Gammarus zhigangi 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 : 11-15

Gammarus zhigangi Hou & Li sp. n. Figs 14, 15, 16, 17, 18, 19, 20

Material examined.

Holotype: male (IZCAS-I-A1424-1), 9.1 mm, Tiantai Mountain National Forest Park (107.05°E, 33.25°N), altitude 865 m, Hanzhong City, Shaanxi Province, China, October 25, 2013, collected by Zhigang Chen. Paratype: female (IZCAS-I-A1424-2), 10.9 mm, same data as holotype.

Etymology.

The new species is named after Mr. Zhigang Chen who extensively collected gammarids from China; noun (name) in genitive case.

Diagnosis.

Antenna II calceoli present in male; merus of pereopod III with long, straight setae on posterior margin; inner ramus of uropod III reaching 0.6 times the length of outer ramus, outer ramus with no plumose setae on outer margin but with a row of plumose setae on inner margin.

Description of holotype male

(IZCAS-I-A1424-1). 9.1 mm.

Head (Fig. 14A): eyes reniform, inferior antennal sinus deep, lateral cephalic lobe rounded.

Antenna I (Fig. 14B, C): peduncle articles I–III in length ratio 1.0: 0.6: 0.3, with distal setae; flagellum with 24 articles, articles V–XXII with aesthetascs; accessory flagellum with three articles; both primary and accessory flagella with short distal setae.

Antenna II (Fig. 14D, E): peduncle articles III–V in length ratio 1.0: 2.8: 2.7, article IV of peduncle with lateral setae and article V of peduncle with clusters of lateral and medial setae; flagellum with ten articles, with setae along ventral margin; articles III–VI with calceoli.

Upper lip (Fig. 14F): ventral margin rounded, bearing short minute setae.

Mandible (Fig. 14H, 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: 3.1: 2.7, second article of palp with 12 marginal setae, article III with four A-setae, two B-setae, a row of D-setae, and five E-setae apically; incisor of right mandible with four teeth, lacinia mobilis bifurcate, with small teeth.

Lower lip (Fig. 14G): inner lobes lacking, outer lobes covered with thin setae.

Maxilla I (Fig. 14J, K): asymmetrical, left inner plate with 15 plumose setae on medial margin; outer plate with 11 robust serrated apical spines, each spine with small teeth; second article of left palp with six slender spines and one seta apically; second article of right palp with five stout spines, one stiff seta and one slender spine.

Maxilla II (Fig. 14L): inner plate with 15 plumose facial setae in an oblique row; inner and outer plates with long setae apically.

Maxilliped (Fig. 14M): inner plate with three stout apical spines and one subapical spine, 15 plumose setae along lateral margin; outer plate bearing a row of 11 blade spines and three plumose setae apically; article IV of palp hooked, with three setae at hinge of unguis.

Pereon.Gnathopod I (Fig. 15A, B): coxal plate bearing three setae and one seta on anterior and posterior margins, respectively; basis with long setae on anterior and posterior margins; carpus 1.3 times as long as wide, 0.7 times as long as propodus, ventral margin bearing three clusters of setae; propodus oval, palm with one medial spine and 13 spines on posterior margin and surface; dactylus with one seta on outer margin.

Gnathopod II (Fig. 15C, D): coxal plate bearing four setae and one seta on anterior and posterior margins, respectively; basis with long setae on anterior and posterior margins; 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 five spines on lateral posterodistal corner; dactylus with one seta on outer margin.

Pereopod III (Fig. 16A, B): coxal plate bearing three setae on anterior margin and one seta on posterior margin; basis elongated, with short setae along anterior margin and long setae along posterior margin; merus with long straight setae on posterior margin and two single spines on anterior margin, anterodistal corner with one spine accompanied by two setae; carpus with straight setae on posterior margin; propodus with three 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 IV (Fig. 16C, D): coxal plate concave, bearing three setae on anterior margin and six setae on posterior margin; basis with two short setae on anterodistal corner and long setae along posterior margin; merus with clusters of setae on posterior margin and one spine on anterior margin, anterodistal corner with one spine accompanied by two setae; carpus with three pairs of spines accompanied by setae on posterior margin, anterodistal corner with one spine accompanied by three setae; propodus with three single 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. 16E, F): coxal plate bearing one seta on anterior margin and two setae on posterior margin; basis with two pairs of setae and six spines accompanied by fine setae on anterior margin, anterodistal corner with one spine accompanied by setae, posterior margin with a row of 11 setae; merus with one spine accompanied by setae on anterior margin and a pair of spines on posterior margin, anterodistal and posterodistal corners with two spines accompanied by setae each; carpus and propodus with groups of spines on anterior margin; dactylus with one plumose seta on posterior margin, and two setae at hinge of unguis.

Pereopod VI (Figs 16G, H): coxal plate bearing one seta on anterior margin and two setae on posterior margin; basis with four 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 ten fine setae; merus with three pairs of spines on anterior margin and one spine on posterior margin, anterodistal and posterodistal corners with four spines each; carpus with two groups of spines accompanied by setae on anterior and posterior margins each, anterodistal corner with five spines accompanied by one fine seta and posterodistal corner with five spines; propodus with four groups of spines on anterior margin; dactylus with one plumose seta on posterior margin, and two setae at hinge of unguis.

Pereopod VII (Fig. 16I, J): coxal plate bearing two setae on posterior margin; basis with four long simple setae and four spines on anterior margin, anterodistal corner with two spines and two fine setae, posterior margin with a row of 11 setae; merus with two groups of spines on anterior margin and a pair of spines on posterior margin, anterodistal corner with four spines accompanied by two setae and posterodistal corner with three spines accompanied by one seta; carpus with three groups of spines on anterior margin and two groups of spines on posterior margin, anterodistal corner with three spines accompanied by one seta and posterodistal corner with three spines; 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 III to V a little longer than bases; gill of pereopod VI a little shorter than basis; gill of pereopod VII smallest, approx. half the length of basis.

