Octopus Sleep
Octopus briareus, Octopus; Eugene Weber © California Academy of Sciences
Casey Watts from Midway, Georgia, asks, “Why do octopuses have three hearts?”
Casey, octopuses need all three hearts to circulate blood through their bodies. Two of the hearts are called branchial hearts. They sit right behind the eyes and are connected to an octopus’s gills, where oxygen gets into its blood. From there, blood goes to the systemic heart, in the octopuses’ center, which pumps the oxygen-rich blood to the rest of its body. With all that blood flow, plus a big, smart brain, a squishy body, and fine-tuned senses – especially eyesight – octopuses can act fast to get in and out of tight spots – sometimes not much bigger than a key-hole.
But octopuses can get sleepy every now and then. And Paul Smith of Fresno, California, wants to know, “How do octopuses sleep?” Paul, octopuses don’t have eyelids. When octopuses in captivity need sleep, they slump into corners of their tanks and catch a few winks by narrowing their pupils. Their bodies turn whitish in color and their breathing slows down. In experiments, octopuses that are kept awake end up needing more rest later on, which shows how important it is that they get enough shut-eye.
They might need it because octopuses have the biggest brains of any invertebrate. That’s our show. Thanks today to the National Fish and Wildlife Foundation, promoting the conservation of native fish, wildlife, plants, and their habitats.
The following person was interviewed for today’s program.
Our thanks to:
Roland C. Anderson, PhD
Puget Sound Curator
The Seattle Aquarium
Seattle, WA
Links
About Octopuses… (Mote Marine Laboratory)
The Octopus Show (PBS.org)
The Octopus (Germantown Elementary School)
Author’s notes:
Octopuses have so many cool features, it is hard to know where to begin.
There are hundreds of species, ranging in size from less than an inch long, in the case of the tiny Californian Octopus (Octopus micropyrsus), to more than 30 feet, in the case of the North Pacific Octopus (Octopus dofleini), which can weigh 100 pounds. Even within species, octopuses are constantly changing their image. With special cells called chromatophores, they can change colors instantaneously to reflect their moods or blend in to their surroundings. Many species have toxic venom in their tentacles to kill shrimp, lobsters, crabs, snails, and other prey. The Australian Blue-Ringed Octopus has venom so potent, it can kill people. And in 1999, scientists discovered a type of octopus whose tentacles actually glow in the dark.
Though common in almost every type of ocean environment, octopuses are hard to see in the wild. They hide during the day, and usually only come out at night and on gloomy days to. Their eight tentacles have an amazing sense of touch that can distinguish between objects. Their eyes are also highly developed and similar to humans. Octopuses are deaf.
When threatened or frightened, octopuses can squirt out a blob of dark ink, which often buys them time to escape. To move, they propel water like a jet engine, which moves them rapidly in any direction.
Additional Teacher Resources
National Public Broadcasting Service, Nature, Featured Program: The Octopus Show
A new age of ocean exploration is lifting the veil of mystery shrouding a creature of legend?the octopus. Dreaded by sailors through the ages, this other-worldly looking denizen of the seas is surrendering the astonishing secrets that have brought it almost mythical status. This site is an excellent resource for any topic concerning the octopus. It has a variety of interactive material including video footage, photographs, and links to more information.
Bio Media, Galleries: What Animal Has A More Sophisticated Eye, Octopus Or Insect?
The insect and the octopus are two types of animals that have evolved sophisticated eyes. This site compares the two explaining the science behind how these two groups have evolved to have such remarkable eyesight.
Bisdragons.com: Octopus
This site provides a brief natural history of the octopus and an explanation of its biological make-up, including its three hearts. This site is useful because it provides both a internal and external diagram of an octopus.
National Oceanic and Atmospheric Administration, Undersea Research Program: In the Octopus’s Garden
This article explores the mystery behind the giant octopus. Including what little is known about the species, what scientists are trying to learn, and how due to a human taste for octopus, endangerment or worse could come well in advance of an understanding of how and where the giant octopus lives.
