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A team of biologists from Macquarie University (Australia) tried to measure the consequences that climate change will have on marine animals such as sharks. For this, they studied eggs of these huge fish and incubated them in a tank that simulated the warm temperatures that will be reached at the end of the century in case global warming does not stop. Many of these creatures did not resist the investigation, and many others became skilled. How does temperature influence preference for the right side of sharks?
Previous research already reported that the warming of ocean temperatures alters the way fish grow and develop. The researchers, who have published their findings in the Symmetry magazine , wanted to find out if these changes would also affect behavior. Specifically, they wanted to find out if sharks raised in a tank heated to temperatures that the ocean is believed to have by the end of the century would show a preference for swimming in one direction or another when faced with a fork.
To test it, they collected shark eggs from Port Jackson from the waters of eastern Australia: they incubated 12 eggs in a tank heated to the current ambient temperature of the bay (about 20.6ºC) and another 12 in a tank that was gradually heated to 23.6 ° C.
Five sharks incubated at high temperatures died within a month of hatching. To test if the remaining sharks had developed a preference, the team placed each of those animals in a long tank with a Y- shaped partition at one end. Behind the partition there was a food reward; the sharks only had to decide whether to swim to the right or left side to reach their snack. The authors found that sharks incubated at elevated temperatures showed a strong preference for turning to the right. But why does it matter that the sharks have become proficient?
When scientists talk about sharks and other marine creatures being left-handed or right-handed, they refer to lateralization: the tendency for half of an animal’s brain to automatically control certain behaviors. Simple and automated behaviors, in theory, release mental energy to perform more complex cognitive functions. In fish , lateralization can mean a default preference for swimming in a certain way, which can help fish look for food or form schools.
For researchers, this sudden preference for the right is an indication that sharks raised in the hottest tank may have developed lateralized brains as a mental shortcut. This would help them compensate for other development obstacles posed by their environment.
Sharks born in warmer waters may be forced to develop more quickly and may be left with physically smaller brains than sharks that develop under current conditions, the team wrote. With less mental energy to spare, sharks may have to automate certain behaviors, such as always turning to the right before an obstacle. “A stronger lateralization can arise as an energy saving mechanism,” they conclude.