Gammarus amabilis, 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 : 6-18

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.10540384
persistent identifier	https://treatment.plazi.org/id/5D2BDE76-FFC8-7130-FF54-FCF8FEAEFEFA
treatment provided by	Felipe
scientific name	Gammarus amabilis
status	sp. nov.

Treatment

Gammarus amabilis sp. nov.

Figs 2A View FIGURE 2 , 6–11 View FIGURE 6 View FIGURE 7 View FIGURE 8 View FIGURE 9 View FIGURE 10 View FIGURE 11

Material examined. Holotype: male (IZCAS-I-A703-1), 11.5 mm, from the Fairy Cave of Dasha River (107.59°E, 28.89°N), Daozhen County, Guizhou Province, China, May 26, 2007, collected by H. Chen. GoogleMaps Paratype: female (IZCAS-I-A703-2), 10.3 mm, same data as holotype.

Etymology. The specific name is from Latin amabilis (lovely), in reference to the peculiarity of shape; adjective.

Diagnosis. Eyes absent; calceoli present; pereopods III–VII with few setae on posterior margins; posterodistal corners of epimeral plates II and III blunt; urosome with clusters of spines accompanied by setae; inner ramus of uropod III reaching about 0.7 times the length of outer ramus, second article of outer ramus short.

Description of male. Holotype (IZCAS-I-A703-1), male 11.5 mm ( Fig. 2A View FIGURE 2 ).

Head ( Fig. 6A View FIGURE 6 ): eyes absent, inferior antennal sinus deep, lateral cephalic lobe nearly straight.

Antenna I ( Fig. 6B, C View FIGURE 6 ): 1 st to 3 rd article of peduncle in length ratio 1.0: 0.7: 0.4, with setae on distal corners; flagellum with 30 articles, 3 rd to 25 th article with aesthetascs; accessory flagellum with 6 articles; both primary and accessory flagella with short distal setae.

Antenna II ( Fig. 6D, E View FIGURE 6 ): about 0.6 times as long as antenna I, length ratio of 3 rd to 5 th article of peduncle in 1.0: 3.0: 2.7, 4 th and 5 th article of peduncle with 2–3 clusters of lateral and medial setae; flagellum with 12 articles and 1 tiny distal article, with setae along ventral margins; calceoli present in 1 st to 7 th articles.

Upper lip ( Fig. 6F View FIGURE 6 ): ventral margin rounded, bearing minute setae.

Mandible ( Fig. 6H, I View FIGURE 6 ): left mandible incisor with 5 teeth; lacinia mobilis with 4 teeth, with 7 pairs of plumose setae along ventral margin; 1 st to 3 rd article of palp in length ratio 1.0: 2.8: 2.4; 2 nd article armed with 14 marginal setae; 3 rd article with 2 clusters of A-setae and B-setae, 25 D-setae and 5 E-setae apically; incisor of right mandible with 4 teeth, lacinia mobilis bifurcate, with small teeth.

Lower lip ( Fig. 6G View FIGURE 6 ): inner lobes lacking, outer lobes covered with thin setae.

Maxilla I ( Fig. 6J, K View FIGURE 6 ): asymmetrical, left inner plate with 19 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 2 stiff setae apically; 2 nd article of right palp with 4 stout spines and 1 stiff seta and 1 slender spine.

Maxilla II ( Fig. 6L View FIGURE 6 ): inner plate with 14 plumose facial setae in an oblique row; inner and outer plates with long setae apically.

Maxilliped ( Fig. 6M View FIGURE 6 ): inner plate with 1 subapical and 3 stout apical spines, some plumose setae along ventral margin; outer plate bearing a row of blade spines and 4 plumose setae apically; 4 th article of palp hooked, with a group of setae at hinge of unguis.

