Gammarus hirtellus, HOU & LI & LI, 2013

HOU, ZHONGE, LI, JUNBO & LI, SHUQIANG, 2013, Ten new Gammarus species (Crustacea: Amphipoda: Gammaridae) from Yunnan-Guizhou Plateau, China , Zootaxa 3687 (1), pp. 1-95 : 51-53

publication ID	https://doi.org/ 10.11646/zootaxa.3687.1.1
publication LSID	lsid:zoobank.org:pub:193BA226-D0D0-42C9-9815-639E8E48EF7A
DOI	https://doi.org/10.5281/zenodo.10540394
persistent identifier	https://treatment.plazi.org/id/5D2BDE76-FFFF-7115-FF54-FAD4FAD4F821
treatment provided by	Felipe
scientific name	Gammarus hirtellus
status	sp. nov.

Treatment

Gammarus hirtellus sp. nov.

Figs 3C View FIGURE 3 , 36–41 View FIGURE 36 View FIGURE 37 View FIGURE 38 View FIGURE 39 View FIGURE 40 View FIGURE 41

Material examined. Holotype: male (IZCAS-I-A666-1), 11.2 mm, from the Xiniu Cave (107.49°E, 27.77°N), Shiqiao Dam , Xihe Town, Meitan County, Guizhou Province, China, May 16, 2006, collected by Y. Lin. GoogleMaps Paratype: female (IZCAS-I-A666-2), 9.2 mm, same data as holotype.

Etymology. The specific name is from Latin hirtellus (hairy), in reference to the long setae on anterior margins of pereopods V–VII; adjective.

Diagnosis. Coxal plates of pereopods III and IV with more setae on anterior and posterior margins; merus and carpus of pereopod III with clusters of curled long setae; merus and carpus of pereopods V–VII with groups of spines accompanied by long setae on anterior and posterior margins; inner ramus of uropod III reaching 0.8 times the length of the outer ramus; urosome with groups of 1 spine and setae.

Description of male. Holotype (IZCAS-I-A666-1), male 11.2 mm ( Fig. 3C View FIGURE 3 ).

Head ( Fig. 36A View FIGURE 36 ): eyes absent, inferior antennal sinus deep.

Antenna I ( Fig. 36B, C View FIGURE 36 ): 1 st to 3 rd article of peduncle in length ratio 1.0: 0.8: 0.4, with setae on distal corner; flagellum with 30 articles, 5 th to 29 th article with aesthetascs; accessory flagellum with 5 articles; both primary and accessory flagella with short distal setae.

Antenna II ( Fig. 36D, E View FIGURE 36 ): about 0.7 times as long as antenna I, 3 rd to 5 th article of peduncle in length ratio 1.0: 3.0: 2.6, 4 th and 5 th article of peduncle with 10–11 clusters of lateral and medial setae; flagellum with 14 articles and 1 tiny distal article, with setae along ventral margins; calceoli present in 2 nd to 10 th article.

Upper lip ( Fig. 36F View FIGURE 36 ): ventral margin rounded, bearing minute setae.

Mandible ( Fig. 36H, I View FIGURE 36 ): left mandible incisor with 5 teeth; lacinia mobilis with 4 teeth, spine row with 8 pairs of plumose setae along ventral margin; 1 st to 3 rd article of palp in length ratio 1.0: 2.2: 1.8, 2 nd article of palp armed with 13 marginal setae, 3 rd article with 3 A-setae, 2 clusters of B-setae, 20 D-setae and 6 E-setae apically; incisor of right mandible with 4 teeth, lacinia mobilis bifurcate, with small teeth.

Lower lip ( Fig. 36G View FIGURE 36 ): inner lobes lacking, outer lobes covered with thin setae.

Maxilla I ( Fig. 36J, K View FIGURE 36 ): asymmetrical, left inner plate with 20 plumose setae on medial margin; outer plate with 11 robust serrated apical spines, each spine with small teeth; 2 nd article of palp with 6 slender spines and 1 stiff seta apically; 2 nd article of right palp with 4 stout spines and 1 slender spine.

Maxilla II ( Fig. 36L View FIGURE 36 ): inner plate with 17 plumose facial setae in an oblique row; inner and outer plates with long setae apically.

Maxilliped ( Fig. 36M View FIGURE 36 ): inner plate with 1 subapical and 3 stout apical spines, some plumose setae along lateral margin; outer plate bearing a row of blade spines and 3 plumose setae apically; 4 th article of palp hooked, with a group of setae at hinge of unguis.

