Pseudocrangonyx sympatricus 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 : 563-566

Pseudocrangonyx sympatricus Sidorov & Gontcharov , sp. nov.

( Figs 3 C, 70–90)

Diagnosis. Small-sized species, sexual dimorphism unknown. Dorsal surface of body segments smooth ( Figs 3 C, 71), teretial, bearing detached fine setae. Eyes absent. Body unpigmented. Interantennal lobe of the head rounded, slightly tapered; inferior antennal sinus moderate ( Fig. 70 ). Antenna 1 about 30% length of body. Palp mandible article 3 with 2 B-seta, 11 D-setae and 3 E-setae. Ventral surface of pereonites 2–7 with sternal humps (blisters). Pereopod 7 largest. Urosome without “ecdysial setae”. Uropod 1 with 1 basofacial seta. Telson emarginated. Body length 5.2–6.25 mm (females).

Type locality. Russia, Far East, southeast part of the Sikhote-Alin Mountain Ridge, the Kievka River basin (43º22.160' N 133º55.485' E), subterranean waters (hyporea), 217 m above sea level.

Material examined. Holotype: female (6.25 mm, oostegites undeveloped), X38655 /Cr-1471-FEFU, Russia, Primory Territory, Lasovsky District, ~ 3 km E of Laso, Kievka River (43º22.160' N 133º55.485' E), 3 Aug 2009, coll. D.A. Sidorov & K.A. Semenchenko. Paratypes: 11/8sd-IBSS, sex unknown (4.5 mm); with same data as holotype. Closely with type locality, 15 Jun 2011, coll. D.A. Sidorov & A.L. Sidorov, 2 females (5.7 mm, 5.2 mm, oostegites undeveloped).

Etymology. The species name sympatricus (adj.) indicate to the sympatry of this species with the congeneric Pseudocrangonyx kseniae . Gender masculine.

Description. Female (6.25 mm), X38655 /Cr-1471-FEFU. Head. Antenna 1 ( Fig. 73 ): about 30% length of body, 60% longer than antenna 2; peduncular articles 1–3 in length ratio 1:0.9:0.4; primary flagellum with 17 articles; aesthetascs present. Antenna 2 ( Fig. 74 ), peduncular articles 4 and 5 in lengths ratio 0.9:1; flagellum with 7 articles; calceoli absent. Left mandible ( Fig. 81 ) incisor 5-dentate; lacinia mobilis 5-dentate; setal row with 4 serrate setae. Right mandible incisor 5-dentate; lacinia mobilis trifurcate. Molar process triturative, with accessory seta. Palp mandible article 3 63% longer article 2; article 3 with 2 B-seta, 11 D-setae and 3 E-setae. Lower lip ( Fig. 83 ), inner lobes absent; mandibular process indistinct (roundish). Maxilla 1 ( Fig. 79 ), inner plate with 3 plumose setae; outer plate with 7 serrate setae; palp article 2 about 3.7× longer than article 1 bearing 3 stiff setae on apex. Maxilla 2 ( Fig. 80 ), inner plate with 4 plumose setae. Maxilliped ( Fig. 84 ) inner plate with 2 short and 1 long simple setae apical and 4 plumose setae sub-apical; outer plate with a row of 7 medial robust setae two of them serrate, 3 apical long stiff setae. Pereon. Coxal plates 1–4 ( Figs 85–87 ) shallow, sub-rectangular. Gnathopod 1 ( Fig. 85 ), carpus 0.5× as long as propodus, rastellate setae absent; propodus palm oblique, defining angle indistinct, palm with cutting margin crenulated, palm with 10 distally notched robust setae in two rows and 6 distally notched robust setae near defining angle; dactylus, inner margin dentate, with 2 setae along outer margin. Gnathopod 2 ( Fig. 86 ), carpus 0.7× as long as propodus, with 3 rastellate setae; propodus palm oblique, defining angle indistinct, palm with cutting margin crenulated, palm with 6 distally notched robust setae in 2 rows and 4 distally notched robust setae near defining angle; dactylus similar to that of gnathopod 1. Pereopods 3 and 4 ( Fig. 87 ) with a row of long and short setae on posterior margin; carpus longer than propodus. Coxal gill 7 absent. Pereopod 7 ( Figs 88, 89 ) longer than pereopod 6. Ventral surface of pereonites 2–7 bearing sternal humps (blisters). Pleon. Epimera 1–3 ( Fig. 72 ): posterior corners obtuse, armed with 1 stiff seta each; ventral margin of plate 1 without setae, plate 2 with 2 setae and plate 3 with 2 setae. Pleopods 1–3 ( Fig. 90 ), peduncular articles with 2 coupling setae (retinaculae). Urosome ( Figs 3 C, 71): urosomite 1, “ecdysial setae” absent. Uropod 1 ( Fig. 75 ): peduncle with 6 setae on outer margin, 4 setae on inner margin two of them couple and very long, 1 basofacial seta; outer ramus 0.7× as long as inner ramus, about 60% length of peduncle; inner ramus armed with 6 setae on both margins and with 2 long setae on ventral face; outer margin of outer ramus armed; rami with 5–6 setae on apices, one or two of them very long. Uropod 2 ( Fig. 76 ): peduncle with 3 setae on outer margin and 4 setae on inner margin two of them couple; outer ramus 0.6× as long as inner ramus; inner ramus 1.4× longer peduncle, armed with setae on both margins; outer margin of outer ramus unarmed; rami with 4 setae on apices, one of them long. Uropod 3 ( Fig. 77 ): uniramous; peduncle with 1 set of stiff setae on distal margin; proximal article of outer ramus 2.4× as long as peduncle, bearing 6 sets of setae on inner and outer margins; terminal article 0.2× as long as proximal article, with 3 setae on apex. Telson ( Fig. 78 ): 1.2× as long as uropod 3 peduncle; 0.2× longer than broad, emarginated; tips of lobes with 2 strong setae apically, one of them long. Oostegites 2–5 on gnathopod 2 and pereopods 3–5 unmatured (barely visible), without marginal setae.

