[News]: How many arms does an octopus have? - Times Online

octobot

Robotic Staff
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Robotic Staff
#1

[SIZE=-2]Times Online[/SIZE]

How many arms does an octopus have?
[SIZE=-1]Times Online, UK - 1 hour ago[/SIZE]
[SIZE=-1]A giant Pacific octopus called Mavis has helped researchers to prove that the one thing everyone knows about the creatures is wrong. The name octopus is ...[/SIZE]
[SIZE=-1]How many arms does an octopus have? Only six, according to scientists [SIZE=-1]Daily Mail[/SIZE][/SIZE]
[SIZE=-1]Octopuses have two legs and six arms [SIZE=-1]Telegraph.co.uk[/SIZE][/SIZE]
[SIZE=-1]Octopuses have only six arms, the other two are actually legs! [SIZE=-1]Thaindian.com[/SIZE][/SIZE]
[SIZE=-1]UK Express[/SIZE]
[SIZE=-1]all 14 news articles[/SIZE]


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octobot

Robotic Staff
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Robotic Staff
#2
[News]: How many arms does an octopus have? Only six, according to scientists - Mail


How many arms does an octopus have? Only six, according to scientists
[SIZE=-1]Mail on Sunday, UK - 17 minutes ago[/SIZE]
[SIZE=-1]By Daily Mail Reporter Ask anyone how many arms an octopus has and the usual answer will be eight. But scientists now insist these nautical animals only ...[/SIZE]


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monty

Colossal Squid
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#4
http://afp.google.com/article/ALeqM5j1MNsYD_Llq2sXaywJpQoul6ojdw

says

"My octopus hates the colour red -- that's quite a natural response in nature -- but he particularly likes yellow. We're starting to build a profile for different octopus," Gerard added.
Um, unless this person has discovered something unpredicted and unlikely, this can't be right. Since octos don't see color, the octopus probably sees dark patterning as more threatening than light, either because other octos get dark to intimidate, or because it looks like shadows of predators.

It's a pet peeve of mine when researchers make assumptions that animals of different species perceive the world the same way we do... particularly cephs, since they (except firefly squids) lack wavelength discrimination to judge colors, and can't differentiate the two diagonal directions, but they do see polarization.

I also think that while the "back two mostly for walking, front 6 for manipulating" result is interesting, the news coverage seems to be overstated and anthropomorphized: Octos that pounce and cover prey in their webbing seem to use all 8 arms, and I've seen octos pull themselves with their front arm pairs when walking on glass.
 

DWhatley

Cthulhu
Staff member
Moderator
#5
Octavarium;122940 said:
I bet each different species uses or favors certain arms more.
I was thinking we should make some daily observational notes on the hummelinckis to see if this casual study with mostly vulgaris holds up. My gut feel without making direct observation and recording it is that the general assumption is wrong but may be observable by species.

AM, since you have two species concurrently, want to join the note taking?
 

octobot

Robotic Staff
Staff member
Robotic Staff
#6
[News]: Octopuses more arms than legs: research - AFP


[SIZE=-2]AFP[/SIZE]

Octopuses more arms than legs: research
[SIZE=-1]AFP - 15 hours ago[/SIZE]
[SIZE=-1]LONDON (AFP) — How many legs does an octopus have? The answer should be easy. But not any more. For new research suggests they are not really eight-legged ...[/SIZE]


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octobot

Robotic Staff
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Robotic Staff
#7
[News]: Photo: New Octopus Arms Facts Reveal They Have Legs & Are Ambidextrous - Pos


[SIZE=-2]Daily Mail[/SIZE]

Photo: New Octopus Arms Facts Reveal They Have Legs & Are Ambidextrous
[SIZE=-1]Post Chronicle - 21 hours ago[/SIZE]
[SIZE=-1]This new octopus study, which is the largest of its kind, was first meant to see if octopuses are ambidextrous, meaning they prefer to use one side when ...[/SIZE]
[SIZE=-1]Research: Octopuses Have Six 'Arms,' Two 'Legs' [SIZE=-1]FOXNews[/SIZE][/SIZE]
[SIZE=-1]Octopuses lose legs, gain arms [SIZE=-1]Melbourne Herald Sun[/SIZE][/SIZE]
[SIZE=-1]all 56 news articles[/SIZE]


