Gammarus sinuolatus, Hou & Li, 2004

Hou, Zhong-E & Li, Shuqiang, 2004, Gammarus Species From Tibet Plateau, China (Crustacea: Amphipoda: Gammaridae), Raffles Bulletin of Zoology 52 (1), pp. 147-170 : 161-169

Gammarus sinuolatus , new species

( Figs. 12-17 )

Material examined. – Holotype - male, 10.1 mm (IZCAS-I-A0071), altitude 3400 m, tributary of Lancang River, near Qamdo Town (31.1 oN, 97.1 oE), 15 Aug.2001.

Paratypes - 8 males, 7 females ( IZCAS) , 2 males, 2 females ( ZRC), same data as holotype .

Diagnosis. – (1) Gnathopod 2: carpus and propodus with long setae on dorsal margins. (2) Pereopods 6 and 7: bases elongate and concave posteriorly, setae on posterior margin relatively long; articles 4 and 5 with 2 groups of spines accompanied by setae along anterior margins. (3) Uropod 3: inner ramus about one-third of outer ramus, both rami armed with long simple setae. (4) Epimeral plates: bearing long setae on ventral margins. (5) Urosomites: urosomites 1-3 armed with groups of long setae on dorsal margins. (6) Telson with long setae on dorsal face.

Description. – Holotype - male, 10.1 mm (IZCAS-I-A0071). Body: slender. Head ( Fig. 12A ): lateral cephalic lobe of head truncate, inferior antennal sinus distinct, eyes ovate. Antenna 1 ( Fig. 14A ): peduncular articles 1-3 in length ratio 1: 0.75: 0.45, with some distal setae; primary flagellum with 22 articles, most with aesthetascs; accessory flagellum with 4 articles. Antenna 2 ( Fig. 15H ): peduncular articles 4 and 5 subequal in length, both with 2-3 clusters of setae along anterior and posterior margins; flagellum with 10 articles, most articles with calceoli.

Upper lip ( Fig. 12E ) convex, with minute setae. Mandibles ( Figs. 12L, J ): left incisor 5-dentate; lacinia mobilis with 4 weak dentitions, molar triturative, article 2 of palp with 10 stiff setae, article 3 a little shorter than article 2, with 5 Asetae on outer face, 3 B-setae on inner face, about 20 D-setae and 4 E-setae; right incisor 4-dentate, lacinia mobilis bifurcate. Lower lip ( Fig. 12F ): inner lobe absent. Maxilla 1 ( Figs. 12H, K ): inner plate with 10 plumose setae, article 2 of left plap with 6 sharp spines and 2 stiff setae; article 2 of right palp broad, with 5 blunt spines and 1 stiff seta. Maxilla 2 ( Fig. 12I ): inner plate with 10 diagonal plumose setae on inner face, outer plate with long apical setae. Maxilliped ( Fig. 12G ): inner plate with 3 apical spines and 1 subapical spine, outer plate with 9 slender spines on medial margin and 5 pectinate setae apically, palp with 4 articles.

Coxal plates: coxal plates 1-3 subrectangular ( Figs. 13A, B , 14B ), with 2 setae on anterior corner and 1 seta on posterior corner; coxal plate 4 excavated ( Fig. 14C ), with 2 setae on anterior corner and 7 setae on posterior margin; coxal plates 5 and 6 ( Figs. 15A, B ), anterior lobe small, with 1-2 setae on posterior corner; coxal plate 7 ( Fig. 15C ) with 3 setae on posterior margin.

Gnathopod 1 ( Figs. 13A, C ): basis with long setae along anterior and posterior margins; carpus and propodus in length ratio 1: 1.33, carpus triangular; propodus pyriform, palm oblique, bearing 1 median palmar spine, 8 spines on posterior margin and 10 spines on inner face; dactylus about half the length of the propodus margin, with 1 seta on outer margin. Gnathopod 2 ( Figs. 13B, D ), basis similar to that of gnathopod 1; carpus a little shorter than propodus, both with long setae (some weakly curled) on dorsal margin; palm of propodus transverse, bearing 1 median palmar spine and 3 spines on posterior corner; dactylus fitting with propodus margin, with 1 seta on outer margin.

Pereopod 3 slender ( Figs. 14B, G ), posterior margin with long straight setae; articles 5 and 6 with 3 groups of spines on posterior margin; dactylus with 1 seta on outer margin and 1 stiff seta at joint of nail. Pereopod 4 ( Figs. 14C, H ) shorter than pereopod 3, armature reduced.

Pereopods 5-7 ( Figs. 15 A-C, I, J): pereopods 6 and 7 longer than pereopod 5; anterior margin of bases with 5 short spines and several long setae proximally, posterior margin nearly straight in pereopod 5, concaved in pereopods 6 and 7, with a row of about 12 setae, inner face of bases of pereopods 6 and 7 with 2-4 setae; articles 4 and 5 with 2 groups of spines accompanied by setae along anterior and posterior margins, setae longer than spines; article 6 with 3 clusters of spines on anterior margin and a few setae on posterior margin; dactylus slender, with 1 seta on outer margin and 1 seta at hinge of nail.

Coxal gills ( Figs. 13B , 14B, C , 15A, C ): coxal gills of pereopods 2-7 sac-like.

Epimeral plates ( Fig. 12B ): epimeral plates 1-3 not acute on posterior corners, with 1-2 short setae on posterior margin, and many long setae on ventral margins. Pleopods ( Figs. 15 D- F) subequal in length, peduncle with dorsal setae, 2 retinacula accompanied by 2 setae; rami with about 20 articles, all fringed with plumose setae.

