Gammarus echinatus, 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 : 26-34

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.10540388
persistent identifier	https://treatment.plazi.org/id/5D2BDE76-FFD4-7100-FF54-F98CFEF3F8B7
treatment provided by	Felipe
scientific name	Gammarus echinatus
status	sp. nov.

Treatment

Gammarus echinatus sp. nov.

Figs 2C View FIGURE 2 , 18–23 View FIGURE 18 View FIGURE 19 View FIGURE 20 View FIGURE 21 View FIGURE 22 View FIGURE 23

Material examined. Holotype: male (IZCAS-I-A1064-1), 10.2 mm, a brook near Xinhua Village (100.18°E, 26.63°N), altitude 2,192 m, Heqing County, Dali City, Yunnan Province, January 26, 2011, collected by L. Lin and H. Pu. GoogleMaps Paratype: 1 female (IZCAS-I-A1064-2), 9.1 mm, same data as holotype GoogleMaps .

Etymology. The specific name is from Latin echinatus (spiny), in reference to spines on dorsal margins of metasome; adjective.

Diagnosis. Peduncle of antenna II with long setae; 3 rd article of mandible palp with 4 groups of A-setae on outer surface; inner ramus of uropod III reaching 1.5 times as long as peduncle, reaching 0.6 times the length of outer ramus; metasome and urosome with some spines on dorsal margins.

Description of male. Holotype (IZCAS-I-A1064-1), male 10.2 mm ( Fig. 2C View FIGURE 2 ).

Head ( Fig. 18A View FIGURE 18 ): eyes reniform, 2.4 times as long as wide; inferior antennal sinus distinct.

Antenna I ( Fig. 18B, C View FIGURE 18 ): 1 st to 3 rd article of peduncle in length ratio 1.0: 0.8: 0.5, with lateral and distal setae; flagellum with 28 articles, aesthetascs present on 7 th to 27 th article; accessory flagellum with 3 articles; both primary and accessory flagella with distal setae.

Antenna II ( Fig. 18D View FIGURE 18 ): 4 th article of peduncle as long as 5 th article, both with 3–5 groups of setae along anterior and posterior margins; flagellum with 9 articles, each article with long setae; calceoli absent.

Upper lip ( Fig. 18E View FIGURE 18 ): convex, with minute setae.

Left mandible ( Fig. 18G–I View FIGURE 18 ): incisor with 5 teeth; lacinia mobilis with 4 teeth; spine row with 7 pairs of setae, 2 nd article of palp with 18 marginal setae, 3 rd article about 0.83 times as long as 2 nd article, with 4 groups of A-setae on outer surface and 4 groups of B-setae, a row of 21 D-setae on posterior margin, and 4 E-setae apically; incisor of right mandible with 4 teeth, lacinia mobilis bifurcate, with small teeth.

Lower lip ( Fig. 18F View FIGURE 18 ): inner lobe absent.

Maxilla I ( Fig. 18J, K View FIGURE 18 ): asymmetrical, left inner plate with a row of 17 plumose setae; outer plate with 11 serrated apical spines, each spine with small teeth; 2 nd article of palp with 6 slender spines and 3 stiff setae on medial surface; right palp wider, 2 nd article with 5 stout spines, 1 pectinate spine and 1 seta.

Maxilla II ( Fig. 18L View FIGURE 18 ): inner plate with a row of 20 plumose setae; outer plate with apical setae and setules on lateral margin.

Maxilliped ( Fig. 18M View FIGURE 18 ): inner plate with 1 subapical and 3 stout apical spines; 4 th article of palp hooked, with a group of setae at hinge of unguis.

Gnathopod I ( Fig. 19A, C View FIGURE 19 ): coxal plate subrectangular, with 2 setae and 1 seta on anterior and posterior margins; basis with setae on anterior and posterior margins; carpus short, 1.5 times as long as wide, about 0.8 times as long as propodus; propodus oval, palm oblique, with 1 medial spine and 10 spines on posterior margin.

