Niphargus montanarius, Karaman, Gordan S., Borowsky, Betty & Dattagupta, Sharmishtha, 2010

Karaman, Gordan S., Borowsky, Betty & Dattagupta, Sharmishtha, 2010, Two new species of the genus Niphargus Schiödte, 1849 (Amphipoda, fam. Niphargidae) from the Frasassi cave system in Central Italy, Zootaxa 2439, pp. 35-52 : 36-43

Niphargus montanarius , n. sp.

( Figs 1–6 )

Material examined. ITALY: “Lago Bugianardo”, cave on left side of the Sentino River at the base of Frasassi Gorge (Genga reg., central Italy), 1 specimen, adult (male, holotype), May, 2008 (leg. Dattagupta, S.); -ibid., September, 15, 2009, 2 specimens (leg. Dattagupta, S.). The holotype and one female specimen are deposited in the Museum of Natural History in Verona, Italy.

Diagnosis. Large species, large unequal gnathopods bearing a row of short setae along outer margin of dactyl. Outer plate of maxilla 1 with 7 spines, each spine bearing 1 or 2 lateral teeth. Dactyl of pereopods 3–7 with several inner marginal spines (more than one on almost all dactyls); segment 2 of pereopods 5–7 narrow, unlobed. Pleopods with 2 retinacula. Epimeral plates 2–3 angular. Uropods 1–2 with rami of equal length (females) or inner ramus slightly longer than outer one (male). Uropod 3 long, second segment of outer ramus long. Telson with gaping lobes.

Description. Male 21.0 mm, mature (holotype):

Body slender, metasomal segments 1–3 with 3 or 4 short dorsoposterior setae each; epimeral plates 1–2 broadly angular, with slightly convex posterior margin, epimeral plate 3 angular with straight posterior margin; epimeral plate 2 with 2 subventral spines, epimeral plate 3 with 3 subventral spines (fig. 3E). Urosomite 1 with 2 setae on each side, and with one ventroposterior spine near peduncle of uropod 1 (fig. 1I); urosomite 2 on each side with 3 slender spines and 1 seta (fig. 1I), urosomite 3 smooth.

Head with short rostrum, lateral cephalic lobes short, slightly rounded, with concave ventroanterior margin (fig. 2A), eyes absent.

Antenna 1 reaching half of body length; peduncular segments 1–3 progressively shorter, peduncular segment 3 reaching nearly half of peduncular segment 2, all sparsely setose (fig. 1A); main flagellum with 25 articles, most of them with one short aesthetasc each; accessory flagellum short, 2-segmented (fig. 1A), almost reaching half the length of peduncular segment 3.

Antenna 2 peduncular segment 5 slightly longer than segment 4, each with several bunches of setae (fig. 1B); flagellum slender, nearly as long as last peduncular segment, consisting of 13 articles; antennal gland cone short (fig. 1B).

Mouthparts. Labrum broader than long, entire (fig. 3A). Labium with inner lobes (fig. 4A).

Maxilla 1: inner plate short, with 2 distal setae (fig. 3B); outer plate with 7 spines [1 or 2 spines with 2 lateral teeth each, other spines with one lateral tooth each]; palp 2-segmented, with 7 distal setae (fig. 3B). Maxilla 2 normal, both plates with marginal setae only (fig. 5A).

Maxilliped: inner plate short, with 4 or 5 distal spines intermixed with single setae (fig. 4B); outer plate with row of inner marginal spines; palp articles 3 at outer margin with 2 median setae; dactyl slender, with one median seta at outer margin; nail shorter than pedestal (fig. 4B).

Mandibles with triturative molar (fig. 1C). Left mandible with 5 incisor teeth, and 9 rakers, lacinia mobilis with 4 teeth (fig. 1D).

Right mandible with 4 incisor teeth and 8 rakers, lacinia mobilis pluritoothed (fig. 1C). Mandibular palp 3-segmented, first segment smooth; second segment with one facial and 14 marginal setae; palp segment 3 subfalciform, longer than palp segment 2, bearing on the outer face one group of A-setae (fig. 1F), on the inner face 5 groups of B-setae (fig. 1E); and along the inner margin nearly 30 short D-setae and 7 distal Esetae (fig. 1E).

