Hexapleomera ulsana, Wi, Jin Hee, Jeong, Man-Ki & Kang, Chang-Keun, 2018

Wi, Jin Hee, Jeong, Man-Ki & Kang, Chang-Keun, 2018, A new species of the genus Hexapleomera Dudich, 1931 from the South Korea, with molecular evidence (Crustacea, Tanaidacea, Tanaididae), ZooKeys 739, pp. 1-28 : 3-13

Hexapleomera ulsana sp. n. Figs 1, 2, 3, 4, 5, 6

Type-specimens.

Holotype. (MABIK CR00235364) ovigerous female dissected and mounted in eight slides, collected from the Ulsan of Korea (35°22'7.47"N, 129°21'25.47"E) in January 2016. Allotype. (MABIK CR00235366) male dissected and mounted in four slides, same locality as for holotype. Paratypes. Four females partially dissected and mounted in three slides (MABIK CR00235365), two slides (MABIK CR00240699), five slides (MABIK CR00240700), and two slides (MABIK CR00240701); two intact females in one vial (MABIK CR00240702); four males partially dissected and mounted in two slides (MABIK CR00235367), four slides (MABIK CR00240703), one slide (MABIK CR00240704), one slide (MABIK CR00240705); two intact males in one vial (MABIK CR00240706). Same locality as for holotype.

Diagnosis.

Uropod endopod 4-articulate. Pleopods 1-3 endopod with one seta on inner margin. Pleopod 3 basal article with four outer setae and no inner seta; pleopods 1-2 each with six outer setae and one inner seta on basal article. Pereopod 1 coxa lacking apophysis and having two dorsal setae. Pereopods 2-3 propodus with two simple setae and one bifurcated pinnate spiniform seta on ventral margin. Mandible setal row consists of two pinnate setae. A maxillule palp with four distal setae. Maxilliped coxa with three proximal setae; endite bearing two long plumose setae, two short plumose spiniform setae, and two simple spiniform setae. Dactylus of male cheliped with spinules along cutting edge.

Description of female.

Body (Fig. 1A): With developed brood sacs each with 20 eggs. Length 3.4 mm, 4.2 times as long as wide. Chocolate brown pigmentation on most of dorsal surface, including antennule and cheliped, patterned with un-pigmented lacunae. Cephalothorax with densely coalescing flecks but pereonites, pleonites, and pleotelson with scattered spots.

Cephalothorax (Fig. 1A): Posterolateral margin rounded, anteriorly narrowing, as long as wide, 22 % of body length, with two anterolateral simple setae, one mid-lateral seta, and posterolateral seta.

Pereon (Fig. 1A): About 55 % of body length, 2.3 times as long as wide, with several fine setae along antero, mid, and posterolateral margins. Pereonites 1-6 proportional lengths of 10.6: 13.3: 16.4: 14.9: 22.2: 21.5: 16.0.

Pleon (Fig. 1A): Pleonites 1-5 18.6 % of body length, 1.2 times as long as wide. Pleonites 1-3 gradually decreasing in width. Pleonite 1 0.8 times as long as pereonite 6, 0.3 times as long as wide, with one simple seta and two plumose setae on lateral margin. Pleonite 2 0.7 times as long as pleonite 1, 0.2 times as long as wide, with two simple setae and two plumose setae on lateral margin. Pleonite 3 almost as long as pleonite 2, 0.3 times as long as wide, with two simple setae. Pleonites 4 and 5 equal in length, each with two simple setae on lateral margin. Pleotelson 0.9 times as long as pleonite 1, half as long as wide, with two simple setae on mid-lateral margin, three simple setae and one broom seta on sub-posterolateral margin, and four simple setae of unequal length terminally.

Antennule (Fig. 1B): 4-articulate, proportional lengths of articles 60.5: 21.1: 16.9: 1.5. Length 68 % of cephalothorax. Article 1 2.7 times as long as wide, outer margin with four medial broom setae and five broom setae and two simple setae on distal margin; inner margin with two distal simple setae. Article 2 1.2 times as long as wide, with four broom setae and seven simple setae on distal and subdistal margins. Article 3 1.5 times as long as wide, with two broom setae and two simple setae on distal and subdistal margins. Article 4 very short, with seven simple setae and six aesthetascs.

Antenna (Fig. 1C): 6-articulate, slightly longer than antennule, proportional lengths of articles 16.6: 23.2: 12.3: 21.8: 18.8: 7.3. Article 1 naked. Article 2 with four simple setae, microtrichia, and setules along outer margin. Article 3 naked. Article 4 with three simple setae on distal margin. Article 5 with two simple and two broom setae. Article 6 with twelve simple setae on distal margin.

