Dolphins: Sponge-worthy? Yes. Antimicrobial? Maybe

Dolphin wearing a sponge tool. (Photo: Eric M. Patterson, from PLoS ONE)

Update added at end.

Back in 2005 I wrote about dolphins that had developed a culture of placing protective sponges over their beaks to root along the seafloor for fish, which was noteworthy as a rare instance of tool use among cetaceans. (In my post on the subject, which I brushed off for use here last February, I also discussed how some dolphins seem to use bubbles as tools, too, and I flagged Emily Anthes’s Wonderland post with video about those.) Now it may be clearer why those dolphins go to so much trouble.  Georgetown University researchers Eric M. Patterson and Janet Mann have reported in PLoS ONE that dolphins off the coast of Western Australia that use this technique can catch more nutritious fish and may thereby improve the odds of their offsprings’ survival.

I was particularly interested in this comment on the work, from a ScienceNOW article by Virginia Morrell:

Patterson’s and Mann’s results also “reinforce a pattern” often seen in other tool-using animals, says Simon Reader, a behavioral biologist at McGill University in Montreal, Canada. “Tool use appears to be almost a last option, taken when other options fail or are unavailable,” he says, noting that woodpecker finches in the Galápagos Islands “turn to tool use only in arid areas,” wielding cactus spines to extract grubs from tree branches. Using tools takes time and energy, Reader says, and animals tend to rely on them only when there’s a guaranteed payoff, such as turning up a fatty fish that most other dolphins (and fishermen) know nothing about.

The generalization that animals engage in tool use only as a last resort isn’t one I remember hearing said before, though it may stand to reason. I do wonder what implications that might have for the evolution of more flexible tool users such as humans, though.

Meanwhile, elsewhere in dolphin news, Michael S. Zasloff, a former dean of research at Georgetown University Medical Center, has speculated in a letter to the Journal of Investigative Dermatology that dolphins may recover quickly from shark bites and other severe wounds because of antimicrobial and possibly regenerative compounds in their blubber. He holds out the possibility that those compounds, if they could be identified, might lead to similarly useful therapeutic compounds for humans, as notes in this press release and other articles.

We can all hope that will be true, but for now, consider it a long shot. Zasloff, you may recall, discovered unusual antimicrobial peptides called magainins in frog skin more than two decades ago, as well as similar antimicrobials in sharks and other creatures. He founded the company Magainin Pharmaceuticals in 1988 to develop those compounds for therapies, but it was nearly destroyed when the Food and Drug Administration rejected its most promising product (a magainin-related drug for treating diabetic foot ulcers) as no better than alternative treatments. Perhaps something derived from dolphins, a fellow mammal, would be more helpful in treating humans, but there are a lot of ifs ahead for it.

Update (7/25): AnimalWise has a particularly thorough retelling of Janet Mann’s work on sponge-using dolphins, if you’d like to know more about that project.

Update (7/27): And now, dolphins are electric. That is, Nicole Czech-Damal of the University of Hamburg has shown in the Proceedings of the Royal Academy B that small, seemingly vestigial pits on the snout of the Guiana dolphin allow the animal to detect electric fields, an ability that sharks and some other types of aquatic life use to detect prey. So far this electroreception has only been demonstrated in the Guiana dolphin species, in which those pits are particularly large, but it’s distinctly possible that other dolphins use it, too. As usual, Ed Yong at Not Exactly Rocket Science tells the story beautifully.

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