Gammarus monticellus, Hou & Li & Li, 2014

Hou, Zhonge, Li, Junbo & Li, Shuqiang, 2014, Diversification of low dispersal crustaceans through mountain uplift: a case study of Gammarus (Amphipoda: Gammaridae) with descriptions of four novel species, Zoological Journal of the Linnean Society 170 (4), pp. 591-633 : 615-623

publication ID	https://doi.org/ 10.1111/zoj.12119
DOI	https://doi.org/10.5281/zenodo.10541918
persistent identifier	https://treatment.plazi.org/id/0E4E223A-5904-FFDB-8576-27454B8EFC10
treatment provided by	Marcus
scientific name	Gammarus monticellus
status	sp. nov.

Treatment

GAMMARUS MONTICELLUS SP. NOV. ( FIGS 16–21 View Figure 16 View Figure 17 View Figure 18 View Figure 19 View Figure 20 View Figure 21 )

Material examined

Holotype (IZCAS-I-A1253-1), male, 12.1 mm, Taiyue Mt National Forest Park (36°39′N, 112°00′E), altitude 1829 m, Linfen City, Shanxi Province, China, 30.v.2012, collected by J. Li and Z. Chen. GoogleMaps Paratypes (from IZCAS-I-A1253-2 to IZCAS-I-A1253-20), ten males and nine females, same data as holotype GoogleMaps .

Other material

Eight males and five females (from IZCAS-I-A1250- 1 to IZCAS-I-A1250-13, voucher number 1250), Taotangyu (36°29′N, 111°51′E), altitude 1258 m, Huozhou City , Shanxi Province, China, 28.v.2012, collected by J. Li and Z. Chen. Fifteen GoogleMaps males and six females (from IZCAS-I-A1250-1 to IZCAS-I-A1250-21, voucher number 1247), Mianshan Mt (36°51′N, 112°00′E), altitude 1558 m, Jiexiu City , Shanxi Province, China, 26.v.2012, collected by J. Li and Z. Chen. GoogleMaps

Etymology

The specific name is from the Latin monticellus (mountain), in reference to the habitat of this species; noun.

Diagnosis

Merus to carpus of pereopod 3 with long, curled setae on posterior margin; epimeral plates 2, 3 with blunt posterodistal corners; inner ramus of uropod 3 reaching about 0.6 times length of outer ramus, both margins densely set with plumose setae.

Description

Holotype: male

Body length: 12.1 mm.

Head ( Fig. 16A View Figure 16 ): eyes reniform, inferior antennal sinus deep, lateral cephalic lobe nearly straight.

Antenna 1 ( Fig. 16B, C View Figure 16 ): peduncular articles 1–3 in length ratio 1.0:0.8:0.4, with distal setae; flagellum with 35 articles, most with aesthetascs; accessory flagellum with four articles; both primary and accessory flagella with short distal setae.

Antenna 2 ( Fig. 16D, E View Figure 16 ): peduncular articles 3–5 in length ratio 1.0:2.8:2.6, peduncular articles 4, 5 with clusters of lateral and medial setae; flagellum with 13 articles and one tiny distal article; calceoli present in articles 1–8.

Upper lip ( Fig. 16F View Figure 16 ): ventral margin rounded, bearing minute setae.

Mandible ( Fig. 16H, I View Figure 16 ): left mandible incisor with five teeth; lacinia mobilis with four teeth, spine row with six pairs of plumose setae along ventral margin; palp articles 1–3 in length ratio 1.0:2.7:1.9; article 2 armed with nine marginal setae; article 3 with four A-setae and two clusters of B-setae, plus 18 D-setae and five E-setae apically; incisor of right mandible with four teeth, lacinia mobilis bifurcate, with small teeth.

Lower lip ( Fig. 16G View Figure 16 ): inner lobes lacking, outer lobes covered with thin setae.

Maxilla 1 asymmetrical ( Fig. 16J, K View Figure 16 ), left inner plate with 16 plumose setae on medial margin; outer plate with 11 robust, serrated apical spines, each spines with small teeth; article 2 of palp with nine slender spines apically; article 2 of right palp with five stout spines, one stiff seta and one slender spine.

