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Getting marron in the mood

Thursday, 03 May 2018

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An Edith Cowan University researcher is the first to successfully mate WA’s critically endangered Hairy Marron (Cherax tenuimanus) in an aquarium setting.

Masters student Emily Lette from the School of Science has had seven of ten pairs of the crustaceans produce fertilised eggs, offering hope that the WA Department of Primary Industries and Regional Development (DPIRD) will be able to restock them in the wild.

Hairy Marron is found only in the Margaret River, and its numbers have dropped dramatically in the waterway over the past four decades to only about 500.

“A 70 per cent breeding success rate is statistically very positive, as it is what we would expect in the wild,” Ms Lette said.

“There have been attempts to breed Hairy Marron in the Pemberton area, but with limited success to date, so our approach involved considering the differences in the Margaret River and Pemberton systems and what modifications might be made.

“In the lab, we found marron in warmer temperatures mated sooner than those in colder tanks, which suggests the water conditions could be hampering breeding.”

However, some Hairy Marron females have abandoned their eggs, indicating other factors also need to be explored.

Competition with other species

The Hairy Marron’s decline in the Margaret River is due largely to the incursion of its more common sister species, the Smooth Marron (Cherax cainii), which was introduced to the waterway in the 1980s.

“We don’t know why the Smooth Marron have become dominant, but we suspect that it is because they spawn earlier and so their young have an advantage,” Ms Lette said.

The Hairy Marron have also likely been affected by illegal poaching.

“If you consider there are only about 500 animals in the wild, a few nets can really affect population numbers,” Ms Lette said.

Next steps: hormones

The next phase of the research involves working with ECU’s Centre for Integrative Metabolomics and Computational Biology to look at hormone levels, particularly methyl farnesoate.

“Methyl farnesoate has never been tested in marron, but is known to indicate mating readiness in other crustaceans,” Ms Lette says.

They’re also investigating metabolites, molecules essential to the metabolic process.

“Metabolites are sensitive to changes in environment, so they can tell us what is happening at a physiological level,” Ms Lette says.

“Adopting a metabolomics approach could be valuable as it might indicate whether environmental factors such as temperature do explain the lack of reproductive success.”

Ms Lette’s research is part of the DPIRD-led Hairy Marron Recovery Team’s larger program, which is focussed on captive breeding, establishment of new populations and stabilising the species’ decline in the wild.

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