Labrum (Fig. 1D): Rounded, ornamented with numerous setules and microtrichia.

Left mandible (Fig. 1E): Incisor stout, smooth. Lacinia mobilis wide, with five denticles along distal margin. Setal row with two pinnate spiniform setae. Molar broad, corrugate and with several distal teeth. Right mandible (Fig. 1F): Incisor with several small denticles on distal margin. Lacinia mobilis reduced to blunt spine partly fused with incisor with small denticles on distal margin. Setal row with two pinnate setae of unequal length. Molar broad, with several distal teeth.

Labium (Fig. 2A): Wide, all lobes covered with setules on distal margin, with twelve lateral proximal spines (arrowed); labial palp rounded, 1.4 times as long as wide, with numerous setules.

Maxillule (Fig. 2B, B’): Endite with seven strong spiniform setae and one slender setulose seta on distal margin and patch of fine simple setae near base of terminal setae on outer margin, surface ornamented with microtrichia, and palp with four distal setae.

Maxilla (Fig. 2C): With sinuous distal margin (arrowed), covered with microtrichia.

Maxilliped (Fig. 2D): Coxa with three inner proximal simple setae. Basis twice as long as wide, with single subdistal seta, and covered with microtrichia. Palp article 1 with one outer subdistal seta. Palp article 2 with one outer seta and seven inner plumose setae. Palp article 3 with twelve inner plumose setae. Palp article 4 with twelve plumose setae. Endite with setules on distal margin, two long densely plumose setae, two setulose spiniform setae, and two round simple spiniform setae.

Epignath (Fig. 2E): With short blunt plumose seta terminally and fringed by setules (arrowed).

Cheliped (Fig. 2F, G): Basis 1.1 times as long as wide, with single seta each on dorsodistal and ventral margin. Merus triangular, with four ventral setae and two dorsal setae. Carpus 1.1 times as long as basis, 1.4 times as long as wide, with four ventro- subdistal setae and one dorso-subproximal and five dorsodistal setae. Propodus 1.3 times as long as carpus, 1.9 times as long as wide, with one plumose inner seta and four simple setae near insertion of dactylus. Fixed finger with five simple ventral setae, two inner simple setae, and six simple setae along cutting edge. Cutting edge distally expanded into rounded lamella. Dactylus with twelve small denticles along cutting edge and inner medial simple seta.

Pereopod 1 (Fig. 3A): Coxa without small apophysis, with two simple setae. Ischio-basis 4.3 times as long as wide, with one broom seta, one ventrodistal and one dorsodistal simple setae on dorsoproximal margin and one ventrodistal simple seta. Merus 0.3 times as long as ischio-basis, with one short ventrodistal simple seta. Carpus 1.2 times as long as merus, with two dorsal simple setae and one ventral simple seta. Propodus 2.1 times as long as carpus, with one distal simple seta and one broom seta on dorsal margin, three simple setae on ventro-subdistal margin, and one inner subdistal seta. Ischio-basis, merus, carpus, and propodus covered by microtrichia. Dactylus and unguis combined 0.6 times as long as propodus. Dactylus with simple seta on dorso-subproximal margin. Unguis 1.3 times as long as dactylus.

Pereopod 2 (Fig. 3B, B’): Ischio-basis 3.2 times as long as wide, with two broom setae and one simple seta on dorsoproximal margin and two ventrodistal simple setae. Merus 0.4 times as long as ischio-basis, with two simple setae and one spiniform seta on ventrodistal margin and one dorsodistal simple seta. Carpus 0.6 times as long as merus, with two spiniform setae and two slender setae on dorsodistal margin and two ventrodistal spiniform setae. Propodus 1.5 times as long as carpus, with two distal simple setae of unequal length and one dorsal broom seta and two simple setae and one short bifurcate pinnate spiniform seta on ventral margin (Fig. 3 B’). Dactylus and unguis combined half as long as propodus. Ischio-basis, merus, carpus, and propodus covered by microtrichia. Dactylus with one dorsoproximal simple seta. Unguis 1.4 times as long as dactylus.

Pereopod 3 (Fig. 3C): Ischio-basis 2.8 times as long as wide, with two broom setae and one simple seta on dorso-subproximal margin and two ventrodistal simple setae. Merus half as long as ischio-basis, setation equal to pereopod 2. Carpus 0.6 times as long as merus, with three ventrodistal setulose spiniform setae and two setulose spiniform setae and two slender setae on dorsodistal margin. Propodus 1.4 times as long as carpus, setation equal to that of pereopod 2. Ischio-basis, merus, carpus, and propodus covered by microtrichia. Dactylus and unguis combined as long as that of pereopod 2. Unguis 1.5 times as long as dactylus.

