Pseudocrangonyx tiunovi Sidorov & Gontcharov

Sidorov, Dmitry A. & Gontcharov, Andrey A., 2013, Studies on subterranean amphipod crustaceans of Primory, Russia. Part 1. Three new species of the genus Pseudocrangonyx from springs and other groundwater habitats in far eastern Russia, Zootaxa 3693 (4), pp. 547-567 : 550-557

Pseudocrangonyx tiunovi Sidorov & Gontcharov , sp. nov.

( Figs 3 A, 4–32)

Diagnosis. Medium-sized species with marked secondary sexual dimorphism. Dorsal surface of body segments smooth ( Fig. 3 A), relatively stout, teretial, bearing sets of fine setae. Eyes absent. Body unpigmented. Interantennal lobe of the head rounded, slightly tapered; inferior antennal sinus moderate ( Fig. 4 ). Antenna 1 about 50% length of body. Antenna 2 with swollen peduncular article 5 in males, both sexes without calceoli. Palp mandible article 3 with 4 B-seta, 15 D-setae and 6 E-setae. Ventral surface of pereonites 2–7 with sternal humps (blisters). Pereopod 6 largest. Urosome without “ecdysial setae”. Uropod 1 with 1 basofacial seta. Inner ramus of male uropod 2 with serrate setae. Telson emarginated. Body length 7.5–9.0 mm (females), 6.0–8.0 mm (males).

Type locality. Russia, Far East, suburb of Vladivostok, not far from the Tikhaya Bay (43º04.951' N 131º57.101' E), spring, 85 m above sea level.

Material examined. Holotype: male, 8.0 mm, X38656 /Cr-1472-FEFU, Russia, Primory Territory, spring (43º04.951' N 131º57.101' E), 11 Apr 2010, coll. I.M. Tiunov & E.A. Gorovaya. Paratypes: 11/6sd-IBSS, 4 females (9.0 mm, oostegites developed, setose, 8.5 mm, oostegites developed, setose, 7.5 mm, oostegites developed, nonsetose, female, fragment, oostegites developed, non-setose); 1 male (6.0 mm); 1 juvenile (4.7 mm); paratypes with same data as holotype.

Etymology. Species named after our colleague ornithologist Ivan M. Tiunov (Institute of Biology and Soil Science, Vladivostok) who found and collected this species.

Description. Male (8.0 mm), X38656 /Cr-1472-FEFU. Head. Antenna 1 ( Figs 4 , 9 ) 50% length of body, 64% longer than antenna 2; peduncular articles 1–3 in length ratio 1:0.8:0.5; primary flagellum with 19 articles; aesthetascs present. Antenna 2 ( Fig. 10 ), peduncular articles 4 and 5 in lengths ratio 1:1; peduncular article 5 swollen; flagellum with 6 articles; calceoli absent. Left mandible ( Fig. 18 ) incisor 5-dentate; lacinia mobilis 5- dentate; setal row with 4 serrate setae. Right mandible ( Fig. 19 ) incisor 5-dentate; lacinia mobilis trifurcate. Molar process triturative, with accessory seta. Palp mandible article 2 slightly shorter than article 3; article 3 with 4 Bseta, 15 D-setae and 6 E-setae. Lower lip ( Fig. 20 ), inner lobes absent; mandibular process distinct (narrow). Maxilla 1 ( Fig. 16 ), inner plate with 4 plumose setae; outer plate with 7 serrate setae; palp article 2 about 3x longer than article 1 bearing 4 robust setae on apex. Maxilla 2 ( Fig. 15 ), inner plate with 5 plumose setae. Maxilliped ( Fig. 21 ) inner plate with 6 strong serrate apical setae; outer plate with a row of 3 medial robust serrate setae, 13 naked setae and 3 apical plumose simple setae. Pereon. Coxal plates 1–4 ( Figs 7, 8 , 22, 23 ) shallow, sub-rectangular. Gnathopod 1 ( Fig. 7 ), carpus 0.4× as long as propodus, with 1 rastellate setae; propodus palm oblique, defining angle indistinct, palm with cutting margin crenulated, palm with 13 distally notched robust setae in two rows and 8 distally notched robust setae near defining angle; dactylus, inner margin dentate. Gnathopod 2 ( Fig. 8 ), carpus 0.6× as long as propodus, with 2 rastellate setae; propodus smaller than gnathopod 1 propodus; palm sub-transverse, defining angle distinct, palm with cutting margin crenulated, palm with 10 distally notched robust setae in 2 rows and 6 distally notched robust setae near defining angle; dactylus similar to that of gnathopod 1. Pereopod 6 longer than pereopod 7. Pereopods 3 and 4 ( Figs 22, 23 ) with a row of short setae on posterior margin; carpus shorter than propodus. Coxal gill 7 absent. Ventral surface of pereonites 2–7 bearing sternal humps (blisters). Pleon. Epimera 1–3 ( Fig. 5 ): posterior corners obtuse, armed with 1 stiff seta each; ventral margin of plate 1 without setae, plate 2 with 3 setae and plate 3 with 4 setae. Pleopods 1–3 ( Fig. 6 ), peduncular articles with 2 coupling setae (retinaculae). Urosome ( Fig. 3 A): urosomite 1, “ecdysial setae” absent. Uropod 1 ( Fig. 11 ): peduncle with 7 setae on outer margin, 1 long seta on inner margin on distal corner and with 1 basofacial seta; outer ramus 0.7× as long as inner ramus, about 50% length of peduncle; inner ramus armed with 5 setae on both margins and with 3 long setae on ventral face; outer margin of outer ramus unarmed; rami with 4–7 setae on apices, one of them very long. Uropod 2 ( Fig. 12 ): peduncle with 4 setae on outer margin and 1 seta on inner margin; outer ramus 0.6× as long as inner ramus; inner ramus longer than peduncle, armed with setae on both margins; outer margin of outer ramus unarmed; rami with 3–6 setae on apices, one or two of them longer and some serrate. Uropod 3 ( Fig. 13 ): uniramous; peduncle with 2 sets of stiff setae on distal margins; proximal article of outer ramus 4.0× as long as peduncle, bearing 8 sets of setae on inner and outer margins; terminal article 0.2× as long as proximal article, with 3 setae on apex. Telson ( Fig. 14 ): 1.8× as long as uropod 3 peduncle; 0.3× longer than broad, emarginated; tips of lobes each with 2 strong setae apically, one of them longer.