Gnathopod I ( Fig. 7A, C View FIGURE 7 ): coxal plate bearing 2 setae and 1 seta on anterior and posterior margins, respectively; basis with setae on anterior and posterior margins; carpus as long as wide, about 0.5 times as long as propodus, posterior margin bearing short setae; propodus oval, palm with 1 medial spine and 14 spines on posterior margin and surface; dactylus with 1 seta on outer margin.

Gnathopod II ( Fig. 7B, D View FIGURE 7 ): 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 1.2 times as long as wide, about 0.5 times as long as propodus, with parallel margins, bearing 6 clusters of setae along ventral margin, 2 clusters of setae on dorsal margin; propodus palm ovate, palm margin evenly with 2 median spines and 5 spines on posterodistal corner; dactylus with 1 seta on outer margin.

Pereopod III ( Fig. 8A, F View FIGURE 8 ): coxal plate bearing 4 setae and 1 seta on anteroventral and posterior margins; basis elongate, with setae along anterior and posterior margins; merus with 6 clusters of setae on posterior margin and 3 clusters of single spine accompanied by 1 seta on anterior margin; carpus and propodus with groups of spines accompanied by short setae on posterior margin; dactylus with 1 plumose seta on posterior margin, and 2 setae at hinge of unguis.

Pereopod IV ( Fig. 8B, G View FIGURE 8 ): coxal plate excavated, bearing 2 setae on anterior margin and 4 setae on posterior margin; basis with setae along anterior and posterior margins; merus with 5 clusters of setae on posterior margin and 1 spine 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. 8C, H View FIGURE 8 ): coxal plate bearing 1 seta on anterior margin and 2 setae on posterior margin; basis with 8 spines on anterior margin, anterodistal corner with 2 spines accompanied by some setae, posterior margin with a row of 12 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.

Pereopod VI ( Fig. 8D, I View FIGURE 8 ): coxal plate bearing 1 seta on posterior margin; basis elongate, with 4 spines on anterior margin, anterodistal corner with 2 spines, posterior margin dwindling distally, with a row of 11 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.

Pereopod VII ( Fig. 8E, J View FIGURE 8 ): coxal plate bearing 3 setae on posterior margin; basis expanded, posterior margin weakly narrowed distally, anterior with 6 spines, posterior with a row of 13 setae, inner surface with 1 spine accompanied by 1 seta; merus to propodus with groups of spines accompanied by setae on anterior margin and propodus with 4 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 a little shorter than bases; gill of pereopod 6 more than half length of basis; gill of pereopod 7 smallest, less than half of basis.

Epimeral plates ( Fig. 9A–C View FIGURE 9 ): plate I ventrally rounded, bearing 4 setae on anteroventral margin and 2 setae on posterior margin; plate II with 2 spines and 3 setae on ventral margin and 3 setae on posterior margin, posterodistal corner blunt; plate III with 2 spines and 2 setae on ventral margin, and 4 setae on posterior margin, posterodistal corner blunt.

Pleopods I–III ( Fig. 9E–G View FIGURE 9 ): similar, peduncles with 2 retinacula accompanied by 1–2 setae; outer ramus slightly shorter than inner ramus, both rami fringed with plumose setae.

Urosome ( Fig. 9D View FIGURE 9 ): dorsally flat. Urosome segment I with 1-1-1-1 spine accompanied by setae on dorsal margin. Urosome segment II with 2-1-1-2 spines accompanied by setae on dorsal margin. Urosome segment III with 1 and 2 spines accompanied by 2 setae on each side and 5 setae on dorsal margin.

Uropods I–III ( Fig. 9H–J View FIGURE 9 ): uropod I peduncle with 1 basofacial spine, with 2 spines on outer margin, 2 and 1 spine on outer and inner distal corners, respectively; inner ramus with 1 spine on inner margin; both rami with 5 terminal spines. Uropod II short, peduncle bearing 1 spine on outer margin, with 1 distal spine on each corner; both rami with 1 spine on inner margin and 5 terminal spines. Uropod III peduncle with 1 spine accompanied by 2 setae on surface and 7 distal spines; inner ramus about 1.9 times as long as peduncle, reaching 0.7 times the length of outer ramus, with plumose setae on both margins, bearing 2 apical spines accompanied by plumose setae; 1 st article of outer ramus with 2 pairs of spines and 1 single spine on outer margin, both margins with plumose setae and few simple setae; terminal article shorter than adjacent spines.

