Gammarus kangdingensis, 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 : 6-10

Gammarus kangdingensis sp. n. Figs 7, 8, 9, 10, 11

Material examined.

Holotype: male (IZCAS-I-A0059-1), 11.8 mm, Erdaohe, Kangding County (30.0°N, 101.9°E), altitude 2470 m, August 19, 2001, collected by Xianjin Peng. Paratype: female (IZCAS-I-A0059-2), 8.5 mm; paratypes: two males and three females (IZCAS-I-A0059-3), same data as holotype.

Etymology.

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

Diagnosis.

Pereopods III and IV with long setae on posterior margins; epimeral plates blunt; uropod III inner ramus length less than half of outer ramus length, outer margin of outer ramus with few plumose setae.

Description of male holotype.

(IZCAS-I-A0059-1), 11.8 mm, slender.

Head. (Fig. 7A, B): cephalic lateral lobe truncated, inferior antennal sinus deep, eyes ovate.

Antenna I (Fig. 7F, G): peduncle articles I–III in length ratio 1.0: 0.7: 0.4, each article with distal setae; primary flagellum with 22 articles, most with aesthetascs; accessory flagellum with five articles.

Antenna II (Fig. 8F): gland cone reaching peduncle article III, peduncle articles VI and V in length ratio 1.0: 0.7, with one or two groups of setae on ventral margin, flagellum with nine articles, each with short setae, calceoli present on articles II–V.

Upper lip (Fig. 7M): convex, with minute setae.

Mandible (Fig. 7 H–J): incisor of left mandible with five teeth; lacinia mobilis with four teeth; second article of palp with 14 stiff setae, third article 77% the length of second article, with three groups of A-setae on outer face, seven B-setae on inner face, a row of 25 D-setae and five E-setae apically. Incisor of right mandible with four teeth; lacinia mobilis bifurcate, with small teeth.

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

Maxilla I (Fig. 7K, L): asymmetrical, left inner plate with 18 plumose setae, outer plate with eleven serrated spines, second article of left palp with eight slender spines and three stiff setae; second article of right palp with five blunt spines and two stiff setae.

Maxilla II (Fig. 8G): inner plate with 15 plumose setae in an oblique row, outer plate broad, with apical setae.

Maxilliped (Fig. 8H): inner plate with three blunt spines and one subapical spine; outer plate broad, with 13 blade spines on medial margin and four plumose setae apically; palp with four articles, terminal article unguis-form, with setae at hinge of unguis.

Pereon. Gnathopod I (Fig. 8A, D): coxal plate weakly dilated distally, with two and one seta on anterior and posterior corners, respectively; basis with long setae along anterior and posterior margins; carpus a little shorter than propodus, with four groups of setae on posterior margin; propodus pyriform, palm oblique, bearing a median spine, ten spines on posterior margin and seven spines on inner face; dactylus reaching half of posterior margin of propodus, with one seta on outer margin.

Gnathopod II (Fig. 9A, D), coxal plate subrectangular, with one seta on anterior corner and one seta on posterior corner, basis slender than that of gnathopod I, bearing four serrated setae distally; carpus as long as propodus, with subparallel margins; propodus subrectangular, palm with a median blunt spine, and six spines on posterior corner; dactylus beyond the palm margin, with one seta on posterior margin.

Pereopod III (Fig. 9C, F): coxal plate with two setae on anterior corner and one seta on posterior corner; basis with long straight setae on posterior margin, merus with one spine accompanied by setae on anterior margin, and long setae on posterior margin; carpus with four groups of spines accompanied by long setae on posterior margin; propodus with four pairs of spines accompanied by few setae on posterior margin; dactylus short, with one plumose seta on anterior margin and one stiff seta at hinge of unguis.

Pereopod IV (Fig. 9B, E): shorter than pereopod III, coxal plate concave, with two setae on anterior corner and six setae on posterior margin; basis with long straight setae on posterior margin; merus with one spine accompanied by one seta on anterior margin and six clusters of long setae on posterior margin; carpus with three pairs of spines accompanied by long setae on posterior margin, posterodistal corner with two spines accompanied by long setae; propodus with four groups of spines accompanied by a few setae on posterior margin; dactylus with one seta at hinge of unguis.

Pereopod V (Fig. 10A, H): coxal plate with one seta on anterior lobe and three setae on posterior lobe; basis weakly expanded, with three groups of long setae and a row of five spines on anterior margin, anterodistal corner with a spine accompanied by setae, posterior margin with a row of 15 fine setae; merus with three groups of setae and spines on anterior margin, and a spine accompanied by setae on posterior margin; carpus with two groups 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. 10B, I): coxal plate with three setae on posterior margin; basis expanded, tapered distally, with six long setae and five spines on anterior margin, anterodistal corner with one spine accompanied with setae, posterior margin with 16 setae, and two setae on inner surface; merus and carpus with spines on anterior and posterior margins; propodus with four spines on anterior margin; dactylus with one plumose seta on posterior margin and two setae at hinge of unguis.

