The evolution of worms


Dr Patricia Hutchings collecting polychaetes.
Image: Gary Cranitch.

 

9 September 2010
 
Research undertaken on the CReefs Lizard Island expedition could contribute to new discoveries about the 600-million-year history of evolution of the most common and widespread group of marine invertebrates.
 
Dr Pat Hutchings, a Senior Principal Research Scientist at the Australian Museum in Sydney, is part of a team of researchers focusing on the segmented, invertebrate marine worms known as polychaetes, as part of the CReefs project.
She has been studying polychaetes for more than 40 years, and the CReefs project ties into ongoing research.
 
The researchers are working to establish a baseline for the diversity of the group and describe new genera and species, as well as to better understand the evolution, distribution and biodiversity of these animals.
 
"Our research is looking at the relationships between the different polychaete families, and where the polychaetes came from," says Dr Hutchings.
 
"Polychaetes are segmented, as are crustaceans, and for a long time science assumed the two groups were closely related. We have since discovered that polychaetes are much more closely related, in the evolutionary sense, to molluscs than to crustaceans," she says.
 
The polychaete research team uses a combination of morphology (the study of shape, colours, structure and anatomy) and molecular biology, including DNA analyses, to classify species.
 
The researchers also consider the fossil record of polychaetes.
 
"Not all polychaetes leave fossils, because they are soft-bodied, but there are examples dating back to the Cambrian period 600 million years ago," Dr Hutchings says.
 
"There are 80-odd families and, in evolutionary terms, they seem to form clusters. We're trying to work out how the clusters are related to each other, bearing in mind that there may have been families that had evolved that have since died out," she explains.
 
Polychaetes as currently constituted are not a monophyletic group, , meaning that within this group there are a number of independent evolutionary lineages and the relationships among these lineages is still being explored
 
Groups that may be descended from the polychaetes include earthworms, leeches, sipunculans, also known as peanut worms, and echiurans, also known as spoon worms.
 
Dr Hutchings' work on the CReefs expedition to Lizard Island is funded by an Australian Biological Resources Study/CReefs grant. The research team is drawn from the Australian Museum, Museum Victoria, the Museum and Art Gallery of the Northern Territory and Charles Darwin University.