Coronatella

Sinev, Artem Y. & Kotov, Alexey A., 2012, New and rare Aloninae (Cladocera: Anomopoda: Chydoridae) from Indochina, Zootaxa 3334, pp. 1-28 : 23-26

Coronatella sp.

Material studied. A single adult parthenogenetic female from, a big pond Bung Jod in "Phoenix" factory, Khon Kaen Province Thailand, 11.04.2003, coll. A. A. Kotov, N. Phukman, sample not saved; a juvenile female from the Ping River, Chiang Mai Province, Thailand, 22.03.2003, coll. L. Sanoamuang.

Description. Parthenogenetic female. In lateral view body low oval ( Fig.12 A, 13A, E), maximum height at the middle of body, length/height ratio about 0.58. Dorsal margin curved, postero-dorsal and postero-ventral angles broadly rounded. Posterior margin convex. Postero-ventral corner of valves with about 15 small setules ( Fig.12 B). A row of about 80 setules, consisting of alternating very long and short setules along posterior margin at some distance from one on inner side of carapace. Ventral margin almost straight, with about 40 setae, first ten setae long, next ten setae very short, setae in posterior portion of margin as long as anterior setae. Valves without distinctive sculpture.

Head ( Fig. 13 D, H) triangle-round in lateral view. Eye and ocellus large, of similar size. Rostrum elongated, with rounded tip ( Fig.12 D). Two main head pores with narrow connection between them ( Fig. 13 B), lateral pores without cosmaria. Labrum relatively small, with narrow oval keel.

Thorax two times longer than abdomen.

Postabdomen ( Fig. 12 C, 13C, G) elongated, with parallel margins, length about 2.3–2.4 height. Ventral margin weakly convex. Distal margin convex, distal angle rounded. Dorsal margin straight in postanal part and convex in anal part, with distal part about 2.3 times longer than preanal one, with postanal portion two times longer than anal one. Preanal and postanal angles well-defined. Preanal margin weakly concave. Postabdomen provided with 6 clusters of 2–3 very small margina denticles on postanal margin, and with 4 groups of marginal spinules on anal margin. Eleven lateral fascicles of setules, posteriormost setae of postanal fascicles very thick and long, in distal fascicles about 3 width of claw base. Postabdominal claw weakly curved, thin, longer than preanal margin of postabdomen. Basal spine very short, less than 0.1 length of claw itself.

Antennule ( Fig. 12 D) relatively small, not reaching the tip of rostrum by far. Antennular seta thin, of about half length of antennule, arising at 2/3 distance from the base; a cluster of long setules located near its base. Nine terminal aestetascs of similar size, about half length of antennules. All aesthetascs not reaching the tip of rostrum.

Antenna relatively short and massive ( Fig. 12 E, 13F), antennal formula setae 0-0-3/1-1-3, spines 1-0-1/0-0-1. Basal segment robust, with cluster of long setules. Branches relatively short, with basal segments 1.5 times longer and more massive than middle and apical segments. Setae arising from basal segment of endopodite short, not reaching the end of endopodite. Setae arising from middle segment of endopodite of same size with apical setae. Spine on basal segment of exopodite 1.3–1.4 times longer than middle segment. Spines on apical segments 1.5 times longer than apical segments segment. Basal and middle segments of exopodite with clusters of long hard setules in distal portion.

Thoracic limbs: five pairs, limb VI not found.

Limb I ( Fig. 12 F–G). Epipodite small, rounded. Accessory seta about 1/3 length of ODL seta. IDL with two setae (2 and 3), both of them long, slender, armed with long setules distally, seta 3 about 3/4 length of ODL seta, seta 2 about 2/3 length of ODL seta. Endite 3 with four setae, seta (c) significantly longer and thicker than others. On endite 2 there are three setae of different length, middle of them (e) as long as ODL seta. Endite 1 with two 2- segmented setae (g–h), and a flat seta (i) shifted to the limb base. Both endite 1 and 2 with rudimentary naked setae on anterior face. Five rows of long setules on ventral face of limb. Two ejector hooks, one of them 1.5 times longer than the other.

Limb II with eight scraping spines, spines 6 thicker and shorter than neighbours.

Limb III ( Fig. 9 H). Exopodite small, rounded, with six setae. Seta 3 longest, seta 4 and 5 about 1/3 and 1/2 length of seta 3, respectively, other setae short. Setae 1–4 plumose, setae 5 with with short thick setules in distal part, seta 6 naked. Distal endite with 3 setae, two distalmost setae scraping, slender, sharp, with spinules in distal part, seta 1 1.5 times longer than seta 2, basalmost seta (3) short, flattened.

Limb IV. Exopodite rounded, with six setae, seta 3 being longest. Setae 1–4 long, plumose. Inner portion of limb IV ( Fig. 12 I) with only three setae, a scraper (1) and two flaming torch setae (2–3), and a sensillum. Both flaming-torch setae broad, with short distal part 3 times larger than others. Three soft setae (a–c) ( Fig.12 J), increasing in size basally, seta c very large. Gnathobase with a long 2-segmented seta and a large projection distally. Filter plate present.

Limb V ( Fig. 12 K). Pre-epipodite setulated. Epipodite oval, without finger-like projection. Exopodite oval, not subdivided into two lobes, with four plumose setae. Setae 1–3 long, evenly decreasing in size basally, seta 4 short, 4 times shorter than seta 1. Inner lobe broad oval, with setulated inner margin. At inner face, two setae, one equal in length to seta 2 of exopodite, other 2.5 times shorter. No filter plate.

Ephippial female and male. Not known.

Size: length of juvenile female was 0.33 mm; length of adult female 0.38 mm.

Distribution. So far known from North-West and North-East Tahiland.

Taxonomic notes. Studied specimens obviously belong to an undescribed new species, but the inadequate material keeps us from making a full description. This taxon can be formally placed into Coronatella , as it shares most diagnostic features of the genus, as defined by Van Damme & Dumont (2008). But it has some interesting unique and rare features: rectangular postabdomen; very long and thin postabdominal claw; strongly developed lateral fascicles of setae on postabdomen, resembling these of Anthalona; cluster of long setules near the base of antennal seta, never observed within Aloninae ; very long and thin IDL setae; only two flaming-torch setae on the limb IV (as in the genus Karualona and Anthalona brandorffi (Sinev & Hollwedel 2002)) . Probably, this species even belongs to a new genus.

Figures

FIGURE 9. Celsinotum macronyx, parthenogenetic female from a paddy field II, near Phitsanulok, foodplain of the River Nan, Phitsanulok Province, Thailand: A – D, specimen in lateral, anterior, antero-ventral and dorsal views. E, head pores. F, head, ventral view. G, postabdomen. H, postabdominal claw. I, distal portion of limb I. Scale bars, A – D, 0.1 mm; E – I, 0.01 mm.

FIGURE 12. Coronatella sp., juvenile female from Ping River, Chiang Mai Province, Thailand. A, lateral view. B, postroventral corner of valves. C, postabdomen. D, antennule and outline of rostrum. E, antenna. F, limb I. G, IDL and ODL of limb I. H, exopodite of limb III. I – J, inner portion of limb IV and its soft setae. K, limb V. Scale bars, A: 0.1 mm; D – K: 0.01 mm.

FIGURE 13. Coronatella sp. from Thailand. A – D, adult parthenogenetic female from a big pond Bung Jod, " Phoenix " factory, Khon Kaen Province. A, lateral view. B, main head pores. C, postabdomen. D, head. E – H, juvenile female from Ping River, Chiang Mai Province. E, lateral view. F, antenna. G, postabdomen. H, head. No scale bars were taken during photographing.