It has been a source of wonder for scientists why marine animals that reside in the deep sea and polar oceans reach large sizes there but nowhere else.
To get to the root of it, Caitlin Shishido, a Ph.D. student at the University of Hawai'i at Manoa zoology and Amy Moran, a UH researcher and also colleague at the University of Montana took to Antarctica. They aimed to test the prevailing theory of the 'oxygen-temperature hypothesis' which implies that animals living in extreme cold can grow to giant sizes due to their very slow metabolisms.
They studied sea spiders, marine relatives of land spiders that breathe through their legs.
Their study was published in the Proceedings of the Royal Society of London, and they performed the study at McMurdo Station, Antarctica, and at UH.
Shishido maintained that it's a massive work for animals to capture oxygen and bring it to their cells and the work is bigger for large animals than for small ones. Shishido concluded that anyone could grow to a large size if cold temperatures make that person need less oxygen.
In their experiment to know whether giant spiders were more affected by warming than small ones, they 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 regular -1.80C to 90C. Counter to predictions; giant animals were able to keep up with the smaller one at every temperature.
Shishido continued that they were shocked to see that not only could the giant animals survive at such high temperatures than they usually see, they also dealt with warm temperatures just like the smaller ones. To them, that is not supposed to happen because larger animals should exhaust their supply of oxygen and run out of gas much sooner than small ones. Sea spiders, which are skin breathers, supposed to be in such a situation, since they have no lungs or gills to help get oxygen, but have to rely on diffusion across the surfaces of their legs.
One big question that faced the researchers was of how the giant sea spiders appear to get around the laws of physics. The question remained unanswered until Shishido and another UH undergraduate student used microscopes to look closely at their legs. They found out that pores covered the sea spiders' legs and as they grow, the exoskeletons of the sea spiders become more and more porous. The researchers confirmed that the exoskeletons of the bigger ones look almost like Swiss cheese.
The consideration from the researchers was their studies were short-term experiments, and the long-term of warming on giant animals are not yet understood. As it is, it appears these giant polar animals may not be as vulnerable to warming oceans as previously considered.
