Gammarus simplex Hou

Zhao, Shuangyan, Meng, Kaibaryer & Hou, Zhonge, 2017, Two new Gammarus species and a new name (Crustacea: Amphipoda: Gammaridae) from Northwest China, Zootaxa 4273 (2), pp. 195-215 : 197-205

publication ID	https://doi.org/ 10.11646/zootaxa.4273.2.3
publication LSID	lsid:zoobank.org:pub:8D3E9B1A-C046-4371-83A3-BB396E7E227C
DOI	https://doi.org/10.5281/zenodo.6000385
persistent identifier	https://treatment.plazi.org/id/03F9C446-3F0C-CE39-0AA1-FEE5FB114E54
treatment provided by	Plazi
scientific name	Gammarus simplex Hou
status	sp. nov.

Treatment

Gammarus simplex Hou sp. nov.

Figs 2–7 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 View FIGURE 6 View FIGURE 7

Material examined. Holotype: male (IZCAS-I-A1346-1), 14.0 mm, Kanas scenic spots (87°E, 48.7°N), altitude 1415 m, Burqin County of Altay Prefecture, Xinjiang Uygur Autonomous Region, China, July 25, 2013, collected by K. Meng, Z. Yao, Z. Zhao and J. Liu . Paratype: female (IZCAS-I-A1346-2), 11.0 mm, same data as holotype.

Etymology. The specific name is from Latin simplex (simple), in reference to the uropod III with simple setae on both rami; adjective.

Diagnosis. Merus to carpus of pereopod III with clusters of long setae on posterior margin; coxal plate of pereopod VII bearing a cluster of fine setae on anterior margin; epimeral plates II and III with blunt posterodistal corners; urosomite I with fine setae on dorsal margin; inner ramus of uropod III subequal to peduncle, reaching 0.5 times the length of outer ramus, both rami with simple setae.

Description of male. Holotype (IZCAS-I-A1346-1), male 14.0 mm.

Head ( Fig. 2 View FIGURE 2 A): Eyes oval, inferior antennal sinus deep.

Antenna I ( Fig. 2 View FIGURE 2 B, C): peduncle articles 1–3 in length ratio 1.0: 0.7: 0.4, with distal setae; flagellum incomplete, most with aesthetascs; accessory flagellum with five articles; both primary and accessory flagella with short distal setae.

Antenna II ( Fig. 2 View FIGURE 2 D, E): peduncle articles 3–5 in length ratio 1.0: 2.8: 2.8, article 3 of peduncle with setae on posterior and anterior corners, articles 4–5 of peduncle with lateral and medial setae; flagellum with 12 articles and one tiny distal article, with setae along ventral margins; articles 1–8 with calceoli.

Upper lip ( Fig. 2 View FIGURE 2 F): ventral margin rounded, bearing short minute setae.

Mandible ( Fig. 2 View FIGURE 2 H, I): left mandible incisor with five teeth; lacinia mobilis with four teeth; spine row with five pairs of plumose setae and a pair of simple setae; articles 1–3 of palp in length ratio 1.0: 2.5: 1.9, second article of palp with seven marginal setae and one medial seta, article 3 with three A-setae, four B-setae, 18 D-setae and five E-setae apically; incisor of right mandible with four teeth, lacinia mobilis bifurcate, with small teeth.

Lower lip ( Fig. 2 View FIGURE 2 G): inner lobes lacking, outer lobes covered with thin setae.

Maxilla I ( Fig. 2 View FIGURE 2 J, K): asymmetrical, left inner plate with 15 plumose setae on medial margin; outer plate with five setae on inner margin, five fine setae apically and 11 robust serrated apical spines; second article of left palp with six slender spines apically and an apical spine with fine setae; second article of right palp with four stout spines and two slender spines.

Maxilla II ( Fig. 2 View FIGURE 2 L): inner plate with 15 plumose facial setae in an oblique row; inner and outer plates with long setae apically.

Maxilliped ( Fig. 2 View FIGURE 2 M): inner plate with four simple setae, three stout apical spines, one subapical spine, and 16 plumose setae; outer plate bearing a row of blade spines and six plumose setae apically; article 4 of palp hooked, with a group of setae at hinge of unguis.

Gnathopod I ( Fig. 3 View FIGURE 3 A, B): coxal plate bearing two setae and one seta on anterior and posterior margins, respectively; basis with setae on anterior and posterior margins, and with three serrated spines accompanied by setae on posterodistal corner; carpus about 1.4 times as long as wide, about 0.9 times as long as propodus, posterior margin bearing short setae and spines similar to that of posterodistal corner of basis; propodus oval, palm with one medial spine and 18 spines on posterior margin and surface; dactylus with one seta on outer margin.

