Ovalona karelica Stenroos 1897, comb. nov.

XVI. Ovalona karelica (Stenroos, 1897) comb. nov.

(Figs. 11A–C)

Stenroos, 1897: 52–53, Fig. 5, 6 (Alona); Herr, 1917: 103–105, Fig. 30–33 (Alona); Herbst, 1962: 88, Fig. 66 (Alona), 1974: 134, Fig. 6–10 (Alona); Smirnov, 1971: 474–475, Fig. 464–465 (Alona); Hudec, 1980: 607–608, Fig. 1 (Alona), 1986: 188–191, Fig. 1–9 (Alona), 2010: 330–332, Fig. 81 (Alona); Floessner, 2000: 309–310, Fig. 114 (Alona); Sinev, 2002a: 936–937, Fig. 3 e, 4e (Alona); Van Damme, Elias-Gutierres & Dumont, 2011: Fig. 1 A, C, E, D, G–I, K, Fig. 2 A–K (Alona).

Type locality. Ondajoki, Finland.

Type material. Non-existent.

Material studied earlier. See Sinev (2002a) for the list of material from Norway.

Diagnosis. Parthenogenetic female. General. Length of adult 0.35–0.46 mm. Body regular oval, height/ length ratio about 0.58–0.62, maximum height at the middle. Postero-dorsal angle with about 60 setulae not organized into groups.

Head. Posterior part of headshield broadly rounded. Three major head pores with connection between them, PP = 0.3–0.5 IP. Lateral head pores minute.

Labrum of moderate size, labral keel broad, with convex anterior margin and a rounded apex, posterior margin of keel without clusters of setulae.

Second abdominal segment without dense setulae. Postabdomen narrow, with parallel margins in postanal portion, length about 2.8–3 height. Distal margin straight, dorso-distal angle prominent, acute with rounded tip. Dorsal margin with distal part about 2 times longer than preanal one; anal and postanal part of same length. Postanal portion of distal margin almost straight, anal portion weakly concave. Preanal angle well-defined, postanal angle weakly defined. 7–8 marginal denticles, evenly decreasing in size basally and with 3–5 groups of marginal setulae on anal margin. Eight-ten narrow, sparsely spaced lateral fascicles of setulae, in postanal portion; longest setule in each fascicle 1.2–1.5 times longer than marginal denticles. Postabdominal claw slightly longer than preanal portion of postabdomen. Basal spine very short, about 0.05 length of claw.

Antennule with antennular seta of 2/3 length of antennule, arising at 2/3 distance from the base. Aesthetascs of similar length, about half length of antennule.

Antenna with seta arising from basal segment of endopodite not reaching the end of endopodite. Spine on basal segment of exopodite about 2/3 length of middle segment. Spines on apical segments shorter than apical segments.

Limb III with exopodite seta 3 being longest; setae 6 of about 1/2 of seta 3; other setae shorter. Limb IV with epipodite with very short projection. Limb V with epipodite with short projection. Exopodite seta 4 four times shorter than seta 1.

Ephippial female with body higher than in parthenogenetic female, ephippium yellow-brown.

Male. General. Length 0.32–0.34 mm. Body low oval, maximum height in the middle of the body; height/ length ratio about 0.58–0.6.

Postabdomen long, rectangular, with parallel margins; dorso-distal angle broadly rounded, not protruding. Length about 2.6 maximum widths. Postanal angle not defined; preanal angle well-defined. Distal part of postabdomen 2 times longer than preanal one. Gonopores located almost at the end of postabdomen. Postabdominal claw long, slightly shorter than preanal portion of postabdomen, basal spine short, about 0.05 of claw length.

Full redescription. See Hudec (2010).

Differential diagnosis. O. karelica differs from most species of Ovalona by very short basal spine of postabdominal claw, this character is shared only by O. bromelicola. O. karelica differs from O. bromelicola by lower body, straight postabdomen, antennule with normally developed aesthetascs and by well-developed eye and ocellus.

Distribution. Known from Germany, Slovakia, North-West Russia, Finland and Norway. According to Ibrasheva & Smirnova (1983), O. karelica is found in Balkhash Lake in Kazakhstan, but this record should be rechecked.