The question arose — the way questions can in science — when the team was faced with a freshly dismembered octopus arm that eagerly clung to everything it touched, with the exception of itself.
Octopuses are among the most extraordinary creatures in the ocean. They can blend into the background, morph into the shape of other beasts, and even regrow limbs lopped off by predators and scientists.
However, for all their impressive feats, the octopus’ walnut-sized brain cannot keep track of what its eight arms are doing. The problem is too hard. Since each arm is studded with suckers that act on contact, the mystery is: How do octopuses not get tangled up in knots?
Researchers in Israel set out to answer the question in a series of experiments that grew steadily more gruesome and in time made full use of the common octopus’ ability to grow back missing appendages.
Binyamin Hochner and his colleagues at the Hebrew University of Jerusalem had studied octopus arms for years. The limbs are intriguing for roboticists, because they are autonomous: None knows what the others are doing and they make many of their own decisions. Of the octopus’ 500 million nerve cells, more than half are in their arms.
However, octopus arms have more than a mind of their own. They can survive for about an hour after being amputated. Lone limbs have been seen to grab food and even pass morsels to where the arm thinks its owner’s mouth must be.
It was a student of Hochner’s who first noticed octopus suckers attached to everything except octopus skin. Something about it turned the suckers off.
“We discovered this by accident. We’re amazed nobody noticed it before,” Hochner said.
On more than 30 occasions, Hochner noticed that amputated octopus arms never latched on to themselves. They would attach to petri dishes, but if half the petri dish was covered in gel soaked in octopus skin extract, the suckers avoided that half. The only time one amputated arm grabbed hold of another was when the latter had been peeled.
Tests on octopuses that had intact limbs were more equivocal. Presented with dismembered arms, some octopuses grabbed them as if they were lumps of food, and brought them to their mouths. They were less likely to do so if the amputated arm was one of their own.
Some octopuses seemed stumped. One repeatedly rubbed its arms over an amputated appendage, touching it, but never activating its suckers. Others grabbed at amputated arms, but only where the flesh had been exposed. Still more brought severed limbs to their mouths and held them with their beaks while the arms quickly let go.
“The octopus cannot hold the arm properly with its suckers, so the only way it can hold it is with its beak,” Hochner said.
The experiments, described in the latest issue of the journal Current Biology, suggest octopuses have a chemical in their skin that stops their suckers from sticking. The mechanism is akin to a default setting, which the octopuses’ brain can apparently override.
“It’s a brilliant solution to what could be a really complex problem,” Hochner said.
The scientists now want to learn which chemical, or combination of chemicals, is responsible for blocking the suckers and how the animals can tell their own flesh from that of others.
EVOLVING SITUATION: Of the latest cases, 23 percent were found to be asymptomatic, but the coronavirus strain in Da Nang is more contagious, authorities said A COVID-19 outbreak that began in the Vietnamese city of Da Nang more than a week ago has spread to at least four city factories with a combined workforce of about 3,700, state media reported yesterday. Four cases were found at the plants in different industrial parks in the central city that collectively employ 77,000 people, the Lao Dong newspaper said. Vietnam, praised widely for its decisive measures to combat the novel coronavirus since it first appeared in late January, is battling new clusters of infection having gone for more than three months without detecting any domestic transmissions. Authorities yesterday reported one new
Three Micronesian sailors stranded on a remote Pacific island have been found alive and well after a rescue team spotted their giant SOS message written into the sand on a beach. Australian and US military aircraft found the three men on tiny Pikelot island, nearly 200km west of where they had set off. Rescuers said that the men were “in good condition” with no significant injuries. The men had been missing for three days after their 7m skiff ran out of fuel and strayed off course. Authorities in the US territory of Guam raised the alarm on Saturday after the men failed to complete
A cat that went missing on a family holiday on the shores of Loch Lomond, Scotland, has been identified 12 years later. Tortoiseshell-and-white Georgie spent October half term in 2008 with her owners at the Rowardennan campsite, but vanished as they were due to return home to Greater Manchester, England. After a search of the site the Davies family departed without Georgie, hoping the three-year-old microchipped feline would be located by someone. Over the intervening 12 years, she remained close to the Queen Elizabeth Forest Park site, being fed and cared for by campsite staff and holidaymakers. After the COVID-19 pandemic hit and lockdown
LIFELONG LOSS: Jiro Hamasumi, who was not quite born when an atomic bomb hit Hiroshima, lost his father and other relatives, but said he thinks about his father daily As Japan marks 75 years since the devastating attacks on Hiroshima and Nagasaki, the last generation of nuclear bomb survivors is working to ensure their message lives on after them. The “hibakusha” — literally “person affected by the bomb” — have for decades been a powerful voice calling for the abolition of nuclear weapons. There are an estimated 136,700 left, many of whom were infants or soon to be born at the time of the attacks. The average age of a survivor now is a little over 83, according to the Japanese Ministry of Health, lending an urgency as they share their testimonies