Stockigidiella aequimana, 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 : 40-42

Stockigidiella aequimana new species

Figs.1–3

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

Sultanate of Oman. (96–22) open, shallow well at Dibab (23º04’31"N; 59º03’22"E), holotype specimen (probable male) collected 26 March 1996; dissected and mounted in Faure’s medium on slides 4559–4562 and deposited in Museo Civico di Storia Naturale Verona (MVRCr 438)

Description

Male (?) (3.7 mm).—Antenna 1 ( Fig. 1 a) less than 1/2 the length of body; ratio of peduncular articles 1–3 = 1:0.9:0.5; article 1 of peduncle with distal spine accompanied by long seta, article 2 with few short setae, article 3 with distal group of 3 elongate aesthetascs; flagellum slightly shorter than peduncle, with 6 elongate articles, articles 1–5 each with 1 elongate aesthetasc; accessory flagellum biarticulate and longer than article 1 of flagellum. Antenna 2 ( Fig. 1 b) as long as antenna 1, gland cone not elongate, article 5 of peduncle slightly shorter than article 4, flagellum distinctly shorter than peduncle, composed of 4 elongate articles and 1 much shorter distal article.

Labrum (upper lip) not seen. Mandibles asymmetrical. Right mandible ( Fig. 2 b): incisor without evident teeth; lacinia mobilis 4­dentate, followed by 3 setulose rakers; molar not triturative, replaced by setulose area inferiorly provided with 2 short + 1 long spines; palp elongate, article 2 with 1 seta on inner margin, article 3 slightly shorter than article 2, outer margin bearing row of 6 B setae and a second row of very short setae distal to the B setae, apex with 4 long E setae. Left mandible ( Fig 2 a): incisor with 3 teeth, lacinia mobilis pluridenticulate followed by 3 spines; molar setulose area inferiorly provided with 4 short + 1 long spines; palp identical to the left one. Labium (lower lip) not seen. Maxilla 1: left and right ( Fig. 2 c) similar; palp reduced and bearing 3 distal setae on article 2; inner plate with 2 naked apical setae, outer plate with 6 spines, 5 bifid and 1 distally denticulate. Maxilla 2 ( Fig. 2 d) relatively short, inner lobe with 3 apical setae, outer lobe with 6 mostly long spines or coarse setae. Maxilliped ( Fig. 2 e): inner and outer lobes relatively short; inner lobe distally with 1 bifid spine, 1 simple spine and few subapical setae; outer lobe with 2 distal spines and row of few setae on inner margin.

Gnathopod 1 ( Fig. 1 c): coxa subrectangular, ratio length:height = 1:0.5, inferior margin weakly concave, with 2 setae on anterodistally rounded corner; basis wide, with 1 strong submedial spine on posterior margin, anterior margin with only 1 subdistal spine; merus with pubescent posterior margin; carpus with relatively small ventral lobe bearing 2 distal spines and light pubescence; propodus large, suboval and relatively elongate, palm at least twice length of posterior margin, distal two­thirds of palmar margin with a row of about 10 small, weakly bifid spines, spaced by short simple spines, proximal third bearing 5 strong spines accompanied by inner row of 5 or 6 long setae; dactylus falcate and closing on defining angle spines; posterior margin short and lightly pubescent distally. Gnathopod 2 ( Fig. 1 d), subsimilar to gnathopod 1 but differing in several ways as follows: basis more elongate, posterior margin with 1 strong spine on proximal third, anterior margin with 3 spines; merus not pubescent; carpus with pubescent, convex ventral lobe bearing 2 long setae; palmar region of propodus generally similar to that of gnathopod 1 but posterior margin longer and strongly pubescent; dactylus slightly shorter than that of gnathopod 1.

Pereopods 3 and 4 generally similar ( Fig. 2 f, g): coxae subrectangular, ratio length:height = 1:0.5; ventral margins weakly concave and bearing 2 setae; dactylus not elongate, ratio propodus:dactylus = 1:0.37. Pereopod 5 ( Fig. 2 h) relatively short; coxa with short anterior lobe and with 1 long spine on posterior lobe; basis suboval; merus distinctly longer tha carpus; carpus with 1 curved posterodistal spine, anterior margin with spines and a row of long setae; posterior margin of propodus with row of long thin, deeply bifid setae, anterior margin with row of 5 spines; dactylus not elongate, ratio propodus:dactylus = 1:0.3. Pereopod 6 ( Fig. 2 i) similar to pereopod 5 but little longer; posterior margin of propodus with row of long, thin, deeply bifid setae; pereopod 7 ( Fig. 2 l) distinctly longer than pereopods 5 and 6; basis little broader than those of pereopods 5–6; merus as long as carpus, and strongly spinose, especially on posterior margin; propodus elongate, longer than carpus, anterior and posterior margins with rows of long thin setae; dactylus elongate, ratio propodus:dactylus = 1:0.6, posterior margin with 3 setae, nail very short. Coxal gills subovate, on segments 3–5, elongate ( Fig. 2 h). Oostegites (brood plates) not observed.

Distoposterior corners of pleonal plates ( Fig. 3 h) tiny and acute, posterior margin of 3 distally convex and bearing 2 setules. Pleopods ( Fig.3 a, b, c) without inner ramus, outer rami reduced in length and gradually stronger from pleopods 1 to 3, peduncles each with 2 coupling spines (retinacles). Uropods 1 and 2 ( Fig. 3 d, e) closely similar except peduncle of uropod 1 bearing strong basofacial spine. Peduncles of uropods 1 and 2 each with 2 distal spines; outer rami slightly shorter than inner and naked except for 3 apical spines. Uropod 3 ( Fig. 3 f): rami approximately equal in length; outer ramus with row of long setae on inner and outer margins; inner ramus bearing 3 to 4 strong spines on distal half of outer margin; both rami each bearing 5 or 6 strong spines apically. Telson ( Fig. 3 g) comparatively short, clearly broader than long; apical margin straight, with 1 long, robust spine inserted just below margin on either side.

Type locality

Open shallow well at Dibab (23°04’31’’N; 59°03’22’’E) in Sultanate of Oman ( Fig. 6 ). According to Stock et al. (1997) the well water with the single specimen was filtered through a Cvetkov net. It was also pointed out that the bottom substrate of the well consisted of sand and gravel and the biota was composed of an amphipod, various mosquito larvae, and green filamentous algae. Water quality was rated moderate to suspect, with high salinity.

Derivatio nominis

The epithet aequimana is derived from the latin aequus (equal) and manus (hand), stressing the morphological similarity of the gnathopods.

Figures

FIGURE 1. Stockigidiella aequimana, new species, male (?) holotype 3.7 mm, Dibab (Sultanate of Oman). a, b, antennae 1, 2; c, d, gnathopods 1, 2.

FIGURE 2. Stockigidiella aequimana, new species, male (?) holotype 3.7 mm, Dibab (Sultanate of Oman). a, left mandible; b, right mandible; c, d, maxillae 1, 2; e, maxilliped; f­l, pereopods 3 – 7.

FIGURE 3. Stockigidiella aequimana, new species, male (?) holotype 3.7 mm, Dibab (Sultanate of Oman). a – c, pleopods 1 – 3; d – f, uropods 1 – 3; g, telson; h, pleonal plates.

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