The evolution of the Ecdysozoa

Abstract

Ecdysozoa is a clade composed of eight phyla: the arthropods, tardigrades and onychophorans that share segmentation and appendages and the nematodes, nematomorphs, priapulids, kinorhynchs and loriciferans, which are worms with an anterior proboscis or introvert. Ecdysozoa contains the vast majority of animal species and there is a great diversity of body plans among both living and fossil members. The monophyly of the clade has been called into question by some workers based on analyses of whole genome datasets. We review the evidence that now conclusively supports the unique origin of these phyla. Relationships within Ecdysozoa are also controversial and we discuss the molecular and morphological evidence for a number of monophyletic groups within this superphylum.

The evolution of the animals: introduction to a Linnean tercentenary celebration

“…Telford et al (2008) discuss this synapomorphy and point out that a monophyletic Protostomia is incompatible with numerous whole genome studies that have claimed evidence for a closer relationship between arthropods and vertebrates (Coelomata) than between arthropods and nematodes (Ecdysozoa).…”

“…Establishing the validity of the Ecdysozoa has set the trend in modern animal (at least protostome) systematics, and Telford et al (2008) review the evidence that has provided this level of stability since Aguinaldo et al (1997) first suggested the clade. Once again, tracking the growth and accumulation of disparate, predominantly molecular markers, the story of the Ecdysozoa provides a satisfying sense of progress but a persistent need to sort out each of the major divisions.…”

Hallucigenia's head

“…His work set the course for nanoscience and quantum theory, but it took 125 years before the physics of the phe nomenon that he observed was attributed to quantum size effects 3 . It is now known that, when CQDs are exposed to light, some of the electrons in these particles are excited as they gain energy from the photons.…”

“…The Ecdysozoa is far and away the richest animal group 3 . It is composed of eight extant phyla that shed their cuticle periodically to accommodate growth 4 -nematode worms and crustaceans are familiar examples.…”

Nematodes ultrastructure: complex systems and processes

“…Nematodes in the animal tree of life are actually related to the arthropods and priapulids in a newly recognized clade of molting organisms, the Ecdysozoa (Telford et al 2008). In helminthes, all morphological aspects must be studied under light microscope (LM), because these structures are very important in the context of their systematic classification (González and Hamann 2010).…”