Gammarus citatus, 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 : 18-26

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.10540386
persistent identifier	https://treatment.plazi.org/id/5D2BDE76-FFDC-7138-FF54-FE38FC9EFA2C
treatment provided by	Felipe
scientific name	Gammarus citatus
status	sp. nov.

Treatment

Gammarus citatus sp. nov.

Figs 2B View FIGURE 2 , 12–17 View FIGURE 12 View FIGURE 13 View FIGURE 14 View FIGURE 15 View FIGURE 16 View FIGURE 17

Material examined. Holotype: male (IZCAS-I-A1069-1), 14.2 mm, Xinsheng Bridge National Forest Park (99.35°E, 26.47°N), altitude 2,453 m, Lanping County near Nujiang River from Yunnan, China, January 27, 2010, collected by L. Lin and H. Pu. GoogleMaps Paratype: 1 female (IZCAS-I-A1069-2), 10.1 mm, same data as holotype GoogleMaps .

Etymology. The specific name is from Latin citatus (quick, rapid), in reference to the quick movement of Gammaridae species; adjective.

Diagnosis. Basis of pereopods V–VII with a row of 14, 15, 16 setae on posterior margins, respectively; inner ramus of uropod III about 0.3 times the length of outer ramus, with simple setae on both margins; telson with simple long setae on each lobe; epimeral plates II and III obtuse; urosome segment 1 only with long setae.

Description of male. Holotype (IZCAS-I-A1069-1), male 14.2 mm ( Fig. 2B View FIGURE 2 ).

Head ( Fig. 12A View FIGURE 12 ): Eyes oval, 1.7 times as long as wide, inferior antennal sinus deep.

Antenna 1 ( Fig. 12B, C View FIGURE 12 ): 1 st to 3 rd article of peduncle in length ratio 1.0: 0.9: 0.4, with 2 setae on distal corner, flagellum with 23 articles, 3 rd to 22 nd article with aesthetascs; accessory flagellum with 4 articles; both primary and accessory flagella with short distal setae.

Antenna II ( Fig. 12D, E View FIGURE 12 ): About 0.7 times as long as antenna I, 3 rd to 5 th article of peduncle in length ratio 1.0: 3.3: 3.3, 4 th and 5 th article of peduncle with lateral and medial setae; flagellum with 11 articles and 1 tiny distal article, with setae along dorsal and ventral margins; 1 st to 6 th article with calceoli.

Upper lip ( Fig. 12F View FIGURE 12 ): ventral margin rounded, bearing short minute setae.

Mandible ( Fig. 12H, I View FIGURE 12 ): left mandible incisor with 5 teeth; lacinia mobilis with 4 teeth; 1 st to 3 rd article of palp in length ratio 1.0: 2.8: 2.0, 2 nd article of palp with 12 marginal setae, 3 rd article with 4 A-setae, 2 B-setae, 24 Dsetae and 5 E-setae apically; incisor of right mandible with 4 teeth, lacinia mobilis bifurcate, with small teeth.

Lower lip ( Fig. 12G View FIGURE 12 ): inner lobes lacking, outer lobes covered with thin setae.

Maxilla I ( Fig. 12J, K View FIGURE 12 ): asymmetrical, left inner plate with 11 plumose setae on medial margin; outer plate with 11 robust serrated apical spines, each spine with small teeth; 2 nd article of left palp with 8 slender spines apically; 2 nd article of right palp with 5 stout spines and 1 slender spine.

Maxilla II ( Fig. 12L View FIGURE 12 ): inner plate with 10 plumose facial setae in an oblique row; inner and outer plates with long setae apically.

Maxilliped ( Fig. 12M View FIGURE 12 ): inner plate with 3 stout apical spines and 1 subapical spine, some plumose setae along lateral margin; outer plate bearing a row of blade spines and 5 plumose setae apically; 4 th article of palp hooked, with a group of setae at hinge of unguis.

Gnathopod I ( Fig. 13A, C View FIGURE 13 ): coxal plate bearing 4 fine setae and 1 seta on anteroventral and posterior margins, respectively; basis with setae on anterior and posterior margins; carpus 2.5 times as long as wide, nearly the same length as propodus, posterior margin bearing short setae; propodus oval, palm with 1 medial spine and 19 spines on posterior margin and surface.

Gnathopod II ( Fig. 13B, D View FIGURE 13 ): coxal plate bearing 3 fine setae and 1 seta on anteroventral and posterior margins; basis with setae on anterior and posterior margins, posterodistal corner with short setae; merus bearing some long setae on posterior margin; carpus 2.2 times as long as wide, about 0.9 times as long as propodus, with parallel margins, bearing 7 clusters of setae along ventral margin, 3 clusters of setae on dorsal margin; propodus subrectangular, palm margin with 1 medial spine and 5 spines on posterodistal corner, with 6 clusters of long setae on inner surface; dactylus with 1 seta on outer margin.

