Maggots, crabs and crazy ants - welcome to Stuart Linton's world

Wed, 13 Aug 2008 13:03:00 +1000

On cold, damp winter's days in Victoria, there would be plenty of people all over the state whose minds would wander to warm, tropical paradises.

Few though have the undeniable excuse to take that mental holiday available to Deakin University's Dr Stuart Linton. A lecturer and researcher in the School of Life and Environmental Science, Dr Linton has been working to help ensure a better understanding - even the survival - of Christmas Island's fabled terrestrial red crab, a.k.a. Gecarcoidea natalis. Famous for its annual breeding migration and unique for the way it digests its food, in recent times the crab has fallen prey to an introduced species from Africa, the Yellow crazy ant. The newcomer is believed to have already killed 20 million of the island's estimated population of 120 million red crabs.

"I have been working with Australia Parks, testing something that we hoped would kill the crazy ant, but not do any harm to the crab," Dr Linton said.

"Unfortunately, my research so far reveals that the proposed substance would harm both, so the search goes on." Finding a way to curb the Yellow crazy ant is not the only research Dr Linton is doing involving the red crab whose breeding migration ritual annually turns parts of Christmas Island into a vast, moving red carpet.

He is keen to learn more about the unique digestive system that allows the crabs to extract nutrition from fallen leaf matter.

 

crab crossing road
crabs crossing road

 

"It's an amazing sight when the migration happens," Dr Linton says. "The crab is taken as part of the furniture by the people who live on Christmas Island because it literally does during the migration, wander through people homes.

"The locals have become a lot more interactive in recent times in making sure the crabs make it to the sea which is good.

"My main interest though is in their digestive systems, work I am doing through funding from the Hermon Slade Foundation, founded by George Hermon Slade who believed that "if there is a way better than another, it is the way of nature".

For the crabs, the way of nature allows them to not just survive but thrive on what appears like a poor diet, rotting leaf matter on the rainforest floor.

"They are the kings of rainforest, that's for sure," says Dr Linton.

"What we have discovered is that the crabs have developed a highly successful digestive process to extract the cellulose and hemicellulose from the plant fibre, thus obtaining a substantial energy source.

"What is still not known is just how they achieve that.

"Cellulose and hemicellulose digestion requires two steps. The first step involves mechanical digestion in which the cellulose fibres are broken up mechanically. Animals possess mandibles and gastric mills within their stomachs to do this. How this process aids in cellulose digestion is not known.

"We think that it reduces the size of the cellulose fibres, solubilises individual cellulose molecules and provides more sites for the second digestive step, enzymatic attack.

"The first part of our project involves examining the anatomy and function of the gastric mill using light and electron miscroscopy. "We think the gastric mills will have tooth like structures that are specifically adapted to grind hard fibrous leaf material.

"We will also look to see just what sort of enzymes the crabs are producing for the second stage of breaking down all this leaf matter. "This project will give us a better understanding of how animals are able to digest cellulose and hemicellulose. It will also give us an insight into how herbivorous crabs are able to efficiently digest leaf matter, a better understanding of how nature does things better." Maggots enter Dr Linton's colourful research life through his interest in forensic medicine and a collaboration involving fellow Deakin scientists Dr Tes Toop, Dr Paul Francis, Dr Melanie Archer and also Professor Michael O'Donnell from McMaster University in Canada. The title of their project is: Digestive physiology of morphine ingestion in forensically important blowflies.

 

red crab
red crab

 

"We have been looking at the impact that heroin has on maggots," he explains.

"The life cycle of flies elsewhere in the world has been used to determine the date and time of death of human beings.

"We want to be able to use the same system here in Australia, so we need to know what impact the existence of morphine in a body might have on the development of the Victorian bush blow-fly if we are going to be able to predict when a drug addict might have died. "Even though they are living in a very toxic environment, our research seems to be indicating that the drug doesn't impact on the growth of the maggot. That provides a handy tool for forensic science.

"We are also looking at how the maggot excretes the drug from its body."

Originally from Sydney, Dr Linton was drawn to Deakin as an institution where research was considered important.

He was also attracted to the intimacy of working in a smaller university, and the ability to be able to live so close to where he works. Well close to where he works except for the times when those thoughts of the swaying palms of Dolly Beach and the march of the red crabs turn into something more real – a trip deep into the Indian Ocean to that place where it's Christmas every day and never winter.

To view footage of the annual red crab migration, visit: www.youtube.com/watch?v=LhsuyhhkO34&feature=related

For more information about Christmas Island National Park: www.environment.gov.au/parks/christmas/index.html


Stuart Linton with red crab
Stuart Linton with red crab
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20th August 2012