August 2, 2013
Can You Stomach This? Starfish Feeding Secrets Revealed
[ Watch the Video: Starfish Feeding Mechanism Better Understood ]
Brett Smith for redOrbit.com - Your Universe OnlineStarfish have a feeding method that is unlike any other. To eat, the echinoderm ejects its stomach from its own body -- placing it over the digestible parts of its prey, typically a mussel or clam. The stomach then partially digests what it can, producing a chowder-like slurry that is then drawn back into the starfishes' ten digestive glands.
According to a new report in The Journal of Experimental Biology, UK scientists have identified a particular signaling molecule responsible for drawing the stomach back into the starfish's body.
"These findings open up the possibility of designing chemical-based strategies to control the feeding of starfish,â€ said study co-author Maurice Elphick, professor of physiology and neuroscience at Queen Mary, University of London.
Humans are constantly competing with starfish for tasty treats at the bottom of the sea, and the study's findings could lead to a fairly non-invasive and humane way to control the starfish population.
"Starfish predation has an economic impact, as they feed on important shellfish such as mussels and clams," Elphick said. "Periodic increases in starfish populations can also cause major destruction to Pacific reef tracts, such as the Great Barrier Reef, since certain species feed on reef-building corals."
Starfish are notorious for ravaging the fragile ecosystems of coral reefs. If the world's reefs become heavily affected by climate change as many predict, scientists may need to consider every tool at their disposal for maintaining these rich sources of biodiversity.
Using DNA sequencing and chemical analysis of starfish nerves, along with other tests, the researchers were able to identify the key neuropeptide used in their stomach retraction.
"Interestingly, we have also found that the neuropeptide behind the stomach retraction is evolutionarily related to a neuropeptide that regulates anxiety and arousal in humans," Elphick said.
The discovery builds on previous research from the same team that found neuropeptides called SALMFamides that cause the starfish stomach to relax and flip inside-out before being sent outside the body.
In addition to having an unusual feeding technique, starfish also have a bizarre way to 'see' the environment around them. In a study released last month, researchers have found new details about how starfish use primitive eyes that are located at the tip of each arm.
While marine biologists have known about these eyes for some time, it wasn't clearly understood how they worked.
In the study, the scientists placed starfish with and without eyes near a coral reef and watched to see how they would navigate toward it. While the starfish without eyes meandered aimlessly, those with eyes made their way directly to the reef.
"The results show that the starfish nervous system must be able to process visual information, which points to a clear underestimation of the capacity found in the circular and somewhat dispersed central nervous system of echinoderms," said Anders Garm, a biologist at the University of Copenhagen who worked on the study.
The researchers noted that the starfish eyes resemble those of crabs and spiders, containing simple photoreceptors that sense or receive light.