Ovalona nuragica ( Margaritora, 1971 )

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: 456-461

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Ovalona nuragica ( Margaritora, 1971 )

comb. nov.

I. Ovalona nuragica ( Margaritora, 1971)  comb. nov.

( Figs. 1–4View FIGURE 1View FIGURE 2View FIGURE 3View FIGURE 4)

Margaritora, 1971: 11–18 ( Alona  ); 1985: 310–313, figs 122, 123 ( Alona  ); Crosetti & Margaritora, 1985: 268–276, figs 3, 4 ( Alona  ); Alonso, 1996: 325–327, fig. 145 ( Alona  ).

Type locality Serra Orrios, Nuoro, Sardegna ( Italy).

Type material. Holotype. A female at Istituto di Zoologia dell’Universita di Roma.

Material studied: over 100 parthenogenetic and ephippial females, 8 adult males from small temporary pond near Laguna de Bonache, near Siles town, Jaem, Spain, 22.04. 1998, coll. by Maria Sahuquillo.

Description. The species was never completely described, so a full description is provided. Parthenogenetic female. General. In lateral view body regularly oval, of moderate height ( Fig. 1View FIGURE 1 A –D, 2 A), maximum height at middle of body, in adults height/length ratio 0.64–0.68. Dorsal margin uniformly curved; postero-dorsal and postero-ventral angles broadly rounded; posterior margin uniformly curved; ventral margin almost straight; anteroventral angle rounded. Body moderately compressed laterally ( Fig. 2View FIGURE 2 B).Valves oblique. Ventral margin ( Fig. 1View FIGURE 1 E) with about 45–60 setae; about 10 first setae long, next 15 setae short, followed by plumose setae, in middle portion of the valves almost as long as setae of anterior group ( Fig. 1View FIGURE 1 F), decreasing in size posteriorly. Distalmost setae located at posteroventral angle of valves ( Fig. 1View FIGURE 1 G), not before it, as usual for the genus. Postero-ventral angle after the last seta bears about hundred short setulae not organized in groups. A row of very small setulae along the posterior margin on inner side of valve.

Head of moderate size, triangle-round in lateral view, rostrum short, pointing downward. Eye larger than ocellus. Distance from tip of rostrum to ocellus in adults slightly greater than that between ocellus and eye. Headshield with maximum width behind mandibular articulation, without any sculpture; rostrum short, broadly rounded; posterior margin of head shield broadly rounded. Three major head pores ( Fig. 1View FIGURE 1 I, 2 C –D) as small rimmed cavities, without any connection between them, PP about 0.3 IP. Lateral head pores ( Fig. 1View FIGURE 1 I, 2 C, E) as small rounded cavities, located at about 1 IP distance from midline, at the level of middle major head pore.

Labrum ( Fig. 3View FIGURE 3 A) of moderate size, labral keel wide (height about 1.5 width), with broadly rounded apex; anterior margin of keel convex, in some specimens with bulge in the middle; posterior margin without any setulae.

Postabdomen ( Fig. 3View FIGURE 3 B) of moderate width, narrowing in postanal portion, length about 2.5 height. Ventral margin straight. Basis of claws separated from distal margin by clear incision. Distal margin straight, distal angle rounded, weakly prominent. Dorsal margin with distal part about 2 times longer than preanal one, with postanal portion 1.5 times longer than anal. Postanal portion of distal margin straight, anal portion weakly concave. Preanal angle well-defined, postanal angle weakly defined. Postabdomen with 12–14 short slender marginal denticles of similar size ( Fig. 3View FIGURE 3 C), most with one-two additional spinules near base of denticle, and with three-four groups of marginal setulae in basal part anal margin. 12–14 lateral fascicles of setulae, postanal fascicles narrow, consisting of 4–6 setulae, with distalmost seta much longer and thicker than others, longer than marginal denticles. Several additional fascicles above the main row in anal portion. Postabdominal claw ( Fig. 3View FIGURE 3 D) weakly curved, slightly shorter than preanal portion of postabdomen. Basal spine about 0.2 length of claw.

Antennule ( Fig. 3View FIGURE 3 E) of moderate size, length about 2.5 widths, with three clusters of long setulae at anterior face and three clusters of setae laterally. Antennular sensory seta slender, about 3 / 4 length of antennula, arising at 2 / 3 distance from the base. Nine terminal aesthetascs of similar length, longest of them about 2 / 3 length of antennula.

Antenna II relatively short ( Fig. 3View FIGURE 3 F –G). Antennal formula, setae 0– 0–3 / 1 – 1–3, spines 1 – 0–1 /0– 0–1. Basal segment robust, branches of moderate length and width; basal segments of both branches 1.5 times longer than others. Basal and middle segments of endopodite with clusters of long setulae. Seta arising from basal segment of endopodite of same length as endopodite. Seta arising from middle segment of endopodite of similar size as apical setae. Spine on basal segment of exopodite slightly shorter than middle segment. Apical spines slightly longer than apical segments.

Thoracic limbs: five pairs.

Limb I ( Figs. 4View FIGURE 4 A –B) of moderate size. Epipodite ovoid. Accessory seta about 1 / 3 length of ODL seta. ODL with a long seta, armed with minute setulae in distal part. IDL with three setae and two-three clusters of small setulae; setae 2 and 3 only slightly shorter than ODL seta, armed with thin setulae in distal part; seta 1 of about 1 / 3 length of seta 3. Endite 3 with four setae, inner seta (1) shorter than outer setae (a –c). Endite 2 with three setae (d – f) and minute sensillum; seta “e long, longer than ODL, seta “f about 2 / 3 length of seta “e. Endite 1 with two 2 - segmented setae, both setulated in distal part, and minute sensillum. No inner setae on endites 1–2. Six rows of thin long setulae on ventral face of limb. Two ejector hooks of similar size.