Coxae 1–7 short, coxae 1–2 much smaller than corresponding gnathopods (fig. 2B, D). Coxa 1 broader than long, with slightly rounded ventroanterior corner (fig. 2B); coxae 2–3 slightly longer than broad, coxa 4 nearly as long as broad, each with very short marginal setae (fig. 3C—D). Coxae 5–7 short (fig. 4 C–E).

Gnathopods 1–2 relatively large, gnathopod 2 much larger than 1 (fig. 2 B,D).

Gnathopod 1: segments 3–4 along posterior margin with one posterior group of setae each (fig. 2B); segment 5 shorter than 6; segment 6 trapezoid, slightly longer than broad, with nearly 10 posterior groups of setae on the margin (fig. 2B); palm slightly convex, oblique; nearly 2/3 of propodus length, defined on outer face by one strong corner spine accompanied laterally by 3 shorter slender toothed spines (fig. 2B–C) and 2 longer setae on outer face (fig. 2B), one short spine sitting close behind a strong corner spine on the inner face (fig. 2C). Dactyl reaching posterior margin of segment 6, bearing a row of 8 short single marginal setae, nail short.

Gnathopod 2: segments 3–4 with one posterior group of setae each; segment 5 much shorter than 6, narrow (fig. 2D). Segment 6 large, subtriangular, but almost egg-shaped, slightly longer than broad, bearing nearly 14 posterior marginal groups of setae; palm slightly convex, but extremely oblique to the basis of segment 6 (propodus), defined on outer face by one strong corner spine accompanied by 3 short slender toothed spines sitting behind corner spine, and by 2 long setae (fig. 2D), on inner face by one short spine near the corner (fig. 2E). Dactyl not reaching posterior margin of segment 6, bearing a row of 8 short single setae along outer margin, nail short.

Pereopods 3–4 long and slender, posterior margin of segment 6 with row of single spines accompanied by short setae (fig. 3C–D); posterior setae on segments 4–5 of pereopod 3 are slightly longer than those of pereopod 4. Dactyls short, not exceeding 1/3 length of segment 6, their nail slightly shorter than pedestal, bearing at outer margin one medial seta, and at inner margin 2–3 single spines (pereopod 3) or 2 spines only (pereopod 4) (fig. 3C–D).

Pereopods 5–7 long and slender, progressively longer towards pereopod 7, their segments 4–6 bearing bunches of short spines and setae along both margins (fig. 4C–E); segment 2 narrow, slightly more than twice as long as broad, with straight or slightly concave posterior margin bearing row of short setae, ventroanterior and ventroposterior lobe not developed. Dactyl of pereopods 5–7 short, several times shorter than segment 6, bearing one median plumose seta at outer margin, and one spine at inner margin (pereopods 5–6) or 2 spines (pereopod 7); nail shorter than pedestal (fig. 4C–E).

Pleopods 1–3 with 2 retinacula each. Peduncle of pleopod 1 with row of 4 short setae along anterior margin (fig. 5B); peduncle of pleopod 2 with only one anterior seta (fig. 5C); peduncle of pleopod 3 with row of posterior short setae (nearly 8 setae) (fig. 5D).

Uropod 1: peduncle with row of dorsoexternal row of spine-like setae, and with row of setae along dorsointernal margin (fig. 1I); rami slender, each with bunches of short spines and setae; outer ramus slightly shorter than inner ramus, both with short distal spines (fig. 1I).

Uropod 2: outer ramus slightly shorter than inner one, both rami with lateral and distal short spines (fig. 1I).

Uropod 3 long, peduncle short; inner ramus short, scale-like, with 2 distal and one lateral spine; outer ramus 2-segmented, long; first segment with short spines and setae along both margins; second segment slightly shorter than first one (fig. 1H), bearing short setae on both margins and at tip.

Telson short, slightly longer than broad, with gaping lobes (fig. 1G), each lobe with 4 distal short spines and one inner marginal spine; a pair of short plumose setae appears near the middle of each lobe.

Gills on gnathopods 1–2 and pereopod 3–4 distinctly shorter than the corresponding segment 2 (figs. 2D, 3C–D). Gills on pereopods 5–6 short, ovoid (fig. 4C–D).

