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article imageGreen sea slug can steal plant genes and produce chlorophyll

By Stephanie Dearing     Jan 15, 2010 in Science
The green sea slug can produce its own chlorophyll and is, as you might have guessed, green in colour. Oddly enough, the slug is shaped like a leaf. Is it a plant or is it an animal?
Seattle - Normally only plants can produce chlorophyll, but this sea slug can produce its own chlorophyll, making it the only known living creature with the capacity for photosynthesis. The findings, a culmination of 20 years of study of the green sea slug, were presented by Sidney K. Pierce at the Annual Meeting of the Society for Integrative & Comparative Biology in Seattle last week.
In the past, it was thought a symbiotic relationship between the green sea slugs and algae gave the sea slug the chlorophyll boost.. However, its studies showed the slugs were able to maintain chlorophyll production even when they were deprived of the algae they normally eat. Pierce, who has been studying the slug species for years, found that the slug was able to appropriate and integrate the chlorophyll producing genes.
Pierce and his co-researchers, Michael Middlebrooks and Susan Bell, believe the slugs have 'stolen' the chlorophyll producing cells from the algae they eat. Not only can the slugs integrate the genes, they can pass them on to the next generation of sea slugs. Pierce's research team showed green sea slugs did not require any food for at least one year once the animals had extracted the genes from algae.
The findings will likely pave the way to a rethink of how evolution works, now that scientists know that genes can be transferred between species. Pierce and his co-scientists also found the green sea slugs were able to pass on the stolen genes to the next generation of slugs, making the transfer an evolutionary trait. The incorporation of plant genes means that the green sea slug might actually be part animal and part plant. It is well known that microbes are capable of trading genes, but this is thought to be the first instance of such behaviour between two different species.
It has been known for years that the green sea slugs were ingesting the chloroplasts from algae. In 2008 research was published that demonstrated that the slugs could continue photosynthesis after being deprived of the algae for months, with scientist Mary Rumpho able to isolate the stolen gene in the slug.
There are at least two other species of sea slugs which may have transferred genes from plant species - the so-called solar-powered sea slug, or the Placida cf. dendritica; and the Pteraeolidia ianthina.
The green sea slug, otherwise known as Elysia chlorotica, can be found along the east coast of the USA and Canada.
Chlorophyll is a pigment that enables plants to capture energy from sunlight through the process called photosynthesis, and until now, it has been thought that only plants could produce chlorophyll.
Rumpho and Pierce have collaborated in the past on green sea slug research.
More about Green sea slug, Photosynthesis, Solar powered slugs, Gene transfer
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