Niphargus echion, Karaman, Gordan S., Mato, Sanja Gottstein & Ec, 2006

Karaman, Gordan S., Mato, Sanja Gottstein & Ec, 2006, Niphargus echion, a new species of amphipod (Crustacea Amphipoda, Niphargidae) from Istra, Croatia, Zootaxa 1150, pp. 53-68 : 55-66

Niphargus echion , n. sp.

( Figs 1–7 )

Material examined

“Pliškovićeva jama” cave,Š ikuti village, St. Vinčenat, Istra ( Croatia); 6 August 2000, coll. B. Jalżić, 2 specimens. Holotype (coll. no. C1587, male 11.0 mm), and paratype (coll. no. C1588, female 10.3 mm) are deposited in the Croatian Natural History Museum, Zagreb.

Diagnosis

Outer plate of maxilla 1 with 19–20 spines, each with 1 or 2 very slender lateral and elongated distal bifurcations. Dactylus of maxilliped with 2 nails. Pleopods with 2 or 3 retinaculae. Gnathopod 2 basis with 4 or 5 long outer setae near corner spine; dactyl with row of outer marginal setae. Dactyl of pereopods 3–7 with 1 strong spine on inner margin. Epimeral plates with angular or subacute posteroventral corner. Uropods 1 and 2 with subequal rami. Second segment of uropod 3 in males moderately elongated.

Description

ADULT MALE (holotype). Body: moderately slender, metasomal segments 1–3 with 10–15 dorsoposterior short marginal setae [segment 3 with 15 setae] (fig. 4F). Epimeral plates 2–3 with poorly acute posteroventral corner, never produced, plates 2–3 with 2 ventrofacial spines each (fig. 4F).

Urosomite 1 with one posteroventral spine (fig. 3F). Urosomite 1 on each dorsolateral side with 2 strong spines; urosomite 2 on each dorsolateral side with 2 strong spines. Urosomite 3 smooth (fig. 3F).

Head with slightly convex dorsal margin (in lateral view); rostrum short, lateral cephalic lobes short and subrounded, anteroventral sinus shallow (fig. 1A). Eyes absent.

Antenna 1: slightly shorter than half body length (4.7: 11); peduncular segments 1–3 relatively stout, progressively shorter; peduncular segment 3 slightly shorter than half peduncular segment 2; primary flagellum longer than peduncle, consisting of 22 articles bearing one short aesthetasc each (fig. 1B); accessory flagellum short, 2­segmented (fig. 1C).

Antenna 2: much shorter than antenna 1; peduncular segment 4 slightly longer than segment 5 (4.3: 5.3); flagellum moderately slender, longer than last peduncular segment and consisting of 9 articles; antennal gland cone short (fig. 1D).

Coxae: relatively short, coxa 1 slightly broader than long, with subrounded anteroventral corner; ventral margin with about 10 short marginal setae (fig. 2A).

Coxae 2–4 slightly longer than broad, with up to 12 relatively short, marginal setae (figs 2D, 3A & E). Coxae 5–7 short (fig. 4A, C & D).

Mouthparts: Labrum short, subrounded (fig. 5A). Labium normal, broader than long, outer lobes entire (fig. 5B).

Maxilla 1: inner plate conical, with 5 distal setae; outer plate not dilated, but provided with 19 or 20 spines bearing 1 or 2 lateral long and slender teeth each. Palp short, 2­ segmented, reaching distal margin of outer plate, and bearing 6 distal setae (fig. 5C & D).

Maxilla 2: normal, both lobes with numerous distal setae only (fig. 1E).

Maxilliped: inner plate with 4 or 5 distal chisel­like spines intermixed with single setae; outer plate with row of spines along inner margin and distal tip, reaching nearly half of palp segment 2; dactyl (segment 4) of palp with 2 nails (fig. 1F & G).

Mandibular palp: 3­segmented, first segment smooth, second segment with 13 strong, spine­like setae along posterior margin; palp segment 3 slightly longer than segment 2, bearing 22 D­setae, 8 distal E­setae, on outer face one group of 5 setae, on inner face 5 groups of B­setae (fig. 1E & F).

Gnathopod 1: size moderate, slightly smaller than gnathopod 2; segment 3 with one posterior group of setae only; segment 5 markedly shorter than segment 6. Segment 6 longer than broad, poorly dilated distally, and with 9 groups of posterior marginal setae; palm slope oblique nearly 3/8 of posterior margin of segment 6, defined on outer face by short corner spine accompanied laterally by 3 slender toothed spines and 5 long outer setae; on inner face defined by one short subcorner spine; dactyl reaching posterior margin of segment 6, with row of 9 setae along outer margin, setae sitting in group of 1 or 2 only (1–1–2–1–1–1–2) (fig. 2A, B & C).

