In “Sea slug surprise: It’s half-plant, half-animal” (MSNBC.com, January 12, 2012), Clara Moskowitz reports on a classic example of horizontal gene transfer:
Note: This observation has been questioned in recent research, which found that two of four species were only using the chloroplasts for food. [But two were using them then?]
“This is the first time that multicellar animals have been able to produce chlorophyll,” Pierce told LiveScience.
The sea slugs live in salt marshes in New England and Canada. In addition to burglarizing the genes needed to make the green pigment chlorophyll, the slugs also steal tiny cell parts called chloroplasts, which they use to conduct photosynthesis. The chloroplasts use the chlorophyl to convert sunlight into energy, just as plants do, eliminating the need to eat food to gain energy.
“We collect them and we keep them in aquaria for months,” Pierce said. “As long as we shine a light on them for 12 hours a day, they can survive [without food].”
The offspring seem to inherit the genes for producing chlorophyll, but not the chloroplasts:
The babies of thieving slugs retain the ability to produce their own chlorophyll, though they can’t carry out photosynthesis until they’ve eaten enough algae to steal the necessary chloroplasts, which they can’t yet produce on their own.
Just how the slugs make the genetics work remains unclear.