Scientists: Octopus and squid can hear
The discovery resolves a century-long debate over whether cephalopods, the group of sea creatures that includes octopus, squid, cuttlefish and nautiluses, can hear sounds underwater.
Compared to fish, octopus and squid do not appear to hear particularly well.
But the fact they can hear raises the possibility that these intelligent animals may use sound to catch prey, communicate with one another or listen out for predators.
The question of whether cephalopods can perceive sound has been controversial since the early 20th Century. Some experiments suggested that blind octopus seemed able to locate the sounds produced by boats or by tapping on the outside of a tank.
But most cephalopods lack a gas-filled chamber, such as the swim bladders that fish can use to hear. That suggested they could not detect the pressure wave component of sound.
However, sensory physiologist Hong Young Yan of the Taiwan National Academy of Science in Taipei, Taiwan suspected that octopus and squid might use another organ called the statocyst to register sound.
The statocyst is a sac-like structure containing a mineralised mass and sensitive hairs.
Fish also use it to detect sounds, and in previous research, Yan showed that prawns can use their statocysts to hear. “So we extended our work from prawns to cephalopods,” says Yan.
Yan’s team tested the auditory capabilities of two species, the Common octopus Octopus vulgaris and the squid Sepioteuthis lessoniana, often called the Bigfin reef squid.
They discovered that the octopus can hear sounds between 400Hz and 1000Hz. The squid can hear an wider range of sound from 400Hz to 1500Hz, they report in Comparative Biochemistry and Physiology, Part A. ”That indicates that squid have a better hearing capability than the octopus,” says Yan. “Interestingly though, both species hear best at a frequency of 600Hz.”
Avoiding being eaten
The discovery could open up a new understanding of cephalopod behaviour.
“The key question which I would like to investigate is what kind of sounds are they listening to?” says Yan.
“Perhaps they listen to sound to evade predators and can eavesdrop to sounds made by their prey. Or, perhaps they even could make sounds to communicate among themselves.”
French man breaks record for holding breath
CRAU, FRANCE (NBC) – A 37-year-old French man has shattered the world record for holding one’s breath while under water.
The old mark of 10 minutes and 12 seconds was set by a German man in 2008.
The new mark belongs to Stephane Mifsud.
He stayed underwater while holding his breath for 11 minutes and 35 seconds, and there’s a catch, this attempt was an international discipline known as static apnea, simply put, it means you cannot use oxygen before the attempt.
Mifsud trained for six months by practicing 30 hours a week holding his breath from two to eight minutes at a time.
He said he’ll need about two months to recover from the record-breaking attempt.
Sharks can be cuddled like dolphins, say scientists
Sharks can be trained like dolphins to feed from keepers, roll over and enjoy cuddles, according to new research.
In experiments carried out in the US some varieties of shark allowed themselves to be picked from the water and cuddled.
Keepers at the UK’s Sea Life Centres will now use the training techniques in the hope that they will end up with hundreds of trained sharks.
The experts at the aquariums are to begin a period of intensive tuition by using coloured boards and sounds to train the sharks in a similar way to that used by the scientist Ivan Pavlov in training dogs.
It will mean that feeding becomes easier because each shark in a tank will know when it is their turn to feed.
The Sea Life centres have many different types of shark and within just three months the brightest ones should be responding to commands.
Sharks learn the signals then, when they see or hear them, they approach the keeper who holds a “target stick”.
The sharks then rub their noses against the stick and wait until they are fed.
No one had attempted to train sharks in this way before, but it could now teach experts a great deal about the creatures.
Carey Duckhouse, of Sea Life, said: “The US team has shown that many varieties of sharks can quickly learn to respond to a combination of audible and visual signals.
“A shark answers its own sound and colour signal by putting its nose on a target-stick held by the trainer, and keeping it there until it receives food.
“Some species, such as zebra sharks, will even roll over to have their tummies scratched or allow themselves to be lifted from the water without any kind of struggle.
“The implications for improving shark welfare are enormous. It means when we have to move them we can get the sharks to swim to a certain spot rather than have to chase them around.”
For more under the sea tales head to underwatertimes.com
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