Pleuroxus trigonellus Garibian & Neretina & Klimovsky & Kotov 2018

Field: Agricultural and Biological Sciences (Life Sciences)

Pleuroxus trigonellus (O.F. Müller, 1776) (Figs. 1–7) Lynceus trigonellus O.F. Müller, 1776 in Müller (1776): p. 199; Müller (1785): p. 74–75, pl. 10, figs. 5–6. Pleuroxus trigonellus (O.F. Müller) in Sars (1861): p. 124, pl. 91; Lilljeborg (1901): p. 534–537, pl. 74: figs. 13–23; Šrámek- Hušek et al. (1962): p. 376–378, fig. 141; Flössner (1972): p. 355–357, figs. 165–166; Negrea (1983): p. 240–242, fig. 96; Margaritora (1985): p. 211–213, fig. 84; Flössner (2000): p. 250–253, fig. 93; Smirnov (1966): figs. 8, 15, 16, 24, 25; Frey (1993): table 1, figs. 1–8; Røen (1995): 281–284, fig. 128; Hudec (2010): p. 421–423, fig. 104; Szeroczyńska et al. (2007): p. 63–64, figs. 322–332. Pleuroxus trigonellus trigonellus (O.F. Müller) in Smirnov (1971): p. 226, figs. 208–215. Pleuroxus ornatus Schödler, 1862 in Schödler (1862): p. 25, pl. 2: fig. 32? (no captions in the paper, fig. 38 in text, this is a mistake!); Schödler (1863): 47–48, pl. 2: fig. 32. Pleuroxus Bairdii Schödler, 1863 in Schödler (1863): p. 50–51. Type material. Lost, as whole material of O.F. Müller (Müller 1867; Frey 1980). Type locality. Denmark. The type locality was not specified, but it is known that O.F. Müller collected at least some samples in the ponds at his summer house in Frederiksdal (Frey 1980). Material examined. 10 parthenogenetic females, 3 ephippial females, 5 males from Dobrasee, Brandenburg, Germany, coll. by M. Belyaeva, AAK M-0919; 5 parthenogenetic females from Lake Glubokoe (N 55.75361°, E 36.50417°), Moscow Area, Russia, coll. 15.08.2005 by N.N. Smirnov, AAK 2006-109; 5 parthenogenetic females from the same location, coll. 16.08.2016 by A.A. Kotov, AAK M-3476; 2 parthenogenetic females from the same location, AAK M-3477; 1 parthenogenetic female from the same location, AAK M-3486; 2 parthenogenetic females from the same location, AAK M-3487; 3 parthenogenetic females from a small pond (N 55.56242°, E 39.82352°), Moscow Area, Russia, coll. 0 4.08.2014 by A.A. Zharov, AAK M-2730; 2 parthenogenetic females from the same location, AAK M-2731; 2 parthenogenetic females from Sen’ga River (N 55.8839°, E 39.52012°), Vladimir Area, Russia, coll. 0 6.08.2014 by A.A. Zharov, AAK M-2740; 5 parthenogenetic females from a small pond 50 m from the shore of Chudskoe Lake, near the village Zapol'je (N 58.63642°, E 27.78997°), Pskov Area, Russia, coll. 19.08.2007 by A.A. Kotov, AAK M-0596; 2 parthenogenetic females from a small lake ffi 1 in the vicinity of Penza, Sosonivka, (N 53.1739°, E 45.0767°), Penza Area, Russia, coll. in May of 2009 by E.I. Bekker, AAK M-0934; 2 parthenogenetic females from a small lake ffi 2 in the vicinity of Penza (N 53.212°, E 45.088°), Penza Area, Russia, coll. 0 5.05.2010 by E.I. Bekker, AAK M-1807; 2 parthenogenetic females from Cherepovets Reservoir, Vologda Area, Russia, coll. 17.07.1966 by N.N. Smirnov, NNS 1998-183; 3 parthenogenetic females from Gor’kovskoe Reservoir (N 56.8°, E 43.3°), Nizhny Novgorod Area, Russia, coll. 28.08.1961 by N.N. Smirnov, NNS 1999-056. Diagnosis (adapted after Frey 1993). Body transparent. Parthenogenetic and ephippial female with length up to 0.60 mm. Median dorsal keel absent. Sculpture of valves and head moderately or strongly developed. Rostrum sharply pointed, directed downwards. Labral keel short (not projected behind tip of rostrum), triangular, its anterior margin slightly convex, distal angle acute. Posteroventral angle of valve with few denticles. Postabdomen moderately elongated, tapered distally, postanal margin almost straight, with strong postanal teeth, on postabdominal claw proximal basal less than half size of distal one. Antenna I in female elongated, with a basal peg and nine aesthetascs of unequal size. Apical swimming setae of antenna II subequal in size. Filter plate of gnathobase II with eight setae; filter plate III with 8 setae; filter plate IV with 6 setae; filter plate V with 4 setae. Male with length up to 0.45 mm. Rostrum shorter as compared to the female. Distal portion of the postabdomen shaped as a tube lacking setules, postanal teeth transformed into bunches of long, thin setules. Gonopore opens ventrally at level of postabdomen narrowing (base of the tube). Antenna I in male without a basal peg and with nine aesthetascs of unequal size. Redescription. Parthenogenetic female. General. Body transparent. In lateral view body subovoid, high (body height/ body length = 0.71–0.73 in adults). Maximum height in middle of body (Figs. 1 A–B, 2A–B). In dorsal and anterior view body compressed laterally, lacking a median dorsal keel (Figs. 1C, 2 C–F). Dorsal margin evenly arched from tip of rostrum to posterodorsal angle, without a depression between head and the rest of body. Posterior margin relatively straight, posteroventral angle almost straight, with teeth, ventral margin with a slight prominence in thirst half of body behind head (Figs. 1 A–B, 2A–B), with a row of marginal setae (Figs. 