Eoniphargus toriii, Shintani & Lee & Tomikawa, 2022

Shintani, Aki, Lee, Chi-Woo & Tomikawa, Ko, 2022, Two new species add to the diversity of Eoniphargus in subterranean waters of Japan, with molecular phylogeny of the family Mesogammaridae (Crustacea, Amphipoda), Subterranean Biology 44, pp. 21-50 : 21

publication ID	https://dx.doi.org/10.3897/subtbiol.44.86914
publication LSID	lsid:zoobank.org:pub:1865B081-1072-4900-BFC7-563C0D29DA7D
persistent identifier	https://treatment.plazi.org/id/2A3DFB47-9FEC-46E4-A003-923CCD93E20D
taxon LSID	lsid:zoobank.org:act:2A3DFB47-9FEC-46E4-A003-923CCD93E20D
treatment provided by	Subterranean Biology by Pensoft
scientific name	Eoniphargus toriii
status	sp. nov.

Treatment

Eoniphargus toriii View in CoL sp. nov.

Figs 2 View Figure 2 , 3 View Figure 3 , 4 View Figure 4 , 5 New Japanese name: Torii-chikayokoebi View Figure 5

Eoniphargus kojimai : Tomikawa et al. 2007, 647, figs 2-6.

Type material.

Holotype: ♂ 4.3 mm (NSMT-Cr 16652), Seto River (34.880555°N, 138.218888°E), Terajima, Fujieda, Shizuoka Prefecture, Japan, collected by T. Torii on 3 June 2004. Paratypes:2 ♀♀, 4.6 mm and 4.3 mm (NSMT-Cr 16653 and 16654), data same as for the holotype.

Diagnosis.

Urosomite 3 without dorsal setae. Epimeral plates 2-3 without ventral setae. Peduncular article 1 of antenna 1 with robust seta on posterodistal corner. Antenna 2 with peduncular article 2 gland cone not exceeding end of article 3; calceoli present in male. Mandible with 5-dentate left incisor; left lacinia mobilis 4-dentate, right one bifid with three or four teeth. Inner plate of maxilla 1 with six plumose setae. Inner plate of maxilla 2 with seven facial seta in oblique row. Peduncle of pleopod 3 with seta. Uropod 1 with peduncle bearing basofacial robust setae. Uropod 3 with inner ramus 0.3 times as long as outer ramus; outer ramus two-ariticulate, with plumose setae on medial margin. Telson length 1.1 times width, cleft for 67% of length.

Etymology.

The new species is named after Dr. Takaaki Torii, who collected the species.

Description.

Male holotype, NSMT-Cr 16652. Head (Fig. 2A View Figure 2 ) as long as pereonites 1 and 2 combined; eyes absent; inferior antennal sinus distinct with rounded angle. Dorsal margins of pleonites 1-3 (Figs 2A View Figure 2 , 5A-C View Figure 5 ) each with four setae. Epimeral plates 1-3 (Figs 2A View Figure 2 , 5N-P View Figure 5 ) with weakly pointed posterodistal corners; ventral margins without setae; posterior margins of plates 1-3 with one, zero, one seta, respectively. Dorsal margins of urosomites 1 and 2 with robust seta, urosomite 3 dorsally bare.

Antenna 1 (Figs 2A View Figure 2 , 3A View Figure 3 ) length 0.6 times as long as body; length ratio of peduncular articles 1-3 in 1.0: 0.8: 0.4; posterodistal corner of peduncular article 1 with robust seta; accessory flagellum three-articulate (Fig. 3B View Figure 3 ); primary flagellum with approximately 22 articles, each article with one aesthetasc (Fig. 3C View Figure 3 ). Antenna 2 (Figs 2A View Figure 2 , 3D View Figure 3 ) length 0.6 times as long as antenna 1; peduncular article 4 length 0.9 times as long as article 5; right peduncular article 5 with calceoli, left one lacking calceoli; flagellum 16-articulate, with calceoli (Fig. 3E View Figure 3 ).

Upper lip (Fig. 2B View Figure 2 ) with rounded apical margin bearing fine setae. Mandibles (Fig. 2C-E View Figure 2 ) with left and right incisors comprising five and five-six teeth, respectively; left lacinia mobilis comprising four teeth, right lacinia mobilis bifid with three teeth; molar process triturative with plumose seta; length ratio of palp articles 1-3 in 1.0: 2.4: 1.9; palp article 1 without setae; palp article 2 with eight marginal setae; palp article 3 with pair of A-setae, many D-setae and E-setae, lateral face with fine setae. Lower lip (Fig. 2G View Figure 2 ) lacking inner lobes; outer lobes broad, shoulder rounded, with fine setae. Maxilla 1 (Fig. 2H-J View Figure 2 ) with triangular inner lobe, bearing six plumose setae on medial margin; outer plate rectangular, with 11 serrate robust setae apically; palp 2-articulate, article 1 without setae, article 2 with six robust setae apically. Maxilla 2 (Fig. 2K View Figure 2 ) with inner plate bearing seven plumose setae in oblique row. Maxilliped (Fig. 2L-O View Figure 2 ) with inner plate reaching end of palp article 1, subquadrate, bearing three subapical robust setae and medial robust seta; outer plate ovate, reaching middle of palp article 2, with row of robust setae along apical to medial margins; palp 4-articulate, article 2 longest with medial setae, nail of article 4 distinct.

