Chaetoniphargus lubuskensis, Karaman & Sket, 2019

Karaman, Gordan S. & Sket, Boris, 2019, New genus and species of the family Niphargidae (Crustacea: Amphipoda: Senticaudata), Chaetoniphargus lubuskensis gen. nov., sp. nov. from Croatia, Zootaxa 4545 (2), pp. 249-263 : 250-261

Chaetoniphargus lubuskensis sp. nov.

Figs 1–8

Type material. Holotype, female, 3.9 mm with setose oostegites, cave Lubuška jama, Hajdučki Kukovi, Northern Velebit Mt. , Croatia, 26.8.2017, leg. V. Sudar , deposited as NC 340 in Croatian Natural History Museum, Zagreb, Croatia, together with 2 paratypes. Two paratypes are deposited in Karaman`s Collection in Podgorica , Montenegro, same collection data as holotype.

Material examined. S-7339 = Cave Lubuška jama, Hajdučki Kukovi, Northern Velebit Mt., Croatia, 26.8.2017, 5 exp. (leg. V. Sudar).

Diagnosis (females only). Body inflated in the middle, covered with various single strong setae on dorsolateral side; urosome low, naked. Epimeral plates subrounded. Head with short lateral cephalic lobes, eyes absent. Mouthparts: see diagnosis of the genus.

Coxae of moderate size, coxa 4 unlobed; coxae 5–6 bilobed, coxa 5 is larger than coxa 4. Gnathopods 1–2 weak, subchelate, with dactylus bearing one median seta at outer margin. Pereopods 4–7 strong, with dactylus bearing one spine at inner margin; basipodit of pereopods 5–7 narrowed, unlobed. Pleopods biramous, well developed, with 2 retinacula. Uropods 1 and 2 are biramous, rami of uropod 1 equal, inner ramus of uropod 2 is longer than outer one. Uropod 3 is very short, inner ramus scale-like, outer ramus with one short article bearing distal spines. Coxal gills on pereopods 2 and 4 are narrow, linear, coxal gill on leg 3 is very large, ovoid, coxal gills on legs 5–6 are short, ovoid. Oostegites large.

Description. Female 3.9 mm with setose oostegites (holotype). Body stout, slightly inflated in the middle (figs 7, 8). Head with short rostrum and short subrounded lateral cephalic lobes, ventroanterior sinus shallow (fig. 1A), eyes absent. Mesosomal segments 1–4 naked; mesosomal segments 5–6 on each dorsolateral side with one strong submarginal seta, mesosomal segment 7 on each dorsolateral side with one submarginal and one mediolateral strong seta (fig. 5B); metasomal segment 1 on each side with 1–2 dorsoposterior and 2 medioposterior setae (fig. 5B); metasomal segment 2 on each dorsolateral and lateral side with one strong seta; metasomal segment 3 naked. Urosomal segments 1–3 are low; urosomal segments 1–3 are dorsally naked. Urosomal segment 1 at ventroposterior corner without spine or seta (fig. 5D).

Epimeral plates 1–3 are of subequal size and shape, subrounded, with remarkably convex ventral (distal) margin defined by one weak small seta, posterior convex margin with 1 weak seta; ventral spines absent (fig. 5B).

Antenna 1 remarkably shorter than half of body-length (fig. 8); peduncle relatively slender, peduncular articles 1–3 progressively shorter (ratio: 52:36:19), first article distally with 3 long setae; second article at dorsal margin with one median and 2 distal setae; at ventral margin with 2 short setae; third article short (fig. 1B). Main flagellum consisting of 13 slender articles bearing short setae and single aesthetasc of approximately half article lengths (fig. 1B). Accessory flagellum 1-articulate, shorter than half of last peduncular article and provided with 2 distal simple setae (fig. 1C).

Antenna 2 remarkably shorter than antenna 1, peduncle with relatively short articles: article 3 very short; article 4 longer than article 5 (ratio: 36:26), both articles almost naked (fig. 1D); flagellum remarkably longer than peduncle, consisting of 7 articles provided with scarce number of very short setae. Antennal gland cone conical, hardly exceeding tip of peduncular article 3 (fig. 1D).

