Gammarus tranquillus, 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 : 85-93

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.10540400
persistent identifier	https://treatment.plazi.org/id/5D2BDE76-FF99-717D-FF54-FD0DFB2EFAFB
treatment provided by	Felipe
scientific name	Gammarus tranquillus
status	sp. nov.

Treatment

Gammarus tranquillus sp. nov.

Figs 5A View FIGURE 5 , 60–65 View FIGURE 60 View FIGURE 61 View FIGURE 62 View FIGURE 63 View FIGURE 64 View FIGURE 65

Material examined. Holotype: male (IZCAS-I-A1161-1), 10.7 mm, from the Mawan Cave (107.07°E, 28.20°N), altitude 937 m, Dishui Village , Kuankuo Town, Suiyang County, Guizhou Province, China, May 17, 2010, collected by Z. Zha. GoogleMaps Paratype: female (IZCAS-I-A1161-2), 8.5 mm, same data as holotype.

Etymology. The specific name is from Latin tranquillus (quiet), in reference to the habitat of this species, which was collected in a lentic water; adjective.

Diagnosis. Merus to carpus of pereopod III armed with clusters of curled long setae; 2 nd article of right palp in maxilla I with 4 stout spines; inner ramus of uropod III reaching 0.8 times the length of outer ramus; both margins densely set with plumose setae and few simple setae; urosome segment I with 2 groups of setae on dorsal margin and 1 spine accompanied by 1 seta on each side, urosome segment II with 1-1-1-1 spine accompanied by 1 seta on dorsal margin, urosome segment III with 2 groups of spines accompanied by 1 seta on each side.

Description of male. Holotype (IZCAS-I-A1161-1), male 10.7 mm ( Fig. 5A View FIGURE 5 ).

Head ( Fig. 60A View FIGURE 60 ): eyes absent, inferior antennal sinus deep, lateral cephalic lobe nearly straight.

Antenna I ( Fig. 60B, C View FIGURE 60 ): 1 st to 3 rd article of peduncle in length ratio 1.0: 0.9: 0.6, with setae on distal corner; flagellum with 28 articles, 5 th to 26 th article with aesthetascs; accessory flagellum with 4 articles; both primary and accessory flagella with short distal setae.

Antenna II ( Fig. 60D, E View FIGURE 60 ): about 0.5 times as long as antenna I, 3 rd to 5 th article of peduncle in length ratio 1.0: 3.4: 3.1, 4 th and 5 th article of peduncle with 7–10 clusters of lateral and medial setae; flagellum with 10 articles and 1 tiny distal article, set with setae along ventral margins; calceoli present in 1 st to 8 th article.

Upper lip ( Fig. 60F View FIGURE 60 ): ventral margin rounded, bearing minute setae.

Mandible ( Fig. 60H, I View FIGURE 60 ): left mandible incisor with 5 teeth; lacinia mobilis with 4 teeth, spine row with 8 pairs of plumose setae along lateral margin; 1 st to 3 rd article of palp in length ratio 1.0: 2.7: 2.5, 2 nd article of palp with 13 marginal setae, 3 rd article with 3 A-setae, 2 B-setae, 12 D-setae and 5 E-setae apically; incisor of right mandible with 4 teeth, lacinia mobilis bifurcate, with small teeth.

Lower lip ( Fig. 60G View FIGURE 60 ): inner lobes lacking, outer lobes covered with thin setae.

Maxilla I ( Fig. 60J, K View FIGURE 60 ): asymmetrical, left inner plate with 15 plumose setae on medial margin; outer plate with 11 robust serrated apical spines, each spine with small teeth; 2 nd article of palp with 7 slender spines and 1 stiff seta apically; 2 nd article of right palp with 4 stout spines and 1 slender spine.

Maxilla II ( Fig. 60L View FIGURE 60 ): inner plate with 13 plumose facial setae in an oblique row; inner and outer plates with long setae apically.

Maxilliped ( Fig. 60M View FIGURE 60 ): 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 2 plumose setae apically; 4 th article of palp hooked, with a group of setae at hinge of unguis.

