Gammarus qinling Hou & Li

Hou, Zhonge, Zhao, Shuangyan & Li, Shuqiang, 2018, Seven new freshwater species of Gammarus from southern China (Crustacea, Amphipoda, Gammaridae), ZooKeys 749, pp. 1-79 : 6-11

Gammarus qinling Hou & Li sp. n. Figs 8, 9, 10, 11, 12, 13

Material examined.

Holotype: male (IZCAS-I-A1416-1), 8.3 mm, Zibo Mountain National Forest Park (106.82°E, 33.67°N), altitude 1352 m, Liuba County, Hanzhong City, Shaanxi Province, China, October 24, 2013, collected by Yunchun Li and Jincheng Liu. Paratype: female (IZCAS-I-A1416-2), 9.4 mm, same data as holotype.

Etymology.

The specific name is derived from the type locality; noun in apposition.

Diagnosis.

Antenna II calceoli present in male; pereopods III and IV with short straight setae on posterior margins of merus and propodus; epimeral plates II and III with blunt posterodistal corners; uropod III inner ramus reaching half the length of outer ramus, terminal article of outer ramus a little longer than adjacent spines, both rami with plumose setae on inner and outer margins.

Description of holotype male

(IZCAS-I-A1416-1). 8.3 mm.

Head (Fig. 8A): eyes oval, inferior antennal sinus deep, lateral cephalic lobe rounded.

Antenna I (Fig. 8B, C): peduncle articles I–III in length ratio 1.0: 0.6: 0.4, with lateral and distal setae; flagellum incomplete, articles II–XIX with aesthetascs; accessory flagellum with four articles; both primary and accessory flagella with short distal setae.

Antenna II (Fig. 8D, E): peduncle articles III–V in length ratio 1.0: 2.7: 2.4, article III with distal setae, articles IV and V with clusters of lateral and medial setae; flagellum with 11 articles and one tiny distal article, with setae along dorsal and ventral margins; articles III and IV with calceoli.

Upper lip (Fig. 8F): ventral margin rounded, bearing short minute setae.

Mandible (Fig. 8H, I): left mandible incisor with five teeth; lacinia mobilis with four teeth; spine row with five pairs of plumose setae; articles I–III of palp in length ratio 1.0: 3.7: 3.8, second article of palp with nine marginal setae, article III with three A-setae, three B-setae, 12 D-setae and five E-setae apically; incisor of right mandible with four teeth, lacinia mobilis bifurcate, with small teeth.

Lower lip (Fig. 8G): inner lobes lacking, outer lobes covered with thin setae.

Maxilla I (Fig. 8J, K): asymmetrical, left inner plate with 13 plumose setae on medial margin; outer plate with 11 robust serrated apical spines, each spine with small teeth; second article of left palp with seven slender spines apically; second article of right palp with four stout spines and two slender spines.

Maxilla II (Fig. 8L): inner plate with three fine setae and 12 plumose facial setae in an oblique row; inner and outer plates with long setae apically.

Maxilliped (Fig. 8M): inner plate with three stout apical spines and one subapical spine, 17 plumose setae along lateral margin; outer plate bearing a row of 13 blade spines and three plumose setae apically; article IV of palp hooked, with a group of setae at hinge of unguis.

Pereon.Gnathopod I (Fig. 9A, B): coxal plate bearing three setae and one seta on anterior and posterior margins, respectively; basis with setae on anterior and posterior margins; carpus 1.1 times as long as wide, 0.6 times as long as propodus, ventral margin bearing four clusters of setae; propodus oval, palm with one medial spine and ten spines on posterior margin and surface; dactylus with one seta on outer margin.

Gnathopod II (Fig. 9C, D): coxal plate bearing three setae and one seta on anterior and posterior margins, respectively; basis with setae on anterior and posterior margins, and with two serrated spines accompanied by two setae on posterodistal corner; carpus 1.7 times as long as wide, 0.8 times as long as propodus, bearing six clusters of setae along ventral margin, two clusters of setae on dorsal margin; propodus subrectangular, palm margin with one medial spine and four spines on lateral posterodistal corner; dactylus with one seta on outer margin.