Pereopod III ( Fig. 14A, F View FIGURE 14 ): coxal plate bearing 3 fine setae and 1 seta on anteroventral and posterior margins; basis elongate, with setae along anterior and posterior margins; merus with clusters of long setae on posterior margin and 1 spine accompanied by 1 seta on anterior margin, anterodistal and posterodistal corner with 1 spine accompanied by setae respectively; carpus and 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. 14B, G View FIGURE 14 ): coxal plate excavated, bearing 3 fine setae on anteroventral corner and 4 setae on posterior margin; basis with 1 cluster of setae on anterodistal corner and 6 clusters of long setae on posterior margin; merus with clusters of long setae on posterior margin and 1 spine accompanied by 1 seta on anterior margin, anterodistal with one spine accompanied by setae; 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. 14C, H View FIGURE 14 ): coxal plate bearing 3 fine setae on posterior margin; basis expanded, with 4 simple setae and 6 spines on anterior margin, anterodistal corner with 2 spines and 2 simple setae, posterior margin with a row of 14 setae; merus with 3 clusters of simple setae on anterior margin and 2 spines on posterior margin, anterodistal and posterodistal corner with 1 and 3 spines accompanied by setae respectively; carpus and propodus with groups of spines accompanied by setae on anterior margin; dactylus with 1 plumose seta on posterior margin, and two setae at hinge of unguis.

Pereopod VI ( Fig. 14D, I View FIGURE 14 ): coxal plate bearing 4 fine setae on posterior margin; basis elongate, with 3 simple setae and 4 spines on anterior margin, anterodistal corner with 1 spine and 1 simple seta, posterior margin dwindling distally, with a row of 15 setae; merus with 2 groups of spines accompanied by setae and 1 spine on anterior and posterior margins, respectively, anterodistal and posterodistal corners with 3 spines accompanied by setae respectively; carpus and 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. 14E, J View FIGURE 14 ): coxal plate bearing 4 fine setae on posterior margin; basis expanded, posterior margin weakly narrowed distally, anterior with 3 simple setae and 5 spines, posterior with a row of 16 setae; merus with 2 groups of spines accompanied by setae and 1 spine on anterior and posterior margins, anterodistal and posterodistal corners with 2 spines accompanied by some setae, respectively; carpus and 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: coxal gill of gnathopod II and gills of pereopods III–V a little shorter than bases; gill of pereopod VI more than half length of basis; gill of pereopod VII smallest, less than half of basis.

Epimeral plates ( Fig.15A–C View FIGURE 15 ): plate I ventrally rounded, bearing 5 setae on anteroventral margin and 4 setae on posterior margin; plate II with 3 spines on ventral margin and 7 setae on posterior margin, posterodistal corner obtuse; plate III with 3 spines and 3 simple setae on ventral margin, and 6 setae on posterior margin, posterodistal corner subrounded.

Pleopods I–III ( Fig. 15E–G View FIGURE 15 ): similar, peduncle of pleopod II with 3 retinacula accompanied by 1 seta; outer ramus slightly longer than inner ramus, both inner and outer rami fringed with plumose setae.

Urosome ( Fig. 15D View FIGURE 15 ): dorsally flat. Urosome segment I with clusters of setae on dorsal margin; urosome segment II with 3 spines and 6 setae on dorsal margin; urosome segment III with 2 spines and 8 setae on dorsal margin.

Uropods I–III ( Fig. 15H–J View FIGURE 15 ): uropod I peduncle with 1 basofacial spine, 2 and 1 spine on outer and inner margins, with 1 and 2 spines on inner and outer distal corners, respectively; both rami with 1 spine on inner margin and 5 terminal spines. Uropod II short, peduncle bearing 2 spines on outer margin; inner ramus with 1 spine on inner margin; both rami with 5 terminal spines. Uropod III peduncle with simple setae on posterior margin; inner ramus as long as peduncle, reaching 0.3 times the length of outer ramus, with long simple setae on inner margin and 1 distal spine accompanied by long setae; 1 st article of outer ramus with 2 groups of spines accompanied by long setae on outer margin, both margins with simple setae, terminal article slightly shorter than adjacent spines.

Telson ( Fig. 15K View FIGURE 15 ): deeply cleft, as long as wide, each lobe with 3 long setae on dorsolateral margins; left lobe bearing 1 apical spine accompanied by 5 setae, right lobe with 3 setae apically.

Description of female. Paratype (IZCAS-I-A1069-2), 10.1 mm.

