Cadmium and lead concentrations were compared in tissues of cutlassfish, Trichiurus lepturus L., its intestinal nematode Hysterothylacium sp. type MB larvae, and in water from the same location in the Sea of Oman. Metal accumulation in hosts, parasites and sea water was measured by ICP-OES. Hysterothylacium larvae from the intestinal lumen and visceral cavity showed much higher metal concentrations than in host tissues or sea water. Statistical analyses revealed no significant differences in metal accumulation between infected and uninfected hosts. Cadmium concentration in the host muscle was lower than in intestine, liver and gonad tissues. The mean concentrations of lead and cadmium in nematodes were 289·03 and 81·5 times higher than in host intestine, 188·4 and 225 times higher than in host muscle, 108·6 and 65·3 times higher than in host gonads, 70·5 and 19·5 times higher than in host liver and 3351 and 148 times higher than in sea water. The results show the value of this and possibly related nematodes as bioindicators of heavy metals and their potential use in environmental studies.

Freshwater ostracodes from the Northern Territory and the Kimberleys, Western Australia, are described. They comprise 17 species of which 6 are new: Cyprinotus kimberleyensis, Zsocypris williamsi, "Strandesia" dorsoviridis, Candonocypris Jitzroyi, Cypretta baylyi, and Cypretta lutea. The ostracodes include the first records from Australia of Isocypris, Strandesia, and Heinicypris, and exhibit affinities with those of eastern Australia, Indonesia, and South Africa.

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Cladograrns resemble directed Prim networks or Wagner trees, and are usually programmed by parsimony, i.e. the program searches for the least number of steps to achieve a cladistic synthesis. Large matrices can yield an almost infinite number of possible trees; and even when differences of only a few steps are involved there are numerous plausible solutions. Parsimony and other factors, such as Nelson and Platnick's assumptions, act as Occam's razor, reducing these to a manageable few.