Female 17.0 mm, mature: Body with setose oostegites and 22 juv. specimens in marsupium. Epimeral plate 1 broadly angular (fig. 6H), plates 2–3 with distinct ventroposterior corner and with one subventral spine (plate 2) or 3 subventral spines (plate 3) (fig. 6H).

Urosomite 1 on each dorsolateral side with 1 seta, urosomite 2 on each dorsolateral side with 2 spines, urosomite 3 smooth. Ventroposterior corner of urosomite 1 with one bunch of 2 spines (fig. 5M).

Antenna 1 slightly exceeding half of body length (ratio: 10:17), main flagellum of antenna 1 with 31 articles, that of antenna 2 with 11 articles. Maxilla 1: inner plate with 3 setae, outer plate like that in male, palp with 7 setae.

Inner plate of maxilliped with 4 distal spines, palp segment 3 at outer margin with 1 or 2 median setae. Mandibular palp segment 2 with 17 setae, palp segment 3 with 26 D-setae, one group of A-setae and 6 groups of B-setae.

Coxa 1 broader than long, coxae 2–3 slightly broader than long, coxa 4 nearly as long as broad (fig. 6 length A–D).

Gnathopods 1–2 large. Gnathopod 1: much smaller than 2, segment 6 slightly longer than broad, with 9 groups of setae along posterior margin; palm, convex, inclined 2/3 of propodus length, bearing one strong corner spine accompanied laterally on outer face by 4 slender toothed spines, and on inner face by one short subcorner spine (fig. 6E); dactyl reaching posterior margin of segment 6, with row of 8 setae along outer margin (fig. 6E).

Gnathopod 2: segment 6 almost egg-shaped, slightly longer than broad, with 12–14 groups of setae along posterior margin; palm defined on outer face by 1 or 2 strong corner spines, accompanied by 3 or 4 slender toothed spines lateral to the corner spine and on the inner face by one short subcorner spine (fig. 6F–G); dactyl not reaching posterior margin of segment 6, with 7 short setae along outer margin (fig. 6G).

Pereopods 3–4 as in male, but dactyls of pereopod 3 along inner margin with 1–3 spines each (fig. 5H); dactyl of pereopod 4 along inner margin with 3 or 4 spines (fig. 5 I).

Segment 2 of pereopods 5–7 with narrow segment 2 more than twice as long as broad, without distinct ventroposterior and ventroanterior lobe (fig. 5 E–G). Dactyl of pereopods 5 and 7 with 2 spines at inner margin, that of pereopod 6 with one spine along inner margin (fig. 5 J–L).

Pleopods 1–3 with 2 retinacula each. Peduncle of pleopod 1 with 4 posterior and one anterior seta; that of pleopod 2 with 2 anterior setae only; peduncle of pleopod 3 with 4 anterior setae.

Uropods 1–2 slender. Uropod 1: peduncle with row of dorsointernal strong setae and dorsoexternal row of spines (fig. 5M), rami of equal length, bearing lateral and distal short spines and lateral bunches of simple setae.

Uropod 2: rami of equal length, each with short lateral and distal spines (fig. 5N).

Uropod 3 relatively long, reaching half of body-length. Inner ramus short, scale-like, with 2 distal spines; outer ramus 2-segmented: first segment with spines along both margins and with single plumose setae along inner margin; second segment reaching nearly 1/3 of first segment, with simple setae along both margins and tip (fig. 5O).

Telson nearly as long as broad, with gaping lobes bearing 3 distal spines each and up to 1 inner marginal spine; a pair of short plumose setae appears near the middle of each lobe (fig. 5P).

Coxal gills relatively short, not reaching tip of corresponding segment 2 of pereopods. Oostegites broad, with marginal setae.

Variability. The presence of 2 strong corner spines on segment 6 of one gnathopod 2 in the female is atypical (usually only one spine is present), but this is common within the Niphargus taxa.

The number of spines along the inner margin of the dactyl of pereopods 3–7 is variable, but there are usually at least several spines on each dactyl.

