The protochordates (amphioxus and tunicates) occupy a pivotal position in chordate phylogeny, being the closest living invertebrates to the vertebrates. In spite of their evolutionary significance, these animals do not feature commonly in modern developmental biology research. This has not always been the case; indeed, amphioxus ranked as one of the principal animals for embryological description in the early part of this century. The ascidia (one group of tunicates) have received intensive study as a model for determinative development, and considerable experimental and molecular data have been accumulated over the past few decades (1).
The realization that many genes playing key roles in early development have been widely conserved in animal evolution has helped bring protochordates back toward the mainstream of developmental biology research. The existence of homologous control genes in divergent species is a starting point for investigating evolutionary changes in...
KeywordsSperm Duct Ascidian Species Ciona Intestinalis Separate Petri Dish Sodium Thioglycolate
We thank Nicholas Holland and Linda Holland (Scripp's Institution of Oceanography, San Diego, CA) for extensive and invaluable advice on collection and spawning of amphioxus, and Noriyuki Satoh, members of his laboratory (Kyoto University, Japan), and Yusuke Marikawa (University of Toronto, Canada) for advice on ascidia.
- 1.Satoh, N. (1994) Developmental Biology of Ascidians. Cambridge University Press, Cambridge, UK.Google Scholar
- 2.Holland, N. D. and Holland, L. Z. (1993) Embryos and larvae of invertebrate deuterostomes, in: Essential Developmental Biology: A Practical Approach (Stern, C. D. and Holland, P. W. H., eds.), IRL Press at Oxford University Press, Oxford, UK, pp. 21–32.Google Scholar