Evolution of sea slugs
A result of symbiosis, sea slugs are animals capable of photosynthesis, "actual plant-animal hybrids". The ancestor of the sea slugs ate green algae. Instead of being digested, the algae entered the animal's tissue, allowing the animal to acquire photosynthetic genes. Today, adult sea slugs never eat. Instead, they crawl to the shore and sunbathe like plants do. Whereas the ancestors were grey, sea slugs are green. A 2015 study examined sea slug DNA and found it includes genes from algae. While Peter Kropotkin's Mutual Aid explored the cooperative interaction within species, symbiosis offers examples of cooperative interaction between species. The sea slug emerged not from competition or random mutations, but from a merger between an animal species and a plant species.
- Lynn Margulis and Dorion Sagan, Acquiring Genomes: A Theory of the Origins of Species (New York: Basic Books, 2002), 13.
- Janet Fang, "Sea Slug Steals Photosynthesis Genes from Algae," IFL Science, 4 February 2015, http://www.iflscience.com/plants-and-animals/sea-slug-steals-photosynthesis-genes-its-algae-meal.