Euryalona Sars, 1901

Sinev, Artem Y., 2016, Key for identification of Cladocera of the subfamily Aloninae (Anomopoda: Chydoridae) from South-East Asia, Zootaxa 4200 (4), pp. 451-486 : 469

Euryalona Sars, 1901

Parthenogenetic female short description. Body rounded, with convex posterior margin, head and valves without keel ( Fig. 10A ). Valves without sculpture. Posteroventral angle of valves without denticles. Rostrum short, truncated. Main single head pore as rounded rimmed field; lateral head pores as elongated slits ( Fig. 10B ). Labral keel of moderate width, with rounded apex and without clusters of setulae on posterior margin.

Postabdomen long, curved, narrowing distally in postanal portion, with prominent distal angle with rounded tip; length about 4.5–5.5 heights ( Fig. 10C ). Preanal angle and postanal angles well-defined. Postanal denticles large, numerous; length of distalmost denticles over 2 widths of postabdominal claw base ( Fig.10D ). Postanal lateral groups of setulae of moderate length; in distalmost groups, length of setulae about the width of base of postabdominal claw. Postabdominal claw long, weakly curved, with short basal spine.

Antennule without lateral aesthetasc; all terminal aesthetascs of similar length. Antennal seta arising from well-defined tubercule. Antenna with thin seta on basal segment of endopodite ( Fig. 10E ). Spine on basal segment of exopodite about half length of middle segment. Spines on apical segments about 1/4 length of apical segments. IDL of limb I with three setae; seta 1 short; seta 2 of moderate size, armed with strong spinulae; seta 3 very large and thick, hook-like.

Single species, Euryalona orientalis (Daday, 1898) ( Fig. 10A–E ). Length of adult 0.8–1.1 mm. Common in the region. Littoral species, associated with vegetation. Species presumed to be pantropical ( Rajapaksa & Fernando 1987b). For detailed description see Rajapaksa and Fernando (1987b) and Van Damme & Maiphae (2013).

Figures

FIGURE 10. A – E. Euryalona orientalis (Daday, 1898). A, lateral view. B, head pores. C, postabdomen. D, postanal margin of postabdomen. E, antenna. F, IDL of limb I. F – H, Flavalona costata (Sars, 1862). F, lateral view. G, head pores. H, postabdomen. I, Flavalona cheni (Sinev, 1999), head pores. J – L. Graptoleberis testudinaria (Fischer, 1851), J, lateral view. K, posteroventral corner of valves. L, postabdomen. (A – E, J – L, orig.; F – H, from Sinev et al., 2015; I, from Sinev (1999 )).