Neastacilla paralongipectus sp. nov. Figures 12, 13, 14, 15

Material examined.

Holotype. South Korea • 1 ♂ (10.2 mm); Jeju-do, Seogwipo-si; 33°13'00"N, 126°19'30"E; 30 m; 31 Jan. 2018; Smith-McIntyre grab; NIBRIV0000862799.

Paratypes. South Korea • 1 ovigerous ♀ (3.3 mm); Jeju-do, Seogwipo-si; 33°13'12"N, 126°32'12"E; 33 m; 1 Feb. 2018; Smith-McIntyre grab • 1 ovigerous ♀; Jeju-do, Seogwipo-si; 33°11'24"N, 126°18'18"E; 30 m; 28 Apr. 2018; Smith-McIntyre grab • 1 ♂; Jeju-do, Seogwipo-si; 33°13'54"N, 126°36'24"E; 38 m; 26 Apr. 2018; Smith-McIntyre grab; NIBRIV0000880422.

Description of holotype male.

Body (Fig. 12A, B) 10.2 mm, smooth, 12 × as long as wide. Cephalon (Fig. 12A, B) with deeply concaved anterior margin possessing small median process; anterolateral lobe expended anteriorly; eye large, round, positioned on lateral margin. Pereonites II and III subequal in length; pereonite IV elongated, ~ 7 × longer than pereonites II and III together; pereonites V-VII ~ 1.9 × longer than pereonites II and III, surface of pereonites with small tuberculate elevations possessing setae. Pleon 1.3 × longer than pereonites V-VII; pleotelson gradually tapering posterior region; apex rounded; lateral margin with two pairs of wings; proximal wing indistinct, but distal wing distinct.

Antennule (Fig. 13A) over second peduncular article of antenna, consisting of three peduncular articles and single-articled flagellum; peduncular article I square to globular, articles II and III cylindrical; article II slightly longer than article III; flagellum elongated oval, with five aesthetascs along with anterodistal region and three simple setae on distal end.

Antenna (Fig. 13B, C) slender, exceeding half of body length, composed of five peduncular articles and 3-articled flagellum; peduncular articles I and II subequal to each other; article IV longest; article V slightly shorter than article IV; articles IV and V with I-III pairs of simple setae; flagellar articles I and II with one row of spines resembling saw-teeth, article II with five simple setae on distal end.

Left mandible (Fig. 13D), incisor 3-toothed; lacinia mobilis 2-toothed, with three serrated setae; molar process broad, rough distally. Right mandible (Fig. 13E), incisor 3-toothed; lacinia mobilis 3-toothed, with one serrated seta; molar process, strongly serrated distally. Maxillule (Fig. 13F) with fine setae on lateral margin; inner lobe with one plumose seta and two distally bifid simple setae on distal end; outer lobe with four serrated robust setae and five robust simple setae on distal end. Maxilla (Fig. 13G) with fine setae laterally, consisting of three lobes; inner lobe with six stout circum-plumose setae, three plumose setae, four simple setae; mesial lobe with three comb setae; outer lobe with three plumose setae. Maxilliped (Fig. 13H), endite rounded distally, almost 1.2 × wider than palp article III, with two coupling hooks medially, seven circum-plumose setae distally, one plumose seta mesially; palp article I with one plumose seta on mesial margin; article II with three plumose setae on medial margin; article III with 15 plumose on medial margin; article IV with five plumose setae medially and three simple setae distally; article V with six simple setae apically.

Pereopods I-IV (Fig. 14A-D) slender, sequentially longer, without unguis and flexion between carpus and propodus. Pereopods V-VII (Fig. 14E-G), sequentially shorter. Pereopod I (Fig. 14A) shorter than pereopods II-IV; basis longest, with one penicillate seta and four simple setae on superior margin, one simple seta on superodistal angle; ischium to dactylus with numerous plumose setae on inferior margin, 0-4 plumose setae on distal end; carpus and propodus subequal in length; propodus with ten comb setae on dorsal margin; dactylus as long as wide. Pereopods II-IV (Fig. 14B-D), basis to propodus with numerous plumose setae along with inferior margin; merus to propodus with several short simple setae on inferior margin; basis ~ 1.2 × longer than ischium; ischium with oblique end distally; merus and carpus similar in length; dactylus reduced and claw-like. Pereopods V-VII (Fig. 14E-G) similar to each other; basis, with 3-7 penicillate setae on superior margin; ischium almost 1.7 × longer than merus; merus and carpus subequal in length, with one penicillate seta on superior margin in pereopod VI; propodus with two or three penicillate setae on superior margin; dactylus bi-unguiculate, secondary unguis tiny.

