Hangangbathynella mihoensis, Ji & Lee & Min, 2021

Ji, Su-Jung, Lee, Chi-Woo & Min, Gi-Sik, 2021, A new species of Hangangbathynella (Crustacea, Bathynellacea, Parabathynellidae) from South Korea, ZooKeys 1046, pp. 143-155 : 143

publication ID	https://dx.doi.org/10.3897/zookeys.1046.66141
publication LSID	lsid:zoobank.org:pub:EBF998BA-F525-437E-A2FC-EB59C8A2D908
persistent identifier	https://treatment.plazi.org/id/66F67C7D-E5E0-4C35-B7AA-2208792C239F
taxon LSID	lsid:zoobank.org:act:66F67C7D-E5E0-4C35-B7AA-2208792C239F
treatment provided by	ZooKeys by Pensoft
scientific name	Hangangbathynella mihoensis
status	sp. nov.

Treatment

Hangangbathynella mihoensis sp. nov.

Type locality.

Seokhwa-ri (36°38'09"N, 127°21'27"E), Cheongju-si, Chungcheongbuk-do, Korea. On a sandbank of the Miho Stream, collected by Hee-Min Yang and Su-Jung Ji (31 May 2019).

Type material.

Holotype: male, dissected on 9 slides (NIBRIV0000879484). Allotype: female, dissected on 12 slides (NIBRIV0000879485). Paratypes: 9 females (NIBRIV0000879486, NIBRIV0000879487, NIBRIV0000881724, and NIBRIV0000881737-881742) and 6 males (NIBRIV0000881731-881736).

Diagnosis.

Antennule seven-segmented without aesthetascs on the fifth segment, and with three simple setae on inner distal margin of the sixth segment; antenna seven-segmented with setal formula 0 + 0/0 + 0/1 + 0/1 + 1/0 + 0/0 + 2/4(1); labrum with 14 teeth; mandible palp two-segmented; maxilla four-segmented with setal formula 3-3(2)-10-6; exopod of thoracopods I-VII two-segmented; thoracopods III-VII each with an epipod; inner protuberance of male thoracopod VIII with three distal spinules; female thoracopod VIII with two teeth and two distal setae; uropod sympod with 8 to 10 spines of similar size; furcal ramus with 4 to 5 spines; anal operculum protruded.

Description of adult male

(Figs 2 View Figure 2 - 5 View Figure 5 ). Body length 1.13 mm (Fig. 2A View Figure 2 ), approximately 10 times as long as wide. Head as long as anterior three thoracic segments combined.

Antennule (Fig. 2B View Figure 2 ) seven-segmented, first segment with one small seta on inner distal margin, two simple dorsal setae of different sizes, three plumose setae on outer margin; second segment with two simple setae on inner distal margin, one group of four plumose setae on outer margin; third segment with one simple dorsal and one ventral seta on inner distal margin, and with two simple setae of different sizes and one tiny seta on outer margin; inner flagellum of third segment with three simple setae; fourth segment with one stub seta and one plumose seta on dorsal margin, two stub setae and two plumose setae on outer distal apophysis, which is slightly protruded; fifth segment with one dorsal simple seta, distally with two setae on inner distal margin; sixth segment with three simple setae on inner distal margin, two aesthetascs and one simple seta dorsally, one aesthetasc on outer margin; seventh segment with three subterminal aesthetascs and four distal simple setae.

Antenna (Fig. 2C View Figure 2 ) seven-segmented; as long as antennular segments 1-6 combined; setal formula 0 + 0/0 + 0/1 + 0/1 + 1/0 + 0/0 + 2/4.

Labrum (Fig. 2D View Figure 2 ) flat with eight median teeth of similar size, two central teeth slightly smaller than the rest, flanked by three teeth on each side; inner surface with two pairs of nipple-like lateral protrusions and with ctenidia and two tiny projections in middle region.

Mandible (Fig. 2E View Figure 2 ) with incisor process of four teeth; tooth of ventral edge triangular; spine row consisting of seven spines; palp two-segmented with one apical seta not exceeding incisor process in length.

