Water fleas

Code OG999999

See Key to Families of Australian Aquatic Crustacea

An order of Crustacea (with segmented, chitin-encased body and articulated appendages). The Cladocera are placed with the orders Conchostraca, Anacostraca and Notostraca in the Branchiopoda (with segmented, chitin-encased body and articulated appendages). Cladocerans are distinguished by the bivalved carapace that typically encloses the trunk and appendages -as in conchostracans, but which leaves the head protruding. The head is often somewhat triangular in shape, with a distinct eye. The first antennae are single-branched (uniramous) and the second two-branched (biramous). Within the carapace the trunk is free, comprising a thorax bearing 4-5 pairs of legs and the abdomen ends in a claw-less furca.

Cladocerans inhabit most inland waters (a few are marine), where many species can undergo parthenogenesis. Many cladocerans move by swimming with the second antennae - others crawl using antennae and other appendages. Cladocerans are filter feeders and scrapers.

The Australian fauna comprises the families Sidiidae, Chydoridae, Macrothricidae, Moinidae, Bosminidae, Daphniidae and Ilyocryptidae.

SIDIIDAE (Code OG019999) lack the long fused antenna of Bosminidae and Chydoridae, with a large head, feathery antenna and setose valve margin, and some species may have a well-developed rostrum.

CHYDORIDAE (Code OG039999) are small sized (less than 0.5mm), hemispherical-shape in lateral view, and the partial or complete obscuring of the first antenna by the rostrum. The Australian fauna, which comprises 82 described species in 28 genera, is the continent's most diverse cladoceran family. The taxonomy is in need of further study despite the revision of Smirnov and Timms (1983). Shiel (1995) provides a key to the species of the genus Chydorus .

MACROTHRICIDAE (Code OG069999) lack the long fused antenna of Bosminidae and Chydoridae, lack any rostrum, and have a distinctive postabdomen without any basal spines behind the terminal claw. Shiel (1995) keys the four genera from Australian inland waters.

MOINIDAE (Code OG079999) lack the long fused antenna of Bosminidae and Chydoridae, lack any rostrum, and have a distinctive postabdomen with a bifurcate tooth just behind the terminal claw. There are two genera of Moinidae in Australia: Moina and Moinodaphnia , both predominantly planktonic. Shiel (1995) keys the genera and species from Australian inland waters.

BOSMINIDAE (Code OG029999) are small sized (less than 0.5mm), hemispherical-shape in lateral view, and the fusion of the elongate first antenna to the head. The Bosminidae in Australia comprises the genera Bosmina and Bosminopsis , each with one described species, which probably under-represents the diversity. Bosimina meridionalis is a common species in south-east Australia, Bosminopsis dietersi appears to be more tropical, extending as far south as Sydney. Korinek, in Smirnov and Timms (1983), keys the known Australian bosminids.

DAPHNIIDAE (Code OG049999) lack the long fused antenna of Bosminidae and Chydoridae. Some daphniids are distinguished by the acute angle or spine at the posteroventral corner of the carapace. Those taxa that lack this projection have a distinct but small rostrum. Daphniids are common inhabitants of the plankton and littoral zones of standing waters of all kinds. They function as grazers of bacteria and zooplankton, and provide a major food resource for young fish. Shiel (1995) provides a key to the five genera, and notes and species-level keys to several taxa.

ILYOCRYPTIDAE (Code OG059999) lack the long fused antenna of Bosminidae and Chydoridae, lack any rostrum, and have a distinctive postabdomen with numerous fine teeth behind the terminal claw. The family comprises a single genus, Ilyocryptus , comprising an unknown number of species.

References:

Korovchinsky, N.M. (1992) The Sidiidae and Holopediidae (Crustacea: Daphniiformes). Guides to the Identification of the Microinvertebrates of the Continental Waters of the World. 3 : 1-82. SPB Academic Publishers, The Hague.

Shiel, R.J. (1995) A Guide to Identification of Rotifers, Cladocerans and Copepods from Australian Inland Waters . Co-operative Research Centre for Freshwater Ecology Identification Guide No. 3., Albury, NSW.

Smirnov, N.N. and Timms, B.V. (1983) Revision of the Australian Cladocera (Crustacea). Records of the Australian Museum Supplement 1 : 1-132.