Niphargus mirocensis, Petković, Matija, Delić, Teo, Lučić, Luka & Fišer, Cene, 2015

Petković, Matija, Delić, Teo, Lučić, Luka & Fišer, Cene, 2015, Description of a new species of Niphargus (Crustacea: Amphipoda: Niphargidae): the first record of a lake ecomorph in the Carpathian Mountains, Zootaxa 4027 (1), pp. 117-129 : 119-124

Family Niphargidae

Niphargus mirocensis sp. n. Figs. 1–7

Material examined. Type locality. A pit Rakin ponor (N 44º30’45.4” E 22º16’45.0”), near village Kopana Glavica, mt Miroč, eastern Serbia ( Fig. 1 ).

Collection notes: The animals were collected in a siphon on the bottom of the pit (depth - 285 m). The cave entrance is at 380 m above sea level.

Material examined. The holotype 17.95 mm long female. Paratype 19.72 mm long female.

Etymology. The species is named by Mount Miroč, where the species was found.

Diagnosis. Large and stout species, pleon segments ornamented with setae; telson with apical spines and one dorsal spine on each lobe. Maxilla I outer lobe with pectinate teeth. Gnathopod propods huge and hoof-shaped, pereopods III–VII with simple dactyli bearing single dorsal plumose seta, and tiny spine and seta at the base of nail.

Description of holotype. Head and trunk ( Fig. 2 ). Body length up to 17.95 mm. Head length up to 10% of body length; rostrum absent. Pereonites I–VII without setae.

Pleonites I–III with up to 2 setae along the entire dorso-posterior margin. Epimeral plate II slightly inclined, posterior and ventral margins straight and convex, respectively; ventro-postero-distal corner distinct but not produced; along ventral margin 3 spiniform setae; along posterior margin 2 stout setae and 5 thin setae. Epimeral plate III slightly inclined, posterior and ventral margin straight and slightly convex, respectively; ventro-posterodistal corner distinct but not produced; along ventral margin on one side 4 spiniform setae; along posterior margin 2 stout setae and 5 thin setae.

Urosomite I postero-dorso-laterally with a row of 4 strong spiniform setae and 1 thin seta on each side; urosomite II postero-dorso-laterally with 4 strong spinifrom seta on each side; urosomite III without seta and spines. At the base of uropod I single strong spiniform seta.

Telson length-width ratio is 1:1; cleft is 0.67 telson length; telson margins convex and narrow apically. Each telson lobe ornamented with 4 or 5 apical spiniform setae (left-right lobe asymmetry) of up to 0.33 telson length; mesial and lateral margins without setae; dorsal surface with single spiniform setae by lobe. Pairs of plumose setae inserted mid-laterally.

Antennae ( Fig. 6 ). Antenna I 0.57 of body length. Flagellum with up to 32 articles; each article with 1 aesthetasc. Peduncle articles in ratio 1-3 1:0.88:0.47. Proximal article of peduncle dorso-distally slightly produced. Accessory flagellum biarticulated; distal article proximately one third of proximal article length.

Length ratio antenna I: antenna II as 1:0.40. Flagellum of antenna II with 12 articles; each article with setae and elongate sensilla of unknown function. Peduncle articles lengths 4:5 is 1:0.94; flagellum 0.56 of length of peduncle articles 4+5.

Mouthparts. Labrum (not drawn) broader than long with fine hair distally; 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 a row of thick serrated setae, long seta at the base of molar. Right mandible: incisor with 4 teeth, lacinia mobilis with 2 teeth, between lacinia and molar a row of thick serrated setae. Ratio of mandibular palp article 2: article 3 (distal) is 1:1. Proximal palp article without setae; the second article with up to 14 setae; distal article with a group of 7 A setae; 4 groups of B setae; 37 D setae and 6 E setae.

Maxilla I inner lobe with 7 apical and subapical setae. Outer lobe of maxilla I with 7 stout spiniform setae, each of them with lateral denticles (from two to seven). Palpus 2-articulated: first article naked; second article narrower, short, not reaching the tip of the spines of the outer plate and bearing 10 apical setae.

