The sex–love connection

Sea squirts have finally shown us what we had always hoped was true: there is some connection between love and sex. That connection, or at least a connection between heart cell and germ cell development, comes at the very earliest stages of a sea squirt's life, according to Brad Davidson and Michael Levine (University of California, Berkeley, CA). They suggest that the two developmental events may also be connected in vertebrates.

Davidson selected the sea squirt Ciona intestinalis for his study of heart development because, he says, it is “one step before becoming a vertebrate.” It has some of the advantages of the fruit fly—genetic manipulability, and relatively little genetic redundancy—but as a urochordate is in the last branch before the chordate lineage yielded vertebrates.

He used the genome sequence of Ciona to...