You’re walking along the sidewalk and suddenly, someone accidentally bumps into your arm pretty hard. As a Canadian you instinctively say ‘sorry’, but you toss back a dirty look and continue on your way, not noticing that your arm is also back there on the ground.
Image 1: Arm regeneration of sea star; one arm dividing in two. (Photo credit: http://coolmarinescience.blogspot.ca/2012/01/heart-of-silk-sea-star-self.html)
Now this would probably result in a significant amount of blood loss and most likely death for a human. But sea stars have the ability to lose their arms (autotomize) without any serious implications on the animal. Sea stars can regrow arms lost after a disturbance, this is most likely an adaptation to predation, where losing one arm to a predator is better then being totally eaten and dying.
An interesting kind of sea star is the Feather star, which raises its arms into the water and feeds on particles that get caught. They also are able to autotomize their arms and regrow them.
Image 2: Feather star arm with tube feet extended.
An experiment done at the University of British Columbia, by Dr. Angela Stevenson, looked at the rates of arm regeneration in a local species of Feather star, and whether they are effected by climate change. Regrowth requires energy to form new cells and this may or may not depend on temperature, if the animal becomes stressed because of it.
What she found was that Feather stars in high temperature climates, had faster growth rates than those at the normal temperature, at which they are found in nature. This means that Feather stars in British Columbia, may actually be affected positively by increases in temperature caused by climate change.
While this potential increase in temperature may positively impact regrowth in Feather stars, the surrounding community may be negatively affected. This is because, Feather stars produce feces that are usually high in calorie content at their normal temperature, and other animals stay by the Feather star and eat it. But at higher temperatures, the feces is lower in calories because the sea stars take up more nutrients from their food to supply energy for their fast regrowth. Image 3: Small crab waiting to feed on Feather star feces.
Now the creatures, like crabs and worms, relying on this food source won’t be getting as much energy, but the direct impacts of this are unknown. This example shows just how complicated climate change will impact individuals and whole communities, directly and indirectly through the food web.