Gnathopod I ( Fig. 37A, C View FIGURE 37 ): coxal plate bearing 3 and 4 setae on anterior and posterior margins, respectively; basis with setae on anterior and posterior margins; carpus 1.2 times as long as wide, about 0.6 times as long as propodus, posterior margin bearing short setae; propodus oval, palm evenly with 2 median spines and 15 spines on posterior margin and facial surface.

Gnathopod II ( Fig. 37B, D View FIGURE 37 ): coxal plate bearing 4 setae and 3 setae on anterior and posterior margins; basis with setae on posterior margin, posterodistal corner with short setae; carpus 1.9 times as long as wide, about 0.7 times as long as propodus, with parallel margins, bearing 10 clusters of setae along ventral margin; propodus palm ovate, palm margin evenly with 2 median spines and 4 spines on lateral posterodistal corner.

Pereopod III ( Fig. 38A, F View FIGURE 38 ): coxal plate bearing 6 and 4 setae on anteroventral and posterior margins; basis elongate, with setae along posterior margins; merus to propodus armed with clusters of curled long setae on posterior margin; carpus and propodus with groups of spines accompanied by setae on posterior margins; dactylus with 1 plumose seta on posterior margin, and 2 setae at hinge of unguis.

Pereopod IV ( Fig. 38B, G View FIGURE 38 ): coxal plate excavated, bearing 5 setae on anterior margin and 7 setae on posterior margin; basis with long setae along posterior margin; merus with 6 clusters of setae on posterior margin and 1 spine accompanied by 1 seta on anterior margin, anterodistal corner with 1 spine accompanied by 1 seta; carpus and propodus with groups of spines accompanied by setae on posterior margin; dactylus with 1 plumose seta on anterior margin, and 2 setae at hinge of unguis.

Pereopod V ( Fig. 38C, H View FIGURE 38 ): coxal plate bearing 1 seta on anterior margin and 2 setae on posterior margin; basis with 2 setae and 7 spines on anterior margin, anterodistal corner with 1 spine accompanied by 1 seta, posterior margin with a row of 11 setae; merus to carpus with groups of spines accompanied by setae on anterior and posterior margins; propodus with spines on anterior margin; dactylus with 1 plumose seta on posterior margin, and 2 setae at hinge of unguis.

Pereopod VI ( Fig. 38D, I View FIGURE 38 ): coxal plate bearing 2 setae on posterior margin; basis elongate, with 2 setae and 7 spines on anterior margin, anterodistal corner with 1 spine accompanied by setae, posterior margin dwindling distally, with a row of 13 setae; merus to carpus with groups of spines accompanied by setae on anterior and posterior margins; propodus with 2 groups of setae on posterior margin; dactylus with 1 plumose seta on posterior margin, and 2 setae at hinge of unguis.

Pereopod VII ( Fig. 38E, J View FIGURE 38 ): coxal plate bearing 4 setae on posterior margin; basis expanded, posterior margin weakly narrowed distally, anterior with 1 seta and 7 spines, posterior with a row of 11 setae, inner surface with 1 spine accompanied by 1 seta; merus to carpus with groups of spines accompanied by setae on anterior and posterior margins; propodus with 4 groups of setae on posterior margin; dactylus with 1 plumose seta on posterior margin, and 2 setae at hinge of unguis.

Coxal gills: coxal gill of gnathopod II and gills of pereopods III–V reaching the length of bases; gill of pereopod VI more than half the length of basis; gill of pereopod VII smallest.

Epimeral plates ( Fig. 39B–D View FIGURE 39 ): plate I ventrally rounded, bearing 5 setae on anteroventral margin and 4 setae on posterior margin; plate II with 1 seta and 3 spines on anteroventral margin, with 6 setae on posterior margin, posterodistal corner blunt; plate III with 3 spines on anteroventral margin and 4 setae on posterior margin, posterodistal corner blunt.

Pleopods I–III ( Fig. 39E–G View FIGURE 39 ): similar, peduncles with 2 retinacula accompanied by 1 seta; outer ramus slightly shorter than inner ramus, both rami fringed with plumose setae.

Urosome ( Fig. 39A View FIGURE 39 ): dorsally flat. Urosome segment I with 1-1-1-1 spine accompanied by 2 – 3 setae on dorsal margin. Urosome segment II with 2 groups of 1 spine accompanied by 2 setae on dorsal margin, with 1 spine accompanied by 1 seta on each side. Urosome segment III with 1 spine accompanied by 1 seta on each side.