Pereopod 4 (Fig. 3D): Ischio-basis 2.7 times as long as wide, with two dorso-subproximal broom setae, one ventro-subdistal broom seta, and two ventrodistal simple setae. Merus 0.6 times as long as ischio-basis, with three dorsodistal setae and two setulose spiniform setae and one seta on ventro-subdistal margin. Carpus 0.7 times as long as merus, with two slender setae and five setulose spiniform setae on distal margin. Propodus 1.2 times as long as carpus, with one dorso-subdistal broom seta, three subdistal simple setae, and two ventral slender simple setae. Ischio-basis, merus, carpus, and propodus covered by microtrichia. Dactylus and unguis fused into claw, with comb-like lateral rows of five flattened setae distally.

Pereopod 5 (Fig. 4A): Ischio-basis 2.5 times as long as wide, with two dorso-subproximal broom setae and two ventrodistal simple setae. Merus 0.4 times as long as ischio-basis, with four simple setae and two seutlose spiniform setae. Carpus 0.8 times as long as merus, with five setulose spiniform plus two simple setae on distal margin. Propodus 1.4 times as long as carpus, setation equal to that of pereopod 4. Ischio-basis, merus, carpus, and propodus covered by microtrichia. Dactylus and unguis similar to those of pereopod 4.

Pereopod 6 (Fig. 4B): Ischio-basis 3.1 times as long as wide, with two dorso-subproximal broom setae and two ventrodistal setae. Merus 0.4 times as long as ischio-basis, with three dorsodistal setae and two setulose spiniform setae and two simple setae on ventrodistal margin. Carpus slightly longer than merus, with five setulose spiniform setae and three setae. Propodus 1.1 times as long as carpus, with seven flat tened denticulate spiniform setae and one simple seta on subdistal margin, one dorsal broom seta, two distal setae, and two ventral slender simple setae. Ischio-basis, merus, carpus, and propodus covered by microtrichia. Dactylus and unguis similar to those of pereopod 5.

Pleopod 1 (Fig. 4C, D): Basal article as long as wide, with one inner and five outer plumose setae. Exopod with 27 plumose setae along outer margin. Endopod with one inner and eleven outer plumose setae and one robust spiniform plumose seta bearing two spines and one setulose seta (arrowed in Fig. 4D).

Pleopod 2 (not figured): Similar to pleopod 1, except for outer margin of exopod with smaller plumose setae (26).

Pleopod 3 (Fig. 4E): Basal article lacking inner seta (arrowed) and with four outer plumose setae. Exopod with 24 outer plumose setae. Endopod with one inner plumose seta and ten outer plumose plus one robust setae.

Uropod (Fig. 1A, G): Basal article 1.7 times as long as wide, with three outer distal setae and two inner distal setae. Endopod 4-articulate.

Description of male.

Body (Fig. 5A): Length 3.4 mm, three times as long as wide. Pigmentation similar to female. Cephalothorax pear-shaped, one-third of body length, 1.1 times as long as wide, with antero- and mid-lateral simple setae, tapering towards to rostrum.

Pereon (Fig. 5A): 44 % of body length, 1.3 times as long as wide, with several fine setae along lateral margins. Pereonites 1-6 proportional lengths of 13.7: 13.2: 15.6: 21.0: 20.5: 16.0.

Pleon (Fig. 6A): Pleonites 1-5 18.1 % of body length, 0.7 times as long as wide. Pleonites 1-3 gradually decreasing in width. Pleonite 1 almost equal length of pereonite 6, 0.2 times as long as wide, with two simple and two plumose setae on lateral margin. Pleonite 2 0.7 times as long as pleonite1, 0.2 times as long as wide, with two simple and two plumose setae on lateral margin. Pleonite 3 slightly shorter than pleonite 2, 0.2 times as long as wide, with two simple setae on anterolateral margin. Pleonites 4 and 5 combined half as long as pleonite 3, 0.7 times as wide as pleonite 3, each with two lateral simple setae. Pleonite 4 with two anterodorsal setae. Pleotelson (Fig. 5A) about 0.7 times as long as pereonite 1, 0.3 times as long as wide, with three simple setae on sub-anterolateral margin, one broom seta and two simple setae on sub-posterolateral margin, and four simple setae of unequal length on distal margin.