Labrum strong, broader than long (ratio: 62:44), poorly convex distally, epistom carinate (fig. 2A).

Labium strong, outer lobes are entire and broad, haired distally, with narrowed lateral process; inner lobes are long and narrowed, bearing numerous distomarginal very fine short setae (fig. 3A).

Mandible rather asymmetric, molar molar bluntly conical, with strong lateral seta. Right mandible: incisor with 4-teeth, lacinia mobilis not observed (fig. 1F). Left mandible: incisor with 4 teeth, lacinia strong, with 4 teeth (fig. 1E). Behind the incisor appear a large row of over 16 rakers. Mandibular palpus small, obsolete, reduced to one small article, sometimes indistinctly partially separated in two parts (fig. 1E, F) and provided with one shorter or longer distal seta.

Maxilla 1: inner plate small, conical, with short distal seta; outer plate with nearly 18 distally compressed pectinate spines sitting in two rows; palpus small, obsolete, reduced to one small article provided with one distal simple seta (fig. 5A).

Maxilla 2 very small, outer plate is remarkably larger than inner one, with nearly 10 distal setae, inner plate with 5 distal setae (fig. 1G).

Maxilliped: inner plate long and narrow, with one distal spine accompanied by numerous short setae (fig. 1H); outer plate very broad, not exceeding half of outer tip of palpus article 2, provided with 8 distomarginal short spines and numerous very short facial setae (fig. 1H); palpus strong, consisting of 4 articles: first article short, at mesial margin with 4 long setae; article 2 along mesial margin with numerous setae; palpus article 3 in distal part with numerous setae; article 4 at outer margin with one median seta, at inner (mesial) margin with one seta near basis of the nail.

Coxae of moderate size, coxa 1 poorly broader than long (ratio: 35:31), with subrounded unproduced ventroanterior corner and provided with 5 unequal marginal setae (fig. 2B). Coxa 2 distinctly larger than coxa 1, nearly as long as broad, with 5 unequal setae along ventral margin (fig. 2E). Coxa 3 square, as long as broad, along ventral margin with 5 unequal setae (fig. 3D). Coxa 4 is hardly broader than long (ratio: 57:54), with 6 marginal unequal setae and without a distoposterior lobe (fig. 3F).

Coxa 5 is relatively large, approximately the size of coxa 4, broader than long (ratio: 78:56), with posterior lobe almost as large as anterior one, 7–8 setae are attached at the margin of this coxa (fig. 4A). Coxa 6 remarkably smaller than coxa 5, bilobed, broader than long (ratio: 57:46), along ventral margin with nearly 6 unequal setae; posterior lobe poorly smaller than anterior one (fig. 4C). Coxa 7 much smaller than coxa 6, entire, broader than long (ratio: 47:32), with anterior part broader than posterior one (fig. 4D).

Gnathopods 1 and 2 weak and small (fig. 2B, E). Gnathopod 1 is smaller than gnathopod 2, with article 2 provided along anterior and posterior margin with 3 long median setae (fig. 2B). Article 3 at posterior margin with one single or paired short setae; article 4 short, at posterior margin with 4 long setae. Article 5 almost triangular, along posterior convex margin with rows of long setae, along anterior margin with one distal short seta. Propodus subtrapezoidal, longer than broad (ratio: 113:88), proximally slightly narrower than at the palmar angle, along posterior margin with 3 transverse rows of setae (3–2–1) (fig. 2C); palm slightly convex, inclined almost to the half of propodus-length, defined on outer face by one corner S-spine accompanied laterally by one weak L- spine-like seta and 2 facial M-setae, on inner face by one strong subcorner R-spine (fig. 2D). Dactylus reaching posterior margin of propodus, along outer margin with one median seta (fig. 2C).

