Spot the difference

An as yet undescribed species of Stenetriidae.
Image: Gary Cranitch


25 May 2010
Chad Buxton, from the Museum of Tropical Queensland, is almost certain that he has discovered a new species of marine life.
Chad's focus is on the order of crustaceans called isopods. He specifically studies the Stenetriidae family, which are free-living on coral reefs and are microscopic in size, ranging from two to five millimetres.
"Stenetriidae haven't been particularly well-described on Australian coral reefs, so most of the species that I'm pulling up are likely to be new to science," he says.
Chad has been diving and examining the material from the Autonomous Reef Monitoring Structures (ARMS) to collect isopod specimens. He found the new species in an ARMS sample. Since then, he has also found the same species free-living on the reef.
"The antennae of these particular isopods are banded yellow and clear, and they have a distinct black dot on the posterior region of their dorsal side," he explains.
"They are significantly different from other species I've seen, so I suspect that when I get them back in the lab under a high-powered microscope, I will be able to confirm that they are a new species," he says.
The colouration, banding patterns, dots and speckling is a good indicator of species in some genera of isopod, such as the Joeropsidae studied by Senior Curator at the Museum of Tropical Queensland Dr Niel Bruce, Chad's supervisor and a participant on previous CReefs expeditions.
Although Chad's discovery is based on unique colouration, species in the Stenetriidae family are typically identified by differences in the first pereopod, the first pair of legs or front claws.
"Stemetriium have chelate first legs or claws, and the shape of the claw is a good trait for identifying species: some are narrow, some wide, some have a large hook, and some are very setose, that is, they have a lot of hairs," Chad says.
Chad is endeavouring to establish a more accurate taxonomic categorisation for the Stemetriidae, identifying new species, and tracing the ancestry, evolution, spread and diversification of species. The fossil record of isopods dates back 300 million years.
Chad's participation in this project may also reveal more about the role isopods play in coral reefs. It is thought that they provide a food source for fish, and also help to clean the oceans by feeding on dead fish and other detritus.
"Isopods are widespread and found in large numbers in some parts of the ocean, so they are likely playing an important role in the ecosystem of coral reefs and in the oceans at large," Chad says.
To date, there are more than 10,000 known species of isopod, classified into approximately 100 families. Around half of the known species are found in marine environments.