Alona costata

Sinev, Artem Yu, 2008, A new species related to Alona costata Sars, 1862 (Cladocera: Anomopoda: Chydoridae) from South Africa, Zootaxa 1707, pp. 23-36 : 34

Key for the world fauna of the Alona costata -group

1. Distal angle of postabdomen obtuse, with clearly defined tip .......................... A. weltneri Keilhack, 1900

- Distal angle of postabdomen acute or with broadly rounded apex ............................................................ 2

2. Three major head pores, distance between the anterior major head pore and the central one much smaller than between the central one and the posterior one. Subterrain species ............... A. bessei Dumont, 1983

- Three major head pores, distance between the anterior major head pore and the central one equal or greater than distance between the central one and the posterior one, or two major head pores ................ 3

3. - Lateral head pores long, length exceed 0.5 IP. Distal angle of postabdomen acute. ( costata -branch) ...... 4

- Lateral head pores short, length about 1/3 IP. Distal angle of postabdomen rounded. ( rustica -branch) ... 7

4. - Lateral head pores pockets deep, rounded, depth about 1–2 pore length .................................................. 5

- Lateral head pores pockets shallow, depth about 1/3 pore length ............................................................. 6

5. - Two major head pore. .......................................................................................... A. setigera Brehm, 1931

- Three major head pores .............................................................................................. A. costata Sars, 1862

6. - Sculpture of valves as weak longitudinal striae or hexagons. P6 narrow, length about 3 maximal width ... ..................................................................................................................................... A. cheni Sinev, 1999

- Sculpture of valves as dense, broad longitudinal ridges. P6 broad, length about 2 maximal width ............. ....................................................................................................................................... A. natalensis sp. n.

7. Anterior margin of labrum with one–two denticles .................................................. A. bicolor Frey, 1965

- Anterior margin of labrum without denticle .............................................................................................. 8

8. - Length of adult female up to 0.7 mm. Exopodite V with five setae ............................................................. ........................................................................... A. hudeci Sinev, 1999 (syn. A. rusticoides Hudec, 1998 ).

- Length of adult female not exceeding 0.52 mm. Exopodite V with four setae ......................................... 9

9. - Central major head pore located closer to the posterior one. Epipodites IV–V with finger-like projections longer than epipodite body itself. Exopodite V subdivided into two lobes .................................................. ............................................................... A. iheringula Kotov et Sinev, 2004 (syn. A. iheringi Sars, 1901 )

- Central major head pore located at the middle between anterior and posterior pores. Epipodites IV–V without finger-like projections. Exopodite V not subdivided into two lobes ........... A. rustica Scott, 1901