Left gnathopod 2: article 2 along anterior margin with one distal short seta only, along posterior margin with 2 long median setae (fig. 2E); article 3 at posterior margin with one seta; article 4 short, with 2–3 posterior setae; article 5 almost triangular, nearly as long as propodus, along posterior margin with 3 bunches of long setae (each row is consisting of a few setae only), at anterior margin with one short distal seta. Propodus subtrapezoidal, almost subovoid, longer than broad (ratio: 124:93), along posterior margin with 5 transverse rows of setae (fig. 3B). Palm slightly convex, inclined slightly less than half of propodus-length (fig. 3C), defined on outer face by one corner S- spine accompanied laterally by one long seta and 2 facial M-setae, R-spine is not observed (probably aberrant corner of propodus). Dactylus reaching posterior margin of propodus, with one median seta at outer margin (fig. 3B).

Right gnathopod 2: propodus longer than broad (ratio: 124:90), along posterior margin with 5 rows of setae (fig. 2F); palm convex, inclined slightly less than half of propodus-length, defined on outer face by one corner Sspine accompanied laterally by one slender L-spine and 2 facial M-setae (fig. 2G), on inner face by one strong subcorner R-spine. Dactylus reaching posterior margin of propodus, along outer margin with one median seta.

Pereopods 3 and 4 relatively stout. Pereopod 3: article 2 with 2 distal short setae along anterior margin, along posterior margin attached 2 long median and one short distal seta (fig. 3D). Articles 3–6 of unequal length (ratio: 23:36:27:43), article 3 naked; article 4 at posterior margin with 2 short median and 2 distal short setae, along anterior margin with distal bunch of 3 setae; article 5 at posterior margin with 3 distal setae, along anterior margin with one median and 2 distal setae. Article 6 hardly recurved (distorted), along posterior margin with one median and one distal short seta, at anterior margin with 2 groups of median setae and one distal seta; dactylus strong, shorter than article 6 (ratio: 19:43), slightly recurved, along outer margin with one median plumose seta, at inner margin with one strong spine and short seta near basis of nail (fig. 3E), nail strong, slightly shorter than its pedestal (ratio: 35:42).

Pereopod 4 mainly like pereopod 3, but slightly shorter. Article 2 along anterior margin with 3 short setae, along posterior margin with one long median seta and one short distal seta; article 3 naked; article 4 along posterior margin with 2 short setae, along anterior margin with bunch of long distal setae; article 5 at posterior margin with 3 short setae, along anterior margin with single median and 2 distal short setae (fig. 3F). Article 6 at posterior margin with one seta, at anterior margin with 3 median and bunch of distal short setae. Dactylus like that in pereopod 3.

Pereopods 5–7 are short and stout. Pereopod 5: article 2 much longer than broad (ratio: 69:40), along anterior margin with 2 distal short setae, along posterior convex margin attached nearly 7 long setae of unequal length, ventro-posterior lobe absent (fig. 4A). Articles 3–6 of unequal length (ratio: 20:42:47:60). Article 3 along anterior margin with 2–3 short distal setae; article 4 at anterior margin with one median and 3 distal short setae, along posterior margin appear one median and 3 distal long setae, as well as one distal spine. Article 5 at anterior margin with one median and one distal group of spines, at posterior margin appear 3 groups of long setae accompanied by single spines. Article 6 shorter than article 2 (ratio: 60:69), provided at anterior margin with one median and one distal group of short spines, along posterior margin appear 3 groups of long simple setae. Dactylus strong, shorter than article 6 (ratio: 25:60), at inner margin with one strong spine and short seta near basis of the nail, at outer margin with one median plumose seta; nail shorter than pedestal (fig. 4B).

