USE OF X-RAY IMAGES AND A CONTRASTING AGENT TO STUDY THE BEHAVIOR OF ANIMALS IN SOFT SEDIMENTS

We developed a means of observing and recording the burrowing behavior of animals in soft sediments by using X-ray images. The poor contrast between animal burrows and sediment was compensated for by the additi on to sediment of a dense inert compound, molybdenum carbide. This con trasting agent allowed us to quantify the development in space and ove r time of burrows made by a variety of small animals, as well as to de termine the exact location and orientation of animals in a burrow syst em. Nymphs of the mayfly Hexagenia are confirmed to be very active bur rowers in comparison with other sympatric insect taxa and are thus lik ely to be key animals in influencing community irrigation and bioturba tion rates. The considerable variation observed in the depth of burrow s constructed by various taxa could influence their potential exposure to vertically stratified food particles and sedimentary contaminants. We also used the contrasting agent in the held to demonstrate that bu rrow structures could be observed in situ. The radiographic technique we tested should be useful in determining the influence of animals on the physics and chemistry of sedimentary deposits. as well as the impa ct of sedimentary contaminants on the burrowing and feeding of benthic animals in either marine or freshwater systems.