Pseudocrangonyx camtschaticus Birstein, 1955

Sídorov, Dmitry, Labay, Vjacheslav & Gontcharov, Andrey, 2020, New species and records of the subterranean amphipod genus Pseudocrangonyx Akatsuka and Komai (Crustacea: Pseudocrangonyctidae), representing the northernmost distribution of the group, Journal of Natural History 54 (27 - 28), pp. 1759-1795 : 1783-1786

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.

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.

Variation

Not observed.

Figures

Figure 2. Habitus of examined specimens: (a) Pseudocrangonyx spangsbergi sp. nov., holotype, female, 5.5 mm; (b) Pseudocrangonyx setosus sp. nov., holotype, female, 5.5 mm; (c) Pseudocrangonyx myaochanicus sp. nov., holotype, female, 3.2 mm; (d) Pseudocrangonyx borealis sp. nov., holotype, female, 4.5 mm; (e) Pseudocrangonyx camtschaticus Birstein, 1955, female, 7.5 mm.

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.

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.

Figure 21. Pseudocrangonyx camtschaticus Birstein, 1955, 11/11-DAS, female, 7.5 mm: (a) epimera I–III; (b) pleopod I; (c) pleopod II; (d) pleopod III;(e) uropod I; (f) uropod II; (g) uropod III;(h) telson.Scale bar:0.2 mm.