Supplemental information for:
Huffard C. L., F. Boneka, and R. J. Full (2005) Underwater bipedal locomotion by octopuses in disguise. Science. 307:1927 pdf
Follow up paper:
Huffard, C.L. (2006). Locomotion by Abdopus aculeatus (Cephalopoda: Octopodidae): walking the line between primary and secondary defenses. The Journal of Experimental Biology 209, 3697-3707 pdf
HIGHLIGHTS
1. Two species of octopuses walk on two of their eight arms using a rolling gait.
2. This is the first example of bipedal locomotion using a hydrostatic skeleton rather than rigid support.
3. We hypothesize that this locomotion proceeds with minimal neural feedback from the brain.
4. This behavior allows octopuses to move quickly without giving up their primary defense (camouflage).
SUMMARY
We reviewed videotape of octopuses to describe the kinematics of their bipedal locomotion. They walk along the bottom on their ventral (backmost) two arms using a flexible, rolling gait. Amphioctopus marginatus draws six arms up to the rounded body and walks backward. Abdopus aculeatus coils and raises the other arms above the head as it walks, even over rugged terrain.
1. Two species of octopuses walk on two of their eight arms using a rolling gait.
2. This is the first example of bipedal locomotion using a hydrostatic skeleton rather than rigid support.
3. We hypothesize that this locomotion proceeds with minimal neural feedback from the brain.
4. This behavior allows octopuses to move quickly without giving up their primary defense (camouflage).
SUMMARY
We reviewed videotape of octopuses to describe the kinematics of their bipedal locomotion. They walk along the bottom on their ventral (backmost) two arms using a flexible, rolling gait. Amphioctopus marginatus draws six arms up to the rounded body and walks backward. Abdopus aculeatus coils and raises the other arms above the head as it walks, even over rugged terrain.
Previously known examples of bipedal locomotion involved the support of a rigid skeleton. Bipedal vertebrates, such as people and lizards, use an endoskeleton, while previously known bipedal invertebrates, such as cockroaches, use an exoskeleton. Instead, octopus arms use a muscular hydrostat for support. Flexible bands of transverse, longitudinal and oblique muscles manipulate the arm, while the arm’s internal volume remains constant and provides support (Kier and Smith, 1985).
OUR HYPOTHESIS
Underlying the gait is a bend that moves down each walking arm as it rolls along the bottom. To illustrate this bend propagation in O. aculeatus we flipped over the gait diagram and focused on movements of the right arm. In orange, we illustrate the portion of the arm we can actually see in these frames (7/60s lapse between each frame). In purple, we hypothesize what is going on under the body. This bend propagation looks a lot like an arm movement described previously by other workers (Gutfreund, et al. 1998; Sumbre et al, 2001). The stereotyped movement they described did not require feedback from the brain. In other words, octopuses might walk without using their brains, as happens in many other animals. A bend also propagates down the arm of A. marginatus, but the arms are curled less, perhaps because they are thicker.
OTHER FORMS OF LOCOMOTION AND ARM USE BY OCTOPUSES
Shallow-water octopuses have eight flexible arms that are lined on the oral side with two rows of suckers. They use their arms in a variety of ways. In this video we can see a female using arms to display, crawl and attempt to catch food, while the displaying male is being dragged behind her by his mating arm (called a hectocotylus). When an octopus crawls, the arms sprawl around the body, using the suckers to help push and pull the body along (Mather, 1998). They move over rugged terrain, change direction, and stop to investigate possible food sources. So far, no regular sequence of arm movements during multi-armed crawling by shallow-water octopuses has been described. Click here to see video of Wunderpus photogenicus crawling with several arms. To move quickly, octopuses jet through the water (much like a squid), or swim and crawl along the bottom.
BEHAVIORAL CONTEXT OF WALKING BEHAVIOR
The primary defense of most octopuses is crypsis (camouflage), but it generally requires the animal to remain still (Hanlon and Messenger, 1996; Hanlon et al. 1999). Once an octopus moves, it can become visually obvious to a predator. Click here to see how well camouflaged the “White V” octopus is when it sits still on the sand, and how easily we can see it when it swims along the bottom. The large Octopus cyanea ceases camouflage when it swims, and instead mimics fish (Hanlon et al. 1999). By contrast, A. aculeatus looks to us like a clump of algae, and A. marginatus resembles a coconut while walking. They can move quickly without giving up camouflage, their primary defense. In its natural habitat, A. aculeatus drifts along with algae in the surge. Amphioctopus marginatus, which hides in coconut shells, is rumored to lift those shells up around the body and stick two arms out to walk bipedally along the bottom.
