Phylum Cycliophora on Lobster Mouthparts

Molecular Biology Research Suggests Many Species of Symbion

Feb 23, 2009 John Blatchford

Symbion was first found on scampi, but is now known to live on other lobsters as well.

Small animals that might look the same can reveal their differences when molecular studies are undertaken. 1995 saw a new animal phylum added to the list (which now stands at over 35). The Cycliophoran (Symbion pandora) was first discovered attached to the mouthparts of Scampi (Nephrops norvegicus), and recent research suggests that there might be many distinct species of Symbion - each on a different host animal.

Biology of Cycliophora

These small animals (less than a millimeter long) have only been found on the mouthparts of lobster-like animals so far. They were first noticed by 1995 by Reinhardt Kristensen (who also discovered the Loricifera) and Peter Funch in 1995 on the mouthparts of Nephrops norvegicus.

• They have an adhesive pad at one end which keeps them stuck on the crustacean’s body, and a mouth surrounded by ciliated funnel which wafts in some of the lobster’s leftovers.

• There are separate sexes, but things are a bit more complicated than that! Lobsters, like all crustaceans, moult regularly as they grow. Obviously there is not much point remaining attached to a lobster exoskeleton that has just been discarded, so the reproduction of cycliophorans has to take moulting into account.

• Between moults (of the host animal) cycliophorans reproduce asexually by budding off new individuals from the parent animal. Just before the host moults the cycliophorans reproduce sexually, and the impregnated female swims away to settle on new lobster mouthparts. She already has small, swimming (but non-feeding) larvae inside her, and these are released to search for a new home.

• But it gets stranger than this! Males are much smaller than females, to which they are permanently attached. They have no feeding parts of their own and so must live parasitically off their mates.

Anatomical studies suggest that the cycliophorans are related in some way to the Goblet Worms (Entoprocta) and the Moss Animals (Bryozoa) – both of which will be the subjects of future articles – but molecular studies have not yet been able to confirm this.

• Both known species of the phylum Cycliophora (Symbion pandora and S. americanus) look the same, but molecular work suggests that they have been different species for a very long time. This research shows that there may in fact be several species, each on a different host, and that the one on scampi is a relative newcomer (Obst, Funch and Giribet, 2005.) Baker and Giribet are still working on this, and in 2007 they stated that ‘further studies are necessary to more precisely describe the evolution … of S. americanus’.

Newly Discovered Animals and Classification

Reinhardt Kristensen has stated that: ‘This is only the beginning. When we have finished, the zoological system will be turned upside down.'

The more zoologists look in strange places for small animals the more they discover, and often the new animals are very different from anything ever seen before.

The copyright of the article Phylum Cycliophora on Lobster Mouthparts in Zoology is owned by John Blatchford. Permission to republish Phylum Cycliophora on Lobster Mouthparts in print or online must be granted by the author in writing.

Scampi

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