Centipedal hemocyanin: its structure and its implications for arthropod phylogeny.

The oxygen carrier hemocyanin occurs in the blood of Scutigera coleoptrata, a uniramous arthropod, as well as the crustaceans and chelicerates. The native polymer appears to be composed of substructures having the same size and electron-dense image as those of other arthropod hemocyanins but assembled into a unique multiple and arranged in a unique configuration. The simplest explanation of these findings is that the arthropod hemocyanins have a common origin, exemplifying a derived (as opposed to primitive) character shared by each of the three living groups.