Scyphomedusae and their polyps are the same immunologically: implications for systematics.

1. Polyp and medusa of the scyphozoans Aurelia aurita and Pelagia colorata (phylum Cnidaria) are indistinguishable by radioimmunoassay of whole animals, yet differ from other cnidarians against which they were tested. 2. We infer that proteins distinguishing species swamp those that differentiate the two (very distinct) life history phases. 3. Thus, at least for some taxa and some systematic techniques analyzing proteins, using organisms at the same developmental phase may be unnecessary, contrary to conventional wisdom.