In 1941, Ed Ricketts, a marine biologist from Pacific Grove, and his friend John Steinbeck traveled by boat to the tip of Baja. In the book “The Log from the Sea of Cortez”, Steinbeck, makes some remarkable observations about the colonial existence of Botryllus schlosseri.
‘there were colonies of pelagic tunicates which have taken a shape like the finger of a glove. Each member of the colony is an individual animal, but the colony is another individual animal, not at all like the sum of its individuals. Here are two animals, and yet the same thing. Which is the animal, the colony or the individual? …. Why it’s two animals and they aren’t alike any more than the cells of my body are like me.’ John Steinbek
Botryllus schlosseri is a colonial protochordate that follows the chordate plan of development following sexual reproduction, but invokes a stem cell-mediated budding program during subsequent rounds of asexual reproduction. Thus positioned between vertebrate and invertebrates, it is an ideal model for studying genomic changes that accompanied the invertebrate-vertebrate divergence, and for analyzing ancestral mechanisms regulating alternative modes of reproduction, natural transplantation reactions, and stem cell-mediated regeneration.