Protracheoniscus pokarzhevskii Gongalsky & Turbanov

Gongalsky, Konstantin B., Turbanov, Ilya S., Medvedev, Dmitry A. & Volkova, Julia S., 2018, Description of a new species of the genus Protracheoniscus Verhoeff, 1917 and redescription of Protracheoniscuskryszanovskii Borutzky, 1957 from the southeast of European Russia (Isopoda, Oniscidea, Agnaridae), ZooKeys 801, pp. 189-205 : 189

Protracheoniscus pokarzhevskii Gongalsky & Turbanov sp. n.

Type material.

Holotype: ♂ (ZMMU), Russia, Republic of Kalmykia, 1 km N of Bolshoy Tsaryn (47.9040N, 45.3929E), dry steppes ( Artemisia austriaca , Festuca valesiaca , Tanacetum achilleifolium ), 29.04.2017, K. Gongalsky leg. Paratypes: 2 ♂♂, 2 ♀♀ (ZMMU), 3 ♂♂, 4 ♀♀ (private collection of K. Gongalsky), same date, location and collector.

Other material examined.

Protracheoniscus politus (C. Koch, 1841): 3 ♂♂, 6 ♀♀, Hungary, Budapest, János-Hegy (47.5158N, 18.9602E), 29.08.2017, K. Gongalsky leg. Protracheoniscus nogaicus Demianowicz, 1932: 2 ♂♂, Russia, Republic of Kalmykia, 1 km N of Bolshoy Tsaryn (47.9040N, 45.3929E), 29.04.2017, K. Gongalsky leg. Protracheoniscus major (Dollfus, 1903): 6 ♂♂, 15 ♀♀, same date, location, and collector. Desertoniscus zaitsevi Gongalsky, 2017: 3 ♂♂, 5 ♀♀, same date, location, and collector.

Diagnosis.

A species of Protracheoniscus characterized by the antennal flagellum with the articles of a ratio close to 1:1; male exopod of pleopod 1 with almost rounded apex; telson with distal part elongated and distal corner forming triangle; and one of four medial spines of outer endite of maxillula is twice as small as the others.

Description.

Somatic characters. Maximum body length: male 5.0 mm; female 5.5 mm. Holotype body length 4.7 mm. Body color dark grey-brown; frontal part of head much darker than rest of the body; light grey-brown spots at base of coxal plates of pereonal segments 2-7 (Figure 1A). Dorsal surface of tergites smooth. Posterior edges of coxal plates of pereonites straight (Figs 1A, 2B). Distal part of head covered with scattered sharp triangular dorsal setae (Figure 2A). Noduli laterales on pereonites located close to coxal plates edges (Figure 2B). Body relatively elongated; pleon not continuous with pereon outline (Figure 1A). Cephalic lobes poorly developed; distal edge of median lobe rounded (Figure 2C). Telson with distal part elongated and distal corner forming triangle (Figure 2D).

Appendages. Uropods (Figure 2D) colored as dorsal body surface; exopods elongated. Antennula of three articles (Figure 2E); first article wide and relatively long, second article slightly shorter than first, third article almost as long as first and narrow, bearing a tuft of aesthetascs at apex. Antenna reaching pereonite 3 (Figure 1A); flagellum of two articles, proximal article slightly shorter than distal one (Figure 2F). Left mandible (Figure 3A); pars incisiva with two teeth and lacinia mobilis with straight edge; molar penicil consisting of ca. ten setae. Right mandible smaller than left mandible, pars incisiva with three teeth and lacinia mobilis with two teeth, molar penicil consisting of ca. ten setae (Figure 3B). Maxillula (Figure 3C): medial corner of inner endite with two strong penicils; apical edge of outer endite bearing 4 + 4 teeth with simple tips, with one tooth in medial group twice smaller than other three. Maxilla with bilobate edge, medial half of apical edge of outer lobe with dense brush of short setae (Figure 3D); inner margin with subapical tubercle. Maxilliped with outer corner of endite with two acute tips and large spine near inner corner (Figure 3E). Pleopods (Figure 5). All exopods with monospiracular covered lungs.

Male: Pereopods (Figure 4 A–C): pereopod 1 with dactylus slightly bent ventrally; carpus with brush of setae with split tips. Pereopod 6 and 7 ischia with sternal margin straight. Genital papilla slightly extended at tip (Figure 5H). Exopod of pleopod 1 (Figure 5A) with almost rounded tip and ca. ten setae at apex, outer margin slightly concave. Endopod of pleopod 1 with split distal part: straight sharp triangular tip bearing row of spines and lateral bulb (Figure 5B). Pleopod 2: exopod triangular with concave outer margin bearing two setae with split tips (Figure 5C); endopod much longer than exopod, narrow, with parallel sides (Figure 5D). Pleopod 3-5: exopods (Figure 3 E–F) trapezoidal, slightly decreasing in size from 3 to 5. Pleopod 5 exopod with sharp medial corner (Figure 5G).

Remarks.

This species is morphologically closest to Protracheoniscus politus (C Koch, 1841) in the similar shape of the endopodite of the male pleopod 1. However, the new species differs from P. politus in the following: (i) exopod of the male pleopod 1 with shorter posterior lobe; (ii) tip of endopod of pleopod 1 not bent laterally; (iii) telson with less concave sides and shorter and less acute tip; (iii) ratio of articles of flagellum is close to 1:1 (almost close to 1:2 in P. politus ) ( Gruner 1966; Tomescu et al. 2016).

Recently, two close species of Protracheoniscus were described from north Iran ( Kashani and Hamidnia 2016). Protracheoniscus pokarzhevskii sp. n. differs from P. kiabii Kashani & Hamidnia, 2016 in (i) the noduli laterales located much closer to the pereonites’ margins; (ii) much shorter uropods; (iii) straight instead of concave sternal margin of the male pereopod 7 ischium; (iv) sharp tip of endopod of the male pleopod 1. From P. golestanicus Kashani & Hamidnia, 2016 it differs in (i) different shape of both exopod and endopod of the male pleopod 1; (ii) different position of noduli laterales. Evidently, a molecular analysis is needed for the complex of these small species of Protracheoniscus .

Distribution.

The new species has only been found between the Volga and Vostochnyi Manych Rivers. It occupies the steppes of Kalmykia ( Artemisia austriaca , Festuca valesiaca , Tanacetum achilleifolium ).

Etymology.

The species is named after Prof Dr Andrey D Pokarzhevskii (1946-2006), a prominent Russian soil zoologist who encouraged the first author to study terrestrial isopods.