Gnathopod I ( Fig. 61A, C View FIGURE 61 ): coxal plate bearing 2 setae and 1 seta on anterior and posterior margins, respectively; basis with setae on anterior and posterior margins; carpus 1.6 times as long as wide, about 0.8 times as long as propodus, posterior margin bearing short setae; propodus oval, palm with 1 medial spine and 15 spines on posterior margin and facial surface.

Gnathopod II ( Fig. 61B, D View FIGURE 61 ): coxal plate bearing 3 setae and 1 seta on anterior and posterior margins; basis with setae on anterior and posterior margins, posterodistal corner with short setae; carpus 1.9 times as long as wide, about 0.8 times as long as propodus, with parallel margins, bearing 7 clusters of setae along ventral margin; propodus ovate, palm margin with 1 median spine and 4 spines on lateral posterodistal corner.

Pereopod III ( Fig. 62A, F View FIGURE 62 ): coxal plate bearing 3 setae and 1 seta on anteroventral and posterior margins; basis elongate, with setae along anterior and posterior margins; merus to carpus with clusters of curled long setae on posterior margin; propodus with groups of spines accompanied by setae on posterior margin; dactylus with 1 plumose seta on posterior margin, and 2 setae at hinge of unguis.

Pereopod IV ( Fig. 62B, G View FIGURE 62 ): coxal plate excavated, bearing 3 setae on anterior margin and 6 setae on posterior margin; basis with long setae along posterior margin; merus with 5 clusters of setae on posterior margin and 2 spines on anterior margin, anterodistal with 1 spine accompanied by some setae; carpus and propodus with groups of spines accompanied by short setae on posterior margin; dactylus with 1 plumose seta on anterior margin, and 2 setae at hinge of unguis.

Pereopod V ( Fig. 62C, H View FIGURE 62 ): coxal plate bearing 1 seta on anterior margin and 2 setae on posterior margin; basis with 1 seta and 6 spines on anterior margin, anterodistal corner with 1 spine accompanied by some setae, posterior margin with a row of 10 setae; merus to carpus with groups of spines accompanied by setae on anterior margin; propodus with 3 groups of setae on posterior margin; dactylus with 1 plumose seta on posterior margin, and 2 setae at hinge of unguis.

Pereopod VI ( Fig. 62D, I View FIGURE 62 ): coxal plate bearing 2 setae on posterior margin; basis elongate, with 6 spines on anterior margin, anterodistal corner with 1 spine, posterior margin dwindling distally, with a row of 11 setae; merus to carpus with groups of spines accompanied by setae on anterior margin, and 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. 62E, J View FIGURE 62 ): coxal plate bearing 2 setae on posterior margin; basis expanded, posterior margin weakly narrowed distally, anterior with 4 spines, posterior with a row of 13 setae; merus to propodus with groups of spines accompanied by setae on anterior margin; dactylus with 1 plumose seta on posterior margin, and 2 setae at hinge of unguis.

Coxal gills: present in gnathopod II and pereopods III–VII, progressively decreased in size.

Epimeral plates ( Fig. 63B–D View FIGURE 63 ): plate I ventrally rounded, bearing 4 setae on anteroventral margin and 3 setae on posterior margin; plate II with 2 spines on anteroventral margin and 2 setae on posterior margin, posterodistal corner blunt; plate III with 4 spines on anteroventral margin and 4 setae on posterior margin, posterodistal corner blunt.

Pleopods I–III ( Fig. 63E–G View FIGURE 63 ): similar, peduncle of pleopod I with 1 seta, peduncles of pleopods II and III with 2 retinacula accompanied by 1 setae; outer ramus slightly shorter than inner ramus, both rami fringed with plumose setae.

Urosome ( Fig. 63A View FIGURE 63 ): dorsally flat. Urosome segment I with 2 groups of setae on dorsal margin and 1 spine accompanied by 1 seta on each side. Urosome segment II with 1-1-1-1 spine accompanied by 1 seta on dorsal margin. Urosome segment III with 2 spines accompanied by 1 seta on each side.

