Saturday, June 16, 2018

[Crustacea • 2018] Stenasellus tashanicus • A New Species of Stenasellus Dollfus, 1897 (Isopoda, Stenasellidae) from Iran, with A Key to the western Asian Species

Stenasellus tashanicus

 Khalaji-Pirbalouty, Fatemi, Malek-Hosseini & Kuntner, 2018

A new stenasellid isopod is described from Tashan Cave, Khuzestan Province, south-west Iran, belonging to the genus Stenasellus Dollfus, 1897. The first recorded species of Stenasellidae from Iran, Stenasellus tashanicus sp. n., is diagnosed by the presence of antennae with a minute squama bearing paired, long, robust setae; a maxilliped endite with six coupling hooks; and slender appendix masculina with an acute apex. A revised generic diagnosis is provided with a key to the six known western Asian Stenasellus species.

Keywords: Iran, Stenasellus, Stenasellidae, Stygobitic, Tashan Cave

Figure 1. Tashan Cave. A Cave opening B a pool inside the cave
C live specimen of Stenasellus tashanicus sp. n., in its habitat D Stenasellus tashanicus sp. n., and cave fish Garra tashanensis Mousavi-Sabet, Vatandoust, Fatemi & Eagderi, 2016.

Aselloidea Latreille, 1802
Family Stenasellidae Dudich, 1924
Genus Stenasellus Dollfus, 1897

Type species
Stenasellus virei Dollfus, 1897, by monotypy.

Diagnosis: Diagnoses to the genus can be found in Dollfus (1897) and Magniez (1966). The generic diagnosis presented here is more detailed than has been previously presented: Body lateral margins parallel and setose; pereonite VII longest; the antennal peduncle is 6-articulate, article VI longest, approximately 1.6 times the article V. Left mandible with incisor and lacinia mobilis bearing four cusps. Pereopod I with triangular carpus, dactylus elongated, an inferior margin with a row of contiguous scale-like flattened setae. Pereopods II-VII with an oval basis bearing some long distally plumose setae on the superior margin; dactylus shorter than elongated main unguis, bearing two secondary unguis. Pleopod I uniramous, protopod mesial margin with a simple RS or a single coupling hook, exopod elongated, mesial margin with a row distally plumose setae, distal margin fringed with a row of tiny simple short setae. Pleopod II exopod 2-articulate, article I short and without setae, article II longer than I, oval or round.


Stenasellus tashanicus sp. n.

Diagnosis: Body dorsal surface smooth, with scattered marginal setae. Antenna reaching to pereonite V posterior margin in male specimen, with a squama bearing three simple setae on the outer margin of the third article. Maxilla lateral and middle endites each bearing 11 curved pectinate RS; mesial margin of maxilliped endite with six coupling hooks. Appendix masculina slender, elongated, tapering to a curved acute apex; endopod of pleopods III–V distally bifurcated.

Etymology: The name of this species comes from the type locality, the Tashan Cave, Iran.

Habitat: The isopods were collected from two pools in the dark zone of the Tashan Cave (at 20 to 200 cm depths). They were observed in all life cycle stages. They were observed crawling on the floor and hiding inside the sediment and cavities of the pools, as well as swimming in the water column. Mousavi-Sabet et al. (2016) described a blind fish from this cave (see Fig. 1D).

 Valiallah Khalaji-Pirbalouty, Yaser Fatemi, Mohammad Javad Malek-Hosseini and Matjaž Kuntner. 2018. A New Species of Stenasellus Dollfus, 1897 from Iran, with A Key to the western Asian Species (Crustacea, Isopoda, Stenasellidae).  ZooKeys. 766: 39-50.  DOI: 10.3897/zookeys.766.23239

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