Pereopod III (Fig. 10A, B): coxal plate bearing two setae on anterior margin and one seta on posterior margin; basis elongated, with setae along anterior and posterior margins; merus with straight setae on posterior margin and two spines on anterior margin, anterodistal corner with one spine accompanied by setae; carpus with three spines accompanied by long setae on posterior margin; propodus with five spines accompanied by short 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. 10C, D): coxal plate concave, bearing two setae on anterior margin and five setae on posterior margin; basis with setae along anterior and posterior margins; merus with clusters of short straight setae on posterior margin and one spine on anterior margin, anterodistal and posterodistal corners with one spine accompanied by setae each; carpus with three pairs of spines accompanied by setae on posterior margin, anterodistal corner with one spine accompanied by one seta; propodus with three pairs of 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 V (Fig. 10E, F): coxal plate bearing two setae on posterior margin; basis sub-oval, with three simple setae and five spines accompanied by fine setae on anterior margin, anterodistal corner with two spines, posterior margin with a row of ten setae; merus with three spines accompanied by setae on anterior margin and two spines on posterior margin, anterodistal and posterodistal corners with three spines accompanied by one seta each; carpus with two pairs of spines on anterior and posterior margins each; propodus with three groups of spines on anterior margin; dactylus with one plumose seta on posterior margin, and two setae at hinge of unguis.

Pereopod VI (Fig. 10G, H): coxal plate bearing one seta on anterior and posterior margins each; basis expanded, with three simple setae and four spines accompanied by setae on anterior margin, anterodistal corner with two spines and two fine setae, posterior margin with a row of 11 fine setae; merus with two groups of spines on anterior margin and a pair of spines on posterior margin, anterodistal and posterodistal corners with four spines each; carpus with groups of spines on anterior and posterior margins, anterodistal corner with five spines accompanied by one fine seta and posterodistal corner with five spines; propodus with groups of spines on anterior margin; dactylus with one plumose seta on posterior margin, and two setae at hinge of unguis.

Pereopod VII (Fig. 10I, J): coxal plate bearing three setae on posterior margin; basis with two simple setae and five spines accompanied by setae on anterior margin, anterodistal corner with three spines and two fine setae, posterior margin with a row of 12 setae; merus with two groups of spines on anterior margin and a pair of spines on posterior margin, anterodistal and posterodistal corners with four spines each; carpus with two groups of spines on anterior margin and three spines on posterior margin, anterodistal corner with three spines accompanied by two fine setae and posterodistal corner with five spines accompanied by one seta; propodus with three groups of spines 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 gills of pereopods IV and V a little longer than bases; gill of pereopod III approx. as long as basis; gill of pereopod VI a little shorter than basis; gill of pereopod VII smallest, more than half the length of basis.

Pleon.Epimeral plates (Fig. 9 E–G): plate I ventrally rounded, bearing five setae and one spine on anteroventral margin and two tiny setae on posterior margin; plate II with two spines on ventral margin and five tiny setae on posterior margin, posterodistal corner blunt; plate III with three spines on ventral margin and three tiny setae on posterior margin, posterodistal corner subacute.

Pleopods I–III (Fig. 11 A–C): similar, peduncle with two retinacula accompanied by one or two plumose setae; outer ramus slightly shorter than inner ramus, both inner and outer rami fringed with plumose setae.

Urosome.Urosomites (Fig. 9H). urosomite I with two-one-one-two spines accompanied by setae on dorsal margin; urosomite II with two-one-one-two spines accompanied by setae on dorsal margin; urosomite III with two spines accompanied by one seta on each side and one spine accompanied by three setae on dorsal margin.

