A review of the biology of Australian halophilic anostracans (Branchiopoda: Anostraca)

Brian Timms

Australia has two species of Artemia: A. franciscana introduced to salt works and apparently not spreading, and parthenogenetic Artemia presently spreading widely through southwestern Australia. In addition, and unique to Australia, there are 18 described species of Parartemia in hypersaline lakes. All Parartemia use a lock and key mechanism in amplexus and hence have distinctive antennal-head features in males and thoracic modifications in females. Various factors, including climatic fluctuations and isolation, contribute to a far higher diversity in the southwest of the continent. There are few congeneric occurrences of Parartemia possibly due to their consuming largely uniform allochthonous organic matter rather than multisized planktonic algae. In P. zietziana there are 2-3 cohorts a year each persisting 3-9 months. Up to 80% of assimilation is used in respiration and at times energy balance is negative, which accounts for its continuous mortality, inconsistent growth rates and unpredictable recruitment. Many species are as osmotically competent as Artemia, but are at a disadvantage in hypersaline waters >250 g L(-1) as they lack the haemoglobin of Artemia. Parartemia acidiphila and P. contracta live in markedly acid waters to pH 3.5, where dissolved carbonate and bicarbonate are unavailable, and hence they must have evolved an additional proton pump to produce ATP from endogenous CO2. Occurrences of some species have been severely curtailed by lake salinisation (which includes acidification and changes in hydroperiod), so that their continued existence is in doubt. A few species of the otherwise freshwater Branchinella occur in mainly hyposaline waters.