Gammarus jaspidus, 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 : 154-161

Gammarus jaspidus , new species

( Figs. 6-11 )

Material examined. – Holotype - male, 11.5 mm (IZCAS-I-A0067), altitude 4500 m, the Lake YamzhoYumco (about 8 km away from Yarlung Zangbo River), (28.8 oN, 91.0 oE), Nagarze County, 28 Aug.2001.

Paratypes - 4 males, 3 females, 3 juveniles ( IZCAS) , 2 males, 1 female ( ZRC), same data as holotype .

Diagnosis. – Pleonites: pleonites 1-3 weakly elevated. Urosomites: urosomites 1 and 2 with laterally compressed, dorsal elevations, bearing 3-3-1 and 2-2-2 spines on dorsal margin, respectively.

Description. – Holotype, 11.5 mm. Head ( Fig. 6A ): cephalic lateral lobe truncate, inferior antennal sinus distinct, eyes subreniform. Antenna 1 ( Fig. 6D ): peduncular articles 1-3 in length ratio 1: 0.59: 0.34, with distal setae; flagellum with 24 articles, most articles with aesthetascs; accessory flagellum with 3 articles, article 3 small. Antenna 2 ( Figs. 9D, E ): peduncular article 4 about as long as article 5, both with 3 clusters of short setae along both margins; flagellum with 12 articles, some articles with calceoli.

Upper lip ( Fig. 6E ) subrounded, with minute setae. Mandibles ( Figs. 6F, G ): left incisor 5-dentate, lacinia mobilis with 4 dentitions, molar triturative, article 2 of palp with 12 setae, length of article 3 about 73% of article 2, with 4 A-setae on inner face, 4 B-setae on outer face, a row of D-setae and 5 E-setae; right incisor 4-dentate, lacinia mobilis bifurcate, molar triturative, with 1 seta. Lower lip ( Fig. 6I ): inner plate lacking. Maxilla 1 ( Figs. 6J, K ): inner plate with 17 plumose setae, article 2 of left palp broad, with 8 slender spines and 2 stiff setae; article 2 of right palp broader, with 5 blunt spines and 2 stiff setae. Maxilla 2 ( Fig. 6L ): inner plate with a row of 27 plumose setae on inner face; outer plate broad, with apical setae. Maxilliped ( Fig. 6H ): inner plate with 3 apical spines and 1 subapical spine, outer plate with 10 slender spines on medial margin and 4 pectinate setae apically, article 4 of palp slender.

Coxal plates: coxal plates of pereopods 1-3 subrectangular ( Figs. 7A, B , 8D ), with 1-3 setae on anterior corner and 1 seta on posterior corner; coxal plate 4 excavated ( Fig. 8E ), with 1 anterior seta and 4 setae on posterior margin; coxal plates 5 and 6 ( Figs. 8A, B ): anterior lobes small, posterior lobe with 2-3 short setae on posterior corners; coxal plate 7 ( Fig. 8C ) with 4 setae on posterior corner.

Gnathopod 1 ( Figs. 7A, E ): basis with long setae on anterior and posterior margins, and 5 spinulate setae on distal margin; carpus triangular, about 70% of propodus in length; propodus pyriform, palm oblique, bearing 1 median palmar spine, with 10 spines on posterior margin and 6 facial spines; dactylus with 1 seta on outer margin. Gnathopod 2 ( Figs. 7B, F ): carpus about 70% of propodus in length, parallel-sided; palm of propodus with 1 median spine and 6 spines on posterior corner; dactylus fitting with palm margin of propodus.

Pereopod 3 ( Figs. 8D, F ): pereopod 3 with long straight setae on posterior margin; articles 5 and 6 accompanied by several spines on posterior margin; dactylus slender, with 1 seta on outer margin and 2 setae at joint of nail. Pereopod 4 ( Figs. 8E, G ): shorter than pereopod 3, posterior margin with long straight setae.

Pereopods 5-7 ( Figs. 8 A-C, H, I): pereopods 6 and 7 longer than pereopod 5, anterior margin of bases of pereopods 5-7 slightly convex, with 5 short spines and several setae proximally, posterior margin nearly straight in pereopod 5, weakly sinusoid in pereopods 6 and 7, with a row of 12 short setae, inner face of bases of pereopods 6 and 7 with a few short setae; articles 4-6 with groups of spines on anterior margin, without long setae; dactylus slender, with 1 seta on outer margin and 2 setae at joint of nail.

Coxal gills ( Figs. 7B , 8B, C, E ): coxal gills of pereopods 2- 7 ovate.

