Ovalona, Van Damme & Dumont, 2008

Damme, Kay Van & Dumont, Henri J., 2008, Further division of Alona Baird, 1843: separation and position of Coronatella Dybowski & Grochowski and Ovalona gen. n. (Crustacea: Cladocera), Zootaxa 1960 (1), pp. 1-44 : 3-4

Genus Ovalona gen.nov.

Type species. Ovalona weinecki ( Studer, 1878) = Alona weinecki Studer, 1878

Etymology. Ovalona (from “ovo-”, “egg” and Alona ) refers to the relatively ovoid habitus of species of the weinecki- complex.

Diagnosis. The genus Ovalona consists of medium-sized (0.5–0.8mm) Aloninae with ovoid body, arched, no posteroventral notch on valves, three main head pores and simple or transverse small pores, wedge-shaped labrum with naked keel (no ventral setules), first antenna with short aesthetascs, second antenna with thick and well developed first endopod seta. Postabdomen relatively short and robust with deep preanal portion and short, unmerged marginal denticles. Five pairs of limbs. P1 with reduced anterior elements and IDL with three setae, P2 with exopodite seta reduced to absent, fcII with seven setae of which first not markedly short, no additional soft setae near scraper 1, P3 with seven setae in exopodite of which third longest, fcIII with seven setae, P4 with six exopodite setae of which last two not narrowed, fcIV with five long setae, P5 with four exopodite setae, ovalround inner lobe and reduced gnathobase (0–1 setae).

Description. Adult parthenogenetic female. Body globular, highly arched in lateral view, broad in dorsal view, with convex ventral margin, deepest point in middle; medium-sized alonines (0.55–0.8 mm). Head with short blunt rostrum, three main head pores and two small pores lacking additional structures. Carapace lacking a dorsal keel, ornamentation variable; posteroventral corner rounded, no notch; marginal setae decreasing gradually in length towards posteroventral corner, row ending at corner (not far before); these setae followed by fine spinules, continuing close to margin. Postabdomen broad, two times as long as wide, with expanded deep preanal corner; postanal margin and anal margin of similar length (anal may be longer than postanal); well developed sharp preanal angle; postanal margin convex and anal margin concave; marginal denticles consisting of unmerged groups of small spines; lateral fascicles short slender spines, of which posteriormost may be little longer but not strongly different in thickness. Terminal claw about as long or longer than anal margin, curved. Basal spine as long as or longer than claw width at base. First antenna about two times as long as wide, with sensory seta implanted between 1/3–1/2d from apex; nine apical aesthetascs varying in length, much shorter than antennular corm. Second antenna with spinal formula 001/101 (these spines strongly developed) and setal formula 113/003. First endopod seta on antenna relatively thick and long; a group of narrow spinules on external side of second exopod segment. Labrum relatively long and wedge- shaped, with straight to concave labral keel and roundly obtuse ventral tip; lateral bulges at base; keel naked, lacking setules. First maxilla with two thick, setulated setae. Five pairs of limbs. First limb. First endite with two ( weinecki ) or three ( meridionalis ) marginal setae, second endite with three setae of which one much longer than others, third endite with four setae of similar length; anterior elements on en1–2 strongly reduced to absent. ODL with one slender seta, IDL with three setae, third seta naked; armature of IDL setae fine long setules. Accessory seta present. Anteriorly on corm, six to seven setule groups with more than six fine setules in each group; setules in each group do not decrease in size ventrally. Ejector hooks relatively small and of similar size; epipodite round, with or without long projection. Gnathobase a single setulated seta. Second limb. Exopodite with reduced seta (absent in weinecki ); endites with eight scrapers of which first five long, slender and with fine denticles, last three shorter and with relatively stronger denticles; gnathobasic ‘brush’ short round, gnathobase with a sensillum and three modified elements, filter comb with seven setae of which the first thicker and brushlike. Third limb. Exopodite with rectangular corm and seven long setae in 2+5 arrangement (if elegans would be included, diagnosis should read six or seven setae); third exopodite seta longest, fourth and fifth long, fifth and sixth setae with mixed (pappose and plumose) setulation. External endite with three setae (1’–3’) of which first two scraper-like and with minute element in between; four well developed plumose setae on inner side (1”–4”); one element and four small setulated setae on internal endite preceding gnathobase; gnathobase with a bottle-shaped sensillum and large plumose seta with two naked elements at its base. Filter comb with seven long setae. Fourth limb. Epipodite oval-round, with or without short projection. Exopodite square, with six plumose setae of which third relatively longest and fifth and sixth setae of similar thickness than others. Endite with marginal row of four setae, first scraper-like, longer than ft setae; three flaming torch setae about as thick as wide, decreasing in size towards gnathobase, and one marginal round naked sensillum on this margin; gnathobase with one long setae, bent over endite and two reduced naked elements; on inner side, three well developed plumose setae and a filter comb with five setae. Fifth limb. Epipodite oval round, with or without short projection. Exopodite shape oval-rectangular, with straight to slightly concave margin between setae three and four; four exopodite setae, of which first longest, about as long as exopodite itself and oriented dorsally; inner lobe elongated oval, with long terminal setules; two thick endite setae (1’–2’) of which first longer than second and bent over inner lobe; behind second endite seta, a small element; gnV with 0–1 setae. Adult male with clear sexual dimorphic postabdomen with gonopores opening ventrally, subapical to terminal claw; marginal denticles consisting of unmerged groups of setules. Male IDL with three setae; thick copulatory hook with terminal rugae.

Species. Two valid species, possibly a third. Ovalona weinecki ( Studer, 1878) comb. nov. and Ovalona meridionalis ( Sinev, 2006) comb. nov. Status of Alona subantarctica Ekman, 1905 , a possible third species of Ovalona , is unclear.