Shallow-water octopuses have eight flexible arms that are lined on the oral side with two rows of suckers. They use their arms in a variety of ways. In this video we can see a female using arms to display, crawl and attempt to catch food, while the displaying male is being dragged behind her by his mating arm (called a hectocotylus). When an octopus crawls, the arms sprawl around the body, using the suckers to help push and pull the body along (Mather, 1998). They move over rugged terrain, change direction, and stop to investigate possible food sources. So far, no regular sequence of arm movements during multi-armed crawling by shallow-water octopuses has been described. Click here to see video of Wunderpus photogenicus crawling with several arms. To move quickly, octopuses jet through the water (much like a squid), or swim and crawl along the bottom.
BEHAVIORAL CONTEXT OF WALKING BEHAVIOR
The primary defense of most octopuses is crypsis (camouflage), but it generally requires the animal to remain still (Hanlon and Messenger, 1996; Hanlon et al. 1999). Once an octopus moves, it can become visually obvious to a predator. Click here to see how well camouflaged the “White V” octopus is when it sits still on the sand, and how easily we can see it when it swims along the bottom. The large Octopus cyanea ceases camouflage when it swims, and instead mimics fish (Hanlon et al. 1999). By contrast, A. aculeatus looks to us like a clump of algae, and A. marginatus resembles a coconut while walking. They can move quickly without giving up camouflage, their primary defense. In its natural habitat, A. aculeatus drifts along with algae in the surge. Amphioctopus marginatus, which hides in coconut shells, is rumored to lift those shells up around the body and stick two arms out to walk bipedally along the bottom.
Frame of A. marginatus was taken from video footage (copyright Sea Studios, Inc., cameraman Bob Cranston).
Footage of A. aculeatus was shot by Christine Huffard using Roy Caldwell’s Sony DCR- VX 2000 video camera and Amphibico underwater housing.
Supported by an American Malacological Society Student Research Grant to C.L.H. and by NSF Frontiers in Integrative Biological Research grant no. 0425878 to R.J.F. Video of A. marginatus was provided by Sea Studios, Inc., Monterey, CA, USA (cameraman, Bob Cranston).
Literature cited:
Gutfreund, Y., T. Flash, G. Fiorito, G., B. Hochner, J. Neurosci. 18, 5976 (1998);
Hanlon, R.T., J.B. Messenger. Cephalopod Behavior. Cambridge University Press. (1996).
Hanlon, R. T., J. W. Forsythe, D. E. Joneschild, Biol. J. Linn. Soc. 66, 1 (1999).
Kier, W. M., K .K. Smith, Zool. J. Linn. Soc. 83, 307-324 (1985).
Mather, J. A. J. Comp. Psych. 112, 306 (1998).
Norman, M. D., F. G. Hochbreg. Phuket Marine Biological Center Research Bulletin 66, 127-154 (2005).
Sumbre, G., G. Y. Gutfreund, G. Fiorito, T. Flash, B. Hochner. Science 293, 1845 (2001).
Footage of A. aculeatus was shot by Christine Huffard using Roy Caldwell’s Sony DCR- VX 2000 video camera and Amphibico underwater housing.
Supported by an American Malacological Society Student Research Grant to C.L.H. and by NSF Frontiers in Integrative Biological Research grant no. 0425878 to R.J.F. Video of A. marginatus was provided by Sea Studios, Inc., Monterey, CA, USA (cameraman, Bob Cranston).
Literature cited:
Gutfreund, Y., T. Flash, G. Fiorito, G., B. Hochner, J. Neurosci. 18, 5976 (1998);
Hanlon, R.T., J.B. Messenger. Cephalopod Behavior. Cambridge University Press. (1996).
Hanlon, R. T., J. W. Forsythe, D. E. Joneschild, Biol. J. Linn. Soc. 66, 1 (1999).
Kier, W. M., K .K. Smith, Zool. J. Linn. Soc. 83, 307-324 (1985).
Mather, J. A. J. Comp. Psych. 112, 306 (1998).
Norman, M. D., F. G. Hochbreg. Phuket Marine Biological Center Research Bulletin 66, 127-154 (2005).
Sumbre, G., G. Y. Gutfreund, G. Fiorito, T. Flash, B. Hochner. Science 293, 1845 (2001).