Maxilla II inner lobe slightly smaller than outer lobe; inner and outer lobe setose apically and subapically.

Maxilliped inner lobe short, with 5 flattened thick setae apically and 11 serrated setae. Maxilliped outer lobe nearly reaching half of palpus article 2, with 12 flattened thick setae mesially and 10 serrated setae apically and subapically. Palp article 2 with rows of setae along inner margin; distal article with a dorsal seta and a group of long setae at the base of the nail.

Coxal plates, gills and oostegites ( Figs 2 , 3 , 4 ). Coxal plate I deep and of parallelogram shape, antero-ventral corner subrounded; anterior and ventral margin of coxa I with 12 setae. Coxal plates II–III depth: width in respective ratios 1:0.62 and 1:0.67; anterior and ventral margins of respective coxal plates with 15 and 10 setae. Coxal plate IV depth: width ratio is 1:0.51; posteriorly convex; along antero-ventral margin 8 setae. Coxal plates V–VI: anterior lobe well developed and larger than posterior; posterior margin with 1 strong setae. Coxal plate VII half-egg shaped with 1 strong posterior seta. Gills II–VI ovoid and reach up to the mid of basis, oostegites large ovoid, with long setae

Gnathopod I ( Fig. 3 ). Ischium with 1 group of 13 postero-distal setae. Carpus 0.54 of basis length and 0.83 of propodus length. Anterior margin of carpus only with the distal group of setae; carpus posteriorly with transverse rows of setae proximally, a row of lateral setae; postero-proximal bulge large (1/3 of carpus length), positioned proximally. Propodus trapezoid, palm convex and slightly inclined. Along posterior margin 10 rows of setae. Anterior margin with 31 setae in 4 groups in addition to antero-distal group of 13 setae. Proximally to palmar spiniform seta one long facial seta; several groups of short setae on the inner surface present. Palmar corner with strong palmar spiniform seta, single supporting spiniform seta on inner surface and 4 denticulated thick spiniform setae on outer side. Nail length 0.3 of total dactylus length; along anterior margin 10 seta; along inner margin a row of short setae.

Gnathopod II ( Fig. 3 ). Basis width: length is 1:0.30. Ischium with a group of 6 postero-distal setae. Carpus 0.88 of basis length and 0.74 of propodus length. Anterior margin of carpus only with distal row of setae; carpus posteriorly with transverse rows of setae proximally and a row of lateral setae; postero-proximal bulge large (1/3 of carpus length), positioned proximally. Propodus large-sized (circumference measures approximately 0.25 of body length) and larger than propodus of gnathopod I (II: I as 1:0.69). Propodus trapezoid, palm convex and slightly inclined. Posterior margin with 14 rows of setae. Anterior margin with 13 setae in 3 groups in addition to 9 anterodistal setae. Group of 3 facial setae proximally of palmar spiniform seta; individual surface setae present. Palmar corner with strong palmar spiniform seta, single supporting spiniform seta on inner surface and 3 denticulated thick-spiniform setae on outer side. Nail length 0.29 of total dactylus length. Along anterior margin 9 setae; along inner margin few short setae.

Pereopods III–IV ( Fig. 4 ). Lengths of pereopods III: IV equal to ratio 1:1.06. Dactylus IV 0.46 of propodus IV; nail length 0.47 of total dactylus length. Dactyli III–IV with dorsal plumose seta; at the base of nail tiny seta and 1 spiniform setae.

Pereopods V–VII ( Fig. 4 ). Lengths of pereopods V:VI:VII is 1:1.34:1.28. Pereopod VII length 0.60 of body length.

Bases V–VII length: width respective ratios as 1:0.60, 1:0.59 and 1:0.62; posterior margins convex, without distal lobes; posteriorly 13, 11 and 11 setae respectively; anteriorly 9, 10 and 7 groups of spines respectively. Dactyli V-VI with dorsal plumose seta; at the bases of nails a tiny seta and 1 spinform setae; dactylus VII with no plumose seta observed; at the base of the nail a tiny seta and 1 spinform setae.

