La Jornada: Ocean acidification reduces squid brain size

Madrid. An ongoing research project at Acadia University in Canada is exploring the effects of increasing ocean carbon dioxide levels on the neurology of squid. Their results, presented at the Society for Experimental Biology conference in Florence, Italy, reveal that exposure to future levels of ocean acidification could reduce your brain volume by about 50 percent.

This severe brain reduction appears to be most pronounced in areas that interpret visual information, which correlates with significant reductions in normal feeding behaviors and suggests serious consequences for the future of squid and other cephalopods.

Most intelligent cephalopods

“Cephalopods are considered one of the most intelligent groups of animals that live in the ocean,” confirms Dr. Garett Allen, associate professor at Acadia University. The Coleoidea subclass, which includes squid, cuttlefish and octopuses, is believed to be the most intelligent invertebrates on Earth, with a number of neurons similar to that of dogs.

Acidification, caused by elevated levels of atmospheric carbon dioxide, is known to pose a serious threat to many marine species, but this project reveals a previously unknown impact of ocean acidification on the neural anatomy of cephalopods.

Preliminary data from this study suggest that largefin reef squid, Sepioteuthis lessonianareared from hatching in elevated levels of dissolved carbon dioxide, exhibited significant changes in brain physiology; The most striking was an average 49 percent reduction in brain volume compared to a control group.

To investigate the effects of future ocean acidification on the mollusk’s neurology, the researchers raised squid in two parallel water tanks: one representing the current oceans (pH 8.2) and another representing the oceans in the year 2100 under a predicted climate change scenario (pH 7.8). After 90 days, the squid were removed and their heads were preserved for visual analysis using diffusion MRI.

After viewing the images and evaluating the morphometric characteristics of the brain, the team of researchers discovered that the brains of the squid in the ocean acidification tank were considerably smaller than those of the squid in the control tank.

The study found no effect of carbon dioxide on total body size, so brain volume was normalized to mantle length to account for variation in body size. This volume reduction was observed throughout the brain, but the largest reductions were found in regions identified as the optic lobes and optic tracts, which were 52 and 62 percent less voluminous than squid raised in modern ocean conditions, respectively.