Alona floessneri, Sinev, Artem Y., Alonso, Miguel & Sheveleva, Natalia G., 2009

Sinev, Artem Y., Alonso, Miguel & Sheveleva, Natalia G., 2009, New species of Alona from South-East Russia and Mongolia related to Alona salina Alonso, 1996 (Cladocera: Anomopoda: Chydoridae), Zootaxa 2326, pp. 1-23 : 10-15

Alona floessneri sp. nov.

( Figs. 5–8 )

Etymology. The species is named after German cladocerologist Dietrich Flössner.

Type locality. Uvs Nuur (Nuur = lake), Uvs aimag, north-west Mongolia –Russian border, 50º06’55”N, 92º24’25”E.

Holotype. parthenogenetic female, preserved in 80% ethanol, deposited at ZMOU, Ml-79.

Paratypes. 18 parthenogenetic females from type, preserved in 80% ethanol, deposited at ZMOU, Ml-80. 20 parthenogenetic females, 5 gamogenetic females and 8 males from lake Khar Nuur, Hövsgöl aimag, North –central Mongolia. (49º23’38”N, 98º25’19”E), preserved in 80% ethanol, deposited at the first author personal collection in Institute for Ecology and Evolution, Moscow.

Diagnosis.

Female. Of moderate size, length up to 0.56 mm. Body irregular oval, of moderate height, height /length ratio about 0.70–0.74, maximum height in the middle of the body. Whole carapace covered by narrow longitudinal lines. Head shield with broadly rounded posterior margin, rostrum short and rounded. Three narrowly connected major head pores, central pore located at the middle between other pores. PP about 0.8– 0.9 IP. Lateral head pores dot-like, located at 1.0–1.2 IP distance from midline. Labral keel suboval, with rounded apex, without clusters of setules on posterior margin.

Postabdomen of moderate width (length about 2.5–2.6 height), with almost parallel margins and broadly rounded dorsodistal angle. Dorsal margin with distal part about 1.9–2.2 times longer than preanal one, with postanal portion 1.4–1.6 times longer than anal. Preanal angle moderately prominent, an incursion in place of postanal angle. Postanal portion of dorsal margin convex, anal portion almost straight. Eight–ten clusters of small marginal denticles along preanal margin, decreasing in size basally, and 3 wide clusters of very short setules on anal margin. About 10 lateral fascicles of setules along dorsal margin; 6 fascicles in postanal portion very wide, with setules 2 time longer than marginal denticles. All setules in fascicles of similar width. Postabdominal claw of moderate length, slightly longer than preanal portion of postabdomen. Basal spine long and thin, about 1/3 of length of claw.

Antennula with 9 terminal aesthetascs, longest of them of about half length of antennula. Antennal formula, setae 0-0-3/1-1-3, spines 1-0-1/0-0-1. Seta arising from basal segment of endopodite as long as endopodite. Spine on basal segment of exopodite shorter than middle segment. Spine from apical segment of exopodite slightly shorter than this segment. Apical spine of endopodite of same length as this segment.

Limb I with very long accessory seta, IDL of limb I with three setae, IDL seta 1 very small, two others armed with short setules distally. Exopodite of limb II with very small seta, scraping spines not differentiated. Exopodite of limb III with six setae, seta 3 being longest, seta 4 three times shorter than seta 5. Exopodite IV with 6 setae, setae 4 and 6 of exopodite IV about 2/3 length of seta 5. Exopodite V with 4 setae, filter plate I consist of single seta. Epipodites IV and V without projections. Limb VI absent.

Male. Body regular oval, of moderate height, height/length ratio about 0.66–0.70, maximum height at the middle of the body. Postabdomen short, with narrowing anal portion, subrectangular postanal portion, and a distinct bulk at ventrodistal portion of postabdomen.. Dorsodistal angle not defined. Sperm duct openings located almost at the end of postabdomen. Clusters of short setules in place of marginal denticles, lateral fascicles of setules same as in female. Postabdominal claw 1.5 times shorter than that of female, basal spine 2 times shorter than in female.

Antennule with 10 terminal and 2 lateral aesthetascs. Male seta arising at 1/4 length from tip, about 1/3 of antennule length. Thoracic limb I with U-shaped copulatory hook, IDL seta 1 absent, setae 2 and 3 subequal in length, male seta thick, curved, as long as seta 3.