Gnathopod II ( Fig. 3 View FIGURE 3 C, D): coxal plate bearing three fine setae and one seta on anterior and posterior margins; basis with setae on anterior and posterior margins, posterodistal corner with three serrated spines accompanied by setae; merus bearing setae on posterodistal corner; carpus 1.5 times as long as wide, about 0.75 times as long as propodus, with parallel margins, bearing eight clusters of setae along ventral margin, three serrated spines accompanied by setae on posterodistal corner, two clusters of setae on dorsal margin; propodus subrectangular, palm margin with one medial spine and four spines on posterodistal corner; dactylus with one seta on outer margin and two fine setae subdistally.

Pereopod III ( Fig. 4 View FIGURE 4 A, B): coxal plate bearing two setae and one seta on anterior and posterior margins, respectively; basis elongate, with setae along anterior and posterior margins; merus with clusters of long setae on posterior margin and three spines accompanied by one seta on anterior margin, anterodistal corner with one spine accompanied by setae; carpus with groups of setae on posterior margin, anterodistal corner with one spine and posterodistal corner with two spines accompanied by setae; propodus with four spines accompanied by setae on posterior margin and two spines on posterodistal corner; dactylus with one plumose seta on anterior margin, and two setae at hinge of unguis.

Pereopod IV ( Fig. 4 View FIGURE 4 C, D): coxal plate excavated, bearing two fine setae on anterior margin and four setae on posterior margin; basis with one spine on anterodistal corner, with clusters of setae on posterior margin; merus with clusters of setae on posterior margin and two spines accompanied by fine setae on anterior margin, anterodistal corner with one spine accompanied by setae; carpus and propodus with groups of spines accompanied by setae on posterior margin; dactylus with one plumose seta on anterior margin, and two setae at hinge of unguis.

Pereopod V ( Fig. 4 View FIGURE 4 E, F): coxal plate bearing two fine setae on posterior margin; basis expanded, with fine setae and five spines on anterior margin, anterodistal corner with one spine and one fine seta, posterior margin with a row of 13 setae; merus with two spines accompanied by fine setae on anterior margin and two spines on posterior margin, anterodistal and posterodistal corners with two spines accompanied by setae respectively; carpus and propodus with groups of spines accompanied by fine setae on anterior margin; dactylus with one plumose seta on posterior margin, and two setae at hinge of unguis.

Pereopod VI ( Fig. 4 View FIGURE 4 G, H): coxal plate bearing one fine seta and three fine setae on anterior and posterior margins, respectively; basis elongate, with two long setae and five spines on anterior margin, anterodistal corner with one spine accompanied by setae, posterior margin dwindling distally, with a row of 17 fine setae; merus with three groups of spines accompanied by setae on anterior margin and two spines on posterior margin, anterodistal and posterodistal corners with four and two spines accompanied by setae respectively; carpus and propodus with groups of spines accompanied by setae on anterior margin; dactylus with one plumose seta on posterior margin, and two setae at hinge of unguis.

Pereopod VII ( Fig. 4 View FIGURE 4 I, J): coxal plate bearing a cluster of fine setae on anterior margin and five setae on posterior margin; basis expanded, with four simple setae and six spines accompanied by fine setae on anterior margin, anterodistal corner with three spines accompanied by setae, posterior margin with a row of 16 setae; merus with two groups of spines accompanied by setae on anterior margin and one spine on posterior margin, anterodistal and posterodistal corners with four and three spines accompanied by some setae, respectively; carpus and propodus with groups of spines accompanied by setae on anterior margin; dactylus with one plumose seta on posterior margin, and two setae at hinge of unguis.

Coxal gills: coxal gill of gnathopod II and gill of pereopod III about as long as bases; gills of pereopods IV and VI much shorter than bases; gill of pereopod V longer than basis; gill of pereopod VII missing.

Epimeral plates ( Fig. 5 View FIGURE 5 A–C): plate I ventrally rounded, bearing eight setae on anteroventral margin and two setae on posterior margin; plate II with one spine on ventral margin and four setae on posterior margin, posterodistal corner blunt; plate III with four spines on ventral margin and three setae on posterior margin, posterodistal corner blunt.

Pleopods I–III ( Fig. 5 View FIGURE 5 E–G): similar, peduncle with two retinacula accompanied by two or three setae; outer ramus subequal to inner ramus, both inner and outer rami fringed with plumose setae.

Urosomites ( Fig. 5 View FIGURE 5 D): urosomite I with clusters of fine setae on dorsal margin; urosomite II with two groups of two spines accompanied by fine setae on dorsal margin; urosomite III with three spines accompanied by fine setae on each side.

