How to get a head in evolution

SMALL PRINT:THE PLOVER bird gets a good meal while cleaning the crocodile's teeth, and we all know the mutual benefits of the relationship between the flower and the honey bee. However, another striking example of symbiosis was outlined by US marine biologist Dr Tierney Thys on a visit to Ireland last week.

Thys is not only an ocean scientist and conservationist, she is also a media producer and National Geographic “emerging explorer”, with a passion for the world’s largest bony fish, Mola Mola.

Speaking to students and staff at Galway Atlantaquaria in Salthill, she described how the sunfish, which are “all head and no body”, were built for comfort, not speed, and how they evolved from coral-reef species.

Just four million years ago, when we were learning to walk, the Mola Mola took to the sea, and as such is “highly derived” and a sort of “evolutionary masterpiece”, she explained.

She has dived with, tagged and filmed colonies of the sunfish off the warm waters of her native California, and Indonesia. However, the jellyfish-eating sunfish does appear in Irish waters in summer months, and one of the largest on record was tagged off the coast of Dingle in Co Kerry by a group of international scientists.

The fish, which are related to puffers and porcupine fish, are known for their dorsal fins, which seem to “wave” to scientists studying them. So how come the fish spend so much time at the surface, where they can unfortunately become a by-catch in commercial fisheries?

Thys has an interesting answer. Not only do they swim up for heat and to replenish the body’s oxygen, but they can also “cast a shadow” which then attracts cleaner fish to rid them of the many parasites on their skin.

What’s more, seabirds will also consume those pesky critters nibbling skin around their head and dorsal fin – areas the cleaner fish may not able to reach.

Sunfish are known to have tiny brains. Tiny, but good on strategy, it would seem. See oceansunfish.org