Uropods I–III ( Fig. 39H–J View FIGURE 39 ): uropod I peduncle with 1 basofacial spine, with 2 spines on outer margin, 2 and 1 spine on outer and inner corners; inner ramus with 1 spine on inner margin; both rami with 5 terminal spines. Uropod II short, with 1 spine on outer and inner margins, with 1 distal spine on each corner; both rami with 1 spine on inner margins and 5 terminal spines. Uropod III peduncle with 1 spine accompanied by 2 setae on the surface and 5 distal spines with some setae; inner ramus about 2.1 times as long as peduncle, reaching 0.8 times the length of outer ramus, with plumose setae on outer and inner margins, bearing 1 apical spine accompanied by some setae; 1 st article of outer ramus with 1 single spine and 2 pairs of spines accompanied by plumose setae on outer margin, both margins densely set with plumose setae and few simple setae; terminal article shorter than adjacent spines.

Telson ( Fig. 39K View FIGURE 39 ): deeply cleft, nearly as long as wide, both lobes with some setae on surfaces and with 1 apical spine accompanied by 6–7 setae, respectively.

Description of female. Paratype (IZCAS-I-A666-2), 9.2 mm.

Gnathopod I ( Fig. 40A, C View FIGURE 40 ): coxal plate bearing 4 and 4 setae on anterior and posterior margins, respectively; basis with long setae on posterior margin; propodus oval, palm with 10 spines on posterior margin; dactylus with 1 seta on outer margin.

Gnathopod II ( Fig. 40B, D View FIGURE 40 ): coxal plate bearing 6 setae and 3 setae on anterior and posterior margins; basis with setae on anterior and posterior margins, posterodistal corner with short setae; propodus subrectangular, palm margin with 5 spines on posterodistal corner, bearing simple setae along anterior and posterior margins; dactylus with 1 seta on outer margin.

Pereopods III–IV ( Fig. 41A–B View FIGURE 41 ): with shorter setae on posterior margins than those of male.

Pereopods V–VII ( Fig. 41C–E View FIGURE 41 ): similar to those of male; merus to carpus with spines accompanied by setae.

Uropods I–III ( Fig. 39L–N View FIGURE 39 ): uropod I peduncle with 1 basofacial spine, with 3 and 1 spine on outer and inner margins, 2 and 1 spine on outer and inner corners; both rami with 1 spine on inner margins. Uropod II short. Uropod III peduncle with 1 spine accompanied by 2 setae on the surface and 5 distal spines accompanied by some setae; inner ramus 1.6 times as long as peduncle, reaching 0.8 times the length of outer ramus, with plumose setae on lateral margin; 1 st article of outer ramus with 3 pairs of spines accompanied by simple setae on outer margin, both margins of inner and outer rami densely with plumose setae; terminal article shorter than adjacent spines.

Oostegite ( Fig. 41F–I View FIGURE 41 ): oostegite of gnathopod II broad, with marginal setae, oostegites of pereopods III and IV elongate, oostegite of pereopod V smallest.

Variability. The armature of uropods I and II variable from bare to 1–2 spines on both margins of both rami; the spines on anteroventral margins of epimeral plates various from 2–5.

Habitat. Specimens were collected from underground river of Xiniu Cave. The cave is about three kilometers long.

Remarks. Gammarus hirtellus sp. nov. is similar to G. xianfengensis Hou & Li, 2002 in: eyes absent; calceoli present; 2 nd article of uropod III short, inner ramus reaching about 0.8 times the length of outer ramus. The new species can be distinguished from G. xianfengensis by the following characters ( G. xianfengensis in parentheses): merus and carpus of pereopod III with clusters of curled long setae (with few setae); merus and carpus of pereopods V–VII with groups of spines accompanied by long setae on anterior and posterior margins (with few setae); epimeral plates II and III with 3 spines on anteroventral margins, posterodistal corners blunt (with 5–6 spines on anteroventral margins, posterodistal corners subacute); both lobes of telson with 1 apical spine accompanied by 7 longer setae (with 3 apical spines accompanied by few setae).

The new species can be distinguished from G. lichuanensis Hou & Li, 2002 by the following characters ( G. lichuanensis in parentheses): merus and carpus of pereopod III with clusters of curled long setae (with few setae); pereopods III–VII normal (slender); outer ramus of uropod III with 2 articles (with 1 article); epimeral plates II and III with 3 spines on posteroventral margin, posterodistal corners blunt (with 1–2 spines, posterodistal corners subacute); both lobes of telson with 1 apical spine accompanied by 7 longer setae (with 3 apical spines).