Alona subantarctica Ekman, 1905

Damme, Kay Van & Dumont, Henri J., 2008, Further division of Alona Baird, 1843: separation and position of Coronatella Dybowski & Grochowski and Ovalona gen. n. (Crustacea: Cladocera), Zootaxa 1960 (1), pp. 1-44 : 37-38

Comment on Alona subantarctica Ekman, 1905 .

Alona populations from islands of the Scotia Arc previously identified as weinecki may belong to a different species. The occurrence of weinecki sensu lato includes two different biogeogeographic provinces, the Maritime Antarctic and the Sub-Antarctic (see Pugh et al. 2002) and these may contain two species. The Scotia Arc comprises South Sandwich, South Orkney, South Shetland Islands and South Georgia, together with the Antarctic Peninsula. Populations described in this paper are closer in origin to the “true” weinecki described from Kerguelen by Studer (1878). Also Rühe (1914) and Frey (1988) indicate some differences, yet treat all as weinecki . Our populations of Ovalona weinecki from Heard Island, which lies just south of Kerguelen, correspond to the same species as those from Marion and we think these are true weinecki . Paggi (op. cit.) brought subtle differences to our attention between the specimens he studied from Deception Island, South Shetlands (depicted in Paggi 1987) and ‘true’ weinecki . For example, Deception specimens show differences in P2 (seventh seta longer than eight instead of shorter for weinecki ) and second antenna (length of apical endopod spine, longer in eastern populations). Also, marginal denticles in postanal portion of the postabdomen seem relatively longer in western specimens (see Paggi 1987; Frey 1988). Frey (1988) noted that A. weinecki in the eastern islands is likely not the same as in the western islands. Specimens from Kerguelen may be different from the populations he revised from South Georgia (from Ekman’s and Sars’ material; Ekman 1905; Sars 1909). Yet, like most authors, Frey (1988) synonymized the “western” Alona subantarctica Ekman, 1905 with “eastern” Alona weinecki Studer, 1878 .

Originally described as Alona bukobensis var. subantarctica by Ekman (1905), these ‘subantarctic’ populations are unrelated to bukobensis , which belongs to Coronatella (see above). Raised to species level by Sars (1909), subantarctica was frequently synonymized with weinecki (e.g., Rühe 1914; Frey 1988). The name subantarctica is available if differences between the western populations and true weinecki are of (sub)species level. Exact type locality of Alona subantarctica is unclear, types derive from South Georgia ( Frey 1988) or the Falklands ( Kotov and Gololobova 2005), but in any case originate from the western subantarctic. Pesta (1928) described another Alona from subantarctic South Georgia, Alona inermis Pesta, 1928 . Suggested as a member of Armatalona by Sinev (2004b), we regard it here as an Ovalona due to 1. similarities in postabdomen and 2. its origin. It is likely a synonym of A. subantarctica (listed as synonym of A. weinecki in Pugh et al. 2002). Material of A. subantarctica is available in the collections of Sars (1909), Ekman (1905) and Frey (1988) but detailed study was beyond the scope of this paper. New collections of the western populations, from South Georgia, Falklands and South Shetlands may be useful for comparison.

To conclude, O. subantarctica Ekman, 1905 may be a valid (sub)species, not simply a synonym of O. weinecki as currently accepted. For now, both O. subantarctica and O. weinecki can be considered as part of Ovalona weinecki sensu lato, pending revision.