Striking new underwater images have revealed a previously unknown relationship between juvenile fish and stinging sea anemones.
Captured through blackwater photography – a technique in which divers take pictures in the open ocean at night – the photos show several species of young fish carrying larval anemones in their mouths.
Researchers, who published their findings in the Journal of Fish Biology, say the behaviour represents a surprising new kind of symbiosis: the fish use the anemones' sting as a form of protection, while the larval anemones may benefit as the fish transport them beyond their usual dispersal range.
“Some species of vulnerable larval or juvenile fish use invertebrate species apparently for defensive purposes,” explains Rich Collins, a diver from the Florida Museum of Natural History who contributed to the research.
Collins has observed many unexpected behaviours through blackwater dives, including fish interacting with dangerous invertebrates. He recalls one occasion when he witnessed filefish carrying box jellyfish in their mouths despite their dangerous sting – “they’ll find something that’s noxious or stingy, and they just carry it around.”
The remarkable photographs featured in the new study were taken during a series of night-time dives off Palm Beach in Florida and Tahiti in French Polynesia. They show filefish, driftfish, pomfrets and a young jack transporting anemones, seemingly for self-defence. While the sting from a larval anemone may not kill a predator, it could make the fish unpalatable, says the study's lead author, Gabriel Afonso.
This behaviour may also benefit the anemone by helping it disperse across greater distances. “The anemones have a relatively low speed compared to juvenile fish,” says Afonso. “As far as I know, this is the first relationship of an open-water fish interacting physically with an anemone that looks to be carrying the invertebrate.”
Afonso hopes the research encourages more curiosity about the mysterious relationships hidden in the ocean’s depths.
Blackwater photos: fish and anemones
Top image: Juvenile filefish. Credit: Rich Collins
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