Gnathopod II ( Fig. 19B, D View FIGURE 19 ): coxal plate with 3 setae and 1 seta on anterior and posterior margins; basis with long setae along anterior and posterior margins; carpus with parallel margins, 1.4 times as long as wide, about 0.8 times as long as propodus; propodus subrectangular, palm margin subacute, with 1 medial spine and 5 spines on posterodistal corner.

Pereopod III ( Fig. 20A, F View FIGURE 20 ): coxal plate with 3 setae on anterior margin; basis with setae on anterior and posterior margins; merus and carpus densely set with long setae on posterior margin; propodus with 5 groups of spines accompanied by setae on posterior margin; dactylus with 1 plumose seta on posterior margin, and 1 seta at hinge of unguis.

Pereopod IV ( Fig. 20B, G View FIGURE 20 ): coxal plate with 3 setae on anterior corner and 7 setae on posterior margin, posterior margin excavated; merus with 6 groups of straight setae on posterior margin; carpus and propodus with groups of spines accompanied by setae on posterior margin; dactylus with 2 stiff setae at hinge of unguis.

Pereopod V ( Fig. 20C, H View FIGURE 20 ): coxal plate with 2 setae on posterior margin; basis posterior margin straight, posterior corner subrectangular, with 4 spines on anterior margin, 3 spines on distal corner, a row of 11 setae on posterior margin; merus to propodus with groups of spines on anterior margin, propodus with 2 groups of setae and spine on posterior margin; dactylus with 1 plumose seta on posterior margin and 1 seta at hinge of unguis.

Pereopod VI ( Fig. 20D, I View FIGURE 20 ): coxal plate with 2 setae and 3 setae on anterior and posterior margins; basis elongate, with 2 spines on anterior margin and 3 spines on distal corner, posterior margin processed proximally, with a row of 14 setae; merus to propodus with groups of spines accompanied by short setae on anterior margin; dactylus with 1 plumose seta on posterior margin and 2 setae at hinge of unguis.

Pereopod VII ( Fig. 20E, J View FIGURE 20 ): coxal plate with 5 setae on posterior margin; basis with 4 setae and a row of 3 spines on anterior margin, 2 spines on distal corner, posterior margin expanded, shape convex, with 10 setae on posterior margin; merus to propodus with groups of spines accompanied by short setae on anterior margin; dactylus with 1 plumose seta on posterior margin and 2 stiff 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 VI about half the length of basis; gill of pereopod VII smallest, less than half the length of basis.

Epimeral plates ( Fig. 19E–G View FIGURE 19 ): plate I ventrally rounded, with 4 setae on anterior margin and 3 setae on posterior margin; plate II with 4 spines on ventral margin and 4 setae on posterior margin, posterodistal corner acute; plate III with 4 spines on ventral margin and 3 setae on posterior margin, posterodistal corner acute.

Pleopods I–III ( Fig. 21C–E View FIGURE 21 ): peduncle with 2 retinacula accompanied by 2 setae on anterodistal corner; both inner and outer rami fringed with plumose setae.

Metasome ( Fig. 21A, B View FIGURE 21 ): weakly with dorsal hump, metasome segment I with 5 spines on dorsal margin; metasome segment II with 9 spines on dorsal margin; metasome segment III with 9 spines on dorsal margin.

Urosome ( Fig. 21A, B View FIGURE 21 ): urosome segment I with 2 spines on dorsal margin and 1 spine on each side; with no setae; urosome segment II with 2 spines on dorsal margin and 1 spine on each side; urosome segment III with 1 spine on dorsal margin, with 1 spine on each side.

