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14 Jul 2005
Researchers discover a deep sea creature covered with red photophores that imitate shrimp.
A species of deep sea jelly that attracts small fish by wiggling hundreds of glowing red lures has been discovered by a team of US and UK scientists. According to the researchers, this is the first marine invertebrate that has been found to display red bioluminescence. (Science 309 263)
Red bioluminescence is extremely rare and the prevailing view among marine biologists is that most deep-sea animals cannot detect red light at all. The work of the US-UK group now suggests that some sea-dwelling creatures not only see red light, but use it routinely to find food.
Using remotely operated vehicles, the team from Monterey Bay Aquarium Research Institute (MBARI), US, Yale University, US, and National Oceanography Centre, UK, observed the creature at depths of between 1600 to 2300 m. The scientists identified the specimen, known as a siphonophore, as belonging to the genus Erenna, a group that contains corals and jellyfish. Covered with branched tentacles known as tentilla, the creature uses an array of 3000 stinging cells to kill its prey.
Researchers were fascinated by the siphonophore's photophores, which sit alongside the tentilla and produce a multimodal fluorescence emission that spans from yellow (583 nm) to red (680 nm). The marine invertebrate's size and unique rhythmic behaviour led scientists to believe that the Erenna was using its glowing red tentilla to imitate shrimp and attract prey.
"Most siphonophores set a big web of tentacles to catch animals that happen to swim by, but this jelly doesn't deploy its tentacles very far," said Steve Haddock from MBARI. "In a [deep sea] environment where fish are rare, it uses deception to attract fish instead of casting a wide net to capture them."
The discovery could force scientists to re-examine the role of long-wavelength light in marine visual ecology.
Author
James Tyrrell is reporter on Optics.org and Opto & Laser Europe magazine.
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