The not-so-common bloodworm

The common bloodworm Marphysa sanguinea is an inshore marine polychaete worm much-used as a baitworm for fishermen, but perhaps more importantly as a model organism for studies in marine genetics, physiology, reproductive biology, ecology, environmental management and ecophysiology.

All studies to date have relied on the assumption that M. sanguinea is a cosmopolitan species. So, scientists have often simply collected some worms that look like M. sanguinea from their local area, and used them in their studies.

For example, studies on the biochemistry of galactosylceramides and lectins used specimens obtained from fishing shops in Japan; studies on erythrocruorin used specimens from the Swan River in Western Australia and Pivers Island in North Carolina; studies on phenols used specimens from Sydney; studies on development of polychaete sex gonads used specimens from Shandong Province, China; studies on reproduction used specimens from Morocco; studies on metabolism and excretion used specimens from Dalian, China; studies on ecology used specimens from South Korea; studies on genetic elements used another set of specimens from Japanese fishing and bait shops (clearly a popular source—saves getting wet at the beach); studies on population genetics used specimens from somewhere in China; and studies on the ecophysiology of microplastics used specimens from Geoje Island, South Korea.

The problem is, almost all of these studies are probably using entirely different species, all called M. sanguinea. This is the conclusion of a very nice study recently published by Nicolas Lavesque from the University of Bordeaux and colleagues, including Australian polychaete taxonomist Pat Hutchings from the Australian Museum.

Careful taxonomic assessment has shown that the true Marphysa sanguinea is not cosmopolitan at all, but is restricted to coastlines of the English Channel. Elsewhere in the world there exists a wide range of mostly un-named species that are only now being taxonomically resolved, using a careful combination of genetics and micromorphology.

The study has also shown that GenBank, an important and popular tool often used for the genetic identification of specimens, won't help. Many GenBank sequences are also not the true M. sanguinea. Some, in fact, are not Marphysa at all. Unfortunately, specimens used for DNA sequencing are often not deposited as vouchers in museums, so some GenBank sequences cannot be identified at all.

This great study shows the pitfalls of assuming a simple taxonomy, before the real taxonomy has been done. It also shows that if you really want to study the model organism Marphysa sanguinea, you'll probably need to spend time on the north coast of France.

There's always a bright side.

For more on this story, see this blog on the Australian Museum's website