Male. Unknown.

Variability. The species is not extremely variable. The character of variability of outer rami of uropods 1 and 2 is common with above described species.

Taxonomic comments. P. sympatricus , sp. nov. is distinguished from sympatric P. kseniae by the following characteristics (characteristics of the latter in parentheses): inteantennal lobe obtuse (truncate); antenna 1 about 30% length of body (50%); antenna 2 about 0.4x shorter than antenna 1 (0.5x); peduncular articles 4, 5 of antenna 2 in length ratio 1:0.9 (1:0.5); gland cone of antenna 2 tapered (obtuse); serrate setae on outer plate of maxilliped present (absent); maxilla 2 with 4 plumose setae in oblique row (2 setae); vestigial inner lobes of lower lip absent (present); female gnathopod 1 with 6 notched setae at defining angle (9 setae); pereopod 7 longer than pereopod 6 (shorter); distal margin of epimeron 1 armed (unarmed); uropod 3 with 6 sets of setae (with 2 sets); outer rami of uropods 1, 2 in female armed (unarmed); telson 1.2× as long as uropod 3 peduncle (1.8× – 2.0×); telson emarginated (entire).

P. sympatricus , sp. nov. resembles P. korkishkoorum by distinctly short palp article 2 of mandible. The shape and structure of uropod 3 with 6 sets of setae on the proximal article of outer ramus and short terminal article is similar in P. shikokunis and P. asiaticus sensu Ueno, 1966 . The character setation of inner and outer plates of maxilliped and longer pereopod 7 are unique features distinguishing P. sympatricus , sp. nov. from all known species of the genus.

Distribution and Ecology. Known only from type locality, where it occurs together with P. kseniae . Stygobiont crustaceans Paramoera (Ganigamoera) myslenkovi Sidorov, 2010 , Asellus sp., Mackinia sp., Acanthocyclops orientalis Borutzky, 1966 , Diacyclops sp., Diacyclops ex gr “ languidoides ” and several interstitial species of water mites were collected from this same locality.

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 70 – 78. Pseudocrangonyx sympatricus, sp. nov., female, 6.25 mm, holotype X 38655 / Cr- 1471 - FEFU: (70) head; (71) urosome; (72) epimera 1 – 3; (73) antenna 1; (74) antenna 2; (75) uropod 1; (76) uropod 2; (77) uropod 3; (78) telson. Scale bars 0.2 mm.

FIGURES 79 – 84. Pseudocrangonyx sympatricus, sp. nov., female, 6.25 mm, holotype X 38655 / Cr- 1471 - FEFU: (79) maxilla 2; (80) maxilla 1; (81) mandible, left; (82) upper lip; (83) lower lip; part; (84) maxilliped. Scale bars 0.2 mm.

FIGURES 85 – 90. Pseudocrangonyx sympatricus, sp. nov., female, 6.25 mm, holotype X 38655 / Cr- 1471 - FEFU: (85) gnathopod 1; (86) gnathopod 2; (87) pereopod 3; (88) pereopod 7; (89) pereopod 6; (90) pleopod 1. Scale bars 0.2 mm.