Omangidiella parvidactyla, Iannilli, Valentina, Holsinger, John R., Ruffo, Sandro & Ronald, 2006

Iannilli, Valentina, Holsinger, John R., Ruffo, Sandro & Ronald, 2006, Two new genera and two new species of the subterranean family Bogidiellidae (Crustacea, Amphipoda) from groundwaters in northern Oman, with notes on the geographic distribution of the family, Zootaxa 1208, pp. 37-56 : 46-50

Omangidiella parvidactyla new species

Figs. 4 , 5

Material examined (expedition station number in parentheses is from Stock et al. 1997)

Sultanate of Oman. (96–67) border of wadi Taww at Halban (23°34’N; 58°01’ E), 3 paratype specimens, 1 April 1996, with thermosbaenaceans, cyclopid copepods, oligochaetes, diverse insect larvae; (96–75) Wadi Bani Henay (26°30’35"N; 57°19’34"E), pump in gravel at 50 cm below sediment surface, 10 paratype specimens, 1 April 1996, with thermosbaenaceans, stenasellid isopods, oligochaetes, chironomids; (96–76) same place and date as (96–75), probe; at 1.20 cm, 10 paratype specimens (very damaged), with thermosbaenaceans, stenasellid isopods, cyclopid copepods; (96–77) Wadi Bani Henay (26°30’35"N; 57°19’34"E) pump in gravel probe at 90 cm, 1 female paratype, 1 April 1996, with thermosbeanaceans, stenasellids, chironomids. Wadi Nakhl (ca. 23° 26’ N 57° 52’ E), Oesterreich Expedition, female holotype (collection date unknown) dissected and mounted in Faure’s medium on slides 4577–4581, 2 paratypes (slides 4582–4591) deposited in Museo Civico di Storia Naturale Verona (MVRCr 444), and 5 paratypes in ethanol deposited in Zoological Museum Amsterdam.

Description

The description is based on the holotype female from Wadi Nakhl, with exception of the mouthparts, which are based on a paratype female from Wadi Bani Henay (see above).

Female (3.0 mm) with oostegites.— Antenna 1: ( Fig. 4 a) ratio of articles 1–3 of peduncle = 1:0.8:0.5, articles without spines, with only few short setae; flagellum little longer than peduncle, with 13 articles increasing in length distally, bearing only fine setae, and without aesthetascs; accessory flagellum uniarticulate, shorter than article 1 of flagellum. Antenna 2 ( Fig. 4 b) shorter than antenna 1, with few short setae; gland­cone not elongate; articles 4 and 5 of peduncle subequal in length; flagellum less than half length of peduncle, with 5 articles, the distal one very short.

Mouthparts: labrum (upper lip) rounded distally ( Fig. 4 c). Left mandible ( Fig. 4 d): incisor 5­dentate; lacinia mobilis also 5­dentate and followed by 4 setulose rakers; molar triturative and articulated on short conical base, bearing 1 long plumose seta; mandibular palp reduced in length, article 2 longer than article 3; article 3 bearing only single apical seta; right mandible ( Fig. 4 e) similar to left but lacinia mobilis pluridenticulate; labium (lower lip) ( Fig. 4 f) with well developed inner lobes and rather short, blunt lateral processes. Maxilla 1 ( Fig. 4 g); palp reduced in length and bearing only 2 apical setae; outer plate with 7 serrate spines (3 external ones 4­toothed and 4 internal ones pectinate); inner plate with 3 naked apical setae. Maxilla 2 ( Fig. 4 h): inner plate little shorter than outer, with many fine setae along inner margin distally, apically with 6 distal spines, the 2 inner ones plumose. Maxilliped ( Fig. 4 i): coxal endite partially fused with inner lobe and similar to those of Nubigidiella , bearing fine setae distally and 1 spine apically; inner lobe bearing 2 short, stout bifid spines apically; outer lobe scarcely expanded, bearing 3 blade spines subapically on inner margin; palp article 2 expanded; dactylus as long as preceding article, with fine pubescence on inner face.

Gnathopod 1 ( Fig. 4 l): coxa subrectangular, ratio length:height = 1:0.7, with 2 setules on anterodistally rounded corner; basis relatively broad, with 3 long setae on posterior margin; merus with pubescent posterior margin; carpus produced into narrowly rounded ventral lobe, partly pubescent and bearing 2 long distal and 2 long subdistal setae; propodus ( Fig. 4 l’) subtrapezoidal, palm rather short, only about 40 percent as long as the posterior margin, margin uneven and bearing only few setae and 1 or 2 spines near defining angle; posterior margin nearly straight, without spines or setae; dactylus falcate and closing on defining angle. Gnathopod 2 ( Fig. 4 m, n) strikingly different from gnathopod 1: coxa similar to coxa 1 but ventral margin weakly rounded; basis with 2 long setae on posterior margin; carpus elongate, as long as basis and longer than propodus, posterior margin pubescent and bearing 2–4 groups of 2 long setae each; propodus ( Fig. 4 n’) elongate and weakly suboval but little shorter than carpus, medial and lateral faces with inferior and superior rows of numerous short, fine setae; palmar margin very short, without defining spines; posterior margin with approximately 9 long setae; dactylus reduced to small, curved, toothlike process.

