Joeropsis denticulatus sp. nov.

Figs 2A, 3, 4, 5

Material examined.

Holotype, designated here: South Korea • 1 ♂ (5.0 mm); Jeju-do, Jeju-si, Chuja-myeon, Chujado Island; 33°55'18"N, 126°19'27"E; 20 m; 17 Apr. 2019; Smith-McIntyre grab; NIBRIV0000862803.

Paratypes: 2 ♂♂ (4.2, 4.8 mm), 3 ♀♀ (3.6, 3.8, 3.8 mm); same data as for holotype; NIBRIV0000896084 .

Additional material.

South Korea • 1 ♂; Jeju-do, Jeju-si, Udo-myeon, Udo Island; 33°31'38"N, 126°57'14"E; 17 Apr. 2019; 15 m; Smith-McIntyre grab • 5 ♂♂, 4 ♀♀; Jeju-do, Seoqwipo-si, Daejeong-eup; 33°11'24"N, 126°16'08"E; 31 Jan. 2018; 30 m; Smith-Mclntyre grab; NIBRIV0000862803 • 1 ♂; Jeollanam-do, Sinan-gun, Jangsan-myeon, Baegyado Island; 34°22'24"N, 126°00'15"E; 12 Apr. 2018; 10 m; SCUBA diving • 1 ♂; Jeollanam-do, Yeosu-si, Samsan-myeon, Sangbaeckdo Island; 34°03'15"N, 127°35'00"E; 15 m; 28 Jun. 2017; SCUBA diving .

Etymology.

The specific name, Joeropsis denticulatus, is derived from the Latin word Joeropsis denticulatus, meaning "with small teeth". This name refers to pereopods possessing serrate cuticular scales.

Description of holotype male.

Body (Figs 2A, 3A) almost 3.9 × longer than width; dorsal surface matte, smooth, without setae. Cephalon 0.7 × as long as wide; lateral margins narrowing anteriorly; eyes positioned sublaterally, globular, dark brown, dorsally bulging. Pseudorostrum (Fig. 3B) 0.7 × as long as proximal wide, narrowing anteriorly; apex rounded. Pereonites not compact; lateral margins smooth. Pleotelson ~ 1.0 × longer than greatest width, shield-shaped, tapering distally; caudomedial lobe subacute, tapering distally; lateral margins slightly convex, with 8 spines.

Antennula (Fig. 3C), peduncular article 1 rectangular, 1.4 × longer than width, with serrate cuticular scales distally, 5 simple setae along with lateral margin, 1 penicillate seta distally, and 5 penicillate setae medially; article 2 oblong, 0.5 × as long as article 1, with 1 simple seta and 2 penicillate setae distally, and cuticular scales laterally; article 3 oblong, 0.6 × as long as article 2, with 2 simple setae laterally and 3 simple setae distally; flagellar article 1 almost 0.5 × as long as peduncular article 3, with 1 penicillate seta and 1 simple seta distally; article 2 ~ 2.0 × longer than flagellar article 1, with 2 simple setae and 2 aesthetascs distally, and 1 simple seta laterally; article 3 minute, with 4 simple setae, 1 penicillate seta, and 1 aesthetasc on distal end. Antenna (Fig. 3D, E) with 10 flagellar articles; peduncular article 3 with 1 process on medial margin; article 5 1.4 × longer than articles 1-4 combined, with serrate lateral cuticular scales and 1 medial process proximally; article 6 0.7 × as long as article 5, widening distally, with serrate cuticular scales, 3 penicillate setae, and several simple distal setae; flagellum with numerous simple setae; flagellar article 1 elongate ovoid, 1.8 × longer than remaining articles combined, 1.3 × longer than peduncular article 6, with cuticular scales laterally.

Mandibles (Fig. 3F, G), molar process distal half finely serrated; incisor with 5 cusps; palp article 2 with serrate setae distally; palp article 3 with serrate setae along with lateral margin. Left mandible (Fig. 3F) with a protrusion between incisor and molar process; spine row composed of 12 serrate setae. Right mandible (Fig. 3G), spine row consisting of 10 serrate setae. Maxillula (Fig. 3H), mesial lobe with 3 robust simple setae and several fine setae distally; lateral lobe with 12 strongly serrate robust setae and several fine setae on distal region. Maxilla (Fig. 3I), mesial lobe shorter than other lobes, with 4 simple setae distally and fine setae along with medial margin; mesial and outer lobes with 4 serrate setae distally. Maxilliped (Fig. 3J, K), endite expanding half of palp article 4, with several short simple setae on medial surface and 2 coupling hooks on medial distal end; distal region of endite rounded and serrated while concave medially, with 4 medial tubercular robust setae; palp article 1 with 2 simple setae distally, article 2 2.8 × longer than article 1, with distally bifid mesial lobe, article 3 square, 0.4 × as long as article 2, with several simple setae distally, article 4 3.0 × longer than article 3, with fine setae on medial margin and several setae laterally, article 5 0.2 × as long as article 4, with several simple setae on distal end; epipod 3.4 × longer than basal width, tapering distally.