Pereopod VII (Fig. 10C, J): coxal plate with five setae on posterior margin; basis expanded, anterior margin with three groups of long setae and five spines, anterodistal corner with a spine accompanied by setae, posterior margin with a row of 15 setae, inner surface with a spine accompanied by setae; merus and carpus with spines on anterior and posterior margins; propodus with four pairs of spines on anterior margin; dactylus with one plumose seta on posterior margin and a seta at hinge of unguis.

Coxal gills (Figs 9 A–C, 10 A–C): present on gnathopod II and pereopods III–VII ovate, gill of pereopod VII smallest.

Pleon. Epimeral plates (Fig. 7D): plate I ventrally rounded, with nine setae on anteroventral margin and two setae on posterior margin; plate II with three spines on ventral margin and three setae on posterior margin, posterodistal corner blunt; plate III with four spines on ventral margin, posterodistal corner weakly acute.

Pleopods I–III (Figs 8B, C, 10G): subequal, peduncle with several marginal setae and two retinacula accompanied by two or three setae; inner and outer rami with approximately 23 articles, fringed with plumose setae.

Urosome. Urosomites I–III (Fig. 7C, E): non-humped, urosomites I–II with four groups of spines accompanied by setae; urosomite III with two dorsal setae and one spine accompanied by setae on each side.

Uropod I (Fig. 10D): peduncle with one basofacial spine, two spines on outer margin, two spines on outer distal corner, one spine on inner distal corner; outer ramus with one spine on each side; inner ramus with one mid-lateral spine on outer margin.

Uropod II (Fig. 10F): peduncle with one spine on inner margin, one spine on inner and outer distal corners each; outer ramus a little shorter than inner ramus, with one spine on outer margin; inner ramus with one spine on inner margin, both rami with five distal spines.

Uropod III (Fig. 10E), peduncle with one marginal spine and four distal spines; inner ramus 0.4 times as long as outer ramus, with one lateral and one distal spines, inner margin with four plumose setae; proximal article of outer ramus only with three pairs of spines on outer margin, inner margin with ten plumose setae, terminal article longer than adjacent spines, with simple setae distally.

Telson (Fig. 8F): deeply cleft, each lobe with one distal spine accompanied by some setae, and some facial short setae.

Description of paratype female.

(IZCAS-I-A0059-2), 8.5 mm.

Pereon. Gnathopod I (Fig. 11A, C): carpus and propodus shorter than those of male, carpus triangular; palm of propodus not oblique as that of male, palm with seven spines on posterior margin; dactylus with one seta on outer margin.

Gnathopod II (Fig. 11B, E): carpus and propodus elongated, carpus parallel-sided; propodus subrectangular, palm with three spines on posterior corner.

Pereopods III–VII (Fig. 11 G–I): similar to those of male.

Oostegites (Fig. 11F, I): present on gnathopod II and pereopods III–V, oostegite of gnathopod II broad, with marginal setae; oostegite of pereopod V smallest.

Urosome. Uropod III (Fig. 11D): inner ramus length approx. half of outer ramus length, inner margins of inner and outer rami with a few plumose setae.

Habitat.

This species was collected from a small stream at the foot of mountain, with weak water flow but many detritus.

Remarks.

Gammarus kangdingensis sp. n. resembles G. emeiensis Hou, Li & Koenemann, 2002 in pereopods III and IV having long setae on posterior margins; pereopods V–VII having marginal spines, but with few setae; and epimeral plates with blunt posterodistal corners. Gammarus kangdingensis sp. n. can be distinguished from G. emeiensis ( G. emeiensis in parentheses) in antenna II peduncle having short setae along anterior and posterior margins, and calceoli (peduncle with long setae on anterior and posterior margins, calceoli absent); uropod III inner ramus 0.4 times the length of outer ramus (inner ramus 0.7 times the length of outer ramus); uropod III terminal article of outer ramus longer than adjacent spines (terminal article as long as adjacent spines).

Gamamrus kangdingensis sp. n. is similar to G. altus sp. n. in the shape of gnathopods I and II. It differs from G. altus sp. n. ( G. altus in parentheses) in having pereopods III and IV with long setae on posterior margins (with a few short setae on posterior margins); and inner ramus of uropod III 0.4 times the length of outer ramus (0.3), inner margins of inner and outer rami with a row of plumose setae (with no plumose setae).