A steady hand
22 May 2010
The creatures that occupy the time of the Museum of Tropical Queensland's Chad Buxton are not easy to find – they're less than five millimetres in length and transparent.
Chad's group of study is an order of crustaceans called isopods. Isopods range in size from 300 micrometres to nearly 50 centimetres in the case of the species, Bathynomus giganteus.
Chad's focus is specifically the family Stenetriidae, which live freely on coral reefs in the Indo-Pacific, and typically measure from one to five millimetres in size.
In order to find Stenetriidae on this CReefs expedition Chad SCUBA dives, looking for reef areas with high-energy and clear water and that have complex reef structures such as coral rubble with holes or pores that provide hiding places for small animals. He brings chunks of these structures back to the sheep-shearing shed (the makeshift research lab on Ningaloo) where he breaks up the structures and adds formalin to the sea water to agitate the isopods out from their hiding spots. He then strains the water through a very fine mesh net up to 15 times, rinsing the net into a sample jar each time, before examining the sample under a microscope.
Only at this point does he know if he has found Stenetriidae.
Chad performs a rough classification in the field laboratory at Ningaloo Station, but when he takes the specimens back to his home laboratory, he will use a compound microscope (and sometimes high-powered scanning electron microscopy) to identify the isopods.
And then he will dissect them.
"We need to create our own needles from tungsten wire and dissect isopods under a dissecting microscope. The needles I am currently using were a gift from Michitaka Shimomura, an isopod expert from Japan," Chad explains.
"Under the microscope, I can examine, for example, the fine detail of setae, the hairs on a claw of a creature that itself might be only three millimetres in size. I have to dissect the isopod legs and even the reproductive structures which are so small they would fit on a pinhead. It's time-consuming and technical work. You have to be very careful and have a steady hand," he says.
Chad is working on an Australian Biological Resources Study grant to study isopods at the Museum of Tropical Queensland in Townsville and is currently pursuing his PhD at James Cook University.