Although the development of the many different taxa of marine invertebrates is very diverse, still, several features are common in the establishment of body pattern formation. The most interesting of all are the colonial groups such as: cnidarians, tunicates, sponges and bryozoans. In order to build a multicellular complex body during development, one should acquire positional information where morphogens play a major role in patterning structures, should follow the rules of pattern-organizing centers due to ectopic expression of genes, or form arrangements following reactiondiffusion mechanisms. The above patterns are dictated by the expression of developmental genes. While the mechanisms were well studied in unitary organisms (including invertebrates such as fruitflies), colonial organisms represent special challenges in understanding developmental features . Colonial corals and tunicates are used as model organisms for understanding developmental patterns of marine invertebrates. To further understand their development, regeneration, stem cell biology, physiological aspects and a detailed follow-up of colony structures are employed. Different modes of coloniality are compared.
Israel Oceanographic and Limnological Research National Institute of Oceanography P.O.Box 8030 Haifa 31080 Israel