Can an Octopus’s Genome Help Scientists Chart Changes in Antarctic Ice?

An octopus (source: Tennessee Aquarium)

Post Author - Ellis Nolan

Octopuses are fascinating creatures with a wide range of characteristics and abilities, such as opening jars, solving mazes, and even changing shapes and colors. However, for one group of researchers, these amazing animals may unlock a new understanding of a key event in the geological history of the Antarctic.

A little more than 100,000 years ago, the Earth experienced a brief warm period during an otherwise frigid string of ice ages lasting millions of years. This period is known as the Last Interglacial, and it saw Earth’s oceans rise 5 to 10 meters higher than modern day, as well as an increase in the average global temperature by 0.5 degrees Celsius. Scientists have long thought that the enormous western ice sheet of the Antarctic collapsed during this period, contributing to the sea level rise. However, this hypothesis was difficult to prove with geological evidence alone.

That is until a group of biologists thought of a creative solution. The scientists examined multiple specimens of Turquet’s Octopus, an organism whose ancestors would have lived in multiple interbreeding populations in the Antarctic prior to the formation of the western ice sheet. Once the ice sheet formed, their passage was blocked, and the populations were not able to interbreed, causing their genetic information to diverge. The researchers hypothesized the following: If the western ice sheet collapsed during the last interglacial, there should be a corresponding convergence in the Turquet’s Octopus’ genome since the different populations would be once again able to interbreed.

Western Antarctica 

Almost 100 samples were taken from the octopuses for this experiment. In analyzing the octopuses' genome, geneticists first grouped the octopuses into populations, using patterns called SNPs (single-nucleotide polymorphisms). They then ran a computer simulation that examined the average mutation rates of the octopuses in three scenarios: the ice sheet collapsing fully and allowing all populations to interbreed, collapsing partially and only allowing some populations to interbreed, and, finally, not collapsing at all. The octopuses’ genome, the researchers report, most closely matched the first scenario, and dated the resume of the populations’ interbreeding to roughly 100,000 years ago.

That the western ice sheet likely did collapse fully has wide implications for the modern day. Since global warming is rapidly moving the average planetary temperature to that of the last interglacial, another collapse could mean ocean levels rising 5-10 meters once again, as well as drastic changes in the habitats of Antarctic wildlife, such as the Turquet’s Octopus. One thing is almost certain—this will not be the last thing humans learn from octopuses.