Antennule; C, Antenna; D, Maxilliped; E, Mandible; F, Maxilla. Scale bars = 1 mm (A), 0.1 mm (B – F).

FIGURE 6. Apanthura koreaensis sp. nov., female. A, Pereopod 1; B, Pereopod 2; C, Pereopod 3; D, Pereopod 4; E, Pereopod 5; F, Pereopod 6; G, Pereopod 7. Scale bars = 0.2 mm (A – G).

FIGURE 7. Apanthura koreaensis sp. nov., female. A, Pleopod 1; B, Pleopod 2; C, Pleopod 3; D, Pleopod 4; E, Pleopod 5; F, Uropodal sympod and endopod; G, Uropodal exopod; H, Uropodal exopod (except setation); I, Pleotelson. Scale bars = 0.2 mm (A – I).

Tables

TABLE 2. Comparison based on selected diagnostic characteristics among Apanthura koreaensis sp. nov. and related species.

	Total length (mm)	Mandibular palp: number of setae of article 1, 2, 3	Uropodal exopod: dorsal lobe reaching or not reaching as far posteriorly as ventral lobe
A. koreaensis sp. nov.	7.8	1, 2, 3	Not reaching
A. trioculata	7.2	0, 0, 2	No lobes (elliptical)
A. harringtoniensis	6.0	1, 1, 2	Not reaching
A. tiomanae	4.5	1, 1, 1	Not reaching*
A. bruscai	3.4	1, 1, 4	Not reaching*
A. indonesiensis	5.3	1, 2, 2	Not reaching
A. monodi	4.3	1, 1, 2	Not reaching*
A. pariensis	4.8	1, 1, 1	Not reaching
A. wudu	7.7	0, 3, 3	Not reaching
continued.