Gammarus gonggaensis, Hou, Zhonge & Li, Shuqiang, 2018

Hou, Zhonge & Li, Shuqiang, 2018, Four new Gammarus species from Tibetan Plateau with a key to Tibetan freshwater gammarids (Crustacea, Amphipoda, Gammaridae), ZooKeys 747, pp. 1-40 : 10-12

Gammarus gonggaensis sp. n. Figs 12, 13, 14, 15, 16

Material examined.

Holotype: male (IZCAS-I-A0065-1), 10.0 mm, Hepinggou, Baoxing County (30.3°N, 102.7°E), Gongga Mountains, altitude 2110 m, June 15, 2001, collected by Jinzhong Fu and Yuezhao Wang. Paratype: female (IZCAS-I-A0065-2) 8.6 mm; paratypes: two males (IZCAS-I-A0065-3), same data as holotype.

Etymology.

The specific name is derived from the type locality; adjective.

Diagnosis.

Antenna II with long setae along anterior and posterior margins of peduncle articles IV and V, calceoli absent; pereopods III and IV with long straight setae on posterior margin; inner ramus of uropod III less than half the length of outer ramus, both inner and outer rami with few marginal setae.

Description of holotype male.

(IZCAS-I-A0065-1), 10.0 mm.

Head. (Fig. 12A): Eyes medium in size, oval.

Antenna I (Fig. 15B): peduncle articles I–III in length ratio 1.0: 0.7: 0.5, bearing distal setae; flagellum with 17 articles, aesthetascs present; accessory flagellum with five articles.

Antenna II (Fig. 15A): gland cone reaching peduncle article III, peduncle article III with distal setae, article IV a little shorter than article V, both with five to six groups of long setae along anterior and posterior margins; flagellum with 12 articles, bearing some setae, calceoli absent.

Upper lip (Fig. 12L): convex, with minute setae.

Mandible (Fig. 12G, H, K): incisor of left mandible with five teeth; lacinia mobilis with four teeth; second and third articles of palp in length ratio 1.1: 1.0, second article with 16 setae, third article with four A-setae, four B-setae, 19 D-setae and four E-setae apically. Incisor of right mandible with four teeth; lacinia mobilis bifurcate, with several small teeth.

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

Maxilla I (Fig. 12I, J): asymmetrical, left inner plate with 13 plumose setae, outer plate with eleven serrated spines, second article of left palp bearing ten slender spines; second article of right palp with five blunt spines and two stiff setae.

Maxilla II (Fig. 12E): inner plate with 12 plumose setae in an oblique row; inner and outer plates with long setae apically.

Maxilliped (Fig. 12F): inner plate with three apical spines and several plumose setae; outer plate with nine blade spines on medial margin and five long setae apically; palp with four articles.

Pereon. Gnathopod I (Fig. 13A, C): coxal plate weakly dilated distally, bearing three and one seta on anterior and posterior corners respectively; basis with setae on anterior and posterior margins; carpus and propodus in length ratio 0.6: 1.0; palm of propodus oblique, bearing one spine on medial margin, three pairs of spines on posterior margin and three spines on inner face; dactylus more than half of posterior margin in length, with on seta one outer margin.

Gnathopod II (Fig. 13B, D): coxal plate subrectangular, with three and one seta on anterior and posterior corners respectively; carpus parallel-sided; palm of propodus truncated, bearing one medial spine, five spines on posterior corner; dactylus beyond the palm margin, with one seta on outer margin.

Pereopod III (Fig. 14A): coxal plate with three and one seta on anterior and posterior corners respectively, merus to propodus with groups of long straight setae on posterior margins; carpus and propodus accompanied by five spines on posterior margins, dactylus stout.

Pereopod IV (Fig. 14C, F): coxal plate concave, bearing two and four setae on anterior corner and posterior margin, merus with six groups of long setae on posterior margin; carpus and propodus with four groups of spines accompanied by some setae; dactylus with one seta on anterior margin and two setae at hinge of nail.

Pereopod V (Fig. 14B, G): coxal plate bearing one seta on anterior lobe and two setae on posterior lobe; basis with three setae and three spines on anterior margin, anterodistal corner with one spine accompanied by setae, posterior margin with a row of nine setae; merus with three groups of setae on anterior margin, a spine accompanied by setae on anterodistal corner, two pairs of spines on posterior margin; carpus with two groups of spines on anterior and posterior margins each, anterodistal corner with a spine, posterodistal corner with a group of six spines; propodus with three pairs of spines on anterior margin, and three clusters of setae and spines on posterior margin; dactylus with one plumose seta on posterior margin and a seta at hinge of unguis.

