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Caribbean: 'Cleaner Gobies' Scratch An Itch for Coral Reef Fish |
| November 5, 2004 |
 | Longfin damselfish (Stegastes diencaeus) can often be seen receiving a free 'cleaning service' from tiny gobies that remove parasites from their skin.
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The curious practice by coral reef fish of picking tiny parasites and dead tissue off other fish is considered a textbook example of symbiosis, or a relationship that benefits both parties.
A recent field study in the Caribbean now shows evidence of a direct link between this cleaning behavior and the level of external parasites observed on fish under natural conditions. The findings were reported in the journal Animal Behaviour.
The study’s authors found that parasite loads of longfin damselfish (Stegastes diencaeus) peaked in the morning, correlating with the time of day that these fish were 'cleaned' the most by cleaner gobies (Elacatinus spp.)
The researchers focussed their study on gnathiids - tiny larval crustaceans that latch onto fish and feed on their tissues, earning them their classification as 'ecoparasites.' They found that the number of gnathiids observed on damselfish could be correlated to the timing of the ectoparasites’ emergence from the coral reef each morning.
Although lab studies had shown the correlation between gnathiid load and cleaning interactions, this was the first direct evidence of that link in a field study.
“It was very significant to establish in the field that peaks in gnathiid ectoparasite loads correspond with peaks in interactions with cleaners,” said lead author Dr. Paul Sikkel of Murray State University, Kentucky. “Before this, the only direct evidence of the proximate causes of cleaning interactions has come from lab studies.”
In addition to 'proximate' causes, which include immediate stimuli such as the gnathiids in this study, scientists still debate the ultimate benefits that result from the evolution of cleaning behavior.
“This study brings us closer to that understanding,” said Sikkel.
Reference: “In situ evidence for ectoparasites as a proximate cause of cleaning interactions in reef fish.” Paul C. Sikkel, Karen L. Cheney, and Isabelle M. Cote. Animal Behaviour 2004 68: 241-247.
Source: Earthwatch Institute
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