Female (7.5 mm), 11/6sd-IBSS, sexually dimorphic characters. Head. Antenna 2 ( Fig. 27 ): peduncular articles 4 and 5 densely setose; article 5 non-swollen; flagellum with 7 articles bearing rod-shaped structures; calceoli absent. Pereon. Coxal plate 2 ( Fig. 32 ) trapeziform. Gnathopod 1 ( Fig. 31 ): palm with 6 distally notched robust setae in 2 rows and 5 distally notched robust setae near defining angle; dactylus with 2 setae along outer margin. Gnathopod 2 ( Fig. 32 ): palm with 9 distally notched robust setae in 2 rows and 6 distally notched robust setae near defining angle. Pereopods 3 and 4 with a row of short and long setae on posterior margin; carpus somewhat shorter than propodus. Pleon. Uropod 2 ( Fig. 28 ): inner ramus without serrate robust setae. Uropod 3 ( Fig. 29 ): proximal article of outer ramus 3.0× as long as peduncle, bearing 6 sets of setae on inner and outer margins. Telson ( Fig. 30 ): 1.7× as long as uropod 3 peduncle. Oostegites 2–5 on gnathopod 2 and pereopods 3–5 ( Fig. 32 ) sub-linear, unmatured without marginal setae.

Variability. Flagellum of antenna 2 with 5–7 articles. Slight variation in arming of outer rami of uropods 1 and 2 was observed, as well in slightly different degree of telson emargination.

Taxonomic comments. P. tiunovi , sp. n. resembles P. elenae Sidorov, 2011 by the shape and structure of both gnathopods and by the relatively large body size. The absence of “ecdysial setae” is similar feature with P. levanidovi Birstein, 1955 , P. cavernarius Hou et Li, 2003, P. febras Sidorov, 2009 , P. kseniae Sidorov, 2012 and with both new species described below. The shape and structure of uropod 3 with 6–8 sets of setae on the proximal article of outer ramus and long terminal article is similar in P. bohaensis (Derzhavin, 1927) , P. korkishkoorum Sidorov, 2006 and P. asiaticus sensu Ueno, 1934 but new species differs by structure of mouth parts and by shape and armament of both gnathopods. The swollen article 5 and absence of calceoli on male antenna 2 are unique characters distinguishing P. tiunovi , sp. n. from all currently known species of the genus.

Distribution and ecology. Known only from type locality. Ecology unknown.

Figures

FIGURE 3. (3 A) Pseudocrangonyx tiunovi, sp. nov., from left side, female, 9.0 mm, paratype 11 / 6 sd-IBSS; (3 B) Pseudocrangonyx holsingeri, sp. nov., from left side, female, 3.5 mm, paratype 11 / 7 sd-IBSS; (3 C) Pseudocrangonyx sympatricus, sp. nov., from left side, female, 6.25 mm, holotype X 38655 / Cr- 1471 - FEFU; (3 D) Pseudocrangonyx kseniae Sidorov, 2012, from left side, female, 4.8 mm, paratype 11 / 5 sd-IBSS.

FIGURES 4 – 8. Pseudocrangonyx tiunovi, sp. nov., male, 8.0 mm, holotype X 38656 / Cr- 1472 - FEFU: (4) head; (5) epimera 1 – 3; (6) pleopod 1; (7) gnathopod 1; (8) gnathopod 2. Scale bars 0.2 mm.

FIGURES 9 – 14. Pseudocrangonyx tiunovi, sp. nov., male, 8.0 mm, holotype X 38656 / Cr- 1472 - FEFU: (9) antenna 1; (10) antenna 2; (11) uropod 1; (12) uropod 2; (13) uropod 3; (14) telson. Scale bars 0.2 mm.

FIGURES 15 – 21. Pseudocrangonyx tiunovi, sp. nov., male, 8.0 mm, holotype X 38656 / Cr- 1472 - FEFU: (15) maxilla 2; (16) maxilla 1; (17) upper lip; (18) mandible, left; (19) mandible, right; (20) lower lip; (21) maxilliped. Scale bars 0.2 mm.

FIGURES 22 – 26. Pseudocrangonyx tiunovi, sp. nov., male, 8.0 mm, holotype X 38656 / Cr- 1472 - FEFU: (22) pereopod 3; (23) pereopod 4; (24) pereopod 5; (25) pereopod 6; (26) pereopod 7. Scale bars 0.2 mm.

FIGURES 27 – 32. Pseudocrangonyx tiunovi, sp. nov., female, 7.5 mm, paratype 11 / 6 sd-IBSS: (27) antenna 2; (28) uropod 2; (29) uropod 3; (30) telson; (31) gnathopod 1; (32) gnathopod 2. Scale bars 0.2 mm.