Research Article |
Corresponding author: Valiallah Khalaji-Pirbalouty ( vkhalaji@sci.sku.ac.ir ) Academic editor: Saskia Brix
© 2018 Valiallah Khalaji-Pirbalouty, Yaser Fatemi, Mohammad Javad Malek-Hosseini, Matjaž Kuntner.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Khalaji-Pirbalouty V, Fatemi Y, Malek-Hosseini MJ, Kuntner M (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. https://doi.org/10.3897/zookeys.766.23239
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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.
Iran, Stenasellus , Stenasellidae , Stygobitic, Tashan Cave
The genus Stenasellus Dollfus, 1897, with approximately 37 nominal species (
As species of Stenasellus were reported from southeastern Turkmenistan to the south-eastern corner of the Arabian Peninsula and east Africa (Somalia, Kenya and Oman), it was also expected to document their presence in the intervening geographical regions, such as Iran and Yemen. As reported here, our finding of the new stygobiont isopod species from the Iranian underground environment narrows the gap between these broad geographical areas.
Specimens for this study were collected from Tashan Cave, located inside a hill close to Sarjooshar Village, Tashan City, Behbahan County, Khuzestan Province, south-west Iran (Fig.
Abbreviations: ZMSU – Zoological Museum, Shahrekord University, Iran; RS – robust seta/e; SPS – sensory palmate setae; PMS – plumose marginal setae.
Stenasellus
Dollfus, 1897:130;
Stenasellus virei Dollfus, 1897, by monotypy.
Diagnoses to the genus can be found in
The first restrictive diagnosis to the genus was given by
In this work, two other groups of the genus Stenasellus are proposed: the first group that has pleopod III–V with entirely bilobed endopod are from western and south-eastern Asia: S. bedosae Magniez, 1991 and S. brignolii Pesce & Argano, 1981 (Thailand); S. chapmani Magniez, 1982 (Malaysia); S. covillae Magniez, 1987, S. stocki Magniez, 2001 and S. strinatii Magniez, 1991 (Sumatra); S. grafi Magniez & Stock, 2000; S. henryi Magniez & Stock, 2000 and S. messanai Magniez & Stock, 2000 (Oman). The species of the second group have pleopod II appendix masculina with slender, elongated, and tapering to an acute apex distal article and pleopod III–V with distally bilobed endopod. Except S. cambodianus Boutin & Magniez, 1985 from Cambodia, the remaining species of the second group are distributed in eastern Africa and western Asia: S. kenyensis Magniez, 1975 (Kenya), S. costai Lanza, Chelazzi & Messana, 1970 and S. migiurtinicus Messana, Chelazzi & Lanza, 1974 (Solalia); S. vermeuleni Magniez & Stock, 2000 (Oman), S. tashanicus sp. n. (Iran).
Based on descriptions and illustrations of the nominal species, there are some variations between the included species. The main variation is the shape of the pleopods I–V. The exopod of pleopod 1 is elongated and the medial margin of its protopod has a single coupling hook in most species (e.g., S. virei Dollfus, 1897; S. strinatii Magniez, 1991; S. vermeuleni Magniez & Stock, 2000), while some species have a pleopod 1 with short exopod and without any coupling hook (e.g., S. grafi Magniez & Stock, 2000; S. stocki Magniez, 2001). The second article of the pleopod II is round and possesses less than five marginal setae in some species (e.g., S. henryi Magniez & Stock, 2000; S. grafi Magniez & Stock, 2000; S. nuragicus Argano, 1968), whereas some species have an oval and elongated second article with more than 10 marginal setae (e.g., S. vermeuleni Magniez & Stock, 2000; S. buili Remy, 1949; S. kenyensis Magniez, 1975). Moreover, the endopod of pleopods III–V has a rounded distal margin (e.g., S. virei Dollfus, 1897; S. asiaticus Birstein & Starostin, 1949; S. buili Remy, 1949), some species have distally bifurcated endopod (e.g., S. ruffoi Messana, 1993; S. vermeuleni Magniez & Stock, 2000; S. kenyensis Magniez, 1975) and in some species the endopod is deeply bilobed (e.g., S. javanicus Magniez & Rahmadi, 2006; S. grafi Magniez & Stock, 2000; S. henryi Magniez & Stock, 2000). In addition, the medial margin of their maxilliped endite differs in having a different number of coupling hooks (2–6).