Maxilla 2 ( Fig. 16L View Figure 16 ): inner plate with 17 plumose setae in an oblique row; inner and outer plates with long setae apically.

Maxilliped ( Fig. 16M View Figure 16 ): inner plate with three stout apical spines and one subapical spine, some plumose setae along ventral margin; outer plate bearing a row of blade-like spines and four plumose setae apically; palp article 4 hooked, with a group of setae at hinge of unguis.

Gnathopod 1 ( Fig. 17A, C View Figure 17 ): coxal plate bearing three setae and one seta on anterior and posterior margins, respectively; basis with setae on anterior and posterior margins; carpus about 1.4 times as long as wide, about 0.6 times as long as propodus, posterior margin bearing short setae; propodus oval, palm with one medial spine and 13 spines on posterior margin and facial surface; dactylus with one seta on outer margin.

Gnathopod 2 ( Fig. 17B, D View Figure 17 ): coxal plate bearing three setae and one seta on anterior and posterior margins, respectively; basis with long setae on anterior and posterior margins, posterodistal corner with short setae; carpus about 1.7 times as long as wide, about 0.9 times as long as propodus, with parallel margins, bearing nine clusters of setae along ventral margin and two clusters of setae on dorsal margin; propodus palm ovate, palm margin with one medial spine and five spines on lateral posterodistal corner; dactylus with one seta on outer margin.

Pereopod 3 ( Fig. 18A, F View Figure 18 ): coxal plate bearing three setae and one seta on anteroventral and posterior margins, respectively; basis with long setae along posterior margin; merus with long, curled setae on posterior margin; carpus to propodus with groups of spines accompanied by long, curled setae on posterior margin; dactylus with one plumose seta on posterior margin and two setae at hinge of unguis.

Pereopod 4 ( Fig. 18B, G View Figure 18 ): coxal plate excavated, bearing three setae on anterior margin and four setae on posterior margin; basis with long setae on posterior margin; merus with clusters of straight setae on posterior margin; carpus to propodus with groups of spines accompanied by setae on posterior margin; dactylus with one plumose seta on posterior margin and two setae at hinge of unguis.

Pereopod 5 ( Fig. 18C, H View Figure 18 ): coxal plate bearing one seta on anterior margin and four setae on posterior margin; basis with one seta and five spines on anterior margin, anterodistal corner with one spine, posterior margin with a row of 11 setae; merus to propodus with groups of spines on anterior margin; dactylus with one plumose seta on posterior margin and two setae at hinge of unguis.

Pereopod 6 ( Fig. 18D, I View Figure 18 ): coxal plate bearing three setae on posterior margin; basis elongate, with three seta and four spines on anterior margin, anterodistal corner with two spines, posterior margin dwindling distally, with a row of 12 setae; merus to propodus with groups of spines on anterior margin; dactylus with one plumose seta on posterior margin and two setae at hinge of unguis.

Pereopod 7 ( Fig. 18E, J View Figure 18 ): coxal plate bearing four setae on posterior margin; basis with four setae and five spines on anterior margin, anterodistal corner with one spine, posterior margin with a row of 13 setae, inner surface with two spines; merus to propodus with 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 2 and gills of pereopods 3–5 a little shorter than bases; gill of pereopod 6 more than half length of basis; gill of pereopod 7 smallest, less than half of basis.

Epimeral plates ( Fig. 19A–C View Figure 19 ): plate 1 ventrally rounded, bearing two setae on anteroventral margin, three setae on posterior margin; plate 2 with one seta and three spines on ventral margin, four setae on posterior margin, posterodistal corner blunt; plate 3 with two spines on ventral margin, two setae on posterior margin, posterodistal corner blunt.

Pleopods 1–3 similar ( Fig. 19E–G View Figure 19 ), peduncles with one or two retinacula accompanied by one or two setae; outer ramus slightly shorter than inner ramus, both rami fringed with plumose setae.

