Mongoloniscus parvus Jiang, Li & Huang, 2024

Jiang, Chao, Zhong, Jing, Wang, Zhidong, Li, Weichun & Huang, Luqi, 2024, Taxonomic study on the genus Mongoloniscus Verhoeff, 1930 (Isopoda, Agnaridae) from China: morphological and phylogenetic analyses, ZooKeys 1202, pp. 229-253 : 229-253

Mongoloniscus parvus Jiang, Li & Huang sp. nov.

Figs 4 E, F , 7

Type material.

Holotype. China: ♂ ( 20200913004 ), Liaoning Province, Huanren Manchu Autonomous County: Erpengdianzi Town, Yaoqianshu Village (41.1893 ° N, 125.6383 ° E), 610 m asl., 13. ix. 2020, coll. Chao Jiang.

Paratypes. 3 ♂♂, 2 ♀♀ ( 20200913003 , 2020091300005 ), same data as the holotype ; 3 ♂♂, 2 ♀♀ ( 20200906002 – 20200906005 ), Liaoning Province, Huanren Manchu Autonomous County, Erpengdianzi Town (41.236 ° N, 125.6047 ° E), 560 m asl., 6. ix. 2021, coll. Chao Jiang . 1 ♂, 2 ♀♀ ( 20200913001 , 20200913002 ), Jilin Province, Ji’an, Xihulugou Village (41.3348 ° N, 125.8893 ° E), 670 m asl., 13. ix. 2020, coll. Chao Jiang .

Diagnosis.

Antennal flagellum distal article approximately twice as long as the proximal article. Pereopod 7 ischium sternal margin fringed with sparse setae; carpus slightly expands on tergal margin. Pleopod 1 exopod oval, distal apex slightly concave, forming two inconspicuous lobes, inner lobe bearing one seta.

Description.

Body length of males 5–9 mm and females 4–9 mm. Body elongated and convex, ~ 2.3 × as long as widest pereonite. Dorsum distinctly granulated, brown-gray color with usual yellowish muscle spots. Numerous gland pores along entire margin pereonites margin (Fig. 4 E, F ). Pereonite 1 with rounded posterior margin and postero-lateral corners. Noduli laterales on pereonites 1–4 much farther from lateral margins than those on pereonites 5–7. Telson triangular, ~ 1.5 × as wide as long, lateral margins slightly concave near middle, posterior apex blunted; uropodal exopod 1.2–1.5 × as long as protopod; protopod with an incision on outer margin (Figs 3 F , 4 E , 7 B ).

Cephalon with medial lobe arched, not surpassing lateral lobes in dorsal view. Eyes with 14 or 15 ommatidia. Antenna with fifth article of peduncle and flagellum nearly equal in length; flagellum with distal article twice as long as proximal one (Fig. 7 C ).

Pereopod 1 bearing a brush of long setae on its carpus and merus (Fig. 7 D ). Pereopod 7 ischium rostral surface with shallow depression; carpus slightly expands on tergal margin (Fig. 7 F ).

Pleopods 1–5 exopods with monospiracular internal lungs (Fig. 7 G – K ). Male: pleopod 1 exopod oval, outer margin sinuous, distal apex slightly concave and forming two inconspicuous lobes, inner lobe bearing one seta near apex (Fig. 7 G ). Pleopod 2 exopod almost triangular, slightly concave on outer margin (Fig. 7 H ). Pleopod 1 endopod with broad basal part, narrowed towards apical apex, apex bearing several setae, bent outwards and ending with two pointed tips (Fig. 7 G ); pleopod 2 endopod longer than exopod, distal article thin and long (Fig. 7 H ).

Etymology.

Latin parvus = small. The new species name refers to the pleopod 1 with a small exopod. We suggest the Chinese common name as “ 小蒙潮虫 ”.

Distribution.

China (Liaoning, Jilin).

Figures

Figure 3. Habitus of Mongoloniscus sinensis (Dollfus, 1901), male A dorsal view, the blue circles show the noduli laterales arrangement B cephalon and pereonites 1 and 2 in dorsal view C pleopod 1 exopod D pleopod 1 endopod.

Figure 4. Habitus of Mongoloniscus species A, C, E, G male, holotype B, D, F, H female, paratype A, B M. crenatus sp. nov. C, D M. polyacanthum sp. nov. E, F M. parvus sp. nov. G, H M. orientalis sp. nov. The blue circles show the noduli laterales arrangement. Scale bars: 3 mm.

Figure 7. Mongoloniscus parvus sp. nov., holotype A cephalon, pereonites 1 and 2 in dorsal view B pleonites, telson and uropod in dorsal view C second antenna D pereopod 1 E pereopod 6 F pereopod 7 G pleopod 1 H pleopod 2 I – K pleopods 3–5 exopods. Scale bars: 1 mm.