It is known that some animals can accept into its genome and operate genes from other animals of the species itself or from distant species in the zoological scale (genes for eye formation between insects and mammals or genes of formation of limbs among fish and mammals). The same happens with the exchange of genes between plants or between fungi and bacteria. In essence about to accept and read instructions contained in genes is existing similar genes in distant species. However, there is exceptional case when animal cells genes are being accepted by plant genes.

Elysia chlorotica was discovered in 1870 by Augustus A. Gould in Martha's Vineyard (United States) although its genome was not described until 2010 by Sidney Pierce.

It is a opistobranquio mollusk that feeds from algae called Vaucheria litorea. Once digested cytoplasm of algae, E.chlorotica does a horizontal transfer of "psbO" genes, circulates DNA chloroplast of their own genetic circular structure, so that the cells acquire the ability to perform photosynthesis and produce the food of the mollusk from solar.  Therefore a multicellular animal is able to incorporate into their genes plant cells and make them work.

There are two other animals that perform functions that are similar but are based on other mechanisms: Pteraeolidia ianthina is able to retain algae live in a digestive diverticulum and gets food through the chlorophyll function of dendritic Placida which is acquiring green color for the incorporation of green pigments of algae in their tissues even without chlorophyll function.

Therefore the case of the Elysia chlorotica is an exceptional adaptation of the plant in the animal.