Ovalona garibiani, Sinev & Dadykin & Định, 2024

Sinev, Artem Y., Dadykin, Ivan A. & Đ ịnh, Nguyên, 2024, A new species of the genus Ovalona Van Damme & Dumont, 2008 (Cladocera: Anomopoda: Chydoridae) from South-East Asia, related to Australian Ovalona archeri (Sars, 1888), Zootaxa 5448 (2), pp. 273-282 : 274-279

publication ID	https://doi.org/ 10.11646/zootaxa.5448.2.7
publication LSID	lsid:zoobank.org:pub:6D86D560-150B-4353-858B-D6E93E809FD4
DOI	https://doi.org/10.5281/zenodo.11237926
persistent identifier	https://treatment.plazi.org/id/9542530D-3C08-FF80-F8F0-1266FA18F9C0
treatment provided by	Plazi
scientific name	Ovalona garibiani
status	sp. nov.

Treatment

Ovalona garibiani sp. nov.

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

Idris, 1983: 110–113, fig. 42 ( Alona cf. karelica ); Maiphae, Pholpunthin & Dumont, 2008: 38, fig 4–5 ( Alona archeri ).

Etymology. The species is named after its collector, our friend and colleague, Russian cladocerologist Dr. Petr Grigorievich Garibian.

Type locality. Water hyacinth bed at channel in Tràm Chin National Park, Dong Thap province, Vietnam (10.690834 N, 105.550008 E), 9 April 2023. Material collected by P.G. Garibian and A. A. Kotov. GoogleMaps

Type material. Holotype. Parthenogenetic female from the type locality, deposited at Zoological Museum of M. V. Lomonosov Moscow State University, Ml –272.

Paratypes. 6 parthenogenetic females from the type locality, deposited at Zoological Museum of M. V. Lomonosov Moscow State University, Ml –273 .

Other material studied. Several parthenogenetic females from the type locality were dissected and subsequently not preserved. Few parthenogenetic females from channels at Tràm Chin National Park, Dong Thap province, Vietnam (at localities 10.681685 N 105.555709 E and 10.685221 N, 105.553588 E) 9 April 2023; material collected by P.G. Garibian and A. A. Kotov. GoogleMaps

Description. Parthenogenetic female. General. In lateral view body regularly-ovoid, of moderate height ( Fig. 1A–B View FIGURE 1 , 2A–B View FIGURE 2 ), maximum height at middle of body, in adults height/length ratio 0.65–0.70. Carapace evenly colored in light yellow to almost transparent. Dorsal margin uniformly curved; postero-dorsal and postero-ventral angles broadly rounded; posterior margin uniformly curved; ventral margin almost straight; antero-ventral angle rounded. Body strongly compressed laterally. Valves with tubercular sculpture in all studied specimens; specimens from Malaysia, reported by Idris (1983), have oblique valves. Ventral margin ( Fig. 1C View FIGURE 1 ) with about 35 setae, about 10 anterior setae long, increasing in length distally; next 10 setae short, posterior setae of moderate length. Postero-ventral angle ( Fig. 1D View FIGURE 1 ) with about 100 short setules not organized in groups. A row of very small setules along the posterior margin on inner side of valve.

Head of moderate size, triangular-round in lateral view, rostrum short, pointing downward. Eye two times larger than ocellus. Distance from tip of rostrum to ocellus in adults slightly greater than that between ocellus and eye. Head shield with a tubercular sculpture, its shape typical of the genus; rostrum short, broadly rounded; posterior margin of head shield broadly rounded, slightly wavy in some specimens. Three major head pores ( Fig. 1E–F View FIGURE 1 ) with very narrow connection between them, middle pore smaller than other two pores; PP about 0.3–0.4 IP. Lateral head pores minute, located at about 0.7–0.8 IP distance from midline, at the level between anterior and median main head pore.

Labrum ( Fig. 1G–H View FIGURE 1 ) of moderate size, labral keel wide (height about 1.2–1.3 widths), with blunt apex; anterior margin of keel almost straight in its middle part, posterior margin without any setulae.

Postabdomen ( Fig. 1I–J, L View FIGURE 1 ) narrow, with parallel margins and strongly prominent dorso-distal angle with a rounded tip, length about 2.5–2.8 height. Ventral margin weakly convex. Distal margin clearly convex. 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. Postabdomen with 3–4 large marginal denticles in distal part, followed by five-six much smaller denticles; length of largest denticles about 1.5 widths of postabdominal claw base. Nine to ten narrow groups of lateral setulae, distalmost setula of each fascicle longer and thicker than others, length of longest distalmost setulae close to 1.5 widths of claw base; distance between groups in postanal portion greater or equal to the width of groups. Postabdominal claw slightly longer than preanal portion of postabdomen. Basal spine straight, thin, about 0.2 length of claw.

Antennule ( Fig. 1K View FIGURE 1 ) of moderate size, length about 2.5 widths, with four clusters of short setulae at anterior face. Antennular sensory seta slender, about 2/3 length of antennula, arising at 2/3 distance from the base. Nine terminal aesthetascs, the longest two about 2/3 length of antennule, others of about 1/3 length of antennule.