Uropods I–III ( Fig. 21F–H View FIGURE 21 ): uropod I peduncle with 1 basofacial spine, 3 spines on outer margin and 2 spines on inner margin, with 2 and 1 spine on each corner; outer ramus with 1 spine on outer margin and inner margin; inner ramus with 2 spines on inner margin; both rami with 5 distal spines. Uropod II short, peduncle with 2 spines on inner and outer margins, respectively, with 1 spine on each corner; outer ramus with 1 spine on inner margin; inner ramus with 2 spines on inner margin. Uropod III peduncle with 3 short setae on lateral margin; inner ramus 1.5 times as long as peduncle, reaching 0.6 times the length of outer ramus, with 2 spines on lateral margin; 1 st article of outer ramus with 1 single spine and 2 pairs of spines on outer margin, and 2 pairs of spines on distal margin, outer margin set with simple setae, terminal article shorter than adjacent spines. Both margins of inner ramus and inner margin of outer ramus with plumose setae.

Telson ( Fig. 21I View FIGURE 21 ): deeply cleft, as long as wide, left lobe with 3 distal spines accompanied by 1 seta, 2 setae and 1 spine on surface; right lobe with 3 distal spines.

Description of female. Paratype (IZCAS-I-A1064-2), 9.1 mm.

Gnathopod I ( Fig. 22A, C View FIGURE 22 ): coxal plate with 2 setae and 1 seta on anterior and posterior margins; propodus oval, palm margin not as oblique as that of male, with 7 spines on posterodistal corner; dactylus with 1 seta on outer margin.

Gnathopod II ( Fig. 22B, D View FIGURE 22 ): coxal plate with 2 setae and 1 seta on anterior and posterior margins; propodus subrectangular; palm margin subacute, with 7 spines on posterodistal corner; dactylus with 1 seta on outer margin.

Pereopods III–IV ( Fig. 23A–B, F–G View FIGURE 23 ): with straight setae on posterior margins.

Pereopods V–VII ( Fig. 23C–E, H–J View FIGURE 23 ): similar to those of male.

Uropods I–III ( Figs 21K, L View FIGURE 21 , 22E View FIGURE 22 ): uropod I peduncle with 1 basofacial spine, 2 spines on outer and inner margins, respectively, with 2 and 1 spine on each corner; both rami with 5 distal spines. Uropod II peduncle with 2 spines on inner and outer margins, respectively, with 1 spine on each corner. Uropod III inner ramus about 0.7 times as long as outer ramus, both rami with simple and plumose setae on margins; terminal article of outer ramus as long as adjacent spines.

Telson ( Fig. 22F View FIGURE 22 ): cleft, as long as wide, each lobe with 2 distal spines accompanied by 2 setae.

Oostegite ( Fig. 23K–N View FIGURE 23 ): oostegite of gnathopod II broad, with marginal setae, oostegite of pereopods III and IV elongate, oostegite of pereopod V smallest.

Metasome ( Fig. 21J View FIGURE 21 ): metasome segment I with 7 spines on dorsal margin; segment II with 9 spines on dorsal margin; segment III with 12 spines on dorsal margin.

Urosome ( Fig. 21J View FIGURE 21 ): urosome segment I with 3 spines on dorsal margin and 1 spine on each side; urosome segment II with 2 spines on dorsal margin and 1 spine on each side; urosome segment III with 1 spine on dorsal margin, with 2 spines on each side.

Variability. The spine armature on dorsal margins of metasome and urosome variable; inner ramus of uropod III reaching 0.5–0.7 times the length of outer ramus.

Habitat. This species was collected along the shore of a brook, under the stones and rotten leaves.

Remarks. Gammarus echinatus sp. nov. can be distinguished from G. denticulatus Hou, Li & Morino, 2002 by the following characters: calceoli absent on antenna II (present); propodus of gnathopod II with 9 spines on posterior margin (with 16 spines); coxal plate of pereopod III with 3 setae on anterior corner (1 seta on anterior and posterior margins); bases of pereopods III and IV with a few of setae on posterior margins (many setae on posterior margins); ischium of pereopod IV with 3 spines on posterior distal corner (5 setae on posterior distal corner); basis of pereopod V with a row of 11 setae on posterior margin (4 setae); metasome weakly hump, metasome segment I with 7 spines on dorsal margin, segment II with 9 spines on dorsal margin, segment III with 9 spines on dorsal margin, all segments without setae (metasome with numerous dentations accompanied by setae in dorsal posterior margins).