Sarothrogammarus kalamensis Hou, 2024

Xin, Wenpei, Zhang, Chao, Ali, Abid, Zhang, Xiaoqing, Li, Shuqiang & Hou, Zhonge, 2024, Two new species of Sarothrogammarus (Crustacea, Amphipoda) from Swat Valley, Pakistan, Zootaxa 5432 (4), pp. 509-534 : 524-532

Sarothrogammarus kalamensis Hou sp. nov.

( Figs 3 , 10–15 )

Material examined. Holotype: male (IZCAS-I-A2918-1), 5.4 mm; altitude 2475 m, Kalam , Swat, Khyber Pakhtunkhwa Province, Pakistan (72.46°E, 35.47°N), June 4, 2019, collected by X. Zhang and A. Abid. Paratypes: one female (IZCAS-I-A2918-2), and two males (IZCAS-I-A2918-3,4); same data as the holotype. The two male paratypes were used for molecular analysis, and the sequences were submitted to GenBank (OR730534 and OR729699), (OR730533 and OR729698).

Etymology. The species is named after its type locality, the Kalam Valley.

Diagnosis. Eyes oval; antenna II calceoli absent; gnathopods I–II without robust setae; pereopod III with filtrative setae on posterior margin of merus but few on carpus and propodus; coxal plate IV weakly concave; bases of pereopods V–VII expanded; urosomites I–III with short robust setae; uropod III peduncle reaching 0.5 times the length of outer ramus, inner ramus scale-like, with one robust seta on distal margin, outer ramus biarticulate, first article with two groups of robust setae on both margins, terminal article shorter than adjacent robust setae.

Description of male. Based on holotype (IZCAS-I-A2918-1), 5.4 mm ( Fig. 3A ).

Head ( Fig. 10A ): eyes oval, inferior antennal sinus deep, lateral cephalic lobe rounded. Antenna I ( Fig. 10B ): longer than antenna II. Peduncle articles 1–3 in length ratio 1.0: 0.7: 0.4, with distal setae; flagellum with 21 articles; accessory flagellum with three articles; both primary and accessory flagella with short distal setae. Antenna II ( Fig. 10C ): peduncle articles 3–5 in length ratio 1.0: 2.2: 1.8, article 3 with two distal setae, article 4 slightly longer than article 5, both with setae along anterior and posterior margins; flagellum with eight articles, each article with distal setae; calceoli absent. Upper lip ( Fig. 10D ): ventral margin rounded, bearing minute setae. Mandible ( Fig. 10E, F ): incisor of left mandible with five teeth; lacinia mobilis with four teeth; accessory setal row with seven plumose setae; articles 1–3 of palp in length ratio 1.0: 2.3: 1.9, second article with 15 marginal setae, article 3 with four Bsetae, 14 D-setae and four E-setae apically; incisor of right mandible with four teeth, lacinia mobilis bifurcate, with small teeth. Lower lip ( Fig. 10J ): inner lobe lacking, covered with thin setae. Maxilla I ( Fig. 10G, H ): asymmetrical, left inner plate with 15 plumose setae; outer plate with nine serrate teeth apically; second article of left palp with two simple setae and six plumose setae apically; second article of right palp with five robust setae and one slender seta. Maxilla II ( Fig. 10I ): inner plate with 15 plumose facial setae in an oblique row; inner and outer plates with long setae apically. Maxilliped ( Fig. 10K ): inner plate with three robust setae and 16 plumose setae apically; outer plate with robust setae and short setae; palp 4-articulate, article 2 with a row of simple setae on inner margin; article 4 hooked.

Pereon. Gnathopod I ( Fig. 11A, B ): coxal plate with three setae on anterior margin; basis sub-linear, with four long setae and seven short setae on anterior margin, five setae on posterior margin; merus with two groups of long setae on posterior margin; carpus 1.89 times as long as wide, 82% length of propodus, ventral margin bearing four clusters of setae; propodus 2.0 times as long as wide, palmar margin crenellated only in its proximal (angular) part, with 11 setae and defined by eight robust setae; dactylus reaching approx. 47% length of propodus, posterior margin arc-shaped, with one seta. Gnathopod II ( Fig. 11C, D ): coxal plate with one seta on anterior margin, two setae on lower margin; basis with two long setae and six short setae on anterior margin, posterior margin with six long setae; merus with 14 setae on posterior margin; carpus with a row of setae on posterior margin; propodus 2.1 times as long as wide, subrectangular, with seven robust setae and 11 slender setae on palm margin, posterior margin with a row of setae; dactylus reaching approx. 45% length of propodus.

