Image from Slovak Caves Administration.

The crustacean Superorder Syncarida is composed of only two, strictly-fresh (and brackish) water orders: Anaspidacea and Bathynellacea. Anaspidaceans are represented by 21 species (12 genera) in Australia and the Neotropics. The order is absent from North America. There are 219 species (66 genera) of bathnellaceans worldwide, but only 12 (2 genera) in North America (Camacho & Valdecasas, 2008).

Bathynellaceans have the three crustacean body tagmata: head, thorax, and abdomen. Importantly, they possess the 5-8-6 arrangement of segments presumed to be plesiomorphic to malacostracans but modified in better known taxa (e.g., decapods, isopods, amphipods). That is, the head has five appendages (antennules, antennae, mandibles, 1st and 2nd maxillae), and the thorax has 8 pereopods (none are modified as maxillipeds). The pleopods (= abdominal appendages) are much reduced. As interstitial crustaceans, bathynellaceans are in the μm-mm size range.

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Bibliography

• Covich, A.P., J.H. Thorp & D.C. Rogers. 2010. Introduction to the Subphylum Crustacea. [in] J.H. Thorp & A.P. Covich (eds.). Ecology and Classification of North American Freshwater Invertebrates, 3rd edition: 695-723.
• Camacho, A.I. & A.G. Valdecasas. 2008. Global diversity of syncarids (Syncarida; Crustacea) in freshwater. Hydrobiologia 595: 257-266. [Available online]
• Smith, D.G. 2001. Minor Malacostraca. Pennak's Freshwater Invertebrates of the United States, 4th edition: 545-551.

Web Pages

• Integrated Taxonomic Information System
• WikiSpecies
• Wikipedia
• World Register of Marine Species