Ovalona nigra ( Smirnov, 1996 ) Smirnov, 1996

Sinev, Artem Y., 2015, Revision of the pulchella - group of Alona s. lato leads to its translocation to Ovalona Van Damme et Dumont, 2008 (Branchiopoda: Anomopoda: Chydoridae), Zootaxa 4044 (4), pp. 451-492 : 461-462

II. Ovalona nigra ( Smirnov, 1996) comb. nov.

( Figs. 5A–H )

Smirnov, 1996, p. 14–15, figs 97–106 ( Alona ); Kotov, Sinev & Berrios, 2011: 33–40, fig. 15–18 ( Alona ).

Type locality. Lake Uru-Uru, Oruro Department, Bolivia (3686 m.a.s.l.).

Type material. Holotype: female MGU NNS 3579. Paratypes: females MGU NNS 3571, 3573, 3574, 3575, 3581, 3587, 3589, 3594, 3595.

Material studied earlier. See Kotov et al. (2011) for the list of material from North Chile.

Diagnosis. Parthenogenetic female. General. Length of adult 0.55–0.65 mm. Body regular oval, of moderate height, height/length ratio about 0.7, maximum height at the middle. Ventral margin with about 55 setae. Posterodorsal angle with about 100 setulae organized into groups of 12–18 setulae in each.

Head. Posterior part of headshield broadly rounded. Three major head pores without connection between them, PP = 0.3–0.5 IP. Lateral head pores minute.

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

Second abdominal segment covered by dense setulae. Postabdomen of moderate width, with almost parallel margins in postanal portion, convex distal margin and broadly rounded dorso-distal angle, length about 2.5–2.6 height. Ventral margin almost straight. Dorsal margin with distal part two times longer than preanal one, with postanal portion about 1.5 times longer than anal one. Postanal portion of distal margin almost straight, anal portion weakly concave. Preanal angle well-defined, postanal angle not defined. Distal margin convex, dorso-distal angle broadly rounded. 11–13 marginal denticles, evenly decreasing in size, and with three-five groups of marginal setulae on anal margin. Eleven-twelve moderately wide lateral fascicles of setulae, distalmost seta of each fascicle largest, in postanal portion, longest setule in each fascicle 1.5 times longer than a marginal denticles. Distance between fascicles in postanal portion less than half width of fascicles. Postabdominal claw slightly longer than preanal portion of postabdomen. Basal spine about 0.2 length of claw.

Antennule with antennular seta of half length of antennule, arising at 2/3 distance from the base. Aesthetascs of different length, two longest of them of about half length of antennule. Antenna with seta arising from basal segment of endopodite longer than endopodite. Spine on basal segment of exopodite longer than middle segment. Spines on apical segments 1.5 times longer than apical segments.

Limb I with accessory seta long and thick, about 2/3 length of ODL seta. Limb III with exopodite seta 3 being longest, setae 6 and 7 about 1/3 and 1/4 length of seta 3, respectively, other setae shorter, seta 4 geniculated. Limb IV with epipodite merged with limb body, without projection. Exopodite seta 3 longest, setae 1, 2 and 5 of about 2/ 3 length of seta 3, setae 4 and 6 of about 1/3 length of seta 4. Flaming-torch setae with well-developed distal portion. Limb V with epipodite merged with limb body, without projection. Exopodite seta 4 three times shorter than seta 1.

Ephippial female. Body subrectangular, dorsal and posterior margins of valves almost straight, postero-dorsal angle expressed, ephippium dark brown, almost black.

Male. Length 0.42 mm. Body low oval, maximum height in the middle of the body, height/length ratio about 0.64.

Postabdomen short and wide, narrowing distally, dorso-distal angle not defined. Length about 2.5 maximum width. Postanal angle not defined, preanal angle weakly-defined. Distal part of postabdomen 1.8 times longer than preanal one, anal and postanal portions of similar length. Gonopores located almost at the end of postabdomen. Postabdominal claw very short, 2.5 times shorter than preanal portion of postabdomen, with blunt apex bearing small spine, basal spine about 0.3 of claw length.

Antenna with male seta arising at 1/4 length from tip, about 1/4 of antenna length. Limb I with IDL seta 1 two times smaller than in female, setae 2 and 3 subequal in length, three times shorter and thinner than in female, male seta large, hook-like, 1.5 times longer than seta 3. A group of five long setulae located under copulatory brush, at some distance of it a row of about 11–12 short, robust setulae on ventral face of limb.

Full description. See Kotov et al. (2010).

Differential diagnosis. O. nigra can be easily differentiated from all other Ovalona species by the densely setulated second abdominal segment and peculiar morphology of male postabdomen. Habitually, it is similar to O. nuragica , but differs from it by minute lateral pores.

Distribution. Saline lakes in Andes of Bolivia and North Chile.

Figures

FIGURE 5. A – H, Ovalona nigra (Smirnov, 1996), from Kotov et al. (2010). A – E, parthenogenetic female. A, lateral view; B, head pores; C, middle segment of abdomen; D, postabdomen; E, postanal margin of postabdomen; F – H, adult male. F, lateral view; G, postabdomen; H, distal portion of postabdomen; I – K, Ovalona altiplana (Kotov, Sinev & Berrios, 2010), from Kotov et al. (2010), parthenogenetic female. I, lateral view; J, head pores; K, postabdomen; L – O, Ovalona anamariae (Sinev & Silvabriano, 2012), from Sinev & Silva-Briano (2012), parthenogenetic female. L, lateral view; M, ventral margin of valves; N, head pores; O, postabdomen.