Uropods I–III (Fig. 11 D–F): uropod I peduncle with one basofacial spine, one spine on inner margin and one spine on outer margin, inner and outer distal corners with one and two spines, respectively; inner ramus with one spine on inner margin; outer ramus with one spine on inner and outer margins each; both rami with five terminal spines. Uropod II peduncle with one spine on inner and outer margins each, and with one distal spine on each corner; both rami with one spine on inner margins and five terminal spines. Uropod III peduncle with one spine accompanied by one seta on surface and five distal spines; inner ramus 0.9 times as long as peduncle, reaching 0.5 times the length of outer ramus, with one spine accompanied by four plumose setae and one simple seta on inner margin, two plumose setae and one simple seta on outer margin, and two distal spines accompanied by setae; proximal article of outer ramus with three pairs of spines accompanied by five plumose setae and simple setae on outer margin, with ten plumose setae on inner margin, terminal article with simple setae, a little longer than adjacent spines.

Telson (Fig. 11G): deeply cleft, approx. as long as wide; left lobe with two single setae and a cluster of three setae on surface; right lobe with one spine and two clusters of setae on surface; each lobe bearing two distal spines accompanied by setae.

Description of paratype female

(IZCAS-I-A1416-2), 9.4 mm.

Pereon.Gnathopod I (Fig. 12A, B): coxal plate bearing two and one setae on anterior and posterior margins, respectively; basis with long setae on anterior and posterior margins; propodus oval, palm with six spines on posterior margin, bearing long setae along anterior and posterior margins; dactylus with one seta on outer margin.

Gnathopod II (Fig. 12C, D): coxal plate bearing three and one setae on anterior and posterior margins, respectively; basis with long setae on anterior and posterior margins; propodus subrectangular, palm margin with three stout spines and two stiff spines on posterodistal corner, bearing long setae along anterior and posterior margins; dactylus with one seta on outer margin.

Pereopods III and IV (Fig. 13A, B): carpus with more setae on posterior margins than those of male.

Pereopods V–VII (Fig. 13 C–E): similar to those of male.

Oostegite (Fig. 12 E–H): oostegite of gnathopod II broad, with marginal setae, oostegites of pereopods III and IV elongate, oostegite of pereopod V smallest.

Urosome.Uropods I–III (Figs 11H; 13F, G): Uropods I and II similar to those of male. Uropod III peduncle with one spine accompanied by two setae on surface and five distal spines; inner ramus 1.2 times as long as peduncle, reaching 0.5 times the length of outer ramus, with one spine accompanied by five plumose setae on inner margin and two plumose setae on outer margin; proximal article of outer ramus with three clusters of spines accompanied by plumose setae and simple setae on outer margin, with six pairs of plumose setae on inner margin, terminal article a little longer than adjacent spines.

Telson (Fig. 13H): cleft, approx. as long as wide; left lobe with two single setae and a cluster of three setae on surface; right lobe with one spine accompanied by one seta and a cluster of three setae on surface; each lobe bearing two distal spines accompanied by setae.

Habitat.

Specimens were collected from a spring of Wulong Cave in Zibo Mountain National Forest Park, which is famous for the specific topography of sinkholes. Zibo Mountain is located in the south of Qinling.

Remarks.

This new species of Gammarus qinling Hou & Li, sp. n. is most similar to G. vallecula Hou & Li, sp. n. in pereopods III and IV with short setae on posterior margins; pereopods V–VII with spines along anterior and posterior margins, but few setae; and epimeral plates II and III posterior margins blunt. Gammarus qinling Hou & Li, sp. n. can be distinguished from G. vallecula Hou & Li, sp. n. by the following characters ( G. vallecula in parentheses): antenna II calceoli absent (present); uropod III inner ramus approx. half the length of outer ramus, both rami armed with plumose setae (uropod III approx. half the length of outer ramus, both rami with a few plumose setae on inner margins, outer margins with no plumose setae).

This new species of Gammarus qinling Hou & Li, sp. n. can be distinguished from the closely related species G. murarius Hou & Li, 2004a ( G. murarius in parentheses) by the following characters: merus and carpus of pereopod III with straight setae on posterior margins (with long curled setae); epimeral plate I bearing five setae and one spine on anteroventral margin (only with four setae); and inner ramus of uropod III 0.5 times the length of outer ramus (0.65 times the length of first article of outer ramus).