Pereopod VI (Fig. 14D): coxal plate with two setae on posterior margin; basis narrowing distally, with two long setae and four spines on anterior margin, anterodistal corner with one spine accompanied by setae, posterior margin with a row of 13 setae, and inner surface with two setae on posterior corner; merus with three groups of spines on anterior margin and a pair of spines on posterior margin; carpus with three or two groups of spines on anterior and posterior margins; propodus with four pairs of spines on anterior margin, posterior margin with a seta and a spine accompanied by a seta; dactylus similar to that of pereopod V.

Pereopod VII (Fig. 14E): coxal plate with three plumose setae on anterior margin and three setae on posterior margin; basis with two setae and four spines on anterior margin, posterior margin with a row of 12 setae, inner surface with one spine accom panied by setae on posterior corner; merus and carpus with spines on anterior and posterior margins; propodus with three pairs of spines on anterior margin; dactylus similar to that of pereopod V.

Coxal gills (Fig. 14B, D, E): present on gnathopod II and pereopods III–VII sac-like.

Pleon. Epimeral plates (Fig. 12B): plate I ventrally rounded, with seven setae on ventral margin and two setae on posterior margin; plate II with one seta and two spines on anterior corner, two setae on posterior margin, posterodistal corner blunt; plate III with three spines on ventral margin and two setae on posterior margin.

Pleopods I–III (Fig. 15 G–I): peduncle with some marginal setae, bearing two retinacula accompanied by setae; inner and outer rami nearly the same length, both rami fringed with plumose setae.

Urosome. Urosomites I–III (Fig. 12 C, D): non-humped, with four clusters of spines accompanied by setae.

Uropod I (Fig. 15D): peduncle with one basofacial spine, two spines on outer margin, two spines on outer distal corner, two spines on inner margin, and one spine on inner distal corner; outer ramus with one and two spines on outer and inner margins respectively; inner ramus with one spine on inner margin, both rami with five terminal spines.

Uropod II (Fig. 15C): peduncle with one spine on inner and outer margins each, one spine on inner and outer distal corners each; inner ramus with one spine on inner margin; outer ramus with one spine on outer margin, both rami with five terminal spines.

Uropod III (Fig. 15E): peduncle with one seta on surface, two marginal plumose setae, two distal plumose setae and two distal spines; inner ramus 0.4 times as long as outer ramus, bearing two distal spines accompanied by one long seta; proximal article of outer ramus with two-one-two spines on outer margin and two distal spines, inner margin with a few plumose setae, terminal article shorter than adjacent spines, with distal setae.

Telson (Fig. 15F): cleft, with two distal spines and one facial spine.

Description of paratype female.

(IZCAS-I-A0065-2), 8.6 mm.

Pereon. Gnathopod I (Fig. 16A, B): propodus pyriform, palm slant, bearing four spines on posterior corner.

Gnathopod II (Fig. 16C, D): palm of propodus transverse, with four spines on posterior corner.

Oostegites (Fig. 16F): present on gnathopod II and pereopods III–V, broad, with many long setae.

Urosome. Uropod III (Fig. 16E): peduncle with one marginal spine accompanied by setae, and three pairs of distal spines; inner ramus around half the length of outer ramus, bearing one marginal and three distal spines; proximal article of outer ramus with two groups of spines on outer margin, one spine on inner margin and three spines on distal margin, terminal article shorter than adjacent spines.

Habitat.

This species was collected from a small brook flowing under a large stone, forming a pool with an area of one square meter.

Remarks.

The new species of Gammarus gonggaensis sp. n. is similar to G. kangdingensis sp. n. in pereopods III and IV having long setae on posterior margins; and inner ramus of uropod III 0.4 times the length of outer ramus. Gammarus gonggaensis sp. n. can be distinguished from G. kangdingensis sp. n. ( G. kangdingensis in parentheses) by antenna II peduncle having long setae along anterior and posterior margins, calceoli absent (peduncle with short setae, calceoli present); outer ramus of uropod III with a few plumose setae on inner margin, inner ramus with no plumose marginal setae (with a row of plumose setae on inner margins of inner and outer rami); terminal article of uropod III shorter than adjacent spines (longer than adjacent spines).

Gammarus gonggaensis sp. n. is similar to G. emeiensis Hou, Li & Koenemann, 2002 in antenna II peduncle with long setae along anterior and posterior margins, calceoli absent, and pereopods III and IV with long setae on posterior margins. It differs from G. emeiensis Hou et al., 2002 by uropod III inner ramus 0.4 times the length of outer ramus, while reaching 0.7 times in G. emeiensis .

Gammarus gonggaensis sp. n. differs from G. altus sp. n. ( G. altus in parentheses) by anternna II peduncle with long setae, calceoli absent (with short setae, calceoli present); pereopods III and IV with long setae on posterior margin (with a few short setae); uropod III with plumose setae on inner margin of inner ramus (with no plumose setae), terminal article shorter than adjacent spines (longer than adjacent spines).