Stenasellus tashanensis Bakhshi & Messana

Bakhshi, Yaser, Sadeghi, Saber & Messana, Giuseppe, 2018, First record of the family Stenasellidae (Crustacea, Isopoda) in Iran with the description of a new cave-dwelling species, Subterranean Biology 26, pp. 27-38 : 29-32

Stenasellus tashanensis Bakhshi & Messana sp. n.

Holotype.

Male. 19 mm, Tashan Cave, Behbahan, Khuzestan, Iran 30°51 ’57.00” N, 50°10 ’30.09” E. 16.I.2016 leg. Y. Bakhshi (ZM-CBSU Iso 3421); Paratypes 1 male 19 mm (on three slides), 3 females (1 specimen (18, 15 mm) on two slides) same data as that of holotype (ZM-CBSU Iso 3422), maximum observed length of females is 18,15 mm, maximum observed length of males is 19 mm. The type specimens were deposited at the Zoological Museum of Shiraz University, Collection of the Biology Department (ZM-CBSU).

Diagnosis.

Stenasellus tashanensis can be differentiated from all of the other congeneric species by the following characteristics: the shape of male peleopods I and II, 19 strong spines on dactyl and 19 strong dentate spines on propus of male peraeopod I, three sternal spines on dactylus of peraeopod 7, and seven toothed coupling hooks on endite the maxilliped which is the largest number found in any Stenasellus species.

Description

(complementary to iconography) (Figure 2A). A relatively large Stenasellus with subparallel margins, maximum observed length (in males) 19 mm, maximum observed width (fourth segment) 3.8 mm. Head wider than long, with concave anterior margin, two typical round spots (otoliths of Bellonci’s organs) on anterior lateral angles. Endopodites of pleopods III–V bifid. Uropods/pleotelson length ratio 0.625.

Antenna I (Figure 2B): short, less than half the length of antenna II, not reaching posterior margin of first pereonite; second article of peduncle with three plumose setae on its distal part; flagellum with up to 19 articles, with two aestetascs on distal external angle of each of the last 12 segments.

Antenna II (Figure 2C): long, reaching pereonite V; peduncle with six segments; squama on third article of peduncle (Figure 2C') sub-rounded, equipped with two pointed long setae of different sizes, flagellum with up to 55 articles.

Left mandible (Figure 2H): pars incisiva four-dentate; lacinia mobilis four-dentate; 18-20 lifting spines (12 spinulate); pars molaris with several setae.

Right mandible (Figure 2G): pars incisiva four-dentate; 29-30 lifting spines (19 spinulate); pars molaris with several setae.

Mandibular palp (Figure 2I): tri-articulate; first article with two setae on distal margin, one of them five times longer than the other, second article with several setae including a group of soft short ones and another group of combed long ones, third article with several spines of different sizes, the five distal ones significantly longer than the others.

First maxilla (Figure 2E): exite with 12 dentate combed setae and 8 plumose ones, endite with 3 strong and 2 thinner setose setae.

Second maxilla (Figure 2F): external exite with 10 and median exite with 11 falcate, combed setae; internal exite with 25 denticulate chaetae.

Maxilliped (Figure 2D): with 6 to 7-toothed coupling hooks on endite and 13 plumose setae on distal margin, 18 glabrous setae on the outer surface; palp five-segmented, first article with a single simple seta on the distal inner angle.

Peraeopod I (Figure 3A): strong, subchaelate; with 19 strong setae on dactyl and 19 strong denticulate setae and several simple setae of different sizes on propus.

Peraeopods II–VII (Figure 3 B–G): progressively larger; basis with 9 to 12 long plumose setae; propus and carpus with plumose seta on distal tergal angles; Peraeopods 2-4 also with pectinate seta in same position; dactylus with strong medial spines, three in peraeopod 7 and two in peraeopods 2-6.

Genital papilla (Figure 4H): subcylindrical, passing anterior margin of second pleonite.

Male Pleopod I (Figure 4A): basipodite with one coupling hook; Exopodite with about 33 setae, the eighteen internal of which plumose.

Female pleopod II (Figure 4F): subtriangular; with a strongly convex outer margin, five setae on the sternal surface and ten plumose setae on the distal margin.

Male pleopod II (Figure 4B): sympodite sub-rectangular; significantly longer than wide with subparallel external and internal margins, sternal surface with three paramedial setae; proximal article of exopodite with four glabrous setae, distal article subelliptical relatively elongated (longer than wide) with more than 40 plumose setae along the margin; distal article of endopodite as long as proximal article and with accommodating groove, gutter-like in its caudal part.

Pleopods III–V (Figure 4 C–E): exopodite with transverse oblique suture, submedial in the third and subterminal in the fourth and fifth pleopods; endopodite bilobate in all three pleopods.

Uropods (Figure 4G): exopodite slightly smaller than endopodite which bears seven plumose setae on proximal, medial, and distal parts.

Etymology.

Topotypic, referring to the type locality, Tashan Cave.