Meeting Abstract

S5.10  Jan. 5  More than one way to make a worm HOLLAND, P.W.H.*; JIMENEZ-GURI, E.; PHILIPPE, H.; OKAMURA, B.; REINHARDT, R.; YOUNGER , R.; FURLONG, R.F.; University of Oxford, UK; University of Oxford, UK; University of Montreal, Canada; University of Reading, UK; MPI Molecular Genetics, Berlin; University of Oxford, UK; University of Oxford, UK peter.holland@zoo.ox.ac.uk

Worms dominate bilaterian diversity. Worms can be defined as soft-bodied, flexible, muscular, motile, extremely elongate animals lacking skeletons, but otherwise worms vary greatly in terms of muscle layout, and presence or absence of segmentation, cuticle and body cavities. The worm shape has proved highly adaptable, and was probably instrumental in allowing animals to exploit a third dimension by burrowing through sediment. Phylogenetically, worms are usually considered paraphyletic being found in Ecdysozoa (e.g. nematodes, priapulids), Lophotrochozoa (e.g. annelids, nemerteans) and Deuterostomes (e.g. enteropneusts, amphioxus); in each case descendent from a worm-shaped bilaterian ancestor. Here we describe two other ways in which worms have evolved: one by convergent evolution of the worm-shaped body, the other by degeneration from a skeletal animal.