Pleopods and uropods ( Fig. 5 ). Pleopods I–III with 2 hooked retinacles. Bases of pleopods II–III with distinct stout setae distally. Pleopod II rami with 20 and 21 articles.

Uropod I protopodite with 8 dorso-lateral spiniform setae and 6 dorso-medial spiniform setae. Exopodite: endopodite lengths is 1:1.15; rami straight. Endopodite with 4 individual spiniform setae, one group of 2 stout setae and 4 apical spiniform setae. Exopodite with 13 spiniform setae in 7 groups; apically 4 spiniform setae.

Uropod II exopodite: endopodite lengths is 1:1.22.

Uropod III approximately 0.18 of body length. Protopodite with 5 lateral setae and 7 apical spiniform setae. Endopodite 0.41 of protopodite length, apically with 3 spiniform setae; laterally without setae. Exopodite of uropod III rod-shaped, distal article 0.11 of the proximal article length. Proximal article with 8 groups of plumose, thinflexible and spiniform setae along inner margin and 5 groups of thin-flexible and spiniform setae along outer margin. Distal article with 2 setae groups along inner margin; apically 4 setae.

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

Remarks and affinities. Niphargus mirocensis sp. n. clearly belongs to the lake ecomorph, i.e., species that were traditionally classified as Orniphargus or orcinus -species group, having a large and stout body, rather elongated appendages and huge gnathopods.

In this section we limit our comparison to four characters. The first diagnostic character represents setae along pleon segments. Most species, living along Dinaric ridge have along posterior margins of all three pleon segment strong and spine-like seta, i.e., spiny comb, a clear and easily seen distinguishing character. Using this character, herein described species can be unambiguously identified from N. arbiter ( G. Karaman, 1984) , N. balcanicus ( Absolon, 1927) , N. croaticus (Jurinac, 1887), N. hercegovinensis ( S. Karaman, 1950c) , N. kolombatovici ( S. Karaman, 1950c), N. longiflagelum ( S. Karaman, 1950c), N. orcinus ( Joseph, 1869) , N. salonitanus ( S. Karaman, 1950b) , N. steueri ( Schellenberg, 1935), N. subtypicus ( Sket, 1960), N. trullipes ( Sket, 1958), N. dolichopus ( Fišer et al., 2006), N. dabarensis ( Fišer et al., 2006), N. polymorphus ( Fišer et al., 2006), N. bilecanus ( S. Karaman, 1953), N. kusceri ( S. Karaman, 1950c) , N. vjetrenicensis ( S. Karaman, 1932).

The second character represents pectinate teeth on outer lobe of maxilla I. In this character herein described species differs from several species that have pleon segments armed only with setae, either outside Dinaric area [N. virei ( Chevreux, 1896) ( France), N. vadimi ( Birstein, 1961) (Crymea), N. patrizii ( Ruffo et al., 1968) ( Italy) , N. lourensis ( Fišer et al., 2006) ( Greece), N. macedonicus ( S. Karaman, 1929) and N. pelagonicus ( S. Karaman, 1943) (both from Macedonia) or within Dinarides ( N. lunaris (G. Karaman, 1985) , N. pachytelson ( Sket, 1960) , N. podgoricensis ( S. Karaman, 1934)]. All these species have maxillar spines with up to 3 extra denticles.

The third character represents simple dactyls, making this species distinguishable from species from Middle East area ( N. nadarini ( Alouf, 1972) species complex, N. sertaci ( Fišer et al., 2009a), N. ictus ( G. Karaman, 1986) and W Balkan ( N. rejici ( Sket, 1958) , N. jadranko ( Sket & G. Karaman, 1990) and N. pectencoronatae ( Sket & G. Karaman, 1990). Middle East species share with herein described species both, pleon ornamentation and maxillar teeth whereas Balkan species share only ornamentation of pleon. However, all these species have—unlike N. mirocensis —pectinate dactyls on pereopods III–VII.