1 A–B, 2A, 4C–E). Obscure striation as hexagons on all body surface (Figs. 1A, 2A, 4 A–B). Head with a long, pointed rostrum, protruding downward and posteriorly (Figs. 1 D–E, 2A–F, 4A–B, F). Eye only slightly larger than ocellus, distance from tip of rostrum to ocellus greater than that between ocellus and eye (Figs. 1 A–B, 1E). Head shield elongated, with maximum width immediately behind mandibular articulation (Figs. 1D, 1F, 2F, 4 G–H). In dorsal view rostrum elongated, with acute apex (Figs. 1D, 2 C–F). Two major head pores (Figs. 1 F–G, 4G–H), PP = 1.6 IP. Lateral head pores minute, located at the headshield midline between major pores (Fig. 1G), usually these are positioned somewhat asymmetrically to the midline. Labrum with a fleshy main body and a small distal labral plate (Fig. 1E). Labral keel short (not projected behind rostrum tip), triangular, its anterior margin slightly convex, distal angle acute. Valves large, ventral margin armed with numerous setae of different size in different regions, all plumose and located exactly marginally (Figs. 1 A–B, 2A–B, 3C–E, 4B–E). Posterior margin of valves with few (1–3, mainly 2) teeth (Figs. 1 A–B, 2A–B, 3D–E, 4D–E). Ventral margin bears setae covered by long prominent setules (Fig. 3 C–E, 4C–D). Anterior valve margin broadly rounded (Fig. 3A, 4 A–B). Postabdomen elongated, subrectangular, its ventral margin almost straight (Figs. 3 F–I, 6A–B). Basis of postabdominal setae surrounded by a prominent chitin ring (Fig. 3H, 6D). Preanal margin slightly concave (Figs. 3 F–H, 6A–C), and slightly longer than anal margin, preanal and postanal angle well-defined, postanal margin clearly longer than anal margin, dorsodistal angle almost right (Figs. 3I, 6 E–G). Basis of claws inflated (Figs. 3 H– I, 6E–F). Each side of the postanal portion with a row of long and thickened postanal teeth, increasing in size distally (Fig. 3I, 6G). Laterally to marginal denticles, a row of fascicles consisting of bunches of short, fine setules (Figs. 3 H–I). Postabdominal seta longer than postanal margin, with basal segment approximately as long as preanal margin and distal segment shorter than basal one, implanted with delicate setules (Fig. 3G). Postabdominal claw massive and long (subequal in length to anal and preanal margins), slightly curved (Figs. 3I, 6 E–G). Dorsal edge of claw armed with a row of fine setules decreasing in size distally (Fig. 6G). Two basal spines, distalmost basal spine long (slightly longer than the base of claw), proximalmost basal spine relatively short, two times shorter than distal spine (Figs. 3 H–I, 6E–F). Antenna I not reaching tip of rostrum, narrowing distally, with a well-defined basal peg (Figs. 3 J–K). Antennular sensory seta slender, longer than half of antenna I, arising at half of antennular body. Nine short aesthetascs unequal in length (Figs. 3 J–K). Antenna II relatively short, coxal part with two sensory setae, basal segment robust, with a small spine (Figs. 1 A–B, 3L, 4F). Antennal branches elongated, exopod and endopod subequal in length, all segments cylindrical, covered by transverse rows of fine spinules (Fig. 4F). Antennal formula: setae 0-0-3/1-1-3, spines 1-0-1/0-0-1. Proximal segment of exopod with a short spine. Exopod and endopod apical swimming setae, as well as lateral endopod setae covered by fine long setules; distal segments of apical setae with chitin insertions (Figs. 3 L–M). Apical spines of exopod and endopod subequal in size (Fig. 4F). Limb I (Figs. 5 A–B, 6H): accessory seta, or corm seta in Frey (1993a), present (not represented in Fig. 5A, because it is located on the other side of the limb corm), ODL relatively small, bears a long seta with a naked distal segment, and a short seta with short, setulated distal segment (Figs. 5 A–B). IDL larger than ODL, covered by transverse rows of setules (Fig. 6H). First IDL seta short, naked, second and third IDL setae not equal in size and similarly armed distally with short, fine setules (Figs. 5 A–B). Endite 3 with three soft posterior setae (a–c) and stiff anterior seta 1 of similar length. Endite 2 with short seta anterior (seta d), long (setae e and f), and delicate posterior seta 2 armed with minute setules. Endite 1 with long, slender posterior setae (g–i), a very short seta (j), and anterior seta 3 (it significantly shorter than seta 2). Fascicles of thin setules on inner face of limb, plus bunches of longer thicker setules at ventral margin of limb. Two slender ejector hooks of remarkably different size. A short seta, a remnant of maxillar process, on limb base. Limb II (Fig. 5C) subrectangular. Exopodite subquadrangular, with a short seta. Inner portion of limb with eight setae: setae 1–3 especially long, setae 4–5 shorter, subequal in size, setae 6–8 short, also subequal in size. A series of small projections posteriorly to distal setae, and a small sensillum near scraper 4. Distal armature of gnathobase with a bunch of plumose setules, unique for the anomopods, and four setae. Filter plate with eight setae, two distalmost seta