Pleonites ( Fig. 6B ): weakly elevated, with several short setae on dorsal margins. Epimeral plates: epimeral plates 1-3 with progressively acuminate posterior corners, with a few short setae on posterior margin; epimeral plate 1 ventrally rounded, with 6 setae on anterior corner; epimeral plate 2 with 5 spines on ventral margin; epimeral plate 3 with 3 spines on ventral margin. Pleopods ( Figs. 7C , 9A, B ): subequal in length, peduncle with some long setae, 2-3 retinacula accompanied by 1-3 setae; rami with about 22 articles, fringed with plumose setae.

Urosomites ( Figs. 6B, C ): urosomites 1 and 2 with laterally compressed, dorsal elevations, bearing 3-3-1 and 2-2-2 spines on dorsal margin, respectively; urosomite 3 with 2 spines on dorsal margin. Uropod 1 ( Fig. 9C ): both rami subequal. Uropod 2 ( Fig. 9F ): peduncle with 1-1 and 1-1-1 spines on outer and inner margins, respectively; outer ramus a little shorter than inner ramus. Uropod 3 ( Fig. 9G ): peduncle with 3 distal spines; rami slender; length of inner ramus about 70% of article 1 of outer ramus, with 1 lateral spine; article 1 of outer ramus with 1-1-2-2 lateral spines and 2 distal spines, article 2 stout; both rami armed with plumose setae.

Telson cleft ( Fig. 7D ), each lobe with 2 distal spines accompanied by 5 setae, 1 basolateral spine and 2-3 clusters of facial setae.

Female. – Body length 8.5 mm, ovigerous, with more than 20 eggs. Gnathopod 1 ( Figs. 10B, D ): with long setae on posterior margin, carpus a little shorter than propodus, propodus not as oblique as in male, with 8 spines on posterior margin, dactylus with 1 seta on outer margin. Gnathopod 2 ( Figs. 10A, C, E ): larger than gnathopod 1, propodus subrectangular, with 3 spines on posterior corner. Uropod 3 ( Figs. 11D ): stout, length of inner ramus about 90% of article 1 of outer ramus, both rami ornamented with plumose setae. Oostegites: oostegites in pereopods 2-5 broad or elongate ( Figs. 10C , 11H, I, A ), with many marginal setae.

Etymology. – From the Tibetan language, “YamzhoYumco” meaning jade-colored and changing into Latin “jaspidus ”.

Remarks. – Gammarus jaspidus belongs to G. pulex -group. Gammarus jaspidus is similar to G. lacustris Sars, 1863 in (1) the shape of the gnathopods, (2) the armature of the pereopods 3 and 4, (3) the ratio of the inner and outer ramus of uropod 3. Gammarus jaspidus differs from G. lacustris in (1) the urosomites 1 and 2, which laterally compressed and dorsally elevated, (2) the epimeral plates 2 and 3 not very acute, and (3) the telson with 1 basolateral spine and 3 groups of facial setae.

Gammarus jaspidus differs from G. lasaensis in the relatively slender body (stout in G. lasaensis ) and the palm of propodus of gnathopods 1 and 2 without extra spines except for a main middle spine ( G. lasaensis with 2 and 3 median palmar spines on the gnathopods 1 and 2, relatively).

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

Figures

Fig. 6. Gammarus jaspidus, new species, male, holotype. A. head, B. pleonites and urosomites (lateral view), C. urosomites (dorsal view), D. antenna 1, E. upper lip, F. left mandible, G. incisor of right mandible, H. maxilliped, I. lower lip, J. left maxilla 1, K. palp of right maxilla 1, L. maxilla 2.

Fig. 7. Gammarus jaspidus, new species, male, holotype. A. gnathopod 1, B. gnathopod 2, C. pleopod 1, D. telson, E. propodus of gnathopod 1, F. propodus of gnathopod 2.

Fig. 8. Gammarus jaspidus, new species, male, holotype. A. pereopod 5, B. pereopod 6, C. pereopod 7, D. pereopod 3, E. pereopod 4, F. dactylus of pereopod 3, G. dactylus of pereopod 4, H. dactylus of pereopod 5, I. dactylus of pereopod 6.

Fig. 9. Gammarus jaspidus, new species, male, holotype. A. pleopod 3, B. pleopod 2, C. uropod 1, D. peduncle of antenna 2, E. flagellum of antenna 2, F. uropod 2; G, uropod 3.

Fig. 10. Gammarus jaspidus, new species, female. A. gnathopod 2, B. gnathopod 1, C. oostegite of gnathopod 2, D. propodus of gnathopod 1, E. propodus of gnathopod 2.

Fig. 11. Gammarus jaspidus, new species, female. A. basis of pereopod 5, B. basis of pereopod 7, C, basis of pereopod 6, D. uropod 3, E. dactylus of pereopod 7, F. dactylus of pereopod 5, G. dactylus of pereopod 6, H. pereopod 3, I. pereopod 4.