Limb II ( Fig. 3View FIGURE 3 H –I). Exopodite elongated, with very short seta. Eight scraping setae (1–8), armed with spinules of similar shape, increasing in length distally. Distal armature of gnathobase with four elements. Filter plate with seven setae, the posteriormost seta three times shorter than others.

Limb III ( Fig. 4View FIGURE 4 C –D). Epipodite oval; exopodite subrectangular, with seven setae. Seta 3 being longest; seta 6 about 1 / 3 length of seta 3; setae 1, 4 and 7 of about 1 / 4 length of seta 3; other setae short. Seta 6 armed with thick long setulae in distal part, seta 7 naked, all other setae plumose. Distal endite with three setae, two distalmost members slender, sharp, with distal parts unilaterally armed with sharp denticles; basalmost seta much shorter, bilaterally armed with setulae. Basal endite with four stiff setae, increasing in size towards the base; a small sensillum near the base of distalmost seta. Four soft setae increasing in size basally (a –d). Gnathobase not clearly separated from basal endite. Distal armature of gnathobase with four elements: an elongated, cylindrical sensillum, a thin, bent seta, and two sharp spines. Filter plate III with seven setae.

Limb IV ( Fig. 4View FIGURE 4 D –E). Preepipodite setulated, epipodite with process as long as epipodite itself. Exopodite subquadrangular, with six setae. Seta 3 longest; setae 1–2 slightly shorter than seta 3; setae 4, 5 and 6 of 1 /3, 1/ 2 and 1 / 3 length of seta 3, respectively. Setae 1–4 plumose; on setae 3–4 setulae on distal part much shorter than on basal part; seta 5–6 with long setulae unilaterally. Inner-distal portion of limb IV with four setae and small cylindrical sensillum: seta 1 slender, sharp; three flaming-torch setae (2–4) with well-developed distal part, armed with about 10 long setulae each, decreasing in size basally. Three inner setae (a –c) long, increasing in size basally. Gnathobase with a short 2 -segmented seta, only little longer than seta 1, and a small hillock distally. Filter plate with five setae.

Limb V ( Fig. 3View FIGURE 3 J). Preepipodite setulated. Epipodite oval, with process as long as epipodite itself. Exopodite oval, with four plumose setae, decreasing in size basally; seta 4 four times shorter than seta 1. Inner limb portion as rounded lobe with setulated inner margin, only slightly smaller than exopodite. At inner face, two setae, outer one equal in length to seta 1 of exopodite, inner one 2 times shorter. No filter plate.

Ephippial female. Body ( Fig. 1View FIGURE 1 J, 2 F) as in parthenogenetic female. Ephippium yellow-brown, covered by broad lines and tubercules.

Male. Body of adult male ( Fig. 1View FIGURE 1 K) oval, lower than in female, height/length ratio about 0.6.

Eye and ocellus smaller than in female, eye larger than ocellus.

Postabdomen ( Fig. 3View FIGURE 3 K –L) similar in shape to that of female. Gonopores located ventrally close to end of postabdomen. Distal margin convex, distal angle broadly rounded. Preanal angle well-defined, postanal angle weakly defined. Distal part of postabdomen almost two 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 as in female. Postabdominal claw shorter and thicker than in female, basal spine long, about 1 / 3 of claw length.

Antennule ( Fig. 3View FIGURE 3 M) broad, length about two widths. Ten terminal and two lateral aesthetascs; longest terminal and lateral aesthetascs are of 3 / 4 length of antennule. Male seta short, arising at 1 / 4 length from tip, less than 1 / 5 of antennule length.

Limb I ( Fig. 4View FIGURE 4 F) more massive than in female, copulatory hook U-shaped, its distal portion 1.5 times longer than basal one. A group of about 7 long setulae under copulatory brush, at some distance under it a row of about 15 short thick setulae on ventral face of limb. Endite 3 more broad than in female; its seta 1 much thinner and longer than in female, longer than setae a –c; clusters of short thick setulae near its base. IDL seta 1 reduced to small stub; setae 2 and 3 thinner and three times shorter than in female, male seta large, hook-like, 1.5 times longer than seta 3.

Size. Females. In studied material, in juvenile female of instar I length 0.38–0.45 mm, in instar II juvenile female length 0.48–0.51 mm, in adult female 0.54–0.7 mm. Males. Length 0.42–0.44 mm.

Morphological abnormalities. A parthenogenetic female with abnormal morphology of thoracic limbs was found in the studied material. It had three ejector hooks ( Fig. 4View FIGURE 4 G) and three setae on endite 1 ( Fig. 4View FIGURE 4 H) of both thoracic limbs I. On one of limbs III, inner portion had additional soft seta (d 1), but distal endite was of normal morphology ( Fig. 4View FIGURE 4 I), on the other distal endite had additional scraping seta (1 a) and additional sensillum, but number of soft setae was normal (four) ( Fig. 4View FIGURE 4 J). On both limbs IV, inner portion had additional flaming-torch seta (4 a) and additional soft seta (c 1) ( Fig. 4View FIGURE 4 K). Morphology of limbs II and V was normal.

Differential diagnosis. O. nuragica  differs from all other Ovalona  by the unique morphology of its lateral head pores, shaped as small rounded cavities.

Distribution. Temporary waters of the West Mediterranean.