It’s logical to assume that all animals of the same species would look the same and live in the same type of environment. However, this isn’t always the case.
Scientists from the Field Museum in Chicago, USA recently discovered that Pacific warty octopuses don’t all have the same appearance, nor do they all live at the same ocean depth.
Their findings, which was published in the Bulletin of Marine Science, indicated that the bumpier the octopus’ skin was, the deeper in the ocean they would be found.
In their research, the team examined 50 Pacific warty octopuses from the Northeast Pacific Ocean, as well as specimens from the University of Miami Marine Laboratory and the California Academy of Sciences.
By counting the warts in a line across the octopus’ back and head as well as the number of suckers on their arms, the researchers discovered that the deep-sea specimens were smaller in size, had fewer arm suckers, and they also had bumpier skin than their counterparts from shallower depths.
Why the difference?
Although the scientists could not explain how the depth difference caused variations in skin texture, they speculated that the size differences were due to the availability of food.
In the ocean, prey becomes more scarce the deeper it gets. As a result, “… these animals have to work harder to find food to eat. And that means at the end of their lives, they'll be smaller than animals who have more food,” said lead author Janet Voight, associate curator of zoology at the Field Museum.
Likewise, their eggs would be smaller and had less yolk compared to their counterparts in shallower waters. This means smaller hatchlings and subsequently, smaller adult octopuses.
The researchers also discovered that the male octopuses from deeper waters had fewer suckers on this arm that transports their sperm packets to the femaie, compared to the octopuses from shallower waters, prompting them to suggest that this could be due to the size of the eggs.
“They had less energy to fuel their growth before they left the egg, so they made fewer suckers,” said Voight.
Hence, although this Pacific warty octopus may look different depending on whether they live in shallow or deep waters, their DNA sequences had only minor differences, meaning that they were of the same species.