Ovalona pulchella (King, 1983)

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: 483-485

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Ovalona pulchella (King, 1983)

comb. nov.

XVII. Ovalona pulchella (King, 1983)  comb. nov.

( Figs. 11View FIGURE 11. A – C D –N).

King, 1853: 260, pl VIII ( Alona  ); Sars, 1988: 59–62, Fig 5–6View FIGURE 5. A – HView FIGURE 6. A – E ( Alona laevissima  ); Smirnov, 1971: 373, Fig 442 ( Alona  ), Fig. 444–446 ( Alona cambouei  ); Smirnov & Timms, 1983: 41–43, Fig 42 ( Alona cambouei  ), 49, Fig. 56 ( Alona  ); Sinev 2001 b: 9–13, Fig. 1View FIGURE 1 –33 ( Alona  ).

Type locality. Varroville, near Denham Court, St. Leonards, near Sydney.

Type material. Non-existent.

Material studied earlier. See Sinev (2001 b) for the list of material from Australia.

Material studied here. 12 parthenogenetic females, 1 adult male from White's lagoon near Turnbridge, Tasmania, Australia, 12.10. 1972, coll. N. N. Smirnov.

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. Ventral margin with about 40–45 setae. Posterodorsal angle with 50–70 setulae not organized into groups.

Head. Posterior part of headshield broadly rounded, notched or wavy. Three major head pores connected between them, PP = 0.45–0.55 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; in Tasmanian populations, postabdomen somewhat shorter. Distal margin straight; dorso-distal angle prominent, acute with rounded tip. Dorsal margin with distal part about 1.7–2 times longer than preanal one; postanal part 1.5 longer than anal one. Postanal portion of distal margin almost straight; anal portion weakly concave. Preanal angle well-defined, postanal angle weakly defined. 8–10 marginal denticles, evenly decreasing in size basally and with 3–5 groups of marginal setulae on anal margin. Eight-ten wide lateral fascicles of setulae; in postanal portion, longest setule in each fascicle 1.2 times longer than marginal denticles. Postabdominal claw as long as preanal portion of postabdomen. Basal spine about 0.25–0.3 length of claw.

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

Antenna with seta arising from basal segment of endopodite reaching the end of endopodite. Spine on basal segment of exopodite slightly shorter than middle segment. Spines on apical segments slightly longer than apical segments.

Limb I with accessory seta about 1 / 4 length of ODL seta. Limb III with exopodite seta 3 being longest; setae 4 and 6 about 1 / 3 and 1 / 2 length of seta 3, respectively; other setae shorter. Limb IV with epipodite with very short projection. Exopodite seta 3 longest; setae 1 slightly shorter than seta 3; seta 2 about 2 / 3 length of seta 3; seta 5 about 1 / 2 length of seta 3; setae 4 and 6 shorter than seta 5. Flaming-torch setae with reduced distal portion. Limb V with epipodite with short projection. Exopodite seta 4 four times shorter than seta 1.

Ephippial female. Unknown.

Adult male. Unknown for populations from continental Australia.

Tasmanian populations of O. pulchella  . Studied populations of O. pulchella  from Tasmania did not differ from O. pulchella  from Australia in general morphology ( Fig. 11View FIGURE 11. A – C G), morphology of head pores ( Fig. 11View FIGURE 11. A – C H) and any appendages, but have shorter postabdomen ( Fig. 11View FIGURE 11. A – C I), with length about 2.6–2.7 heights. There were no significant differences between Australian and Tasmanian populations in the armament of postabdomen and in the morphology of postabdominal claw. Such differences should be treated as geographical variability. A single male was found in one population; description is provided below.

General. Body ( Fig. 11View FIGURE 11. A – C J) low oval, height/length ratio about 0.55. Eye larger than in female, ocellus smaller than eye.

Postabdomen ( Fig. 11View FIGURE 11. A – C K) short, slightly narrowing distally. Gonopores located at the end of postabdomen, above the base of claw. Distal margin straight, distal angle obtuse, rounded. Preanal angle well-defined, postanal angle not defined. Distal part of postabdomen almost 1.5 times longer than preanal; anal and postanal portions of similar length. Wide clusters of short setulae in place of marginal denticles. Lateral fascicles of setulae same as in female. Postabdominal claw two times shorter than in female, basal spine very long, about 0.5 of claw length.

Antennule ( Fig. 11View FIGURE 11. A – C L) broad, length about two widths. Ten terminal and two lateral aesthetascs, longest terminal aesthetascs are of 3 / 4 length of antennule, lateral aesthetascs about half length of antennule. Male seta arising at 1 / 4 length from tip, reaching to the end of antennule.

Limb I ( Fig. 11View FIGURE 11. A – C M –N) with U-shaped copulatory hook, its distal portion little longer than basal one. A group of 3 long setulae under copulatory brush, at some distance under it a row of about 20 short thick setulae on ventral face of limb. IDL seta 1 absent, setae 2 and 3 thin, of similar length, male seta curved, shorter than seta 3.

Full description. See Sinev (2001 b).

Differential diagnosis. O. pulchella  is a sibling-species to O. cambouei  and O. glabra  . It differs from O. cambouei  by connected head pores, and from O. glabra  by notched posterior margin of head shield and by the shape and armament of male postabdomen; in O. glabra  it has rectangular distal part and long marginal setulae.

Taxonomic notes. During XX century, Alona pulchella  was reported from Central and South America, Africa and Tropical Asia, but all these records belongs to either Ovalona glabra  (in America) or O. cambouei  (in Old World) ( Sinev, 2001 b, present data). There are no reliable records of O. pulchella  outside of Australia. Revealed here differences in postabdomen morphology between populations from continental Australia and Tasmania are not enough to support independent status of the latter, but male is unknown for the Australian populations of the species. Future studies of Australian Ovalona  are needed to clarify the status of Tasmanian populations. Distribution. Australia and Tasmania.