Early embryonic development of the priapulid worm Priapulus caudatus L. and its palaeobiological significance
Department of Earth Sciences, Palaeobiology, Uppsala University, Sweden.
The relatively poorly known phylum Priapulida is now classified as a member of the group Cycloneuralia (Ehlers et al. 1996) together with nematodes, kinorhynchs, loriciferans and nematomorphs. Up to this point the embryology of Priapulus caudatus, one of the approximately 15 recent priapulid species, is not well documented. Lang (1953) briefly described the development of the priapulid embryo, although no details were presented. This project closely monitors the embryonic development of Priapulus caudatus. Cell lineage and cleavage pattern from the first cleavage until the gastrulation are presented. Noticeable in the discussion concerning the early evolution of the Ecdsyoza (cycloneuralians plus arthropods) is the segmental and ceolomatic features, seen in arthropods. Have these features been lost in the cycloneuralians or were they secondarily gained within the arthropod group? An answer to this will not only help us to resolve several questions seen in the early arthropod evolution, but would indirectly give us new insights concerning the early bilaterian animals and their fossil record.
Ehlers, U.; Ahlrichs, W.; Lemburg, C. & Schmidt-Rhaesa, A. (1996) Phylogenetic systematization of the Nemathelminthes (Aschelminthes). Verh. Dtsch. Zool. Ges. 89 (1), 8.
Lang, K. (1953) Die Entwicklung des Eis von Priapulus caudatus LAM. Und die systematische Stellung der Priapuliden. Arkiv för zoology, Band 5, Nr 5. pp. 321-348.
2005. 64- p.