Uropods I–III ( Fig. 63H–J View FIGURE 63 ): uropod I peduncle with 1 basofacial spine, with 3 spines on outer margin, 2 and 1 spine on outer and inner corners; both rami with 2 spines on inner margin and with 5 terminal spines. Uropod II short, with 1 distal spine on each corner; inner ramus with 2 spines on inner margin and with 1 spine on outer margin; outer ramus shorter than inner ramus, with 1 spine on inner margin and 2 spines on outer margin; both rami with 5 terminal spines. Uropod III peduncle with 2 spines accompanied by 1 seta on surface and 7 distal spines; inner ramus about 2.5 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 2 pairs of spines on outer margin, both margins densely with plumose setae and few simple setae; terminal article shorter than adjacent spines.

Telson ( Fig. 63K View FIGURE 63 ): deeply cleft, 1.3 times as long as wide; left lobe with setae and 1 spine on dorsolateral margins, with 3 apical spines accompanied by 4 setae; right lobe with setae on dorsolateral margins, with 2 apical spines accompanied by 4 setae.

Description of female. Paratype (IZCAS-I-A1161-2), 8.5 mm.

Gnathopod I ( Fig. 64A, C View FIGURE 64 ): coxal plate bearing 1 seta on anterior and posterior margins respectively; basis with setae on both margins; propodus oval, palm with 6 spines on posterior margin; dactylus with 1 seta on outer margin.

Gnathopod II ( Fig. 64B, D View FIGURE 64 ): coxal plate bearing 3 setae and 1 seta on anterior and posterior margins; basis with setae on anterior and posterior margins, posterodistal corner with short setae; propodus subrectangular, bearing simple setae along anterior and posterior margins, palm margin with 4 spines on posterodistal corner; dactylus with 1 seta on outer margin.

Pereopods III and IV ( Fig. 65A–B View FIGURE 65 ): with fewer setae on posterior margin than those of male.

Pereopods V–VII ( Fig. 65C–E View FIGURE 65 ): similar to those of male.

Uropods I–III ( Fig. 63L–N View FIGURE 63 ): uropod I peduncle with 1 basofacial spine, with 3 spines on outer margin, with 2 and 1 spine on outer and inner corners; both rami with 1 spine on inner margin. Uropod II short. Uropod III peduncle with 1 spine and some setae on surface and 3 distal spines; inner ramus 1.3 times as long as peduncle, reaching 0.7 times the length of outer ramus, with some plumose setae on lateral margin; 1 st article of outer ramus with 1 pair of spines accompanied by setae on outer margin; terminal article shorter than adjacent spines.

Telson ( Fig. 65F View FIGURE 65 ): both lobes with 3 apical spines accompanied by 1 seta.

Oostegite ( Fig. 65G–J View FIGURE 65 ): oostegite of gnathopod II broad, with marginal setae, oostegites of pereopods III and IV elongate, oostegite of pereopod V smallest.

Variability. The number of segment in antenna I various from 25 to 35; calceoli present on flagellum 1 st to 8 th article or 1 st to 9 th article in antenna II.

Habitat. This species was collected from underground river in Mawan Cave. The cave is dark and without light.

Remarks. Gammarus tranquillus sp. nov. is similar to G. xianfengensis Hou & Li, 2002 in: eyes absent; calceoli present; urosome with spines and setae. The new species can be distinguished from G. xianfengensis by the following characters ( G. xianfengensis in parentheses): merus to carpus of pereopod III armed with clusters of curled long setae (with fewer setae); epimeral plates II–III with 2–3 spines on posterior ventral margin, posterodistal corners blunt (with 5–6 spines, posterodistal corners subacute); 2 nd article of outer ramus of uropod III longer, inner ramus reaching 0.8 times the length of outer ramus (2 nd article of outer ramus shorter; inner ramus reaching 0.9 times the length of outer ramus).

The new species can be distinguished from G. translucidus Hou, Li & Li, 2004 by the following characters ( G. translucidus in parentheses): urosome segment II with 1-1-1-1 spine accompanied by 1 seta on dorsal margin (with 2 spines on dorsal margin); uropod II with no dorsal setae on peduncle (with a group of long setae on peduncle); inner ramus of uropod III reaching 0.7 times of outer ramus (more than 0.8 times of outer ramus).