Since the earliest days of the field—when a young Charles Darwin worked on his beloved barnacles, shelled shrimplike creatures, cemented to rocks, which lie on their backs and kick food into their mouths—evolutionary biologists have been fascinated by life's myriad odd forms.
Figure 1. Luidia sarsi, a starfish found in the North Sea and along the southern and western shores of the British Isles, develops from a fertilized egg into a larva with bilateral symmetry, inside which grows a juvenile form with the radial symmetry of the starfish. In this unusual life history, the juvenile migrates to the outside and drops off the swimming larva (the translucent shape in this photograph); both continue to live independently for up to three months. Author Williamson’s larval-transfer hypothesis explains this oddity as the expression of genomes fused when two ancestral marine animals hybridized, one becoming the larva of the other. This argument is not only a radical proposal for solving open questions in the evolution of development but also one of several proposals that suggests a bushier shape to the "tree of life" that Charles Darwin proposed.
To discuss our articles or comment on them, please share them and tag American Scientist on social media platforms. Here are links to our profiles on Twitter, Facebook, and LinkedIn.
If we re-share your post, we will moderate comments/discussion following our comments policy.
American Scientist Comments and Discussion
To discuss our articles or comment on them, please share them and tag American Scientist on social media platforms. Here are links to our profiles on Twitter, Facebook, and LinkedIn.
If we re-share your post, we will moderate comments/discussion following our comments policy.