Pereopods 3 and 4 similar ( Fig. 5 a): ratio coxa length:height = 1:0.6, ventral margin with 2 anterodistal setules each; basis broad, anterior margin convex and bearing large lenticular organ; merus, carpus and propodus subequal in length, with few short marginal setae; dactylus rather short, ratio propodus:dactylus = 1:0.4. Posterior and inferior margins of coxal plates 1–4 thinly sclerotized. Pereopod 5 ( Fig. 5 b): coxa anteriorly lobed, with posterodistal spine; basis suboval, anterior and posterior margins with 4 or 5 short spines, distal half with a large lenticular organ; merus, carpus, and propodus subequal in length, with few short marginal spines; ratio propodus:dactylus = 1:0.4. Pereopod 6 ( Fig. 5 c) similar to pereopod 5 but distinctly longer; coxa with anterior lobe of coxa reduced; basis with a large lenticular organ on distal half of posterior margin; ratio propodus:dactylus = 1:0.4. Pereopod 7 the longest ( Fig. 5 d); basis little wider than those of pereopods 5 and 6, without lenticular organ, anterior margin with 4 short spines, posterior margin with 6 short spines; merus, carpus and propodus subequal in length but much stronger than those of pereopods 5 and 6; propodus little longer and more robust than two preceding articles, anterior margin with row of 5 or 6 short spines accompanied by long setae; dactylus comparatively long, ratio propodus:dactylus = 1:0.37. Anterior and inferior margins of coxal plates 5–7 thinly sclerotized. Oostegites on pereopods 2–5, elongate, with long marginal and distal setae.

Pleonal plates: posteroventral corners rounded and not produced ( Fig. 5 e). Pleopods ( Fig. 5 e) greatly reduced; inner rami absent; outer rami reduced to 3 articles, the terminal one very short; peduncles nearly twice length of rami, each with 2 coupling spines ( Fig.

5e’). Uropod 1 ( Fig. 5 f): inner and outer rami subequal in length, armed with only 3 apical spines on outer and 4 on inner; peduncle longer than either rami, armed with 9 or 10 spines on upper margin and 3 basofacial spines. Uropod 2 shorter than uropod 1 ( Fig. 5 g): outer ramus shorter than inner ramus, armed with 4 apical spines; inner ramus as long as peduncle, armed with 4 apical spines; peduncle with 5 spines. Uropod 3 ( Fig. 5 h): rami approximately equal in length (aequiramus), each bearing several sets of lateral spines in groups of 1, 2, or 3; apex with 3 or 4 spines. Telson ( Fig. 5 i) about as broad as long at base but slightly tapered distally; each side with 1 mediolateral spine and 1 penicillate seta; apical margin convex and armed with 2 + 2 distolateral spines.

Male unknown.

Type­locality

Wadi Nakhl, located at approximately 23° 26’ N; 57° 52’ E ( Fig. 6 ). There are no other details available on the date of collection or the physical/chemical characteristics of this locality.

Derivatio nominis

The epithet parvidactyla is derived from the latin parvus (small) and dactylus (finger), denoting the very small dactylus of gnathopod 2.

Figures

FIGURE 4. Omangidiella parvidactyla, new species, female holotype 3 mm, Wadi Nakhl and paratype, Wadi Bani Henay (Sultanate of Oman) (mouthparts). a, b, antennae 1, 2; c, labrum; d, left mandible; e, right mandible; f, labium; g, h, maxillae 1, 2; i, maxilliped; l, gnathopod l; l’carpus, propodus and dactylus of gnathopod 1; m, gnathopod 2, outer side; n, gnathopod 2, inner side; n’, carpus, propodus and dactylus of gnathopod 2.

FIGURE 5. Omangidiella parvidactyla, new species, female holotype 3 mm, Wadi Nakhl (Sultanate of Oman). a, pereopod 3 with oostegites; b – d, pereopods 5 – 7; e, pleonal plate and pleopod; e’ retinacula; f – h, uropods 1 – 3; i, telson.

FIGURE 6. Geographic distribution of Stockigidiella and Omangidiella in the Sultanate of Oman. 1, S. aequimana (solid circle). 2, O. parvidactyla (open circles).