Uropods I–III ( Fig. 5 View FIGURE 5 H–J): uropod I peduncle with one basofacial spine, one and four spines on inner and outer margins, with one and two spines on inner and outer distal corners, respectively; inner ramus with one spine on inner margin; outer ramus with one and two spines on inner and outer margins, respectively; both rami with five terminal spines. Uropod II short, peduncle bearing one and two spines on inner and outer margins respectively and one distal spine on each corner; both rami with one spine on inner and outer margins respectively and five terminal spines. Uropod III peduncle with one spine and six setae on surface and five distal spines; inner ramus about 1.4 times as long as peduncle, reaching 0.5 times the length of outer ramus, with one spine accompanied by simple setae on inner margin, simple setae on outer margin and one spine accompanied by long setae distally; first article of outer ramus with four spines accompanied by simple setae on outer margin, groups of long simple setae on inner margin, and three distal spines, terminal article with simple setae, slightly shorter than adjacent spines.

Telson ( Fig. 5 View FIGURE 5 K): deeply cleft, 0.8 times as long as wide, each lobe with five setae on surface and with two distal spines accompanied by setae.

Description of female. Paratype (IZCAS-I-A1346-2), 11.0 mm.

Antenna I ( Fig. 6 View FIGURE 6 A, B): similar to that of male.

Antenna II ( Fig. 6 View FIGURE 6 C): differ from that of male in calceoli absent.

Gnathopod I ( Fig. 6 View FIGURE 6 D, E): coxal plate bearing two fine setae on anterior margin; basis with long setae on anterior and posterior margins; propodus oval, palm with four spines on posterior margin, bearing long setae along anterior and posterior margins; dactylus with one seta on outer margin.

Gnathopod II ( Fig. 6 View FIGURE 6 F, G): coxal plate bearing three setae on anterior margin and one seta on posterodistal corner; basis with two long setae and six short setae on anterior margin and long setae on posterior margin, posterodistal corner with short setae; propodus subrectangular, palm margin with six spines on posterodistal corner, bearing long setae along anterior and posterior margins; dactylus with one seta on outer margin.

Pereopods III, IV ( Fig. 7 View FIGURE 7 A–D): with fewer straight setae on posterior margin than those of male.

Pereopods V–VII ( Fig. 7 View FIGURE 7 E–J): similar to those of male.

Pleopods I–III ( Fig. 7 View FIGURE 7 K–M): similar to those of male.

Uropods I–III ( Fig. 5 View FIGURE 5 L–N): uropod I peduncle with one basofacial spine, with four and two spines on outer and inner margins, respectively, with one spine on outer and inner distal corners, respectively; outer ramus with two spines on outer and inner margins, respectively; inner ramus with one spine on outer margin and two spines on inner margin; both rami with five terminal spines. Uropod II short, peduncle bearing two spines on outer and inner margins, respectively, each corner with one distal spine; outer ramus with one spine on outer and inner margins, respectively; inner ramus with one and two spines on outer and inner margins, respectively; both rami with five terminal spines. Uropod III peduncle with one spine accompanied by two setae on surface and three distal spines accompanied by setae; inner ramus subequal to peduncle, reaching 0.5 times the length of outer ramus, with one spine and long setae on inner margin and two distal spines accompanied by long setae; first article of outer ramus with three pairs of spines accompanied by long setae on outer margin and simple setae on inner margin, terminal article slightly shorter than adjacent spines.

Telson ( Fig. 7 View FIGURE 7 N): cleft, 0.9 times as long as wide, each lobe with simple setae on surface and with two distal spines accompanied by setae.

Oostegite ( Fig. 6 View FIGURE 6 H–K): oostegite of gnathopod II broad, with marginal setae, oostegites of pereopods III and IV elongate, oostegite of pereopod V smallest.

Habitat. This species was collected from a small stream on the way from New Tuvas Village to Kanas Lake.

Remarks. Gammarus simplex sp. nov. is similar to G. tianshan nom. nov. in inner ramus of uropod III about half of outer ramus, both rami armed with long simple setae; and pereopods III and IV with long setae on posterior margins. The new species can be distinguished from G. tianshan nom. nov. by the following characters ( G. tianshan nom. nov. in parentheses): accessory flagellum of antenna I with five articles (four articles); flagellum articles 1–7 of antenna II with calceoli (calceoli absent), peduncle articles 4–5 with groups of long setae (with a few short setae); epimeral plates II and III with blunt posterodistal corners (slightly pointed on posterodistal corners); urosomite I with clusters of fine setae on dorsal margin and urosomite II with two groups of two spines accompanied by fine setae on dorsal margin (with four groups of one or two spines accompanied by fine setae); and terminal article of uropod III outer ramus slightly shorter than adjacent spines (subequal).