TSAF: The Algae Octopus

You're not safe on land, either

Today’s special animal friend is the algae octopus, Abdopus aculeatus. This small octopus is found in intertidal areas on the shores of Indonesia, the Philippines, and northern Australia. The mantle is about 3” in diameter, and, when the animal is at rest, it resembles an algae-covered shell. Its arms are about 10” long. Like most octopi, the algae octopus can change its color and pattern to blend in with its surroundings. Unlike most octopi, the algae octopus can get up on two of its arms and run across the sand. They can absorb oxygen through their skin when they are out of the water.

We saw this video when we were babysitting a few weeks ago. David Attenborough’s voice is very soothing to babies who are determined that they won’t fall asleep. Without a size comparison, it seems like it could be the Great Old One rising from the sea floor, as big as a refrigerator, but it’s not. It can’t hurt you unless you’re a small crab or other little marine animal. Algae octopi dig small burrows in the sand, where they lurk at night or when they’re munching their food. They clear away the remains of their meals to keep their homes hidden.

Algae octopi sometimes form pair bonds. A male and a female will dig burrows close to one another, and the male will reach his hectocotylus (mating arm) into the female’s den without leaving his own. This has obvious advantages in terms of energy conservation – he doesn’t even have to put down his Nintendo Switch – but the female may allow other males to mate with her if they’re very inconspicuous. Meanwhile, a male with a partner may indulge in casual pickups while he’s out picking up lunch.

The male will die about two weeks after his mating adventures. Regardless of parentage, the females will lay thousands of eggs and care for them until they hatch into planktonic larvae about 2 mm long. After the eggs hatch, the female dies. Their lifespan is up to two years if they don’t mate in the first year. The saddest thing about cephalopods, who are very intelligent and often personable (not the Humboldt Squid, though), is their short lifespans.

Divers often see the algae octopus in shallow water throughout its range. Some are collected for the aquarium trade, and water pollution is a threat in some areas, but their population is believed to be stable, and they are a species of Least Concern to IUCN.