Niphargus dolichopus, Fišer & Trontelj & Sket, 2006

Fišer, Cene, Trontelj, Peter & Sket, Boris, 2006, Phylogenetic analysis of the Niphargus orcinus species- aggregate (Crustacea: Amphipoda: Niphargidae) with description of new taxa, Journal of Natural History (J. Nat. Hist.) 40 (41 - 43), pp. 2265-2315 : 2275-2283

Niphargus dolichopus n. sp. ( Figures 6 , 8–11 )

Type locality. Cave Suvaja pećina, Lušci polje, Sanski most, Bosnia and Herzegovina Material examined. Suvaja pećina, Lušci polje, Sanski most, Bosnia and Herzegovina, 26 July 2004; coll. P. Trontelj; male and female.

Holotype: female, 17.1 mm; two slides labeled ‘‘B’’.

Paratypes: male, 16.7 mm, two slides labeled ‘‘A’’; 5 specimens (males and females) not dissected.

Holotype and paratypes deposited in the collection of Oddelek za biologijo, Biotehniška fakulteta, Univerza v Ljubljani ( Department of. Biology , Biotechnical Faculty , University of Ljubljana).

Etymology. The species was named after its remarkably long pereopods VI–VII.

Diagnosis

Pereonites I–V without spines, pereonite VII with strong spines dorso-posteriorly; posterior margin of urosomite III dorso-laterally with spines; telson cleft shallow. Antenna I very long (1.3–1.35 of body length). Antenna II lengths of peduncle articles 4:5 is 1:1.3; flagellum short consists of 6–8 articles. Pereopods VI–VII extremely elongated, pereopod VII length 0.97–1 of body length.

Description

Head and trunk ( Figures 6 , 11 ). Body length up to 17.5 mm. Head length 10–11% of body length; rostrum absent. Pereonites I–V without setae; pereonite VII with 1–2 posteroventral setae and up to 12 strong spines dorso-posteriorly. Dorsal spines may be present also on pereonite VI.

Pleonites I–III with 14–16 dorso-posterior spines. Epimeral plate II: angle of posteroventral corner approximately rectangular; posterior margin sinusoidal; ventral margin convex. Along ventral margin 2 spines, along posterior margin 7–10 setae. Epimeral plate III: angle of postero-ventral corner acute; posterior margin sinusoidal; ventral margin convex. Along ventral margin 3 spines, along posterior margin 7–10 setae.

Urosomite I postero-dorso-laterally with 3–4 spines; urosomite II postero-dorso-laterally with 3 spines and/or setae; urosomite III postero-dorso-laterally with 2 spines. At the base of uropod I 1 spine.

Telson length: width ratio is 1:0.85–0.9; cleft 0.4–0.6 of length. Only 3 apical spines per lobe present, these are 0.4–0.5 of telson length. Plumose setae inserted laterally, in the middle part of telson.

Antennae ( Figure 8 ). Antenna I 1.3–1.4 of body length. Flagellum with up to 67 articles; each article with 1–2 aesthetascs. Peduncle articles in ratio 1:1–1.05: 0.6. Proximal article of peduncle dorso-distally slightly produced. Accessory flagellum biarticulated; distal article shorter than half of proximal article length.

Length ratio antenna I:II as 1:0.2–0.25. Flagellum of antenna II with 6–8 articles; aesthetascs absent. Peduncle articles lengths 4:5 is 1:1.3; flagellum 0.2–0.25 of peduncle length (articles 4+5). Peduncular article 4 of antenna II with a row of fine setae ventroproximally.

Mouth parts ( Figure 8 ). Inner lobes of labium longer than half of the outer lobes.

Left mandible: incisor with 5 teeth, lacinia mobilis with 4 teeth; between lacinia and molar row of serrated spines, long seta at the base of molar. Right mandible: incisor process with 4 teeth, lacinia mobilis with several small denticles, between lacinia and molar a row of serrated spines; molar process with a long basal seta. Ratio of mandibular palp article 2:article 3 (distal) is 1:1.1–1.2. Proximal palp article without setae; the second article with 9–10 setae groups and single setae; distal article with 1 A group of 7 setae; 3–4 B groups; 37–38 D single setae; 6–7 E single setae.

Maxilla I distal palp article with 8 apical setae. Outer lobe of maxilla I with 7 uni-, bi- or pluri-toothed spines; inner lobe with 2 setae.

Maxilla II inner lobe slightly smaller than outer lobe; both of them apically setose.

Maxilliped palp article 2 with 8–10 rows of setae along inner margin; distal article with a dorsal seta, a group of small setae at the base of the nail. Maxilliped outer lobe with 13 flattened spines and 4 serrated setae; inner lobe with 3–4 flattened apical spines and 8–9 serrated setae.

Coxal plates, gills ( Figures 5 , 9 , 10 , 11 ). Coxal plate I of rhomboid shape, antero-ventral corner pointed; anterior and ventral margin of coxa I with 8 setae. Coxal plate II width:depth is 1:0.9–1; anterior and ventral margin with 8 setae. Coxal plate III width:depth is 1:0.8; along antero-ventral margin 10–12 setae. Coxal plate IV width:depth is 1:0.9–1; posteriorly slightly concave (0.1–0.2 of coxa width); along antero-ventral margin 11–12 setae. Coxal plates V–VI: only anterior lobe developed; along posterior margin 3 setae or spines. Coxal plate VII semicircular, along posterior margin 2 setae and/or spines. Gills II–VI large, irregularly ovoid.