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octobot

Robotic Staff
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Robotic Staff
#8
[News]: Octopuses more arms than legs: research - AFP


[SIZE=-2]Windsor Star[/SIZE]

Octopuses more arms than legs: research
[SIZE=-1]AFP - Aug 13, 2008[/SIZE]
[SIZE=-1]LONDON (AFP) — How many legs does an octopus have? The answer should be easy. But not any more. For new research suggests they are not really eight-legged ...[/SIZE]
[SIZE=-1]How many arms does an octopus have? Only six - the other two are ... [SIZE=-1]Daily Mail[/SIZE][/SIZE]
[SIZE=-1]RUBIK’S CUBE REVEALS SECRET OF THE OCTOPUS [SIZE=-1]UK Express[/SIZE][/SIZE]
[SIZE=-1]Mavis and Olga, a tale of two bipedal hexapuses [SIZE=-1]Nature.com (subscription)[/SIZE][/SIZE]
[SIZE=-1]all 33 news articles[/SIZE]


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Animal Mother

Architeuthis
Supporter
#10
dwhatley;122955 said:
I was thinking we should make some daily observational notes on the hummelinckis to see if this casual study with mostly vulgaris holds up. My gut feel without making direct observation and recording it is that the general assumption is wrong but may be observable by species.

AM, since you have two species concurrently, want to join the note taking?
I got in on the conversation late, but I saw that article the other day. Bull mallarky as my grandfather would say.

Kalypso uses whichever arm is closest to the object he seeks out to manipulate it. I can't speak for him using certain arms for walking because there's not enough open space in the tank. He definitely uses all 8 arms to capture prey. Backwards and forwards seems pretty irrelevant. Sometimes he climbs the glass with his mantle away from it, sometimes with his mantle against it, thus reversing which arms are used to climb.

Grover uses all 8 arms to walk, sometimes just the two front, and usually the two front to climb the glass while the others hold on for traction. Usually when walking though they're all tucked and coiled underneath the rest of his body. Or her body... and they seem to all work equally. Same for climbing glass as Kalypso. Sometimes mantle in, sometimes mantle out.

I thought it was pretty common knowledge that Bi-pedals will use their front arms for walking on occasion. Doesn't seem like this research was well planned out to me. What do I know though. I'm not as educated as those folks.
 

gjbarord

Sepia elegans
Staff member
Moderator
#11
These findings are interesting, though hard to believe. Perhaps if they were to mention their methodology, it may lend more credence to their findings. Merely stating that they had 2000 observations (from visitors??) is not enough. But it is not a scientific paper and something like that was sure to get press. Hopefully, they will release more information if they continue to lay claims to the "2 arm" theory.

Greg
 

mucktopus

Haliphron Atlanticus
Staff member
Moderator
#12
It's possible that the press overstated what the researchers found. I am not surprised by the take-home message- that octopuses tend to use front arms for manipulation and their back arms for locomotion. While many octos involve front arms during crawling, most of the weight is often on the back arms (the back two in bipedal locomotion). Similarly, if a crab comes up to an octo from behind, those arms can capture the prey. But in my experiences, most octos tend to probe for food, hunt and defend themselves from fish using the front arm pairs (front four arms) more than the back arms. This makes sense. Those are the arms that face the direction the octopus sees best. Where documented (basically in O. digueti and A. acuelatus) arm injuries are more common in the front arms than the back arms, hinting that these arms are used more often in situations that might lead to injury. In aculeatus there are few sex differences in arm injury patterns, implying that most injuries probably come from hunting and defending from fish, rather than aggression.

If you watch very closely the 3rd-5th videos down on the link below, you can see that the crawling octopuses push more with the back arms. In the Wunderpus video the front two arms barely even touch the bottom. The hunting aculeatus uses its front arms to proble into a hole. While these are very short clips, they show common behaviors in the wild. http://www.tolweb.org/onlinecontrib...ontributorImagesPage&service=external&sp=2634
 

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