Penes (Fig. 12E) simple, fused, with acute apex.

Pleopod I (Fig. 15A), protopod rectangular, with four coupling hooks medially; rami subequal, plumose setae longer than rami; exopod with six long plumose setae apically and two plumose setae subbasally, slightly notched subbasally; endopod with eight long plumose setae distally. Pleopod II (Fig. 15B) resembling pleopod I; protopod rectangular, ~ 0.8 × shorter than protopod of pleopod I, with three coupling hooks on medial margin; exopod with ten long plumose setae on distal end, endopod with seven long plumose setae on apical end; appendix masculina 1.2 × longer than endopod, tapering distally. Pleopod III (Fig. 15C), protopod square to globular; rami rounded distally; exopod 1.6 × longer than endopod, without plumose setae, tapering distally; endopod with two plumose setae medially. Pleopods IV and V (Fig. 15D, E) resembling each other; protopod square to globular; rami with rounded distal margin; exopod almost 1.5 × longer than endopod, without plumose setae; endopod with one plumose seta subapically.

Uropod (Fig. 15F) elongated oval; protopod ~ 4 × longer than wide, with two plumose setae and several fine setae on subapical margin; exopod triangular, with numerous fine setae; endopod square to rectangular, with two simple setae on distal end.

Description of paratype female.

Body (Fig. 12C, D) ~ 10 × as long as wide, length 7.5 mm. Pereonite IV (Fig. 12C, D) ~ 5.4 × longer than pereonites II and III, shorter than male; anterolateral margins extended laterally. Oostegite IV (Fig. 12D) with suture line on posterior region.

Distribution.

Southern coast of Jeju-do in South Korea.

Habitats.

Sublittoral zone of sandy bottom.

Etymology.

The composite epithet of the specific name Neastacilla paralongipectus is a combination of the Greek prefix para - and the specific name of Neastacilla longipectus Nunomura, 2008, which means near longipectus, refering to the close resemblance to N. longipectus .

Remarks.

Seven species of Neastacilla have pereonite IV at least 5 × as long as pereonites II and III together in female as in the new species: N. algensis Hale, 1924, N. deducta Hale, 1925, N. kanowna King, 2003, N. lawadi King, 2003, N. longipectus Nunomura, 2008, N. monoseta (Guiler, 1949), and N. soelae King, 2003 (Hale 1924, 1946; King 2003b; Nunomura 2008). Among these species, Neastacilla paralongipectus sp. nov. is easily distinguishable from N. algensis, N. lawadi, and N. soelae in terms of the absence of dorsal tubercles on the cephalon in female (vs. presence in the latter species) (Hale 1924; King 2003b). Neastacilla paralongipectus sp. nov. is similar to N. deducta, N. kanowna, and N. monoseta in having a smooth body lacking dorsal elevations (King 2003b). However, Neastacilla paralongipectus sp. nov. differs from N. deducta, N. kanowna, and N. monoseta in that oostegite IV has suture posteriorly (vs. mesially in N. deducta and N. monoseta) and the pleotelson has rounded apex (vs. truncated in N. kanowna) (King 2003b). Neastacilla paralongipectus sp. nov. is easily distinguishable from N. longipectus in terms of the shape of the anterior margin of the cephalon (deeply concave in the former vs. slightly concave in the latter), the shape of the penes (elongated triangle in the former vs. rectangle in the later), and the structure of pereonite I and pleonite I (fused to cephalon and pleotelson, respectively, in the former vs. not fused in the latter) (Nunomura 2008).