Gnathopod 2: segment 3 with one posterior group of setae; segment 5 slightly shorter than segment 6. Segment 6 nearly as long as broad, with 13 groups of setae along posterior margin; palm slope oblique nearly 3/8 of posterior margin of segment 6, defined on outer face by 1 strong corner spine accompanied by 2 slender toothed spines placed laterally and by 4 long setae on outer surface; at inner face by 1 short submarginal spine; dactyl reaching posterior margin of segment 6, provided along outer margin with row of 9 setae (2–2–1–1–1–1–1) (fig. 2D, E & F).

Pereopods 3 and 4: subequal in length, relatively stout; dactyls short, with one strong spine at inner margin, nail poorly longer than peduncle (fig. 3A, B, C & D).

Pereopods 5–7: relatively stout, pereopod 5 remarkably shorter than pereopod 7, all pereopods with segment 2 distinctly longer than broad, without anteroventral or posteroventral lobe, and with slightly convex posterior margin provided with row of short marginal setae (fig. 4A, C & D). Segments 3–6 stout, with spines along both margins. Dactyl of pereopod 5 slightly longer than peduncle, with one strong spine at inner margin (fig. 4B). Dactyl of pereopod 7 with nail as long as peduncle, and with one spine at inner margin (fig. 4E).

Pleopods 1–3 with 2 or 3 retinaculae each (2–3–2, 2–2–2).

Uropod 1: peduncle with row of dorsomedial and dorsolateral row of spines, rami shorter than peduncle, of subequal length, bearing single lateral and 4 or 5 distal short spines accompanied by several setae (fig. 3F).

Uropod 2: rami subequal, outer ramus slightly recurved, and almost reaching tip of inner ramus, both rami provided with single lateral and 4 or 5 distal short spines (fig. 3F).

Uropod 3: slightly elongated, peduncle much shorter than first segment of outer ramus; first segment at both margins with spines, single long plumose seta at its inner margin; second segment of outer ramus slightly exceeding 1/3 of first segment of outer ramus (fig. 3G). Inner ramus short, scale­like.

Telson: not elongated, slightly broader than long, incised nearly 2/3 of its length; each lobe with 3 distal and 2 facial spines, along outer margin with 2 single spines, along inner margin with 1 or 2 spines; a pair of short plumose setae appears near the middle of each lobe (fig. 4G).

Coxal gills: 1–6 moderately long (figs 2D, 3A, 4A).

ADULT FEMALE (paratype): Body: with setose oostegites bearing 10 eggs in marsupium. Metasomal segments 1–3 with row of posterodorsal marginal setae as in male (fig.7E). Urosomite 1 with one posteroventral spine, as in male (fig. 6E). Urosomites 1 and 2 on each side with 2 spines each; urosomite 3 smooth (fig. 6E).

Epimeral plates: 2 or 3 acute, but not pointed, as in male; epimeral plate 2 with 2, and epimeral plate 3 with 3 ventrolateral spines (fig. 7E).

Head: as in male, antenna 1 hardly longer than that of male (4.7: 10.3); primary flagellum consisting of 21 or 22 articles bearing one aesthetasc each. Antenna 2: flagellum with 8 or 9 articles.

Mouthparts: similar to males.

Maxilla 1: inner plate with 3 distal setae only; outer plate with up to 20 slender spines, bearing 1 or 2 slender elongated lateral teeth each; palp 2­segmented, with 6 distal setae.

Maxilliped: as in males: inner plate with 4 or 5 distal chisel­like spines (fig. 7A), dactyl with 2 nails (fig. 7B).

Coxae: similar to males; coxa 1 broader than long (fig. 5G); coxae 2–4 longer than broad (fig. 5H, I & J), all with row of short to slightly longer marginal setae each. Coxae 5–7 as in males.

Gnathopods: 1 or 2 of moderate size, gnathopod 2 moderately larger than gnathopod 1 (fig. 6A, 6C). Gnathopod 1: segment 3 with one posterior marginal group of setae; segment 5 shorter than 6; segment 6 hardly longer than broad, along posterior margin with 9 groups of marginal setae; palm slope oblique slightly less than half of posterior margin of segment 6; outer face with one strong corner spine accompanied by 6 lateral setae and by 3 slender toothed spines sitting laterally of main spine (fig. 6B); corner of inner face with one short submarginal spine; dactyl reaching posterior margin of segment 6, along outer margin with 8 single setae (fig. 6A).

Gnathopod 2: segment 3 with one posterior marginal group of setae; segment 5 shorter than 6; segment 6 hardly broader than long, with palm slope oblique slightly over half of posterior margin of segment 6; palm defined on outer face by 1 strong corner spine accompanied by 5 long setae and by 2 slender toothed spines sitting lateral to main spine (fig. 6D); dactyl reaching posterior margin, and provided along outer margin with row of 11 setae (1–2–1–2–2–1–2) (fig. 6C).

