16 November 2010
The worms studied by Dr Anastassya Maiorova are often on the move. The larvae can travel in currents crossing an ocean, and as adults, some species regularly change homes throughout their lives.
Dr Maiorova, a post-doctoral researcher with the Russian Academy of Sciences, is collecting sipunculids, or unsegmented marine worms, on the CReefs expedition.
Many sipunculid species live in the discarded shells of other animals, and move on to larger shells as they grow. Others burrow into sand or bore into rock. Some will even take over coral habitat, tunnelling into the hard structures created by the coral.
One species, Phascolosoma saprophagicum, has only been found living on the flesh of a decomposing whale skull at an ocean depth of about 900 metres.
Dr Maiorova has collected samples of sipunculids from waters around Russia and Vietnam. She also collected sipunculids from depths of 1700 metres in the Sea of Japan during a SoJaBio expedition for the MAR-ECO project of the Census of Marine Life, of which CReefs is also a part.
Dr Maiorova does not expect to discover new species during this field trip on Heron Island.
There are only 160 species of sipunculids all over the world. Mostly they are common and widespread, and few of them are cosmopolitan: the same species will be found in different oceans around the world," Dr Maiorova explains.
"They are constant; their features have not changed in hundreds of millions of years. There have only been two new species discovered in the past 10 years," she says.
Instead, she is interested in the biodiversity of the known sipunculid phylum.
"I am looking for any species which are living here. There are 38 species of sipunculids known from around Australia, and I have found eight species of those here at Heron Island so far," she says.
Dr Maiorova is snorkelling in shallow waters and examining coral rubble from depths of up to 30 metres to collect specimens of sipunculids.
She is also conducting plankton tows: dragging a long, fine-mesh net behind a boat travelling at slow speed to capture plankton from the water column, which Dr Maiorova then examines for larvae.
While some species of sipunculid are able to reproduce asexually, most species produce larvae. Some of the larvae can travel in ocean currents for up to a year. Dr Maiorova says this may be why some species of sipunculids are found throughout the world.