Antenna relatively short ( Fig. 3A–B View FIGURE 3 ). Antennal formula, setae 0-0-3/1-1-3, spines 1-0-1/0-0-1. Basipodite robust, branches of moderate length and width, basal segments of both branches 1.5 times longer than others. Basal segment of exopodite massive, almost two times wider than middle segment. Middle segments of both branches almost square in lateral view. Middle segment of endopodite with cluster of long setulae. Seta arising from basal segment of endopodite slightly longer than endopodite. Seta arising from middle segment of endopodite of similar size of shortest apical setae. On both branches, one apical seta much shorter than two others. Spine on basal segment of exopodite as long as the middle segment. Apical spines of similar length as the respective apical segments.

Thoracic limbs: five pairs.

Limb I ( Fig. 3C–E View FIGURE 3 ) of moderate size. Epipodite ovoid. ODL with a long seta, armed with minute setules in distal part. IDL with three setae; seta 3 longer than ODL seta, seta 2 slightly shorter than ODL seta, both armed with thin setules in distal part, seta 1 of about 1/3 length of seta 3. Endite 3 with four setae, inner seta (1) shorter and thinner than outer setae (a,b,d). Endite 2 with three setae (c,e,f), seta e as long as ODL seta, seta f slightly shorter than seta e. Endite 1 with two 2-segmented setae, both setulated in distal part. No inner setae on endites 1–2. Six-seven rows of thin long setules on ventral face of limb. Two ejector hooks of similar size.

Limb II ( Fig. 3F–G View FIGURE 3 ). Exopodite elongated, with seta three-four times shorter than exopodite. Eight scraping setae (1–8), armed with spinules of similar shape, increasing in length distally, scrapers 1–5 long, of similar length, scrapers 6–8 much shorter. Distal armature of gnathobase with four elements. Filter plate with seven setae, the posteriormost seta two times shorter than others.

Limb III ( Fig.3H–I View FIGURE 3 ). Epipodite oval; exopodite subtriangular, with seven setae. Seta 3 being longest, seta 6 about 1/2 length of seta 3, setae 1 and 4 of about 1/3 length of seta 3, other setae short. Seta 6 armed with thick long setules in distal part, seta 7 naked, all other setae plumose. Distal endite with three setae, two distalmost members slender, sharp, of similar length; basalmost seta (3) shorter, bilaterally armed with setules. Inner portion of limb of typical for the genus morphology.

Limb IV ( Fig. 3J–K View FIGURE 3 ). Preepipodite setulated, epipodite with very short process. Exopodite rounded, with six plumose setae. Seta 3 longest, setae 1–2 slightly shorter than seta 3, setae 4, 5 and 6 of 1/3, 2/3 and 1/3 length of seta 3, respectively. Inner-distal portion of limb IV with four setae and small cylindrical sensillum: seta 1 slender, sharp; three flaming-torch setae (2–4) decreasing in size basally, armed with 6–7 short setulae each. Small sensillum near the base of seta 2. Three long inner setae (a–c) long, slightly increasing in size basally. Gnathobase with a bisegmented seta, small sensillum, and a small hillock distally. Filter plate with five setae.

Limb V ( Fig. 3L View FIGURE 3 ). Preepipodite setulated. Epipodite oval, without process. Exopodite oval, with four plumose setae, evenly decreasing in size basally; seta 4 three times shorter than seta 1. Inner limb portion as oval lobe with setulated inner margin, only slightly smaller than exopodite. At inner face, two setae, outer one equal in length to seta 2 of exopodite, inner one shorter. No filter plate.

Ephippial female and male. Unknown.

Size. Length of adult female in studied material was 0.36–0.43 mm, height 0.24–0.3 mm. Length of single studied juvenile female of instar II was 0.28 mm, height 0.17 mm.

Differential diagnosis. Ovalona garibiani sp. nov. belongs to the cambouei -group of Ovalona . It differs from species of the nuragica -group by much smaller size and fully connected head pores, and from species of the setulosa -group by narrow, elongated (length over 2.5 heights) postabdomen (see Sinev 2015b). O. garibiani sp. nov. differs from most species of the cambouei -group by postabdomen with narrow, sparsely spaced lateral group of setulae; distance between postanal groups is slightly greater than group width. This character is shared only by its sibling-species, O. archeri . Within the cambouei -group, O. garibiani sp. nov. clearly differs from O. karelica (Stenroos, 1897) and O. bromelicola (Smirnov, 1988) in a well-developed basal spine of postabdominal claw, from O. aguascalientensis (Sinev & Silva-Briano, 2012) , O. capensis (Rühe, 1921) and O. cambouei (Guerne & Richard, 1983) in completely connected main head pores, and from O. cambouei , O. pulchella King, 1853 and O. glabra (Sars, 1901) in a broadly rounded distal angle of postabdomen, protruding forward above the level of the base of the claw.

O. garibiani sp. nov. differs from O. archeri in the proportions of antennal segments (see Fig. 3M View FIGURE 3 ), O. garibiani sp. nov. have much shorter exopodite and endopodite. Length of basal segment of exopodite is only slightly greater than segment width in O. garibiani sp. nov. and it is about two segments width in O. archeri . Spine of basal segment of antenna exopodite is as long as middle segment in O. garibiani sp. nov. and is much shorter that middle segment in O. archeri . Distal angle of postabdomen protrudes forward over the level of the claw base in O. garibiani sp. nov., but does not protrude over the level of the claw base in O. archeri (see Fig. 1M View FIGURE 1 ). Also, these two species differ in proportions of setae of limbs II and III. The differences between the species are summarized in Table I.