Finally, few species from Italy (N. stefanelli ( Ruffo & Vigna-Taglianti, 1968), N. ictus (G. Karaman, 1985) and N. parenzani (Ruffo & Vigna–Taglianti, 1968)) share with N. mirocensis sp. n. several traits, like non-spiny pleon segments, pectinate spines on outer lobe of maxilla I and simple dactyls, but differ from herein described species in ornamentation of telson. Herein described N. mirocensis sp. n. has only apical and dorsal setae, whereas all Italian species have also lateral and mesial setae on telson lobes. In addition, propodi of gnathopods in N. stefanellii ( Ruffo & Vigna-Taglianti, 1968) and N. ictus ( G. Karaman, 1985b) are more quadratic as compared to N. mirocensis sp. n.

Phylogenetic relationship and biogeographic remarks. Phylogenetic analysis suggests that N. mirocensis sp. n. is a sister species to N. stenopus ( Sket 1960) , a species described from SE Slovenia ( Fig. 7 ). It belongs to a clade that has representatives in Italy and in NW Balkan area; the expectation that the species is more closely related to geographically less distant lake ecomorphs from Herzegovina ( Fig. 1 ) turned to be unjustified. New finding site is 360 km E from the eastern-most known locality for any member of this clade; the clade now spans over three regions separated by non-karstic areas: Italy, Dinarides along NW Balkan and Carpathians in Central Balkan ( Fig. 1 ). Given that nowadays members of the clade are all strictly bound to phreatic and epiphreatic parts of the caves, such distribution implies that the clade dispersed in ancient times, when ancestors of the clades were less strictly bound to caves and could spread either through epigean waters, e.g., Miocene lakes (Krstić et al., 2003), or through the system of shallow subterranean habitats (Culver & Pipan, 2014). If this hypothesis is true, present species composition of the clade and their distribution would be a result of fragmentation of populations and vicariant speciation that followed break up of connections between populations. If specialization for the cave environment occurred at the same period, it possibly accelerated the process of population fragmentation.

Figures

FIGURE 1. Distribution map of cave lake ecomorphs belonging to two major clades on Balkan Peninsula. Symbols indicate clade affiliation; closed circles for “ Northern orcinus group ”, triangles for “ Southern orcinus group ” and red circles for newly described species. Note a long distance between N. mirocensis sp. n. and species from the same phylogenetic lineage (400 km) and N. mirocensis sp. n. and closest representative of cave lake ecomorphs (280 km). Data were obtained from SubBio database (http: // subbio. net / db /).

FIGURE 2. Niphargus mirocensis, sp. n., female 17.95 mm (holotype), Rakin ponor. Head and pleosoma I – III are digitally positioned on a drawing, compared with a real holotype. Holotype`s left ppV (damaged) is reconstructed based on the right ppV from the same specimen.

FIGURE 3. Niphargus mirocensis, sp. n., female 17.95 mm (holotype), Rakin ponor: gI – II = gnathopods I – II.

FIGURE 4. Niphargus mirocensis, sp. n., female 17.95 mm (holotype), Rakin ponor: ppIII – VII = pereopods III – VII.

FIGURE 5. Niphargus mirocensis, sp. n., female 17.95 mm (holotype), Rakin ponor: plpII = plepopod II; T = telson; upI – upIII = uropods i – III.

FIGURE 6. Niphargus mirocensis, sp. n., female 17.95 mm (holotype), Rakin ponor: aI – II = antennas I – II; md – R = right mandibula; md – L = left mandibula; mxp = maxilliped; mx 1 – 2 = maxilla I and II.

FIGURE 7. Phylogenetic relationships as inferred from Bayesian analysis. Color of nodes indicates range of posterior probabilities (Black circles = 1, gray circles = 0.95 – 0.99, white circles = 0. 90 –. 94). Clade with focal N. mirocensis sp. n. is indicated.