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Marine Fan Worms: More Diverse, Morphologically Variable (and Confusing) than Currently Thought

By: Dr Pat Hutchings, Category: Science, Date: 11 Dec 2013

Only two marine fan worms from the genus Branchiomma are known from Australia, but new molecular data reveals many more.

Marine Fan Worms: More Diverse, Morphologically variable (and confusing) than currently thought #1

Kenji Nin © Kenji Nin

Sabellids are marine fan worms which are found in many marine environments. To determine which characters are useful in identifying species in this group, Australian Museum scientists Maria Capa (now based in Norway) and I teamed up with Joan Pons of the Instituto Mediterraneo de Estudios Avanzados in Majorca, Spain.

We selected one of the large groups of Sabellids belonging to the genus Branchiomma. Two species have been identified in Australia, but we suspected that this was a huge under-representation of Australia’s diversity. This is an important group to study, as some species of Branchiomma have been reported as being introduced by shipping into non native ports.

Scientists have used a range of morphological characters to identify species. These include the type and number of pairs of eyes on the fan of these worms and the appendages on them which vary in shape and length (see images to the right). So far, over 30 species have been described using these characters, but they are very subjective and often overlap between these so called species.

We therefore decided to use molecular tools to help us determine just how many species of Branchiomma exist in Australia’s waters. We sequenced material from a variety of locations around Australia and at selected sites outside of Australia. We were able to collect specimens from a variety of locations including Botany Bay, Jervis Bay, Heron Island and Ningaloo here in Australia as well as well as Florida USA, Spain and Hawaii.

The results confirm our belief that this genus exhibits high phenetic plasticity, with species in the same species often looking very different in appearance, even in characters which have previously been regarded as stable, and used for identifying species.

We also revealed high genetic variability within species, as well as evidence of translocation- these worms are being moved around by human activities! For example material from Saipan, Hawaii, Florida as well as northern Australia are all identical genetically and this must surely mean that this species is being moved around.

Our molecular results have revealed that the previous studies on the taxonomy of this common group of fanworms needs to be completely rethought as morphological characters previously used for identification are actually shared by species.

Obviously more work is required before we can actually describe these species… so watch this space!

Dr Pat Hutchings
Senior Principal Research Scientist 

More information

Capa, M., Pons, J., & Hutchings, P. (2013). Cryptic diversity, intraspecific phenetic plasticity and recent geographical translocations in Branchiomma (Sabellidae, Annelida). Zoologica Scripta 42(6): 637-655.