Camptocercus lilljeborgi Schoedler 1862

Description. Parthenogenetic female. Body with a well-expressed dorsal keel, low oval (Fig. 12 A, C; 13 A, B); height / length ratio about 0.5 in adult; maximum height at the middle of the body. Body strongly compressed laterally, with developed egg locules (Fig. 13 C). Dorsal margin evenly arched from tip of rostrum to the posterodorsal angle; posterodorsal angle not defined; posterior margin convex; postero-ventral angle very broadly rounded, with a 1 – 3 small denticles. Ventral margin almost straight, anterior corner of valves broadly rounded. Ventral margin (Fig. 12 D) armed with 75 – 85 setae, row of setae ends at 2 / 3 length of margin. About 60 anterior setae (Fig. 12 E, 13 D) are densely spaced, of same length, armed with long setules distally; 15 posteriormost setae (Fig. 12 F, 13 D) are sparsely spaced, armed with short setules, decreasing in length distally. Denticles of posteroventral angle (Fig. 12 G, I; 13 F, G) short, saw-like, with broad bases; distance between denticles about 1 – 2 widths of their bases. Valves with a distinct longitudinal, sometimes anastomosing lines in posterior part. Keel oblique on both head and valves. Head (Fig. 13 H, 14 A) with truncated rostrum, protruding downward. Head keel moderately wide; distance from eye to the keel margin about 1.5 diameters of eye. Ocellus smaller than eye; distance from tip of rostrum to ocellus equal to distance between ocellus and eye. Head shield (Fig. 12 J, K) with maximum width behind mandibular articulation, without distinctive sculpture. In dorsal view, anterior margin of rostrum straight. Posterior margin as prominent, acute angle with rounded tip. Three major head pores (Fig. 12 L, M; 13 I) of same size, with a narrow connection between them. PP about 0.5 IP in adults. Lateral head pores located in small depressions about 1.5 IP distance from midline, at level of middle major head pore. Labrum (Fig. 14 B, D) of moderate size. Labral keel moderately wide (height about 1.5 widths), with a blunt or rounded apex. Anterior margin of keel irregularly convex; posterior margin weakly convex, with 2 – 4 clusters of short setules. Thorax and abdomen (Fig. 13 J) of similar length. Dorsal surface of middle abdominal segment saddle-shaped. Abdominal joint well-developed. Postabdomen (Fig. 12 N, O; 13 J) very long and narrow, unevenly narrowing distally, without defined distal margin. Length about 5 – 5.5 heights. Ventral margin almost straight. Basis of claws more elongated than in the previous species, bordered from dorsal margin by weak incision. Dorsal margin straight in postanal portion and straight to weakly concave in anal one; distal part about 4 times longer than preanal one; postanal portion 3 times longer than anal one. Preanal angle well expressed, prominent; postanal angle weakly defined. Preanal margin convex. Postanal margin (Fig. 12 P, 13 K) with 16 – 21 single, triangular denticles with serrated anterior margin; size of denticles evenly decreasing basally. Length of distal denticles about 2 / 35 width of postabdominal claw base. Postanal portion with 14 – 17 lateral fascicles of 3 – 6 short, robust setules; distalmost setule in each fascicle being longest. Postabdominal claw (Fig. 12 Q, 13 K) straight, with curved distal portion; very long, about 2 lengths of preanal portion of postabdomen; with distinctive pecten of setules on dorsal margin. Several distal elements in basal pecten are spines, length of distalmost spine exceed claw width at the spot. Basal spine slender, about 1 / 5 length of the claw, with short spinules on dorsal margin. Antennule (Fig. 14 E) long, straight, not reaching the end of the rostrum; length about 5 widths; with 4 clusters of setules on outer margin. Antennular seta short, about 1 / 3 length of antennule itself, arising at the middle of antennule from a weakly-defined tubercule. Nine terminal aesthetascs, the longest longer than as antennule; second longest as long as antennule; all other much shorter and thinner, about 1 / 2 – 1 / 3 length of antennule. Antenna relatively short (Fig. 14 F). Antennal formula: setae 0 - 0 - 3 / 0 - 1 - 3; spines 1 - 0 - 1 / 0 - 0 - 1. Basal segment robust, with very short seta between branches. Branches long and slender; in both branches apical and middle segments of same length; basal segment 1.5 times longer and thicker than two others. Seta arising from middle segment of endopodite short, shorter than endopodite. All apical setae of similar thickness. Spine on basal segment of exopodite about 1 / 3 length of middle segment. Spine