New species and records of the subterranean amphipod genus Pseudocrangonyx Akatsuka and Komai (Crustacea: Pseudocrangonyctidae), representing the northernmost distribution of the group Author Sídorov, Dmitry Author Labay, Vjacheslav Author Gontcharov, Andrey text Journal of Natural History 2020 2020-12-09 54 27 - 28 1759 1795 http://dx.doi.org/10.1080/00222933.2020.1820092 journal article 10.1080/00222933.2020.1820092 1464-5262 5030637 Pseudocrangonyx camtschaticus Birstein, 1955 ( Figures 2e , 18–21 ) Pseudocrangonyx camtschaticus Birstein 1955 , p. 80 , figs 3, 4(original description). – Barnard 1958 , p. 71 . – Sidorov 2006 , p. 1493 . – Juberthie et al. 2016 , p. 518 . – Zhao and Hou 2017 , p. 3 , 17. Figure 18. Pseudocrangonyx camtschaticus Birstein, 1955 , 11/11-DAS, female, 7.5 mm: (a) antenna I; (b) antenna II; (c) upper lip; (d) lower lip; (e) left mandible; (f) right mandible; (g) maxilla I; (h) outer plate of maxilla I; (i) palp of maxilla I, left; (j) maxilla II; (k) maxilliped. Scale bars: 0.2 mm. Distribution and ecology Previously recorded from a spawning brook not far from Karymay, located in the lower reaches of the Bystraja River (Malkinskaya) – the main tributary of the Bolschaja River on the west coast of Kamchatka . According to Birstein (1955) , the crustaceans were collected with an Ekman bottom sampler in a layer deeper than 5 cm . New record RUSSIA : two specimens 11/11-DAS: ♀ ca . 7.5 mm (oostegites developed, non-setose), Kamchatka , Ust-Bolsheretsky District , 4 km SE of Kavalerovskoe , Goltcovka River , hyporhea, 52.910278 , 156.625556 , elevation 30 m , leg . I .M . Tiunov , 1 August 2013 ; probably submature ♂ ca . 4.5 mm , 5 km SW of Apacha , Plotnikova River , hyporhea, 52.901495 , 157.045265 , elevation 93 m , leg . T .L. Vvedenskaya , 12 April 2005 . Diagnosis (female) Slender, middle-sized amphipod of typical pseudocrangonyctid habitus (sexual dimorphism unknown); eyes absent; body unpigmented (whitish in colour); dorsal surface of body segments smooth, teretial; last mesosomal segment (pereonite VII) and metasomal segments (pleonites I–III) bearing 2 fine facial setae each; urosomite I with 2 facial setae and urosomite II with 2 notched facial spines, ecdysial setae absent; interantennal lobe of head rounded, inferior antennal sinus sub-quadrate; antenna I about 40% length of body; coxal plates I–IV shallow, sub-rectangular (wider than deep), plates V–VII sub-triangular with broad anterior lobes; posterodistal corners of pleonal plates I–III obtuse; palp mandible article 3 with 2 B-setae, 12 D-setae and 4 E-setae; molar of mandible well developed; propodus of gnathopod I slightly larger than that of gnathopod II; carpus of pereopods III–IV with posterior margin armed with spine; pereopod VI largest, about 50% length of body. Uropod I with 1 basofacial spine-seta. Telson emarginate. Body length 4.5 mm (? ♂ ) – 7.5 mm ( ♀ ). GenBank accession number MN422287 for isolate RUSAB008-19. Description Female (body 7.5 mm long), 11/11-DAS. Head ( Figures 2e , 18a–k ). Antenna I about 20% longer than antenna II; peduncular articles 1–3 in length ratio 1:0.7:0.4; primary flagellum with 12 articles; aesthetascs present. Antenna II peduncular article 4 as long as article 5; flagellum with 7 articles; calceoli absent. Left mandible incisor 5-dentate; lacinia mobilis 5- dentate; setal row with 3 serrate setae. Right mandible incisor 5-dentate; lacinia mobilis with numerous small teeth; molar process triturative, with short accessory seta; palp mandible article 3 is 20% longer than article 2; article 3 with 2 B-setae, 12 D-setae and 4 E-setae. Lower lip inner lobes indistinct; mandibular process brief, roundish. Upper lip without peculiarities. Maxilla I inner plate with 3 plumose setae; outer plate with 7 serrate spines; palp article 2 about 1.7× longer than article 1, bearing 5 spines on apex. Maxilla II inner and outer plates with 3 plumose setae each in oblique row. Maxilliped inner plate with 4 simple spines and 4 long simple setae apically and 3 plumose lateral setae; outer plate with a row of 3 medial robust serrate spines, 5 apical long stiff setae. Pereion ( Figures 2e , 19a, b , 20a–e ). Gnathopod I carpus (article 5) 0.4× as long as propodus, rastellate setae absent; palm oblique, defining angle indistinct, palm with cutting margin smooth, palm with 14 distally notched robust spines in two rows; dactylus, inner margin dentate, with 1 seta along outer margin. Gnathopod II carpus (article 5) 0.5× as long as propodus, rastellate setae absent; propodus palm oblique, defining angle distinct, palm with cutting margin smooth, palm with 12 distally notched robust setae in two rows and 11 distally notched robust setae near defining angle; dactylus similar to that of gnathopod I. Pereopods III and IV sub-similar; bases sub-linear, with a row of long and short setae on posterior margin; carpus (article 5) somewhat shorter than propodus, posterior margin armed with spine. Pereopod VI longer than pereopod VII . Ventral surface of pereonites II–VII bearing sternal humps (blisters). Coxal gills II–VI stalked and saccular. Oostegites II–V on gnathopod II and pereopods III–V developed, without marginal setae. Pleon ( Figure 2e , 21a–h ). Epimera I–III (pleonal plates) posterior corners obtuse, armed with 1 stiff seta each; ventral margin of plate I without setae, plates II and III with 1 seta each. Pleopods I–III peduncular articles with 2 coupling setae (retinacles). Uropod I peduncle with 5 spines on outer margin, 1 spine on inner margin, 1 basofacial spine-seta; outer ramus 0.8× as long as inner ramus, about 48% length of peduncle; inner ramus armed with 5 spines on each margin and with 4 long thin setae on ventral face; outer margin of outer ramus armed with 2 spines; rami with 4–6 spines on apices, one or two of them very long. Uropod II peduncle with 3 spines on outer margin and 1 spine on inner margin; outer ramus 0.8× as long as inner ramus; inner ramus 0.3× shorter than peduncle, armed with spines on both margins; outer margin of outer ramus with 2 spines; rami with 4–6 spines on apices, one or two of them long. Uropod III uniramous; peduncle with 3 spines and 1 seta on distal margin; proximal article of outer ramus 2.4× as long as peduncle, bearing 3 sets of spines on inner and outer margins; terminal article 0.15× as long as proximal article, with 3 setae on apex. Telson 1.3× as long as uropod III peduncle; 0.1× longer than broad, emarginate; tips of lobes with 2 strong spines apically each, one of them long. Figure 19. Pseudocrangonyx camtschaticus Birstein, 1955 , 11/11-DAS, female, 7.5 mm: (a) gnathopod I; (b) gnathopod II. Scale bar: 0.2 mm. Figure 20. Pseudocrangonyx camtschaticus Birstein, 1955 , 11/11-DAS, female, 7.5 mm: (a) pereopod III; (b) pereopod IV; (c) pereopod V; (d) pereopod VI; (e) pereopod VII. Scale bar: 0.2 mm. Variation Not observed.