Pereopod 6 slightly longer than pereopods 5 and 7; article 2 longer than broad (ratio: 75:45), along anterior margin there is one short median seta and one distal short spine and single setae, along posterior margin there are 9 unequally long setae, ventro-posterior lobe absent (fig. 4C). Articles 3–6 of unequal length (ratio: 23:53:52:70). Article 3 at anterior distal margin with one short seta; article 4 at anterior margin with one short median and 3 distal spines, along posterior margin there are 2 groups of long setae and several distal spines; article 5 with one median and one distal group of short spines, along posterior margin with 3 groups of long simple setae as well as one long distal spine. Article 6 shorter than article 2 (ratio: 70:75), at anterior margin with one median and one distal group of short spines, along posterior margin with 4 groups of long simple setae and one distal short spine. Dactylus much shorter than article 6 (ratio: 26:70), at inner margin with one strong spine and short seta near basis of the nail, at outer margin with one median plumose seta; nail shorter than pedestal (fig. 4C).

Pereopod 7: article 2 is longer than broad (ratio: 70:44), anterior margin provided with one short median seta and short distal spine, along posterior margin appear 7 unequal setae, ventro-posterior lobe absent (fig. 4D). Articles 3–6 of unequal length (ratio: 27:56:48:67). Article 3 with one distal short seta at anterior margin; article 4 at anterior margin with one median and one distal bunch of short spines, along posterior margin with 3 groups of long setae and 2 distal spines; article 5 along posterior margin with 3 groups of long setae and 2–3 distal spines, along anterior margin with one median and one distal group of short spines. Article 6 shorter than article 2 (ratio: 67:70), along posterior margin with 3 groups of long 1–2 setae and with one median and one distal short spine. Dactylus shorter than article 6 (ratio: 27:70), at inner margin with one strong spine and short seta near basis of the nail, at outer margin with one median plumose seta; nail shorter than pedestal (ratio: 35:44) (fig. 4E).

Pleopods 1–3 with rather compressed peduncles bearing 2 retinacula each; peduncles naked, bearing rami of subequal length, composed of 6–8 articles (fig. 5C).

Uropod 1 slender, peduncle reaching the end of urosoma; with 2 dorso-external short spines and distal pair of spines, dorso-internal row absent. Outer ramus as long as inner one, provided with distal bunch of 5 unequal spines (figs 5D, 6A); inner ramus with one median spine and distal group of 4 relatively short spines, rami reaching beyond the tips of uropod 2.

Uropod 2 slender, peduncle with distal spine; inner ramus distinctly longer than outer one, both rami with one median spine and distal group of 5 spines (figs 5D, 6B).

Uropod 3 reduced, much shorter than uropod 2 peduncle, longer than broad (ratio: 50:21), bearing 2 distal spines; inner ramus minute, vestigial, with one simple distal seta. Outer ramus consisting of one article, longer than broad (ratio: 36:15), shorter than peduncle; with 5 distal spines of unequal length (the longest spine only slightly shorter than ramus itself (figs 5E, 6C).

Telson short, much shorter than wide (ratio: 20:44), incised distally; lobes subrounded and provided with one distal seta, incision does or doesn`t reach the half length of telson (figs 5E, 6H).

Coxal gills present on the legs 2–6; coxal gill on gnathopod 2 and pereopod 4 narrow and recurved (figs 2E, 3F), coxal gill on pereopod 3 is large, ovoid (fig. 3D), coxal gills on pereopods 5 and 6 ovoid, but smaller than that of pereopod 3 (fig. 4A, C).

Oostegites appear on legs 2–5, very large, with short marginal setae (figs 2E, 4A).

Variability. The number and size of setae on meso- and metasomal segments rather variable, but last metasomal (pleonites) and all urosomal segments (urosomites) without facial setae. Accessory flagellum very small, almost as long as broad (fig. 1C) to twice as long ass broad, with 2 long distal simple setae (fig. 6G).

Aesthetascs present in many flagellar articles, nearly half as long as corresponding article of antenna 1 flagellum.

Epimeral plates 1–3 without ventral spines or setae. The number of posterior transverse groups of setae on gnathopod-propodus rather variable. Propodus of gnathopod 2 usually with one L-spine sitting laterally from Sspine [exceptionally L-spine is produced into long strong seta, probably aberrant] (fig. 3C). Uropod 1 peduncle with dorsoexternal row of spines, dorsointernal margin with 0–1 distal spine only.

