Heat stress due to warming oceans could affect the vision of octopuses and compromise the ability of these animals to survive, even though climate change has caused an increase in the abundance of these cephalopods.
This is suggested by a team of five researchers from institutions in Australia or the US in a study published in the journal Global Change Biology.
"We found several proteins important for vision that were affected by heat stress," says Qiaz Hua, a doctoral student in the School of Biological Sciences at the University of Adelaide (Australia).
Hua adds that one of them is a structural protein found in great abundance in the lenses of animal eyes to preserve the transparency and optical clarity of the lens, and another is responsible for the regeneration of visual pigments in the lenses. photoreceptors of the eyes.
"The levels of both proteins were significantly reduced under projected ocean warming conditions, suggesting that octopus vision is likely to be affected by thermal stress," continues the researcher.
Octopuses are highly visual animals, with 70% of the octopus brain dedicated to vision, which is 20% higher than that of humans.
"The main functions of vision include, among others, visual acuity, brightness discrimination, depth perception, motion detection and polarization, and is crucial for detecting predators and prey, as well as for communication" says Hua.
This researcher adds: "Having vision problems will affect an octopus's chances of survival in the wild through increased predator risk as well as reduced success in searching for food."
To arrive at this finding, the research team exposed Octopus berrima embryos to different temperature treatments: 19 degrees as a control exposure, 22 to model current summer temperatures, and 25 to model projected summer temperatures.
"The projected temperature for the future was based on the increase projected by the Intergovernmental Panel on Climate Change of approximately 3 degrees of warming by 2100," says Hua.
In addition to vision problems, Hua found that rising ocean water temperatures would have a negative effect on baby octopuses. "We found a high mortality rate under future warming conditions. Of three replicate octopus hatchlings, none of the eggs hatched in two of them and less than half of the eggs hatched in the other hatchling," he says.
In offspring where none of the eggs hatched, the mothers died naturally while the eggs were still in the early stages of development.
"Because maternal care of embryos occurs in octopuses, global warming could have a simultaneous impact on multiple generations, with a low embryo survival rate caused by the direct effect of heat stress, as well as the indirect effect of heat stress in mothers," explains Hua.
In his opinion, the study "shows that even for a highly adaptable taxon like octopuses, they may not be able to survive future ocean changes."
Other effects of higher temperatures that have been observed in octopuses include a higher metabolic rate, reduced size at maturity, and even a change in the distribution of some species.