Description.

Parthenogenetic female. General: In lateral view body irregular oval, moderately high ( Fig. 5 A–B, 6A– D). Maximum height in the middle of the body. In adults height/length ratio about 0.70–0.74. Dorsal margin arched, without any depression at the border of valves and head shield. Posterodorsal and posteroventral angles broadly rounded. Posterior margin almost straight. Posterodorsal angle with about 100 setules of equal size, reaching almost to the middle of the posterior margin of valves. A row of about 110 smaller setules along the posterior margin ( Fig. 5 D, 6E) at some distance from it on inner side of carapace. Ventral setae as in previous species ( Fig. 5 C). Anteroventral angle rounded. Whole carapace covered by narrow longitudinal lines ( Fig. 6 A–D). Head as in previous species.

Head shield with gently poligonal sculpture ( Fig. 6 A–C)). Head pores ( Fig. 6 F, 7A–B) and labrum ( Fig. 7 C–E) as in previous species.

Postabdomen ( Fig. 5 F–G, 6G–H) of moderate width, weakly narrowing in postanal portion, with broadly rounded dorso-distal angle. Length about 2.5–2.6 height. Ventral margin almost straight. Incursion between basis of claws and distal margin unclear. Distal margin weakly convex. Dorsal margin with distal part about 1.9–2.2 times longer than preanal one, with postanal portion 1.4–1.6 times longer than anal. Preanal angle well defined, postanal angle as clear incursion. Postanal portion of dorsal margin convex, anal portion almost straight. Preanal margin almost straight. Eight-ten clusters of small marginal denticles along preanal margin, decreasing in size basally, and 3 wide clusters of very short setules on anal margin. A row of about 10 lateral fascicles of setules along dorsal margin; 6 fascicles in postanal portion very wide, with setules 2 times longer than marginal denticles, fascicles in anal portion 2 times shorter, of similar width. All setules in fascicles of similar width. Additional fascicles of setules located above the main row in anal portion. Postabdominal claw of moderate length, slightly shorter than preanal portion of postabdomen. Basal spine long and thin, about 1/3 of length of claw.

Antennule similar to that of the previous species ( Fig. 7 F), but broader, height/width ratio about 2.5. Antenna as in the previous species ( Fig. 6 I, 7G).

Thoracic limbs: five pairs. Limb I as in previous species ( Fig. 7 H–I), but setae of endite III clearly differentiated in size. Limb II as in previous species ( Fig. 7 J). Limb III as in previous species ( Fig. 7 K–M), but seta 5 of exopodite armed with small, thin setules. Limb IV as in previous species ( Fig. 7 N–O), but setae 6 and 4 of exopodite considerable shorter in comparison with seta 5. Limb V as in previous species ( Fig. 7 P).

Ephippial female ( Fig.8 A) similar in shape to parthenogenetic female, body height/body length: 0.66– 0.70. Carapace in contact with ventral border of ephippium with polygons in place of longitudinal striae. Ephippium dark brown. Ocellus of same size as eye or slightly larger.

Male. General shape of adult male ( Fig. 8 B) regularly oval, with convex posterior margin, body height/ body length = 0.66–0.70. Ocellus and eye of same size as in parthenogenetic female.

Postabdomen ( Fig. 8 C–D) short, with narrowing anal portion. Postanal portion subrectangular with distinct ventrodistal bulge. Dorso-distal angle not defined. Preanal and postanal angles well defined. Distal part of postabdomen 1.1 times longer than preanal. Sperm ducts opening ventrally at the end of postabdomen, very close to base of claws.

Clusters of short setules in place of marginal denticles, lateral fascicles of setules same as in female. Postabdominal claw 1.8 times shorter than that of ephippial female, basal spine 3 times shorter than claw.

Antennule ( Fig. 8 E) and thoracic limb I ( Figs 8 F–H) as in previous species.

Size: adult females, length 0.43–0.55 mm, height 0.30–0.35 mm. Ephippial females, length 0.45–0.57 mm, height 0.30–0.38 mm. Males, length 0.34–0.37 mm, height 0.24–0.25 mm.

