A green sea slug appears to be part animal, part plant.
It's the first critter discovered to produce the plant pigment
chlorophyll.
The sneaky slugs seem to have stolen the genes that
enable this skill from algae that they've eaten. With their
contraband genes, the slugs can carry out photosynthesis — the process
plants use to convert sunlight into energy.
"They can make their energy-containing molecules
without having to eat anything," said Sidney Pierce, a biologist at
the University of South Florida in Tampa.
Pierce has been studying the unique
creatures, officially called Elysia chlorotica,
for about 20 years. He presented his most recent findings Jan. 7 at
the annual meeting of the Society for Integrative and Comparative
Biology in Seattle. The finding was first reported by Science
News.
"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 researchers used a radioactive tracer to be sure
that the slugs are actually producing the chlorophyll themselves,
as opposed to just stealing the ready-made pigment from algae. In
fact, the slugs incorporate the genetic material so well, they pass
it on to further generations of slugs.
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.
The slugs accomplishment is quite a feat, and
scientists aren't yet sure how the animals actually appropriate the
genes they need.
"It certainly is possible that DNA from one species can get
into another species, as these slugs have clearly shown," Pierce
said. "But the mechanisms are still unknown."