Pereopods 3–7: as in males. Pereopod 7 segment 2 longer than broad, without distinct anteroventral or posteroventral lobe; posterior margin with row of short marginal setae (fig. 7C). Dactyl of pereopod 7 with nail nearly as long as peduncle, and with one strong spine at inner margin (fig. 7D).

Pleopods 1–3: with 2 or 3 retinaculae each (2–2–3, 2–2–3).

Uropod 1: peduncle with dorsolateral row of spines and dorsomedial row of spine­like setae; rami nearly subequal, with single lateral and 4 or 5 distal short spines (fig. 6E).

Uropod 2: rami subequal, long, with single lateral and 4 or 5 short distal spines (fig. 6E).

Uropod 3: with short second segment on outer ramus, bearing numerous distomarginal setae; first segment with spines on both margins and a row of long single plumose setae along inner margin (fig. 7F). Inner ramus short, scale­like.

Telson: distinctly broader than long, incised slightly less than 2/3 of its length; each lobe with 3 distal and one group of 2 facial spines; along outer margin with 1 or 2 spines, along inner margin with 1 spine; a pair of plumose setae appears near the middle of each lobe (fig. 7G).

Variability

Owing to the very scarce at hand, variability in taxonomic characters is difficult to assess. The number of distal spines on inner plate of maxilliped is rather variable (4 or 5), as well as the number of setae on inner plate of maxilla 1 (3–5). The number of retinaculae is 2 or 3, but not the all pleopods bear the same number. Thus, the variability in the retinacula remains problematic and must be resolved based on a additional material. Among the stable characters are the presence of two nails on each dactyl of the maxilliped, a character already observed and known for Niphargus krameri Schellelenberg, 1935 .

Remarks

Niphargus echion , n. sp. differs from all known species of the genus by the highest known number of distal spines (19 or 20) on the outer plate of maxilla 1 in males and females.

Most known Niphargus species are provided with seven distal spines on outer plate of maxilla 1. Niphargus lunaris G. Karaman, 1985 from Bosnia, however, is provided with eight distal spines; N. sodalis G. Karaman, 1984 , from Italy, is provided with 10–12 distal spines; and N. pasquinii Vigna Taglianti, 1966 , from Italy also, is provided with up to 15 distal spines.

The second very important character is the presence of two nails on the tip of maxilliped palp, a rare condition in Niphargus . Only Niphargus krameri Schellellenberg, 1935 , also from Istra and vicinity, is also provided usually with two nails (rarely with only one) on the dactyl of the maxilliped. Other species of Niphargus are provided with only one distal nail on the dactyl of the maxilliped.

In other taxonomic characters N. echion resembles other Niphargus species.

Etymology

The new species, N. echion , is named after Echion , one of the five surviving warriors in Greek mythology, who was born out of the dragon’s teeth that Cadmus had sown when founding Thebes. The dragon’s triple row of teeth is reminiscent of the numerous distal spines on outer plate of the first maxilla of N. echion , which distinguishes the new species from all other known Congeners.

Ecology

The material was collected from a cave pool in the unsaturated zone.

Distribution

Known from the type locality only.

Figures

FIGURE 1. Niphargus echion, n. sp., holotype male, 11 mm, Pliškovićeva jama cave: A, head; B – C, antenna 1; D, antenna 2; E, maxilla 2; F – G, maxilliped. Scales bars: A, B, D, 1 mm; E, F, 0.25 mm.

FIGURE 2. Niphargus echion, n. sp., holotype male, 11 mm, PliŠkovićeva jama­cave: A – C, gnathopod 1; D – F, gnathopod 2. Scales bars: A, B, D, E, 1 mm.

FIGURE 4. Niphargus echion, n. sp., holotype male, 11 mm, PliŠkovićeva jama cave: A – B, pereopod 5; C, pereopod 6; D – E, pereopod 7; F, epimeral plates 1 – 3; G, telson. Scales bars: A, C, D, F, 1 mm; G, 0.5 mm.

FIGURE 5. Niphargus echion, n. sp., holotype male, 11 mm, PliŠkovićeva jama cave: A, labrum; B, labium; C – D, maxilla 1; E, mandibular palp, inner face; F, mandibular palp, outer face. Female 10.3 mm (paratype): G – J, coxae 1 – 4. Scales bars: A – C, 0.5 mm; E – F, 0.25 mm; G – J, 1 mm.

FIGURE 6. Niphargus echion, n. sp., paratype female, 10.3 mm, PliŠkovićeva jama cave: A – B, gnathopod 1; C – D, gnathopod 2; E, urosome with uropods 1 – 2. Scales bars: A, C, 0.5 mm; E, 1 mm.

FIGURE 7. Niphargus echion, n. sp., paratype female, 10.3 mm, PliŠkovićeva jama cave: A, inner plate of maxilliped; B, dactyl of maxilliped; C – D, pereopod 7; E, epimeral plates 2 – 3; F, uropod 3; G, telson. Scales bars: C, E, F, G, 1 mm.