Remarks. Alona floessneri sp. n. differs from A. irinae sp. n. in body shape, with almost straight posterior margin, in sculpture of the carapace, composed of narrow longitudinal lines, in peculiar shape of the male and female postabdomen, in presence of short groups of distal marginal denticles of female postabdomen, and in shorter setae 4 and 6 of exopodite IV. Alona floessneri sp. n. differs from A. salina in the morphology of the lateral fascicles of setules of postabdomen, in IDL morphology, in the shape of male postabdomen, and in its smaller size. Differences between these species are summarized in Table 1 .

Distribution and ecology. A. floessneri sp. nov. has a wide distribution in saline and subsaline water bodies in Mongolia, which supports the idea that it can appear in similar environments in other Asian countries.

In Mongolia this species is known from Uvs Nuur (85), Kholboo Nuur (109: 45º15’11.9”N, 114º06’45.5”E), Sumiin Bulagriin Nuur (139: 49º08’39”N, 114º52’28.6”E), Khar Nuur (215) and Zuun Khooloi Nuur (309: 47º17’52.3”N, 92º43’53.0”E). In brackets reference numbers and coordinates of the sampling sites in the website http://www.geodata.es/mongolian_lakes where further information and pictures of the water bodies can be seen.

Uvs Nuur is a large (361459 hectares) permanent mesotrophic alkaline salt lake with salinity about 13 g /l, Na/Mg/Cl/SO4 type, pH about 9.0 ( Flössner et al., 2005), and water electrical conductivity of 29400 μS/cm. Macrophytes are scarce. We presume that the species was already reported from this lake by Flössner et al. (2005) as Alona elegans , together with other two halobiont crustaceans, the cladoceran Moina salina Daday, 1888 , and the calanoid Arctodiaptomus salinus (Daday, 1885) . The presence of Alona elegans sensu stricto in the lake is quite improbable, since it is a freshwater species, never reported from saline water ( Alonso 1996; Flössner 2000).

Zuun Khooloi Nuur is a shallow, permanent, 773 hectare playa lake. Water is mesotrophic and highly mineralised (10300 μS/cm) and alkaline (pH 9.1). Accompanying halobiont crustacean species were the cladoceran Moina salina and the calanoid Metadiaptomus asiaticus (Ul’yanin 1875), together with the halotolerant Daphnia magna Straus, 1820 .

Kholboo Nuur (149 hectares and 8120 μS/cm), Sumiin Bulagriin Nuur (1,700 hectares and 7200 μS/cm), and Khar nuur (7 hectares and 13300 μS/cm) are shallow permanent or semi permanent lakes. As in the previous ones, water is highly mineralised but also very turbid because of suspended clay particles. The crustacean community in these lakes is as well characterized by halobiont and halo-tolerant species, namely the calanoid Arctodiaptomus rectispinosus Kikuchi, 1940 , Daphnia magna and Moina brachiata (Jurine, 1820) in Kholboo; M. brachiata in S. Bulagriin; Daphnia triquetra G.O.Sars, 1903 , M. brachiata and the calanoid Metadiaptomus asiaticus in Khar.

Figures

FIGURE 5. Alona floessneri sp. nov., Uvs Nuur lake, parthenogenetic female: A – B—lateral view. C—ventral margin of valve. D—posterio-ventral angle of valve. E—head shield. F – G—postabdomen. Scale bars: 0.1 mm for A-B, E and C, 0.05 mm for D, F-G.

FIGURE 6. Alona floessneri sp. nov., Uvs Nuur lake, parthenogenetic female: A – B—lateral view. C – D—anteroventral and dorsoventral view. E—posteroventral angle of valve. F—head pores. G – H—postabdomen. I—antenna. Scale bars: 0.1 mm for A – D; 0.02 mm for G – I; 0.01 mm for E – F.

FIGURE 7. Alona floessneri sp. nov., Uvs Nuur lake, parthenogenetic female: A – B—head pores. C – E—labrum. Fantennula. G—antenna. H – I—limb I and its ODL and IDL. J—limb II. K – M—exopodite and inner portion of limb III. N – O—exopodite and inner portion of limb IV. P—limb V. Scale bars: 0.1 mm for C – E, G; 0.05 mm for A – B, F, H – P.

FIGURE 8. Alona flossneri sp. nov., Khar Nuur lake, gamogenetic individuals. A—ephippial female. B – H—adult male: B—lateral view, C – D—postabdomen, E—antennula, F – H—general view, inner portion and endite 3 of limb I. Scale bars: 0.1 mm for A – B; 0.05 mm for C – H.