Maxillule (Fig. 2F View Figure 2 ) two-segmented, proximal segment with four setae on distal margin; distal segment with two terminal dentated spines; five dentated spines on inner edge, and three simple setae on outer distal margin.

Maxilla (Fig. 2G View Figure 2 ) four-segmented, setal formula 3-3(2)-10-6.

Thoracopods I-VII (Figs 3A-E View Figure 3 , 4A, B View Figure 4 ) slightly increasing in size up to thoracopod IV, thoracopods IV-VII similar in size; thoracopods III-VII each bearing one epipod on protopod; basis of thoracopod I with two setae, that of thoracopods II-VII with one seta; exopod of thoracopods I-VII two-segmented; endopods of thoracopods I-VII four-segmented, setal formulae:

Thoracopod VIII (Figs 4C View Figure 4 , 6G, H View Figure 6 ) nearly rectangular in lateral view; main axis tilting backwards; protopod massive with prominent penial region displaying distal opening encircled by frontal, median lobes and dentated inner lobe with four dentils; epipod large, gourd-shaped, distal part hardly covering penial region; basis as large as one half of protopod, without setae; exopod round, one half of basis with two distal protuberances; outer protuberance serrated, inner one with three distal spinules; endopod small, with two distal setae.

First pleopod absent (Fig. 2A View Figure 2 ).

Uropod (Fig. 5A View Figure 5 ) with load-shaped sympod bearing eight spines of similar size on inner margin; endopod 28% as long as sympod length, with one large distal spur, two barbed setae and two plumose setae on dorsal surface; exopod longer than endopod, 50% as long as protopod, with one outer seta, two terminal setae and one inner medial seta; inner setae strong, longer and thicker than outer terminal seta.

Pleotelson (Fig. 5B View Figure 5 ) with one lateral seta on each side.

Anal operculum (Fig. 5B View Figure 5 ) protruded.

Furcal rami (Fig. 5B View Figure 5 ) slightly longer than wide, with four spines and two setae, longer one plumose and shorter one barbed.

Description of adult female.

The female differs from the male in thoracopod VIII. Thoracopod VIII (Fig. 6E View Figure 6 ) as a gourd-shaped protuberance with two distal setae and two tiny spines.

Antenna (Fig. 6A View Figure 6 ) seven-segmented, two proximal segments without setae; third segment with one simple seta on inner edge; fourth segment with one simple seta on inner edge and one simple seta on outer distal margin; fifth segment without setae; sixth segment with one simple and one plumose seta on outer distal margin; distal segment with three simple setae and one plumose seta. Labrum (Fig. 6B View Figure 6 ) with 14 teeth. Mandible (Fig. 6C View Figure 6 ) with incisor process of four teeth, tooth of ventral edge triangular, spine row consisting of seven spines. Maxillule (Fig. 6D View Figure 6 ) two-segmented.

Variation.

Body length 0.91-1.14 mm in female (six individuals, NIBRIV0000881737-881742), 1.04-1.13 mm in male (five individuals, NIBRIV0000881732-881736). Uropod protopod with eight to nine, rarely 10 spines. Furcal rami mostly with four spines but five on one side in NIBRIV0000881724 (Fig. 6F View Figure 6 ).

Etymology.

The species name is derived from the stream (Miho, a tributary of the Geumgang River) in which the species was collected.

Molecular analysis.

A total of 606 base pairs of COI sequences (GenBank accession numbers: MW429327, MW429328, and MW624440) were obtained from three individuals of Hangangbathynella mihoensis sp. nov. (NIBRIV0000879486, NIBRIV0000879487, and NIBRIV0000881724). The intra-specific distance of the COI sequences ranged from 0.5% to 1.0%. Although the phylogenetic relationships of Hangangbathynella could not be confirmed owing to the lack of molecular data on Korean bathynellaceans, this result suggests that COI will be useful in distinguishing Korean bathynellacean species in the future.