Acroperus Baird, 1843

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 : 453-457

Acroperus Baird, 1843 .

Parthenogenetic female short description. Body oval, of variable height, head and valves with well-defined keel ( Fig. 5A ). Sculpture of valves as longitudinal lines. Posteroventral angle of valves with several small, closely spaced denticles ( Fig. 5B ). Rostrum triangular in lateral view, with pointed apex. Three main head pores with narrow connection between them, located at widened part of head keel. Lateral head pores minute. Labral keel of moderate width, with rounded apex, without clusters of setulae on posterior margin.

Postabdomen long and narrow ( Fig. 5C ), with parallel margins and prominent, broadly rounded distal angle, length about 4 heights. Preanal angle weakly defined, postanal angle not defined. Postanal denticles very small, in clusters. Postanal lateral groups of setulae long, in distalmost groups length of setulae exceed the width of base of postabdominal claw. Postabdominal claw long, almost straight, with short basal spine. A prominent spine located at middle of claw.

Antennule with a single lateral aesthetasc, this and one of terminal aesthetascs much longer than others. Antennal seta without basal peg. Antenna ( Fig. 5D –E) with thin seta on basal segment of endopodite. Spine on basal segment of exopodite about 1/34 length of middle segment. Spines on apical segments about 1/3 length of apical segments. IDL of limb I with three setae, seta 1 well-developed, seta 2–3 thin, armed with thin setulae.

Taxonomic notes. All early records of Acroperus from the region were attributed to Palearctic Acroperus harpae (see Korovchinsky 2013), but these populations were never studied in detail. S tudied specimens from North-East Thailand have morphology similar to that of recently described from Afrotropical species Acroperus africanus Neretina & Kotov, 2016 , but at the moment presence of of A. harpae in the region cannot be excluded.

These two species can be clearly differentiated by the morphology of apical setae of antenna endopodite. Acroperus is rare in South-East Asia, its populations are found in lakes, associated with vegetation. Idris (1983) did not provide description of antenna for Acroperus harpae , and it is impossible to verify his identification. In book of Maiphae (2014) drawing of Acroperus harpae belongs to male of Disparalona hamata , and drawings of postabdomen and and posteroventral corner of valves, to Camptocercus vietnamnsis Thanh, 1980 .

Figures

FIGURE 5. A – D, Acroperus africanus Neretina & Kotov, 2015. A, lateral view. B, posteroventral corner of valves. C, postabdomen. D, antenna. E, Acroperus harpae (Baird, 1834), antenna. F – I, Alona affinis (Leydig, 1860) s. lato. F, lateral view. G, head pores. H, postabdomen. I, IDL and ODL of limb I. J – M. Alona kotovi Sinev, 2012. J, lateral view. K, head pores. L, postabdomen. M, IDL and ODL of limb I. (A – D, F – I—orig.; E—from Sinev (2009 b); J – M—from Sinev (2012 ))