Urosomites ( Figs. 12C, D ): urosomites 1-2 dorsally flat, with 4 groups of long setae accompanied by few spines; urosomite 3 with 2 groups of setae. Uropod 1 ( Fig. 14E ): peduncle longer than rami, with 1-1-2 and 1-1 spines on outer and inner margins, respectively; inner ramus with 1 mid-lateral and 5 distal spines; outer ramus with 1 spine on each side and 4 distal spines. Uropod 2 ( Fig. 14F ): peduncle with 3 spines, both rami with 1 lateral spine on outer margin. Uropod 3 ( Fig. 14D ): peduncle with 3 setae on dorsal margin and 5 spines accompanied by several long setae on distal margin; inner ramus about 35% of outer ramus; outer ramus with 2 articles, article 1 with 2 lateral spines and 3 distal spines, article 2 small, 8% of article 1; both rami armed with long simple setae.

Telson deeply cleft ( Fig. 15G ), wider than long, with 2 distal spines accompanied by 5-7 long setae, and a cluster of 7 long setae on dorsal face.

Female. – Body length 11.5 mm. Antenna 2: calceoli absent. Gnathopod 1 ( Figs. 16A, E ): basis with long setae on posterior margin, and 7 facial setae; propodus not as oblique as that of male, with 9 spines on posterior margin. Gnathopod 2 ( Figs. 16B, F ): setae of carpus and propodus fewer than those of male, palm of propodus truncate, with 3 spines on posterior corner. Pereopods 3-7 ( Figs. 17 A-J): pereopods 3-7 similar to those of male, but relatively short, with fewer setae. Uropod 3 ( Fig. 16G ): stout, inner ramus about 40% of outer ramus, both rami fringed with simple setae. Telson cleft ( Fig. 16C ), with 2 distal spines accompanied by long setae, 1 facial spine accompanied by long setae, and a clusters of 3-4 long setae on dorsal face. Epimeral plates ( Fig. 16D ): epimeral plates 1-3 with fewer long setae on ventral margin than those of male.

Oostegites ( Figs. 16B , 17 A-C): oostegites of pereopods 2-5 progressively increasing, bearing many long setae.

Etymology. – This specific name comes from its slim and bowed body shape.

Remarks. – Gammarus sinuolatus belongs to the G. pulex - group. Gammarus sinuolatus resembles G. gregoryi Tattersall, 1924 , from Yunnan. Both species have a short inner ramus of uropod 3 (about one-third of outer ramus), and both rami of uropod 3 are densely set with simple setae. Gammarus sinuolatus can be distinguished from G. gregoryi by the urosomite 1 with 4 groups of long setae on the dorsal margin, while G. gregoryi has few setae on the dorsal margin of urosomite 1.

This taxon is similar to G. parucispinus Hou & Li, 2002b , and G. electrus Hou & Li, 2003c , in the uropod 3 with long simple setae and the telson with long setae on dorsal face. Gammarus sinuolatus differs from G. parucispinus in the antenna 2 with calceoli, inner ramus of uropod 3 shorter than half of outer ramus, urosomites and epimeral plates with long setae on dorsal and ventral margins, respectively. Gammarus sinuolatus differs from G. electrus in propodus of gnathopods 1-2 and posterior margin of pereopod 3 with straight setae, while G. electrus with long curled setae on propodus of gnathopods 2 and posterior margin of pereopod 3.

Gammarus sinuolatus , new species, is also similar to G. frigidus , new species, and, G. jaspidus new species. The differences among these three new species and the related species are given in Table 1.

Distribution. – Qamdo, Tibet, China (present study).

Figures

Fig. 12. Gammarus sinuolatus, new species, male, holotype. A. head, B. epimeral plates, C. urosomites (dorsal view), D. urosomites (lateral view), E. upper lip, F. lower lip, G. maxilliped, H. left maxilla 1, I. maxilla 2, J. incisor of right mandible, K. palp of right maxilla 1, L. left mandible.

Fig. 13. Gammarus sinuolatus, new species, male, holotype. A. gnathopod 1, B. gnathopod 2, C. propodus of gnathopod 1, D. propodus of gnathopod 2.

Fig. 14. Gammarus sinuolatus, new species, male, holotype. A. antenna 1, B. pereopod 3, C. pereopod 4, D. uropod 3, E. uropod 1, F. uropod 2, G. dactylus of pereopod 3, H. dactylus of pereopod 4.

Fig. 15. Gammarus sinuolatus, new species, male, holotype. A. pereopod 5, B. pereopod 6, C. pereopod 7, D. pleopod 3, E. pleopod 2, F. pleopod 1, G. telson, H. antenna 2, I. dactylus of pereopod 5, J. dactylus of pereopod 6.

Fig. 16. Gammarus sinuolatus, new species, female. A. gnathopod 1, B. gnathopod 2, C. telson, D. epimeral plates, E. propodus of gnathopod 1, F. propodus of gnathopod 2, G. uropod 3.

Fig. 17. Gammarus sinuolatus, new species, female. A. pereopod 5, B. pereopod 3, C. pereopod 4, D. pereopod 6, E. pereopod 7, F. dactylus of pereopod 3, G. dactylus of pereopod 4, H. dactylus of pereopod 5, I. dactylus of pereopod 6, J. dactylus of pereopod 7.