Mandibular palpus consisting of one small article, sometimes partially divided into 2 parts, but not distinctly 2- articulated (fig. 1E, F, I).

Male is unknown.

Ecology. Numerous specimens have been observed walking deep in the cave on the rocky bottom of pools. The entrance of the cave is at elevation of 1495 m a.s.l, the bottom is nearly 500 m below the entrance. The air temperature is very variable and may be periodically close to 0 o C (Bakšić et al. 2018).

Derivatio nominis. The name “ lubuskensis ” allude to the type locality of this species, cave Lubuška jama.

Figures

FIGURE 1. Chaetoniphargus lubuskensis gen. nov., sp. nov., cave Lubuška jama, Velebit Mt., Croatia, female 3.9 mm (holotype): A= head; B= antenna 1; C= accessory flagellum; D= antenna 2; E= left mandible; F= right mandible; G= maxilla 2; H= maxilliped; I= mandibular palpus of female 4.0 mm.

FIGURE 2. Chaetoniphargus lubuskensis gen. nov., sp. nov., cave Lubuška jama, Velebit Mt., Croatia, female 3.9 mm (holotype): A= labrum; B- gnathopod 1, outer face; C= gnathopod 1 propodus, outer face; D= distal corner of gnathopod 1 propodus, outer face [S=corner S-spine; L=lateral L-spine; M= facial M-setae; R= subcorner R-spine], E= right gnathopod 2, outer face; F= gnathopod 2 propodus, outer face; G= distal corner of right gnathopod 2 propodus [S=corner S-spine; L=lateral L-spine; M= facial M-setae; R= subcorner R-spine].

FIGURE 3. Chaetoniphargus lubuskensis gen. nov., sp. nov., cave Lubuška jama, Velebit Mt., Croatia, female 3.9 mm (holotype): A= labium; B= left gnathopod 2 propodus, outer face; C= distal corner of left gnathopod 2 propodus, outer face [S=corner S-spine; M= facial M-setae; R= subcorner R-spine]; D= pereopod 3, outer face; E= dactylus of pereopod 3; F= pereopod 4.

FIGURE 4. Chaetoniphargus lubuskensis gen. nov., sp. nov., cave Lubuška jama, Velebit Mt., Croatia, female 3.9 mm (holotype): A-B= pereopod 5; C= pereopod 6; D-E= pereopod 7.

FIGURE 5. Chaetoniphargus lubuskensis gen. nov., sp. nov., cave Lubuška jama, Velebit Mt., Croatia, female 3.9 mm (holotype): A= maxilla 1; B= last mesosomal and 3 metasomal segments with epimeral plates 1–3; C= pleopod 1; D= urosome with uropods 1-3; E= telson and uropods 2 and 3, dorsal projection.

FIGURE 6. Chaetoniphargus lubuskensis gen. nov., sp. nov., cave Lubuška jama, Velebit Mt., Croatia, female 3.9 mm (holotype): A= uropod 1; B= uropod 2; C= uropod 3; I= entire animal; female 4.0 mm: D= distal corner of gnathopod 1 propodus, outer face [S=corner S-spine; L=lateral L-spine; M= facial M-setae; R= subcorner R-spine]; E= carpus and propodus of gnathopod 2, outer face; F= distal corner of gnathopod 2 propodus, inner face [S=corner S-spine; L=lateral L-spine; M= facial M-setae; R= subcorner R-spine]; G= accessory flagellum of antenna 1; H= telson.

FIGURE 7. Chaetoniphargus lubuskensis gen. nov., sp. nov., cave Lubuška jama, Velebit Mt., Croatia: living animal on the cave rock of cave Lubuška jama (photo: Branko Jalžić).

FIGURE 8. Chaetoniphargus lubuskensis gen. nov., sp. nov., cave Lubuška jama, Velebit Mt., Croatia: drawing of entire animal, holotype 3.9 mm.