Pleon.Epimeral plates (Fig. 15 E–G): plate I ventrally rounded, bearing three setae and two spines on anteroventral margin and four tiny setae on posterior margin; plate II with two spines on ventral margin and five tiny setae on posterior margin, posterodistal corner subacute; plate III with three spines on ventral margin and five tiny setae on posterior margin, posterodistal corner subacute.

Pleopods I–III (Fig. 17 A–C): similar, peduncle with two retinacula accompanied by one plumose seta; outer ramus slightly shorter than inner ramus, both inner and outer rami fringed with plumose setae.

Urosome.Urosomites (Fig. 15H): urosomite I with one-one-one-one spines accompanied by setae on dorsal margin; urosomite II with one-one-one-two spines accompanied by setae on dorsal margin; urosomite III with one spine accompanied by two setae on each side and three setae on dorsal margin.

Uropods I–III (Fig. 17 D–F): uropod I peduncle with one basofacial spine, two spines on inner and outer margins each, inner and outer distal corners with one and two spines, respectively; inner ramus with two spines 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; inner ramus with two spines on inner margin and one spine on outer margin; outer ramus with one spine on inner and outer margins each; both rami with five terminal spines. Uropod III peduncle with one spine accompanied by one seta on surface and six distal spines; inner ramus 1.4 times as long as peduncle, reaching 0.6 times the length of outer ramus, with two spines accompanied by eight plumose setae and two simple setae on inner margin, five plumose setae on outer margin, and two distal spines accompanied by setae; proximal article of outer ramus with six spines accompanied by simple setae on outer margin, with 13 plumose setae on inner margin, terminal article with simple setae, a little longer than adjacent spines.

Telson (Fig. 17G): deeply cleft, approx. as long as wide; each lobe with clusters of setae on surface, bearing two distal spines accompanied by setae.

Description of paratype female

(IZCAS-I-A1424-2). 10.9 mm.

Pereon.Gnathopod I (Fig. 18A, B): coxal plate bearing three and one setae on anterior and posterior margins, respectively; basis with setae on anterior and posterior margins; propodus oval, palm with seven spines on posterior margin, bearing long setae along anterior and posterior margins; dactylus with one seta on outer margin.

Gnathopod II (Fig. 18C, D): coxal plate bearing five and one setae on anterior and posterior margins, respectively; basis with setae on anterior and posterior margins; propodus subrectangular, palm margin with two stout spines and three 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. 19A, B): with more setae on posterior margins than those of male.

Pereopods V–VII (Fig. 19 C–E): similar to those of male, but with more setae on anterior margins of pereopods V–VI.

Oostegite (Fig. 20 A–D): oostegite of gnathopod II broad, with marginal setae, oostegites of pereopods III and IV elongated, oostegite of pereopod V smallest.

Urosome.Uropods I–III (Fig. 20 E–G): uropods I and II similar to those of male. Uropod III peduncle with one spine accompanied by one seta on surface and five distal spines; inner ramus 1.3 times as long as peduncle, reaching 0.6 times the length of outer ramus, with one spine accompanied by five plumose setae and one simple seta on inner margin and five plumose setae on outer margin; proximal article of outer ramus with three pairs of spines accompanied by simple setae on outer margin, with one spine accompanied by four plumose setae and three simple setae on inner margin, terminal article a little longer than adjacent spines.

Telson (Fig. 19F): cleft, approx. as long as wide; each lobe with one spine accompanied by two setae and two clusters of three setae on surface, bearing two distal spines accompanied by setae.

Habitat.

Specimens were collected from a geyser in Tiantai Mountain National Forest Park. The geyser is influenced by the formation of cavities in the deep strata. When the groundwater is filled with cavities, the geyser will erupt from the rock cracks. The intermittent geyser is considered as person’s breathing, therefore it is known as a breathing spring. This park is located in the middle of the southern slope of Qinling with lush forests; the topography is full of deep valleys and steep mountains.

Remarks.

The new species of Gammarus zhigangi Hou & Li, sp. n. is most similar to Gammarus qinling Hou & Li, sp. n. in antenna II calceoli present; merus of pereopod III with straight setae on posterior margin; and epimeral plates II and III blunt on posterodistal corners. Gammarus zhigangi Hou & Li, sp. n. differs from Gammarus qinling Hou & Li, sp. n. ( Gammarus qinling in parentheses) by pereopod V of male and female with more setae on anterior margin of merus; and uropod III inner ramus 0.6 times the length of outer ramus (0.5 times), outer margin of outer ramus with no plumose setae (with plumose setae).

The new species of Gammarus zhigangi Hou & Li, sp. n. is similar to G. preciosus Wang, Hou & Li, 2009 in antenna II calceoli present; uropod III without plumose setae on outer margin of outer ramus, and terminal article longer than adjacent spines; and telson long than wide. Gammarus zhigangi Hou & Li, sp. n. can be distinguished from G. preciosus Wang, Hou & Li, 2009 ( G. preciosus in parentheses) in epimeral plate I with three setae and two spines on anteroventral margin (with eight long setae on anteroventral margin); epimeral plate III with five setae on posterior margin (with 11 setae on posterior margin); and uropod III inner ramus 0.6 times the length of outer ramus (inner ramus 0.4 times the length of outer ramus).

This new species can be distinguished from G. murarius Hou & Li, 2004 ( 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 three setae and two spines on anteroventral margin (only with four setae); and uropod III without plumose setae on outer margin of outer ramus (with plumose).