Gnathopod I ( Figure 9 ). Ischium with postero-distal row of setae. Carpus 0.6–0.65 of basis length and 0.8–0.85 of propodus length. Anterior margin of carpus with the distal and 1 additional group of setae; carpus posteriorly with transverse rows of setae proximally, a row of lateral setae and rows of submarginal setae; postero-proximal bulge large (1/3 of carpus length), positioned medially. Propodus rectangular, palm short, convex and slightly inclined. Along posterior margin 7 rows of denticulated setae. Anterior margin with 34–37 setae in 7 groups, antero-distal group with 11–12 setae. Group of 3 facial setae proximally of palmar spine; small groups of surface setae present. Palmar corner with strong palmar spine, single supporting spine on inner surface and 3 denticulated spines on outer side. Nail length 0.2–0.25 of total dactylus length; along anterior margin 10 single setae; short setae along inner margin present.

Gnathopod II ( Figure 9 ). Basis width:length is 1:0.3. Ischium with postero-distal row of setae. Carpus 0.6 of basis length and 1–1.05 of propodus length. Anterior margin of carpus with distal and 2 additional groups of setae; carpus posteriorly with transverse rows of setae proximally, a row of lateral setae and submarginal setae groups; posteroproximal bulge large (1/3 of carpus length), positioned medially. Propodus small (compared to the body) and equal to propodus of gnathopod I. Propodus rectangular, palm short, convex and more inclined than palm of gnathopod I. Posterior margin with 9– 10 rows of denticulated setae. Anterior margin with 18–20 setae in 5 groups; antero-distal group with 9–10 setae. Group of 3 facial setae proximally of palmar spine; small groups of surface setae present. Palmar corner with strong palmar spine, single supporting spine on inner surface and 2–4 denticulated spines on outer side. Nail length 0.2–0.25 of total dactylus length. Along anterior margin 10–11 single setae; short setae along inner margin present.

Pereopods III–IV ( Figure 10 ). Lengths of pereopods III–IV equal. Dactylus IV 0.5 of propodus IV; nail length 0.35–0.4 of total dactylus length. Dactyli III–IV with dorsal plumose seta; at the base of nail a spine and a seta.

Pereopods V–VII ( Figure 11 ). Lengths of pereopods V:VI:VII is 1:1.4–1.45:1.4–1.45. Pereopod VII length 0.97–1 of body length.

Bases V–VII narrow, length:width is 1:0.5; posterior margin straight, without distal lobes; posteriorly 12–19 strong hook-like spines; anteriorly 5–6 single/groups of spines and/ or setae. Dactylus VII length 0.2 of propodus VII length. Dactyli V–VII with dorsal plumose seta; at the base of nail a spine and a seta.

Pleopods and uropods ( Figure 10 ). Pleopods I–III each with 2-hooked retinacles and few setae. Pleopod II rami of 23–24 articles each.

Uropod I protopodit with 10 dorso-lateral spines; 4–5 dorso-medial spines. Exopodite:endopodite length is 1:1–1.05; rami straight. Uropod I rami with groups of spines and/or setae along inner and outer margins. Endopodite with up to 8–10 setae and/ or spines in 7–8 groups of spines and/or setae; apically 5 spines. Exopodite with up to 19– 21 setae and/or spines in 10 groups; apically 5 spines.

Uropod II exopodite:endopodite length is 1:1.2–1.25.

Uropod III 0.4 of body length. Protopodite with 2 small lateral setae and 6–7 apical spines and setae. Endopodite 0.4 of protopodite length, apically with a single spine and single seta; laterally 1 spine. Exopodite of uropod III rod-shaped, distal article 0.07–0.08 of the proximal article length. Proximal article with 8–9 groups of setae, plumose setae and spines along inner margin; 7–9 groups of spines and setae along outer margin. Distal article with 1–2 lateral setae groups; setae set along both margins; apically 3–4 setae.

Variability. The studied specimens do not differ in spination and shape; minor differences in number of setae and spines may be a consequence of different body lengths.

Remarks and affinities. In general appearance, N. dolichopus with small gnathopods, extremely long pereopods V–VII without distal lobes on narrow bases and extremely long antenna I, as well as with well-developed spination of pleonites and pereopods, resembles both N. croaticus and N. balcanicus . However, it represents a unique combination of characters that can be found in both species. Short flagellum of antenna II, approximately equal size of propods of gnathopods I and II, shallow telson cleft and spines on urosomite III are characters shared by N. croaticus , from which it can be distinguished by the presence of strong dorsal spines on pereonites VI–VII. These spines are also characteristic of N. balcanicus . However, N. balcanicus has dorsal spination much better developed, also on pereonites I–V; it has a much longer flagellum of antenna II, posteriorly produced coxae V– VI, proxi-posterior lobe on pereopod VII, strong spines on dactyls III–VII, and well developed plumose setae on uropods I–II. On the other hand N. balcanicus lacks spines on urosomite III and additional anterior setae on the carpus of gnathopods I–II.

Figures

Figure 5. Distribution of characters ‘‘type of setae/spines along postero-dorsal margin of pleonites’’ (character 14, CI50.2, RI50.5; left) and ‘‘uropod I rami-spines’’ (character 58, CI50.37, RI50.73; right). Both characters are supposed to be characteristics of ‘‘Orniphargus’’ (S. Karaman (1950c)).

Figure 6. N. dolichopus sp. n. (above) and N. dabarensis sp. n. (below). Holotypes, lateral view.

Figure 8. N. dolichopus sp. n., holotype. Mouthparts.

Figure 9. N. dolichopus sp. n., holotype. Gnathopod I (above) and gnathopod II (below).

Figure 10. N. dolichopus sp. n., holotype. Pereopods III–IV, detail of pereopod IV dactylus. Retinacle of pleopod II. Uropods I–III. Telson.

Figure 11. N. dolichopus sp. n., holotype. Pereopods V–VII. Details of pereopod VII.