Range: Southern Asian coasts to northern shores of Australia

Habitat: Shallow marine water, reefs, seagrass beds and more

Size: Typically 2-3 inches (5-7.6cm) long across mantle with legs about 6 times this

Diet: Crabs

Threats: Humans for bait and pet trade; Also likely fish, sea birds and mammals

Lifespan: One years

Transcript:

Today on Animal Fact Files we’re discussing the algae octopus. These cephalopods get their common name from their ability to camouflage themselves like a small bundle of algae. They hold their arms up at odd angles which makes them look like a clump of seagrass or other floating vegetation on the shore. They can also make their mantle have branched projections which helps add to the illusion and lends to one of their other common names: the prickly octopus.

Algae octopuses live from southern Asian coasts to the shores of northern Australia preferring shallow water and even tidal zones. In fact, they can move around outside of the water if needed by holding up most of their body and cruising along on just two of their eight sucker-covered arms. When they move in this fashion, they're actually walking backwards, and they use the suction cups on their tentacles like treads on a tank. It might seem like a slower way to get around, but for the algae octopus it's just as fast as using jet propulsion in a similar vein to many other octopus species.

The ability to move around in different ways as well as their superior camouflage helps algae octopuses stay safe from predators, but they're not always lucky. These invertebrates are sometimes captured by humans as bait and for the pet trade. They're also likely taken by larger fish, shore birds, and marine mammals. If their camouflage fails them, these animals have one more trick up their sleeves to avoid being eaten. Much like a lizard dropping its tail, an algae octopus can autotomize one of its arms in an effort to distract a predator while the octopus escapes.

The algae octopus is not a large animal. Its mantle averages about two inches, 5 centimeters, long and its arms reach to about 6 times that, although some individuals grow slightly larger. The largest algae octopuses set up den sites near each other so they can easily mate without having to leave the comfort of their own home. A male will simply reach his arm specifically designed for mating into his female neighbor's den. This is a great strategy for keeping both of them out of sight of predators.

These cephalopods use other strategies for mating as well, though. While out and about forging for crabs during the day, they may mate if they see another member of the opposite sex. There are also sneaky males who stealthily crawl up to a female's den and try to mate with her without the other male noticing. If he does notice, however, he'll drive the sneaky male away, meaning these octopuses actually fight over their mates, which isn't super common in the octopus world. The female lays her eggs in her den and watches over them until they hatch into planktonic larvae. As is the case with most cephalopods, the algae octopus dies shortly after mating and brooding its eggs.

An algae octopus lives in shallow water often in seagrass beds, on sandy bottom areas, or within coral reefs. They are diurnal and hunt crabs, using their camouflage to sneak up and then pounce. The octopus uses its beak to break through the crab’s shell and enjoy the muscle inside. When finished, it discards the shell, dragging it away from its den’s entrance if it ate close to home. This may be another tactic to keep predators unaware of its presence in the area.

A big shout out to Dad, SpikeSpeigel93, and the rest of our Patreon family whose generous donations make this channel possible! If you’re able, consider joining them so we can continue bringing you awesome animal facts. Give a thumbs up if you learned something new today, and thanks for watching Animal Fact Files!