Pereopods (Fig. 4A-G), basis and ischium with serrated cuticular scales superodistally; carpus with slightly serrated cuticular scales inferodistally; propodus with 2-4 robust setae inferiorly and numerous short simple setae along with inferior margin. Pereopod 1 (Fig. 4A), basis with 1 penicillate seta superiorly; ischium subequal to basis in length, narrowing proximally; merus 0.6 × as long as ischium; carpus 1.7 × longer than merus; propodus 0.9 × as long as carpus, with 1 penicillate seta on superior distal angle; dactylus 0.2 × as long as propodus, with 2 claws and 1 penicillate seta distally. Pereopods 2-7 (Fig. 4B-G) similar to each other; basis longer than ischium, with 0-2 penicillate setae on superior margin; ischium convex superomedially; carpus ~ 2.0 × longer than merus, with 1 penicillate seta superodistally; propodus similar to carpus in length, with 1 penicillate seta superodistally; dactylus ~ 0.2 × as long as propodus, with 3 claws distally.

Pleopod 1 (Fig. 5A) 2.6 × longer than greatest width, slightly concave laterally, narrowing distally; distolateral lobe projected, extending distally; apical lobe rounded, with marginal simple setae distally. Pleopod 2 (Fig. 5B), protopod 2.7 × longer than mid-width, concave distolaterally bearing cuticular scale-setae, with subacute distal end; endopod positioned at 0.7 length of protopod from proximal region; exopod curved outwardly; appendix masculina reaching distal end of protopod, tapering distally. Pleopod 3 (Fig. 5C), endopod 2.1 × longer than width, with 3 plumose setae distally; exopod with cuticular scale-setae along with lateral margin, first article 3.8 × longer than width; second article 0.4 × longer first article. Pleopod 4 (Fig. 5D), endopod 2.2 × as long as wide, tapering distally; exopod vestigial. Pleopod 5 (Fig. 5E) without exopod; endopod 2.0 × as long as wide, tapering distally.

Uropods (Figs 3A, 5F), protopod extending beyond margin of pleotelson, with strongly produced distal end, serrated medial margin, and 5 simple setae on distal region; endopod with 2 penicillate setae and several simple setae distally; exopod smaller than endopod, with several simple setae distally.

Description of female.

Female similar to male. Pleopod 2 (Fig. 5G) 1.4 × longer than greatest width, tapering distally, with fine setae on distal region; apex subacute, with 2 simple setae.

Size.

Males 4.2-5.0 mm, mean 4.7 mm (n = 3); females 3.6-3.8 mm, mean 3.7 mm (n = 3); all from type series.

Colour pattern.

Whole body is covered with dark brown chromatophores (Figs 2A, 3A).

Variation.

The colour pattern of the body varies between individuals, especially on pereonite 5. Dark brown chromatophores are occasionally faint or not observable on it.

Distribution.

South Korea (southern coast of the Korean Peninsula).

Remarks.

Joeropsis denticulatus sp. nov. can be identified by the following character states: (1) whole body has chromatophores dorsally; (2) lateral margins of the cephalon are smooth and narrowing anteriorly; and (3) basis of pereopods has serrated cuticular scales superiorly.

Among the total of 77 species, Joeropsis denticulatus sp. nov. is similar to five Joeropsis species in having the laterally smooth and narrowing cephalon, anteriorly rounded pseudorostrum, medially lobed maxillipedal palp article 2, laterally serrated pleotelson, and medially serrated uropods: J. adusta Bruce, 2015; J. affinis Kussakin, 1961; J. brevicornis Koehler, 1885; J. dubia Menzies, 1951; and J. salvati Müller, 1989. Among them, J. denticulatus sp. nov. most closely resembles J. dubia in terms of pereopods with serrated cuticular scales on ischium, but the former can be distinguished from the latter by having pereopod 1 bearing serrated cuticular scales on the basis (vs. lacking serrated cuticular scales in the latter) and distally rounded pleopod 1 in males (vs. distally triangular in the latter) (Menzies 1951; Kussakin 1999). The new species can be distinguished from the remaining four species in terms of maxillipedal palp article 2 (having distally bifid medial lobe vs. having not in the latter species) and pereopods (having serrated cuticular scales on the basis in the former vs. lacking in the latter species) (Koehler 1885; Bocquet and Lemercier 1958; Amar 1961; Kussakin 1961, 1999; Kensley 1975; Müller 1989; Bruce 2015). A detailed comparison of Joeropsis species mentioned above is provided in Table 2.