on apical segment of exopodite about 1 / 3 length of the segment. Spine on apical segment of exopodite about 1 / 2 length of the segment. Limb I (Fig. 15 A, B). Epipodite oval, with very long, thick, strongly curved projection. Accessory seta short, about 1 / 4 length of ODL seta. ODL seta as in two previous species. IDL as in C. oklahomensis. Endite 2 – 3 as in C. uncinatus. Endite 1 similar to these of previous species, but with a flat thick geniculated plumose seta (i), absent in previous species. Ventral face of limb with densely spaced thin setules, not organized into clusters, in basal portion. Ejector hooks and maxillar process as in other species. Limb II (Fig. 15 C, D) similar to two previous species, but scraper 3 only about 2 / 3 length of neighbors, with very thick, robust denticles; spine 6 not thicker than neighbors; spines 6 – 8 two times thinner than scraper 5. Limb III (Fig. 15 E, F). Epipodite with thick finger-like projection longer than exopodite itself. Exopodite of irregular shape; setae 1 – 2 short, thin plumose; seta 3 being longest, with very thick basal portion and geniculated distal portion; setae 4 and 5 reduced to subtriangular setulated stubs; setae 6 thin, somewhat shorter than seta 3, unilaterally armed with short thick setules in distal portion; seta 7 thin, about 1 / 2 length of seta 6. Inner portion of the limb similar to that of C. fennicus, but distal endite setae 1 – 2, thin, slender; seta 2 much shorter than seta 1. Limb IV (Fig. 15 G, H). Pre-epipodite setulated; epipodite oval, with thick finger-like projection 1.5 times longer than epipodite itself. Exopodite rounded, with six setae; seta 5 being longest. Setae 1 – 2 very short, plumose; seta 3 with very thick basal portion and densely setulated distal portion, about 3 / 4 length of seta 5; seta 4 reduced to semicircular setulated stub; seta 5 with densely setulated distal portion; seta 6 thin, unilaterally armed with short setules in distal portion, about 1 / 3 length of seta 5. Inner portion of limb similar to that of two previous species, but scraping seta more slender; flaming-torch setae with shorter distal portion, and large elongated sensillum. Inner setae not found. Limb V (Fig. 15 I, J). Pre-epipodite setulated; epipodite oval, with thick finger-like projection 1.5 times longer than epipodite itself. Exopodite large, rounded, with four setae, seta 3 being longer. Setae 1 – 2 plumose, about 2 / 3 length of seta 3; seta 3 with very thick basal portion, plumose in distal portion; seta 4 reduced to semicircular setulated stub. Inner lobe small, narrow, curved, armed with row of thick setules. At inner face, two setae of similar size, distal on densely setulated in distal part. Filter plate V absent. Ephippial female unknown. Male. No adult males were available, for description of male see Smirnov (1971; 1998). Juvenile male of instar II. Body (Fig 12 R) similar to that of juvenile female of instar II. Postabdomen (Fig 12 S) similar to that of female; sperm duct opening located near ventral margin, at 1 / 4 length from the end of postabdomen. Marginal denticles and postabdominal claw same as in female. Antennule (Fig. 14 G) shorter than in female, anlage of male seta located at 1 / 4 antennule length from the tip. Aesthetascs same as in female. Thoracic limb I (Fig. 15 K, M) with anlage of copulatory hook, half as long as limb itself. The IDL with setae 1 – 3 as in female and anlage of male seta. Copulatory brush seta short; ventral face of the limb under the copulatory brush with row of 6 stiff setules. Size. Instar I juvenile female: length 0.45 – 0.47 mm; height 0.21 – 0.22 mm. Instar II juvenile female length 0.54 – 0.58 mm; height 0.24 – 0.27 mm. Adult females length 0.65 – 0.82 mm; height 0.30 – 0.43 mm. Single studied juvenile male of instar II length 0.56 mm; height 0.26 mm. Notes. Morphology of thoracic limbs of C. lilljeborgi was studied by Smirnov (1971), although these illustrations were rather undetailed, agree well with the present data. The species has been found in East Siberia for the first time.

Material examined. Over 40 parthenogenetic females, 1 juvenile male of instar II from Russia, Yakutia Autonomous Republic, an oxbow lake in valley of the Khandyga River, right bank of the Aldan River, 63,112 ºN, 134,0446 º E; 26.08 2010; coll. A. A. Kotov, AAK 2011 - 039. 7 parthenogenetic females, from Russia, Yakutia Autonomous Republic, a swamp at right side of the " Kolyma " Federal Road near crossing with the Suola River, 62,0993 º N, 130,1467 º E; 25. VIII. 2010; A. A. Kotov, AAK 2011 - 059.