Old genes, new tricks

Cephalopods (octopus, squid, and their kin) are a diverse group of molluscs that exhibit a range of novel characteristics not found in other molluscs. Their shell is usually much reduced or absent, their mantle is co-opted for respiration and locomotion, and the muscular molluscan foot is modified into prehensile arms and a funnel. The group is also characterized by a complex central nervous system and well developed eyes. In the August 28 Nature, Patricia N. Lee and colleagues at the University of Hawaii at Manoa report that Hox genes—which specify the body plan of most multicellular animals and are among the most highly conserved of genetic sequences—have been recruited "multiple times and in many ways" in the origin of the morphological novelties of the Cephalopoda (Nature, 424:1061-1065, September 4, 2003).

Lee et al. used whole-mount in situ hybridization to map, for the first time in a cephalopod, the...