Gnathopod 1 (Fig. 3J, K View Figure 3 ) with subquadrate coxa bearing setae along anterior to ventral margins; anterior and posterior margins with long setae; carpus length 0.9 times as long as length of propodus and 1.5 times width of carpus; propodus length 1.9 times width, palmar margin weakly serrate, oblique, with three medial and two lateral robust setae; dactylus not reaching posterodistal corner of propodus. Gnathopod 2 (Fig. 3L, M View Figure 3 ) with coxa expanded proximally bearing setae along anterior to ventral margins; posterior margin of basis with long setae; carpus length 1.2 times as long as length of propodus and 2.8 times width of carpus; propodus length 2.4 times width, palmar margin weakly serrate, almost vertical, with two medial and two lateral robust setae; dactylus not reaching posterodistal corner of propodus.

Pereopod 3 (Fig. 4A, B View Figure 4 ) with subquadrate coxa, proximally expanded, bearing setae along anterior to ventral margins; posterior margin of basis with long setae. Pereopod 4 (Fig. 4D, E View Figure 4 ) with coxa bearing setae along anterior to ventral margins, posteroproximally concave; posterior margin of basis with long setae. Pereopod 5 (Fig. 4G, H View Figure 4 ) with bilobed coxa bearing seta on anterior and posterior lobes; anterior margin of basis with robust setae, posterodistal corner weakly lobate. Pereopod 6 (Fig. 4J, K View Figure 4 ) with bilobed coxa bearing seta on posterior lobe; basis ovate, with robust setae on anterior margin, posterodistal corner weakly lobate. Pereopod 7 (Fig. 4M View Figure 4 ) with subtriangular coxa bearing seta on posterior margin; basis elliptical, with robust setae on anterior margin, posterodistal corner weakly lobate.

Coxal gills (Figs 3L View Figure 3 , 4A, D, G, J View Figure 4 ) ovate with stalks on gnathopod 2 and pereopods 3-6.

Pleopods 1-3 (Fig. 5G-K View Figure 5 ) with peduncles longer than rami, bearing distal seta on pleopod 2 and proximal seta on pleopod 3; retinacula paired (Fig. 5H View Figure 5 ); mediobasal margin of inner ramus with bifid plumose setae (Fig. 5I View Figure 5 ); rami well developed.

Uropod 1 (Fig. 5R View Figure 5 ) with peduncle bearing three basofacial robust setae and dorsal robust setae; inner ramus length 0.7 times as long as peduncle, with two medial and one lateral robust setae, and ventroproximal robust seta; outer ramus length 0.9 times as long as inner ramus, with two robust setae on medial margin. Uropod 2 (Fig. 5S View Figure 5 ) with peduncle bearing dorsal robust setae; inner ramus length 0.8 times as long as peduncle, bearing two medial robust setae and two ventroproximal slender setae; outer ramus length 0.6 times as long as inner ramus, without marginal setae. Uropod 3 (Fig. 5U, V View Figure 5 ) with peduncle length 0.3 times as long as outer ramus, bearing bent robust setae on distal edge; inner ramus length 0.3 times as long as outer ramus, with two robust setae on medial margin; outer ramus 2-articulate, proximal article with plumose setae on medial margin and robust setae on medial and lateral margins, terminal article length 0.3 times as long as proximal article with subapical setae.

Telson (Fig. 5X View Figure 5 ) length 1.1 times width, each lobe with two lateral and three apical robust setae and two dorsolateral penicillate setae, cleft for 67%.

Female paratype, NSMT-Cr 16653. Antenna 1 (Fig. 3F-H View Figure 3 ) with peduncles 1-3 of which length ratio in 1.0: 0.8: 0.5; accessory flagellum 4-articulate (Fig. 3G View Figure 3 ). Antenna 2 (Fig. 3I View Figure 3 ) without calceoli.

Incisor of right mandible 6-dentate (Fig. 2F View Figure 2 ); right lacinia mobilis 4-dentate, weakly bifid. Apical robust setae of inner plate of maxilliped stiffer than those of male (Fig. 2P View Figure 2 ).

Gnathopod 1 (Fig. 3N, O View Figure 3 ) with carpus length 1.8 times width; length of propodus 2.0 times width; dactylus reaching posterodistal corner of propodus. Gnathopod 2 (Fig. 3P, Q View Figure 3 ) with dactylus reaching posterodistal corner of propodus.

Brood plates (Figs 3P View Figure 3 , 4I View Figure 4 ) narrow, lacking setae, on gnathopod 2 and pereopods 3-5.

Peduncles of pleopods 1 and 3 with three and one setae, respectively (Fig. 5L, M View Figure 5 ).

Uropod 2 (Fig. 5T View Figure 5 ) with inner ramus bearing two medial and one lateral robust setae; outer ramus with medial robust seta. Uropod 3 (Fig. 5W View Figure 5 ) with terminal article of outer ramus length 0.2 times as long as proximal article.

Telson (Fig. 5Y View Figure 5 ) as long as wide, cleft for 71%.

Distribution and environment.

The species is known only from its type locality in the Seto River, Shizuoka Prefecture, Japan. Specimens were collected at a depth of 20 cm, from the bank of the river.

Remarks.

Eoniphargus toriii sp. nov. is similar to E. kojimai and E. iwataorum sp. nov., with a head bearing deep antennal sinus, antenna 1 peduncular article 1 with a robust seta on the posterodistal corner, antenna 2 peduncular article 2 with a gland cone not exceeding peduncular article 3, uropod 1 peduncle with basofacial robust setae, and uropod 3 with 2-articulate outer ramus. However, E. toriii sp. nov. differs from E. kojimai and E. iwataorum sp. nov. in the following features: right mandible with lacinia mobilis bearing three or four teeth (more than four teeth in E. kojimai and E. iwataorum sp. nov.) and maxilla 1 having six medial setae on the inner plate (eight medial setae in E. kojimai and E. iwataorum sp. nov.).