Pereopods III–VII ( Fig. 12A–E ), Pereopod III ( Fig. 12A, I ): coxal plate bearing one seta on anterior margin and one seta on lower margin; basis elongated, with setae along anterior and posterior margins; merus with a row of filtrative setae on posterior margin, one slender seta and three robust setae on anterior margin; carpus with two robust setae accompanied by short setae on posterior margin, anterodistal corner with two robust setae accompanied by three slender setae; propodus with a few short setae on posterior margin and one robust seta on posterodistal corner; dactylus with one plumose seta and three setae on anterior margin; two setae at hinge of unguis. Pereopod IV ( Fig. 12B, J ): coxal plate concave, bearing one seta on anterior margin and one seta on lower margin; basis with eight setae along posterior margin, one robust seta on anterodistal corner and four setae on posterodistal corner; merus with three clusters of straight setae on posterior margin and one seta on anterior margin, anterodistal corner with two robust setae; carpus and propodus with robust setae accompanied by short setae on posterior margins and four setae on posterodistal corner; dactylus with one plumose seta on anterior margin, and one robust seta accompanied by three setae. Pereopod V ( Fig. 12C, K ): coxal plate with one seta on posterior margin; basis expanded, with five robust setae and two single setae on anterior margin, anterodistal corner with one robust seta accompanied by three slender setae, posterior margin with 11 setae; merus with two groups of setae on anterior margin and two robust setae accompanied by one short seta on posterior margin, anterodistal corner with four setae and posterodistal corner with one robust seta accompanied by five short setae; carpus and propodus with three to four groups of robust setae accompanied by short setae on anterior margins; dactylus with two setae at hinge of unguis. Pereopod VI ( Fig. 12D, L ): coxal plate bearing four setae on posterior margin; basis elongated, with four robust setae on anterior margin, anterodistal corner with three setae, posterior margin with a row of 11 setae; merus with three robust setae accompanied by short setae on anterior margin and two robust setae on posterior margin, anterodistal corners with one robust seta accompanied by three slender setae and posterodistal corner with two robust setae accompanied by one slender seta; carpus and propodus with groups of robust setae accompanied by short setae on anterior and posterior margins; dactylus with two setae at hinge of unguis. Pereopod VII ( Fig. 12E, M ): coxal plate with three setae on posterior margin; basis with one single seta and four robust setae on anterior margin, anterodistal corner with three robust setae, posterior margin with a row of 16 setae; merus with two groups of robust setae on anterior margin and a pair of robust setae on posterior margin, anterodistal and posterodistal corners with three robust setae accompanied by slender setae, respectively; carpus and propodus with groups of robust setae accompanied by short setae on anterior margins, respectively; dactylus with two setae at hinge of unguis.

Coxal gills: present on gnathopod II and pereopods III–VII; sternal gills absent; coxal gill of gnathopod II and gill of pereopod V approx. as long as bases; gills of pereopod III and IV a little longer than bases; gill of pereopod VI shorter than basis; gill of pereopod VII smallest, less than half of the basis.

Pleon. Epimeral plates ( Fig. 10N–P ): plate I ventrally rounded, with two setae on ventral margin, six setae on posterior margin; plate II posterior corner blunt, with three robust setae on ventral margin and three setae on posterior margin; plate III with two robust setae on ventral margin and five setae on posterior margin.

Pleopods I–III ( Fig. 10M ): similar to each other. Both rami subequal, with plumose setae.

Urosome. Urosomites ( Fig. 10Q ): urosomite I with one robust seta and two short setae on dorsal margin; urosomite II with four robust setae accompanied by one short seta on dorsal margin; urosomite III with one robust seta accompanied by three short setae on dorsal margin.

Uropods I–III ( Fig. 12F–H ): uropod I peduncle with one basofacial seta, two and three robust setae on inner and outer margins, with one robust seta on each corner; inner ramus approximately 0.72 times as long as peduncle, with two robust setae on inner margin and one robust seta on outer margin, and four robust setae distally; outer ramus slightly shorter than inner ramus, with one robust seta on inner margin and four robust setae distally. Uropod II peduncle bearing three robust setae on outer margin and one robust seta on each distal corner; inner ramus with one robust seta on inner and outer margins, respectively, and five robust setae distally outer ramus slightly shorter than inner ramus, with one robust seta on inner margin and four robust setae distally. Uropod III peduncle 0.4 times as long as outer ramus, inner ramus scale-like, with one robust seta on distal margin; outer ramus 2-articulate, first article with three and two groups of robust setae on inner and outer margins, terminal article shorter than adjacent robust setae with two distal setae.

Telson ( Fig. 10L ): deeply cleft, 1.04 times as long as wide, each lobe with four robust setae distally.

Description of paratype female (IZCAS-I-A2918-2), 5.6 mm ( Fig. 3B ).

Head. Antennae and mouthparts ( Fig. 13A–K ) similar to those of male.

Pereon. Gnathopod I ( Fig. 14A, B ): coxal plate with two setae on anterior margin, one seta on lower margin; basis sub-linear, with four long setae and five short setae on anterior margin, five setae on posterior margin; merus with 15 long setae on posterior margin; carpus 1.4 times as long as wide, 82% length of propodus, ventral margin bearing three clusters of setae; propodus 1.73 times as long as wide, palmar margin crenellated only in its proximal (angular) part, with ten setae and defined by six robust setae; dactylus reaching approx. 56% length of propodus, posterior margin arc-shaped, with one seta. Gnathopod II ( Fig. 14C, D ): coxal plate with two setae on anterior margin; basis with two long setae and one short seta on anterior margin, posterior margin with five long setae and two short setae; merus with ten setae on posterior margin; carpus with a row of setae on posterior margin; propodus 2.1 times as long as wide, subrectangular, with three robust setae and eight setae on palm margin, posterior margin with a row of setae; dactylus reaching approx. 43% length of propodus.