Urosomites 1–3 ( Fig. 19D View Figure 19 ): Urosomite 1 with twoone−one−two spines accompanied by setae on dorsal margin. Urosomite 2 with one−one−one−two spines accompanied by setae on dorsal margin. Urosomite 3 with two spines accompanied by one seta on each side.

Uropods 1–3 ( Fig. 19H–J View Figure 19 ): uropod 1 peduncle with one basofacial spine, with three spines on outer margin, one spine on inner margin, two and one spines on outer and inner distal corners, respectively; inner and outer rami both with one spine on inner margins and five terminal spines. Uropod 2 short, peduncle bearing two spines on outer margin, one spine on each corner; outer ramus with one spine on outer margin; inner ramus with one spine on inner margin. Uropod 3 peduncle with one spine accompanied by one seta on surface and four distal spines; inner ramus about 1.6 times as long as peduncle, reaching 0.6 times the length of outer ramus, with one spine on inner margin and two apical spines accompanied by simple setae; article 1 of outer ramus with two pairs of spines and one single spine on outer margin; terminal article longer than adjacent spines, both margins of inner and outer ramus densely set with plumose setae.

Telson ( Fig. 19K View Figure 19 ): deeply cleft, as long as wide, each lobe with clusters of setae and one spine accompanied by two setae on surface, bearing two or three apical spines accompanied by setae.

Female, paratype (IZCAS-I-A1253-2)

Body length: 10.4 mm.

Gnathopod 1 ( Fig. 20A, C View Figure 20 ): coxal plate bearing three setae and two setae on anterior and posterior margins, respectively; basis with setae on anterior and posterior margins; propodus oval, palm with four spines on posterior margin; dactylus with one seta on outer margin.

Gnathopod 2 ( Fig. 20B, D View Figure 20 ): coxal plate bearing three setae and one seta on anterior and posterior margins, respectively; basis with short setae on anterior and posterior margins, posterodistal corner with short setae; propodus subrectangular, palm margin with four spines on posterodistal corner, bearing simple setae along anterior and posterior margins; dactylus with one seta on outer margin.

Pereopods 3, 4 ( Fig. 21A, B View Figure 21 ): with shorter setae on posterior margin than those of male.

Pereopods 5–7 ( Fig. 21C–E View Figure 21 ): similar to those of male.

Uropods 1–3 ( Fig. 19L–N View Figure 19 ): uropods 1 and 2 similar to those of male. Uropod 3 peduncle with one spine accompanied by one seta on surface and four distal spines; inner ramus about 1.4 times as long as peduncle, reaching 0.6 times the length of outer ramus, with two spines accompanied by plumose setae on lateral margin; article 1 of outer ramus with three pairs of spines accompanied by simple setae on outer margin; terminal article longer than adjacent spines.

Telson ( Fig. 21F View Figure 21 ): cleft, each lobe with two clusters of setae and one spine accompanied by two setae on surface, bearing four or three distal spines accompanied by setae.

Oostegite ( Fig. 21G–J View Figure 21 ): oostegite of gnathopod 2 broad, with marginal setae, oostegites of pereopods 3 and 4 elongate, oostegite of pereopod 5 smallest.

Habitat

The species is currently known from three localities in Taiyue Mt., a southern branch of the Taihang Mts; where it occurs at the banks of small streams.

Remarks

Gammarus monticellus sp. nov. can be distinguished from G. shanxiensis (character states in parentheses) by the following characters: merus to carpus of pereopod 3 with long, curled setae on posterior margin (with short setae on posterior margin); epimeral plates 2, 3 with blunt posterodistal corners (subacute); and inner ramus of uropod 3 reaching about 0.6 times the length of outer ramus (0.8 times length of outer ramus).

This species is similar to G. clarus in calceoli present in antenna 2 and both margins of uropod 3 densely set with plumose setae. It differs from G. clarus (character states in parentheses) by pereopod 3 with long, curled setae on posterior (straight setae); epimeral plate 3 with blunt posterodistal corner (acute); and urosomites flat (elevated).