December 30, 2009
A RARE barnacle found only in Bass Strait is the oldest of the species, as well as one of its most unique members, according to researchers who came across the crustacean by a lucky accident.
The tiny ibliform barnacle, which is just 2.5 millimetres long, dates back to the Paleozoic era, about 300 million years ago.
That means the ibliform barnacle pre-dates all other types of barnacles and gives researchers a clue as to how the species evolved.
''Their earliest forms evolved from Bass Strait and the Tasman Sea,'' said John Buckeridge, professor of natural resources engineering at RMIT University.
And unlike most barnacles, which rely on shells and camouflage to protect them from predators, Professor Buckeridge said the cream-coloured barnacle used the toxic substance bromine, collected from sea water, to make itself unpalatable to predators such as carnivorous snails, small fish and crustaceans.
The ibliform, however, has an incomplete shell that does not cover the barnacle's lower, vulnerable areas where the bromine-heavy parts are mostly concentrated.
Professor Buckeridge's research with RMIT research fellow Jessica Reeves, published this month in the journal Integrative Zoology, found up to 7 per cent of some parts of its body is bromine.
''That's a remarkably high percentage,'' Professor Buckeridge said. ''It's much higher than anything else I've ever seen apart from an algae, also found in Bass Strait. It would be more than unpalatable, it would be poisonous.''
He said there was only one other type of barnacle, the deep sea tetrachaelasma found in waters off Madagascar, which had bromine in its body.
''The shells of these ibliform are made of the same stuff as our teeth. It's a primitive feature not found in modern barnacles,'' Professor Buckeridge said.
The ibliform barnacle, which was recognised as a new species in 2006, is so rare that scientists have only six specimens.
It was found by accident after fishermen delivered a coral-like substance to Museum Victoria, not realising there was a barnacle attached.