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While wandering the tide pools at Asilomar State Park in Pacific Grove, California, on a gloomy May day, marine science communicator and conservationist Molly Fishman spotted a curious color. Something purple was there among the brown rocks and green algae. Fishman looked closer and realized he was looking at a complete sea otter skeleton, but it wasn’t just any skeleton. Each and every bone of the skeleton was a bright, iridescent purple.
“The wave of emotions [I] What I felt included elation, gratitude, sadness and peace,” says Fishman. popular science. “It may be common to find bones of marine mammals along the intertidal [zone]. “I have friends who have found a random purple otter bone here or there, but to find the entire skeleton still intact is extraordinary.”
Purple otter bones
Some sea otter bones are purple because many of the furry marine mammals specialize in eating purple sea urchins. Over time, a purple pigment in sea urchins called echinochrome builds up on their teeth and bones and stains them. This phenomenon is called echinochrome staining and can range from a few purple teeth to an entire purple skeleton.
“This otter was an adult, hopefully lived a long life, and I can confirm that it definitely ate a lot of purple sea urchins,” explains Fishman.
Otters aren’t the only organisms whose bodies can change depending on what they eat. Humans who eat too many carrots can develop a similar condition called carotenemia, when pigments called carotenoids build up and dye the skin, hair or nails yellow or orange. Some tree frog bones can turn green, while flamingos get their characteristic pink hue from eating shrimp.
“Although many animals can change color depending on their diet, such as flamingos, that does not necessarily mean that those pigments penetrate their bone structures,” says Fishman.
As exciting as it is to find a purple sea otter skeleton, it’s important to leave bustling ecosystems like tide pools alone, for the animals’ sake and our own.
“I want to reiterate that it is illegal to collect these bones under the Marine Mammal Protection Act,” Fishman says.
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