Gnathopod I ( Fig. 16A, C View FIGURE 16 ): coxal plate bearing 6 fine setae and 1 seta on anteroventral and posterior margins, respectively; basis with 4 setae on anterior margin and long setae on posterior margin; propodus oval, palm with 6 spines on posterior margin.

Gnathopod II ( Fig. 16B, D View FIGURE 16 ): coxal plate bearing 5 fine setae and 1 seta on anteroventral and posterior margins; basis with setae on anterior margin and long setae on posterior margin, posterodistal corner with short setae; propodus subrectangular, palm margin with 4 spines on posterodistal corner, bearing long setae along anterior and posterior margins; dactylus with 1 seta on outer margin.

Pereopods III–IV ( Fig. 17A–B, F–G View FIGURE 17 ): with fewer straight setae on posterior margin than those of male.

Pereopods V–VII ( Fig. 17C–E, H–J View FIGURE 17 ): basis with more setae on posterior margin than those of male.

Uropods I–III ( Fig. 15L–N View FIGURE 15 ): uropod I peduncle with 1 basofacial spine, with 1 and 2 spines on inner and outer margins, respectively, with 1 and 2 spines on inner and outer corners; inner ramus with 1 spine on inner margin; both rami with 5 terminal spines. Uropod II short, peduncle bearing 2 spines on outer margin; both rami with 1 spine and 5 terminal spines. Uropod III peduncle with 4 distal spines and some setae; inner ramus 0.8 times as long as peduncle, reaching 0.4 times the length of outer ramus, with some long setae on lateral margin and 1 distal spines; 1 st article of outer ramus with 2 pairs of spines accompanied by long setae on outer margin, both margins with simple setae, terminal article slightly shorter than adjacent spines.

Telson ( Fig. 16E View FIGURE 16 ): cleft, 1.2 times as long as wide, each lobe with long setae on dorsolateral margins and with 2 and 1 spine accompanied by 4 setae apically, respectively.

Oostegite ( Fig. 17K–N View FIGURE 17 ): oostegite of gnathopod II broad, with marginal setae, oostegite of pereopods III and IV elongate, oostegite of pereopod V smallest.

Variability. The body length relatively large, more than 10 mm; the setation on posterior margins of bases in pereopods V–VII various from 10–20; outer ramus of uropod I with or without marginal spines.

Habitat. Specimens were collected along a brook in Xinsheng Bridge National Forest Park. This park is located between Nujiang River and Lancang River. With the strong cutting of these two large rivers, the topography of this park is full of deep valleys and steep mountains.

Remarks. Gammarus citatus sp. nov. can be distinguished from G. curvativus Hou & Li, 2003 by the following characters ( G. curvativus in parentheses): accessory flagellum of antenna I with 4 articles (2 articles); palm of gnathopod I with 20 spines on posterior margin (13 spines); merus of pereopod III with spines accompanied by 1 seta on anterior margin (with 2 clusters of setae on anterior margin); telson with long setae on each lobe (short setae); epimeral plates II–III obtuse (pointed); urosome segment I only with long setae on dorsal margin (with spines accompanied by short setae).

Gammarus citatus sp. nov. can also be distinguished from G. paucispinus Hou & Li, 2002 by the following characters ( G. paucispinus in parentheses): calceoli present on antenna II (absent); 2 nd article of mandible armed with 12 marginal setae (5 setae); propodus of pereopod IV with simple setae on distal corner (with 4 plumose setae on distal corner); basis of pereopods V–VII with a row of 14, 15, 16 setae on posterior margins, respectively (with 10, 12, 11 setae, respectively); telson with 3 simple long setae on the surface of each lobe and only 1 spine on left lobe apically (telson with 6 simple setae and 1 plumose seta, with 1 spine on an each lobe apically); epimeral plates II and III obtuse (pointed); urosome with more long setae, 3 spines and 6 setae, 2 spines and 10 setae on dorsal margins, respectively (4 short setae, 4 clusters of 1 spine accompanied by 2 setae, 2 clusters of 1 spine accompanied by 4 setae, respectively); uropod III with simple setae on both margins (densely with simple setae).

Gammarus citatus sp. nov. can be distinguished from G. gregoryi Tattersall, 1924 by the following characters ( G. gregoryi in parentheses): eyes oval (reniform); accessory flagellum of antenna I with 4 articles (3 articles); palm of gnathopod I with 20 spines on posterior margin (with 6 spines on posterior margin); urosome segments I–III with long setae, 3 spines and 6 setae, 2 spines and 10 setae on dorsal margins, respectively (2 clusters of setae, 4 spines accompanied by 2 setae, 3 spines and setae, respectively).