Pereopods III–VII ( Fig. 14A–E ): similar to those of male.

Oostegite ( Fig. 14E–H ): present on gnathopod II to pereopod V, longer than wide, and with 15–22 fine smooth-edged setules; smallest in pereopod V.

Urosome. Uropods I–III ( Fig. 15G–I ): uropod I peduncle with two and three robust setae on inner and outer margins, respectively; inner and outer distal corners with one robust seta, respectively; inner ramus approximately 0.79 times as long as peduncle, with one robust seta on inner margin and two robust setae on outer margin, and five robust setae distally; outer ramus slightly shorter than inner ramus, with one robust seta on inner margin and four robust setae distally. Uropod II peduncle bearing two robust setae on outer margin and one robust seta on each distal corner; inner ramus with one robust seta on inner margin, and five robust setae distally; outer ramus slightly shorter than inner ramus, with one robust seta on inner margin and four robust setae distally. Uropod III peduncle 0.5 times as long as outer ramus, inner ramus scale-like, with one robust seta on distal margin; outer ramus 2-articulate, first article with robust setae on inner and outer margins, terminal article a little shorter than adjacent robust setae with two distal setae.

Telson ( Fig. 13L ): deeply cleft, 0.9 times as long as wide, each lobe with four robust setae distally.

Habitat. This species was collected under the debris along a small brook.

Remarks. Sarothrogammarus kalamensis sp. nov. is morphologically most similar to S. miandamensis sp. nov. in having eyes oval, antenna II peduncle with long setae, and pereopods V–VII bases expanded. However, S. kalamensis differs from S. miandamensis in the following features (features for S. miandamensis in parentheses): pereopod III merus with filtrative long setae but carpus and propodus with short setae (merus to propodus with filtrative long setae on posterior margins), urosomite I with one robust seta and two setae on dorsal margin (with setae only).

Sarothrogammarus kalamensis sp. nov. can be distinguished from S. trichiatus (character states for S. trichiatus in parentheses) in the following: antenna I peduncle with long setae on ventral margin (with short setae on ventral margin), and gnathopod II without mid-palmar robust seta (with mid-palmar robust seta).

The comparison between the species of Sarothrogammarus -group is presented in the following key.

Figures

FIGURE 3. Sarothrogammarus kalamensis sp. nov. from Swat Valley, Pakistan. A, habitus of male holotype (5.4 mm); B, habitus of paratype female (5.6 mm).

FIGURE 10. Sarothrogammarus kalamensis sp. nov. male holotype, from Swat Valley, Pakistan. A, head; B, antenna I; C, antenna II; D, upper lip; E, left mandible; F, incisor of right mandible; G, right maxilla; H, left palp of maxilla I; I, maxilla II; J, lower lip; K, maxilliped; L, telson; M, pleopod I; N, epimeral plate I; O, epimeral plate II; P, epimeral plate III.

FIGURE 11. Sarothrogammarus kalamensis sp. nov. male holotype, from Swat Valley, Pakistan. A, gnathopod I; B, propodus of gnathopod I; C, gnathopod II; D, propodus of gnathopod II.

FIGURE 12. Sarothrogammarus kalamensis sp. nov. male holotype, from Swat Valley, Pakistan.A, pereopod III; B, pereopod IV; C, pereopod V; D, pereopod VI; E, pereopod VII; F, uropod I; G, uropod II; H, uropod III; I, dactylus of pereopod III; J, dactylus of pereopod IV; K, dactylus of pereopod V; L, dactylus of pereopod VI; M, dactylus of pereopod VII.

FIGURE 13. Sarothrogammarus kalamensis sp. nov. female paratype, from Swat Valley, Pakistan. A, head; B, antenna I; C, antenna II; D, upper lip; E, right mandible; F, incisor of left mandible; G, left maxilla I; H, right palp of maxilla I; I, maxilla II; J, lower lip; K, maxilliped; L, telson; M, epimeral plate I; N, epimeral plate II; O, epimeral plate III.

FIGURE 14. Sarothrogammarus kalamensis sp. nov. female paratype, from Swat Valley, Pakistan.A, gnathopod I; B, propodus and dactylus of gnathopod I; C, gnathopod II; D, propodus and dactylus of gnathopod II; E, oostegite of gnathopod II; F, oostegite of pereopod III; G, oostegite of pereopod IV; H, oostegite of pereopod V.

FIGURE 15. Sarothrogammarus kalamensis sp. nov. female paratype, from Swat Valley, Pakistan.A, pereopod III; B, pereopod IV; C, pereopod V; D, pereopod VI; E, pereopod VII; F, pleopod I; G, uropod I; H, uropod II; I, Iuropod III; J, dactylus of pereopod III; K, dactylus of pereopod IV; L, dactylus of pereopod V; M, dactylus of pereopod VI; N, dactylus of pereopod VII; O, urosomites (dorsal view).