Scientists have wondered for decades why marine animals that live in the polar oceans and the deep sea can reach giant sizes there, but nowhere else.
Scientists have wondered for decades why marine animals that live in the polar oceans and the deep sea can reach giant sizes there, but nowhere else. University of Hawaiʻi at Mānoa zoology PhD student Caitlin Shishido, with UH researcher Amy Moran and colleagues at the University of Montana, went to Antarctica to test the prevailing theory–the ‘oxygen-temperature hypothesis’-that animals living in extreme cold can grow to giant sizes because their metabolisms are very slow. The animals they studied were sea spiders, marine relatives of land spiders that breathe through their legs.
The study, published in the April 10 issue of Proceedings of the Royal Society of London, was performed at McMurdo Station, Antarctica, and at UH. “The idea is, it’s a lot of work for animals to capture oxygen and bring it all the way to their cells,” said Shishido. “It’s a much bigger job for large animals than for small ones. If cold temperatures make you need less oxygen, you can grow to a larger size.”
To test whether giant spiders were more affected by warming than small ones, the researchers exercised the spiders to exhaustion by flipping them upside-down and counting the number of times they were able to right themselves at a range of temperatures, from their normal -1.8°C all the way up to 9°C. Counter to predictions, giant animals kept up with smaller ones at every temperature.
Read more at University of Hawaiʻi at Mānoa
Photo: Giant sea spider, Colossendeis robusta, used in the thermal tolerance righting assays in experiments done by Shishido and colleagues at McMurdo Station, Antarctica. Photo by Tim Dwyer, courtesy of ARCUS.