Etymology. This species is named for Prof. Dr. Alessandro Montanari, Director of the Osservatorio Geologico di Coldigioco located near Apiro, the Marches, Italy in honor of his comprehensive studies of the Frasassi cave system and the geological history of this part of Italy in general.

Remarks. Niphargus montanarius , n. sp. is distinctly different from all other known Niphargus taxa in Italy. While large unequal gnathopods are present in some other taxa in Italy (especially in the subgenus Orniphargus, as N. patrizii Ruffo & Vigna-Tagl., 1968 , N. parenzani Ruffo & Vigna-Tagl., 1968 , as well as N. sodalis G. Kar., 1984 from Teramo, various species of the N. stygius group, etc.), N. montanarius is unique in its combination of characters: long uropod 3 in males and females, more numerous spines on dactyls of pereopods 3–7, poorly developed armature on urosomites, and spines of outer plate in maxilla 1 with 1 or 2 lateral teeth each.

A shorter dactylus of gnathopod 2 not reaching the posterior margin of segment 6 is also present in large specimens of Niphargus cornicolanus Iannilli & Vigna-Tagl., 2005 , known from Pozzo del Merro, 32 La (Lazio, central Italy), but this species differs significantly from N. montanarus by the short uropod 3 in males and females, the narrow long telson, broader segment 2 of pereopods 5–7, etc.

Other Niphargus species have large gnathopods as well, but these feed by filtering mud and detritus, and the shapes of the gnathopods are modified for this purpose (for example Niphargus trullipes Sket, 1958 from Vjetrenica cave in Herzegovina). The large size and shape of its extreme gnathopods suggests that it may be a predator, which is very unusual in gammarid amphipods.

Figures

FIGURE 1. Niphargus montanarius, n. sp., Lago Bugianardo, male 21.0 mm (holotype): A = antenna 1; B = antenna 2; C = right mandible; D = left mandible; E = mandibular palp, inner face; F = mandibular palp, outer face; G = telson; H = uropod 3; I = urosome with uropods 1 – 2. Scale bars: 1 = 0.25 mm (C, D); 2 = 0.5 mm (E – G); 3 = 1.0 mm (A, B, I); 4 = 2.0 mm (H).

FIGURE 2. Niphargus montanarius, n. sp., Lago Bugianardo, male 21.0 mm (holotype): A = head; B, C = gnathopod 1; D, E = gnathopod 2. Scale bars: 1 = 0.25 mm (C, E); 2 = 0.5 mm (A); 3 = 1.0 mm (B, D).

FIGURE 3. Niphargus montanarius, n. sp., Lago Bugianardo, male 21.0 mm (holotype): A = labrum; B = maxilla 1; C = pereopod 3; D = pereopod 4; E = epimeral plates 1 – 3. Scale bars: 1 = 0.25 mm (A); 2 = 0.5 mm (B); 3 = 1.0 mm (E); 4 = 1.0 mm (C, D).

FIGURE 4. Niphargus montanarius, n. sp., Lago Bugianardo, male 21.0 mm (holotype): A = labium; B = maxilliped; C = pereopod 5; D = pereopod 6; E = pereopod 7. Scale bars: 1 = 0.5 mm (A); 2 = 0.5 mm (B); 3 = 1.0 mm (C – E).

FIGURE 5. Niphargus montanarius, n. sp., Lago Bugianardo, male 21.0 mm (holotype): A = maxilla 2 length B, C, D = peduncle of pleopods 1 – 3. Female 17.0 mm: E – G = segment 2 of pereopods 5 – 7; H – L = dactyl of pereopods 3 – 7; M = uropod 1; N = uropod 2; O = uropod 3; P = telson. Scale bars: 1 = 0.5 mm (A); 2 = 0.5 mm (H – L, P); 3 = 1.0 mm (B – D); 4 = 1.0 mm (E – G); 5 = 1.0 mm (M – O).

FIGURE 6. Niphargus montanarius, n. sp., Lago Bugianardo, female 17.0 mm: A – D = coxae 1 – 4; E = gnathopod 1; F = right gnathopod 2; G = left gnathopod 2; H = epimeral plates 1 – 3. Scale bars: 1 = 1.0 mm (A – F, H).