Telson ( Fig. 9K View FIGURE 9 ): deeply cleft, 0.9 times as long as wide, both lobes with 3 clusters of setae on dorsolateral margins, bearing 1 apical spine accompanied by 5 and 6 setae.

Description of female. Paratype (IZCAS-I-A703-2), 10.3 mm.

Gnathopod I ( Fig. 10A, C View FIGURE 10 ): coxal plate bearing 2 setae and 1 seta on anterior and posterior margins, respectively; basis with setae on posterior margins; propodus oval, palm with 3 spines on posterior margin; dactylus with 1 seta on outer margin.

Gnathopod II ( Fig. 10B, D View FIGURE 10 ): 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, palm margin with 3 spines on posterodistal corner, bearing simple setae along anterior and posterior margins; dactylus with 1 seta on outer margin.

Pereopods III and IV ( Fig. 11A–B, F–G View FIGURE 11 ): with longer setae on posterior margin than those of male.

Pereopods V–VII ( Fig. 11C–E, H–J View FIGURE 11 ): with fewer long setae on posterior margins than those of male.

Uropods I–III ( Fig. 9L–N View FIGURE 9 ): uropods I and II are similar to those of male. Uropod III peduncle with 1 spine accompanied by 1 seta on surface and 6 distal spines; inner ramus 1.4 times as long as peduncle, reaching 0.8 times the length of outer ramus, with 1 spine and some plumose setae on lateral margin; 1 st article of outer ramus with 2 pairs of spines accompanied by simple setae on outer margin, inner margin with plumose setae; terminal article shorter than adjacent spines.

Telson ( Fig. 10E View FIGURE 10 ): cleft, similar to that of male.

Oostegite ( Fig. 11K–N View FIGURE 11 ): oostegite of gnathopod II broad, with marginal setae, oostegites of pereopods III and IV elongate, oostegite of pereopod V smallest.

Variability. The variability pattern is similar to the normal G. pulex type ( Karaman & Pinkster 1977). Body length ranging from 9–12 mm; the inner ramus reaching 0.7–0.8 times the length of outer ramus; outer ramus of uropod II with 1 spine or bare .

Habitat. Specimens were sampled along the underground river in the Fairy Cave of Dashahe Natural Reserve. The river is clear and shows no signs of pollution. The species is known only from the type locality ( Fig. 1 View FIGURE 1 ).

Remarks. Gammarus amabilis sp. nov. is similar to G. xianfengensis Hou & Li, 2002 in: calceoli present; pereopods III–VII with fewer setae on posterior margins; 2 nd article of uropod III shorter than adjacent spines; urosome with spines and setae. The new species can be distinguished from G. xianfengensis by the following characters ( G. xianfengensis in parentheses): inner ramus of uropod III reaching about 0.7 times the length of outer ramus (reaching 0.9 times the length of outer ramus); each lobe of telson with 1 apical spine (with 3 apical spines); epimeral plates II and III with 2 spines on anteroventral margins, posterodistal corners blunt (with 5 spines on each plate, posterodistal corners subacute).

The new species can be distinguished from G. lichuanensis Hou & Li, 2002 by the following characters ( G. lichuanensis in parentheses): calceoli present (absent); gnathopods I and II not as oval as the latter, gnathopod II with 2 median spines (evenly with 4 median spines); pereopods III–VII normal (slender); inner ramus reaching about 0.7 times the length of outer ramus (nearly the same length); epimeral plates with more setae and spines (few setae and spines).