All material from Iran with locality data as follows.
Holotype. ♂ (17.5 mm), Tashan Cave, Sarjooshar Village, Tashan City, Behbahan County, Khuzestan Province, Iran, 13 August 2016, 30°51'54"N, 50°10'29"E (altitude 559 m a.s.l.), coll. Fatemi, Y. (ZMSU 2010).
Paratypes. 3 ♂♂ (17.1, 12.5, 12 mm), 2 ♀♀ (20, 11mm); 2 juveniles (7.3, 8.5 mm), same data as holotype (ZMSU 2011). 1 ♂ (15 mm), 1 ♀ (18 mm); 1 juveniles (5.5 mm), Tashan Cave, Sarjooshar Village, Tashan City, Behbahan County, Khuzestan Province, Iran, 27 August 2016, 30°51'54"N, 50°10'29"E (altitude 559 m a.s.l.), coll. Fatemi, Y. and Malek-Hosseini, M.J. (ZMSU 2012).
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.
Body completely coral pink in the live specimen (Fig.
Pleotelson elongated, 1.4 as long as broad, posterior margin with two slight excavations; with scattered marginal setae.
Antennula (Fig.
Antenna (Fig.
Left mandible (Fig.
Maxillula (Fig.
Maxilla (Fig.
Maxilliped (Fig.
Pereopod I (Fig.
Pereopod II (Fig.
Pereopod III (Fig.
Pereopod VII (Fig.
Penial processes (Figs
Pleopod I (Fig.
Pleopod II (Fig.
Pleopod III (Fig.
Pleopod IV (Fig.
Pleopod V (Fig.
Uropods (Fig.
(Fig.
The name of this species comes from the type locality, the Tashan Cave, Iran.
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.
Stenasellus tashanicus sp. n. can be identified by a slender and distally acute appendix masculina, and a maxilliped endite with six coupling hooks on the mesial margin. The new species is the largest known Stenasellus member: length up to 18 mm in males and 20 mm in females. The new species is similar to S. vermeuleni Magniez & Stock, 2000 (known from Wadi Halban, Oman), in having an appendix masculinum with acute apex. The shape of pleopods III–V in both species is also similar. Based on the drawings and description of S. vermeuleni, the new species differs by having a uropodal exopod smaller than the endopod (rather than subequal in length), pleopod I apical margin with a row of 18 simple fine setae (rather than six), exopodal article II of pleopod II is narrower than pleopod II in S. vermeuleni and pleopod V exopod and endopod subequal in length (rather than a smaller exopod). Based on the description and drawings of S. asiaticus by
1 | Body dorsal surface setose; pleopod endopod of pleopods III–V distally monolobate | S. asiaticus (Turkmenistan) |
– | Body dorsal surface smooth; pleopod endopod of pleopods III–V distally bilobate | 2 |
2 | Pleopod II exopod article II small, with less than five marginal setae; Appendix masculina flat and swollen | 3 |
– | Pleopod II exopod article II large, with more than eight marginal setae; Appendix masculina elongate distally acute | 4 |
3 | Pleopod II protopod heart shaped | S. grafi (Oman) |
– | Pleopod II protopod trapezoid shaped | S. henryi (Oman) |
4 | Appendix masculine dislaolateral margin fringed with tiny setae | S. messanai (Oman) |
– | Appendix masculine dislaolateral margin without setae | 5 |
5 | Antenna squama with three robust setae, exopod of pleopod I apical margin with a raw of ~6 simple fine setae; pleopod II exopod about 1.4 times as long as greatest width | S. vermeuleni (Oman) |
– | Antenna squama with II robust setae, exopod of pleopod I apical margin with a raw of ~18 simple fine setae; pleopod II exopod about 2.4 times as long as greatest width | S. tashanicus sp. n. |
We are grateful to Mr. Baraninejad, the mayor of Sarjooshar Village and his family, Ahmad Farahbakhsh, Abass Moradi, and Vahid Malek-Hosseini for their assistance and hospitality during the field studies. We greatly appreciate the work of Ms. Karolyn Close for revision of the English text. Dr. Saskia Brix (Senckenberg am Meer, German Centre for Marine Biodiversity Research, Hamburg, Germany), Dr. Florian Malard (Université Lyon1, France), and two anonymous referees are appreciated for critically reviewing the manuscript.