X. Ovalona archeri (Sars, 1888) comb. nov.

(Figs. 7 C–G).

Sars, 1888: 59–62, PI. 6, Figs. 1–4 (Alona); Smimov. 1971: 389–390, Fig. 466 (Alona); Smirnov & Timms, 1983: 48, Fig. 43 (Alona); Idris, 1983: 110–113, Fig. 42 (Alona cf. karelica); Smirnov, 1989: 139, Fig. 1 (Alona beverleyae); Sinev 2002c: 257–254, Fig. 1 –30 (Alona); Maiphae, Pholpunthin & Dumont, 2008: 38, Fig 4–5 (Alona).

Type locality. Australia, Queensland, neighborhood of Rockhampton, Water Hole at Cattle Station.

Type material. Lectotype (established by Sinev, 2002c): parthenogenetic female, ZMOU, sample F18326 a. For full list of paralectotypes see Sinev (2002c).

Material studied earlier. All type material (see Sinev 2002c).

Diagnosis. Parthenogenetic female. General. Length of adult 0.38–0.48 to mm. Body regular oval, of moderate height; in adults height/length ratio about 0.6–0.7; maximum height at the middle. Ventral margin with 40–50 setae. Postero-dorsal angle with about 80 setulae not organized into groups. Posterior part of head shield broadly rounded. Three connected major head pores, PP less than 0.3 IP. Lateral head pores minute.

Labrum. Labral keel narrow, with rounded apex, anterior margin of keel convex, posterior margin without any setulae.

Second abdominal segment without dense setulae. Postabdomen narrow, with parallel margins and weakly prominent; almost right dorso-distal angle, length about 2.9–3.1 height. Ventral margin almost straight. Dorsal margin with distal part 1.5 times longer than preanal one; postanal and anal portions of similar length. Postanal portion of distal margin straight; anal portion concave. Preanal angle well-defined, postanal angle weakly defined. Distal margin straight, dorso-distal angle almost right, with rounded tip. 3–5 large marginal denticles in distal part, followed by 5–6 much smaller, thin denticles, and 3–4 groups of marginal setulae on anal margin. Nine-ten narrow, sparsely spaced lateral fascicles of setulae; distalmost seta of each fascicle much longer and thicker than others; in postanal portion, longest setule in each fascicle of similar length with distal marginal denticles. Distance between fascicles in postanal portion equal to the width of fascicles. Postabdominal claw slightly longer than preanal portion of postabdomen. Basal spine straight, thin, about 0.2 length of claw.

Antennule with antennular seta about 1/3 length of antennule, arising at 2/3 distance from the base. Aesthetascs of different length, two longest of them of about 1/2 length of antennule.

Antenna with seta arising from basal segment of endopodite thin, of same length as endopodite. Spine on basal segment of exopodite 1.5 times shorter than middle segment. Spines on apical segments slightly shorter than apical segments.

Limb I with accessory seta about 1/4 length of ODL seta. Limb III with exopodite seta 3 being longest; seta 6, 4 and 7 about 2/3, 1/2 and 1/3 length of seta 3, respectively; other setae shorter. Limb IV with epipodite without projection. Exopodite seta 3 longest; setae 1 about 2/3 length of seta 3; setae 2 and 5 about 1/2 length of seta 3; setae 4 and 6 two times shorter than seta 5. Flaming-torch setae elongated with narrow bases, distal portion not reduced. Limb V with epipodite without projection. Exopodite seta 4 five times shorter than seta 1.

Ephippial female similar in proportion to parthenogenetic female; ephippium yellow-brown.

Male. General. Length 0.27–0.30. Body low oval, height/length ratio about 0.5, maximum height at the middle.

Postabdomen elongated, narrow, weakly narrowing distally; dorso-distal angle well-defined. Preanal angle well-defined, postanal angle not defined. Distal part of postabdomen 1.8 times longer than preanal one. Postabdominal claw short, 1.3 times shorter than preanal portion of postabdomen; basal spine straight and thin, about 0.25 of claw length.

Antennule with male seta arising at 1/4 length from tip, not reaching to the end of antennule.

Limb I with V-shaped copulatory hook. IDL seta 1 absent; setae 2 and 3 subequal in length, three times shorter and thinner than in female; male seta large, hook-like, shorter than seta 3. A group of 7–8 short setulae located under copulatory brush, on ventral face of limb.

Full redescription: see Sinev (2002c).

Differential diagnosis. O. archer i differs from O. bromelicola and O. karelica by well-developed basal spine of postabdomen, and from O. capensis, O. cambouei and O. aguascalientensis by connected head pores. O. archeri differs from O. glabra and O. pulchella by unique armament of postabdomen, with extremely large distal marginal denticles and very narrow, sparsely spaced lateral fascicles of setae.

Taxonomic notes: Maiphae et al. (2008) observed that Thailand populations of O. archeri differs from those from Australia by proportions of body, length of antennula aesthetascs, morphology of labral keel, and proportions of scrapers 1–2 of limb II. These characters are of minor taxonomic significance, and at the moment I agree with Maiphae et al. (2008) that Thailand populations should be treated as O. archeri; such differences can be explained as a result of geographical variability.

Distribution. Australia, South Thailand and Malaysia.