Branching out: a remarkable new branching worm living in a Petrosia sponge
Added on 2012-02-28 01:11:54 by Alvarez, Belinda
Christopher Glasby, Paul Schroeder and Maria Teresa Aguado. Branching out: a remarkable new branching syllid(Annelida) living in a Petrosia sponge(Porifera: Demospongiae). Zoological Journal of the Linnean Society, 2012, 164, 481–497.
A new species and genus of polychaete worm, Ramisyllis multicaudata, capable of branching like a tree was always found living inside a shallow-water species of Petrosia in northern Australia. Its morphology and DNA are so different that we describe it as a new species and genus. It belongs to the same family (Syllidae) as Syllis ramosa, the only other named branching annelid, which was collected by the 1875 Challenger Expedition from deep water glass sponges. Morphological and DNA evidence showed that branching in these two species evolved separately. In the new species, branching occurs after the worm has completed its normal development with new segments added at 90 degrees to existing ones; this appears to be the result of an environmental trigger from the sponge host. Lastly, we consider that the ability to produce side branches is genetically hard-wired into a group of syllids that reproduce by gemmiparity (a type of budding), and therefore that this group would make a good model for investigating the genetics behind branching in annelids.