Camptocercus smirnovi, Sinev & Gavrilko, 2021

Sinev, Artem Y. & Gavrilko, Dmitriy E., 2021, Longitudinal gradient in the Camptocercus lilljeborgi Schoedler, 1862 species group (Cladocera: Anomopoda: Chydoridae), Zootaxa 5047 (2), pp. 123-138 : 133-135

Camptocercus smirnovi sp. nov.

( Fig. 8 )

Sinev, 2014: 199–204, Fig. 12–15 ( lilljeborgi ); Garibian et al., 2019: 46, Fig. 6 ( lilljeborgi ).

Etymology: the species is named after our teacher, famous Russian cladocerologist Prof. Nikolai Nikolaevich Smirnov (1928-2019).

Type locality. An oxbow lake in the valley of the Khandyga River , right bank of the Aldan River, Sakha (Yakutia) Autonomous Republic, Russia, N 63,112°, E 134,0446°, 26.08.2010, coll. A.A. Kotov. The type series was extracted from an initial sample AAK 2011–039 .

Type material. Holotype. A parthenogenetic female from the type locality, deposited at the collection of Zoological Museum of M. V. Lomonosov Moscow State University, accession number Ml –242.

Paratypes. 12 parthenogenetic females from the type locality, deposited at the collection of Zoological Museum of M. V. Lomonosov Moscow State University, accession number Ml –243 .

Material studied earlier and excluded from type series. See list of material in Sinev (2014) and Garibian et al. (2019) (as C. lilljeborgi ). Detailed description of type population, including full description of thoracic limbs was provided by Sinev (2014).

Diagnosis. Parthenogenetic female. Body with a well-expressed dorsal keel, low oval ( Fig. 8A ); height/length ratio about 0.5 in adult; maximum height at the middle of the body. Body strongly compressed laterally, with developed egg locules. Dorsal margin evenly arched from tip of rostrum to the posterodorsal angle; posterodorsal angle not defined; posterior margin convex; postero-ventral angle with 1–3 small denticles. Ventral margin almost straight, anterior corner of valves broadly rounded. Ventral margin ( Fig. 8B ) armed with 75–85 setae, row of setae ends at 2/3 length of margin. About 60 anterior setae are densely spaced, of same length, armed with long setules distally; 15 posteriormost setae are sparsely spaced, armed with short setules, decreasing in length distally. Denticles of posteroventral angle short, saw-like, with broad bases; distance between denticles about 1–2 widths of their bases.

Head 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 without distinctive sculpture. In dorsal view, anterior margin of rostrum straight. Three major head pores 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 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 of similar length. Dorsal surface of middle abdominal segment saddle-shaped.Abdominal joint well-developed.

Postabdomen ( Fig. 8 C-E) long and narrow, unevenly narrowing distally, without defined distal margin. Length about 6-6.5 height at preanal angle. Ventral margin almost straight. Basis of claws more elongated than in the previous species, bordered from dorsal margin by a 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 with 16–21 single, triangular denticles with serrated anterior margin; size of denticles evenly decreasing basally. Length of distal denticles about 2/3 width of post abdominal 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. 8F ) 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 and antenna similar to that of the previous species. Thoracic limbs similar to those of the previous species, with the following differences. IDL of limb I ( Fig. 8G ) with seta 1 being short, three times shorter than seta 3. Limb II ( Fig. 8H ) with scraper 3 bearing much thicker spinules than scraper 4. Exopodite of limb IV ( Fig. 8I ) with seta 5 longer than seta 3, setae 1–2 very short, 5 times shorter than seta 3.

Ephippial female and adult male unknown.

Size. In instar I juvenile female length 0.45–0.47 mm, height 0.21–0.22 mm; in instar II juvenile female length 0.54–0.58 mm, height 0.24–0.27 mm; in adult females length 0.65–0.82 mm, height 0.30–0.43 mm.

Differential diagnosis: C. smirnovi sp. nov. clearly differs from most species of the genus in densely located anterior setae of the ventral margin of the valves; this character is shared only by its sibling-species C. lilljeborgi . It differs from the latter in a (1) low body, (2) setae of ventral margin ending at 2/3 length of ventral margin, (2) shorter and broader postabdomen, and (4) short IDL seta 1 of thoracic limb I. Other minor differences between these two species are summarized in Table 1.

Distribution. The species is known from few localities in Sakha (Yakutia) Republik and Khabarovk Area of Russia, but probably it has a wider area of distribution.

Figures

FIGURE 6. Camptocercus lilljeborgi Schoedler, 1862 from River Levinka, Nizhnii Novgorod, Russia. Parthenogenetic female, thoracic limbs: A, limb I; B, setae a–b of limb I; C, IDL and ODL of limb I (setules on ODL seta did not shown); D, exopodite of limb II; E–F, inner and outer portions of limb II; G, exopodite of limb III; H, distal endite of limb III; I, exopodite of limb IV; J–K, inner portion of limb IV; L, limb V; M, inner setae of limb V. Juvenile male of instar II: N–O, anterior margin and IDL of limb I. Adult male: P, thoracic limb I; Q–R, ODL and IDL of limb I.

FIGURE 8. Camptocercus smirnovi sp. nov. from an oxbow lake in the valley of the Khandyga River, Sakha (Yakutia) Autonomous Republic, Russia (type locality). Parthenogenetic female. A, lateral view. B, ventral margin of valves. C-D, postabdomen. E, distal portion of postanal margin of postabdomen. F, postabdominal claw. G, IDL and ODL of thoracic limb I. H, scrapers of thoracic limb II. I, exopodite of thoracic limb IV. From Sinev (2014).