Appendages similar to those of female except for antennule, antenna, mandible, maxilliped, cheliped, and uropod:

Antennule (Fig. 5B): 4-articulate, elongate. Proportional lengths of articles 63.3: 20: 15.4: 1.3. Length 1.7 times as long as cephalothorax. Article 1 5.6 times as long as wide, outer margin with three subproximal broom setae and two broom plus four simple setae on distal margin; inner margin with two medial simple setae and two broom and two simple setae on distal margin. Article 2 1.8 times as long as wide, with three simple setae and eight broom setae on subdistal margin. Article 3 2.3 times as long as wide, with two broom setae and four simple setae on distal margin. Article 4 small, with six aesthetascs and several simple setae on distal margin.

Antenna (Fig. 5C): 6-articulate, 0.8 times as long as antennule. Proportional lengths of articles 9.3: 24.1: 12.5: 29.5: 17.2: 7.4. Article 1 naked. Article 2 with one medial simple seta and two distal simple setae. Article 3 ornamented with microtrichia. Article 4 longest, with two distal simple setae. Article 5 with one broom seta and one simple seta on inner distal margin. Article 5 shortest, with one broom seta and ten simple setae on distal margin.

Left mandible (Fig. 5D): Incisor with small denticles along distal margin. Right mandible (Fig. 6E): Lacinia mobilis without distal denticles.

Cheliped (Fig. 6A): Much stouter than that of female. Basis 1.3 times as long as wide, with one ventrodistal simple seta and one dorsodistal simple seta. Merus subtriangular, ventrodistally protruded (arrowed), with two ventral simple setae and two dorsal setae. Carpus 1.1 times as long as basis, almost as long as wide, with two ventral protrusions (arrowed), two ventral simple setae, one dorsoproximal simple seta, and two dorsodistal simple setae. Propodus 2.1 times as long as carpus, 1.9 times as long as wide, with one inner plumose seta and four simple setae near dactylus insertion. Fixed finger with five ventral simple setae, two inner distal setae, and ten simple setae along cutting edge. Dactylus with 14 small denticles along cutting edge and inner medial seta.

Uropod (Fig. 6D): Basal article 2.2 times as long as wide, with four outer distal simple setae and three inner distal simple setae.

Cheliped of smaller male (Body length 2.1 mm) (Fig. 6B, C): Basis as long as wide. Merus with one ventral protrusion, two ventral simple setae, and two dorsal simple setae. Carpus with weakly developed protrusion on ventral margin. Propodus 1.5 times as long as carpus, 1.9 times as long as wide, with one inner plumose seta and four simple setae near dactylus insertion. Fixed finger with five ventral simple setae, two inner distal setae, small protrusion bearing small denticles (arrowed in Fig. 6C), and eight simple setae along cutting edge. Dactylus not extended and just weakly curved, and with proximal protrusion (arrowed in Fig. 6C) and small denticles along cutting edge.

Etymology.

The specific name refers to Ulsan, a harbour city near the type locality.

Remarks.

Hexapleomera ulsana sp. n. can be differentiated from other species of the genus by the following combination of characteristics (Table 1): in both sexes, 1) the uropod has five articles; 2) the basal article of the pleopod 3 lacks inner seta and has four outer setae; 3) the pereopod 1 coxa lacks apophysis; 4) the maxillule palp has four distal setae; in the maxilliped, 5) a coxa has three distal setae; 6) the basis has one subdistal seta; 7) each setal row of the right and left mandibles has two pinnate setae; and 8) the propodus of pereopods 2-3 each has two slender simple setae and one bifurcate spiniform seta on the ventral margin. Just as H. urashima , Hexapleomera ulsana lacks an inner seta on the pleopod basal article, has the same number of distal setae on the maxillule endite (6), setae of the mandible setal row (2), and ventral setae on the pereopods 2-3 propodus (3), but can be distinguished by the pereopod 1 coxa lacking apophysis (vs. presence), the number of uropod article (5 vs. 4), and the number of proximal seta on the maxilliped coxa (3 vs. 2). In addition, the findings of the maxilla forming a rugged shape on the distal margin and an epignath with substantially short and blunt spiniform distal seta are noted. In other species of Hexapleomera , the maxilla represents a simple and round shape, and the distal seta of the epignath is much slender. The cheliped of the smaller male is very similar to those of females without any trace of oostegites; however, it differs in the location of a protrusion on the dactylus and fixed finger. Particularly, the cutting edge of the fixed finger of the female is smooth, without a protrusion, while it has a weak protrusion with small denticles in the smaller male.