Cephalopod aggression

Members of the class Cephalopoda include all squids, octopuses, cuttlefish, and nautiluses. These ancient creatures have been depicted on pottery as far back as the Bronze Age. Although the usual diet of a cephalopod consists of crustaceans, other cephalopods, and fish, there have been accounts of attacks by these creatures for centuries. From the ancient kraken of Norwegian lore to the elusive giant squid of Jules Verne’s 20,000 Leagues Under the Sea, tales of aggressive actions from cephalopods, no matter whether they are merely legend or reality, abound in our society.

Defensive mechanisms

Tentacles

Tentacles are the major organs used by a squid for defense or to hunt for food. Tentacles are often confused with arms, but they are different. Octopuses have only 8 arms, while squids and cuttlefish have 8 arms and two tentacles. Tentacles typically have suckers only on the very ends (tentacular clubs) instead of along the whole length, and are generally longer. Some of the largest are the tentacles of the giant squid and colossal squid. These tentacles have powerful suckers and pointed teeth at the ends. The teeth of the giant squid resemble bottle caps, and function like small, circular saws; while the tentacles of the colossal squid wield two long rows of swiveling, tri-pointed hooks. The suckers of these large squids are capable of producing suction forces upwards of 800 kilopascals,^[1] which is roughly equivalent to 100 pounds per square inch. Nautiluses have up to around 90 tentacles, but these have no suckers on them at all and only serve the function of bringing small creatures such as shrimp or small fish. These tentacles have strong gripping power due to their ridged surfaces, but are not used for defense.

Arms

Octopuses and squids both have 8 arms, which are shorter than tentacles. Both groups have suckers all along the arm length. The average octopus has roughly 240 suckers arranged in 2 rows along each arm, which makes for a total of 1920 suckers.^{[citation needed]} Most squid do not have as many suckers on the arms as octopuses. The Humboldt squid has only about 1200 suckers in total, but because there are between 20 and 26 teeth on each sucker for a grand total of 24,000,^[2] it is still quite efficient at grappling. The arms of an octopus or squid serve multiple functions beyond grasping prey. They are also used for locomotion by octopuses and as chemoreceptors to taste what the suction cups are grasping.

Beak

The beaks of cephalopods resemble the beaks of parrots. The beak is a very tough structure made of chitin, and it is the beginning of the digestive system of the cephalopod. One of the largest beaks ever recorded was the beak of a colossal squid that was 495 kilograms in weight. This massive squid had a beak with a lower rostral length (LRL) of 42.5 millimeters,^[3] which corresponds to a beak that is the size of a grown man’s hand. These beaks are used for shearing and slicing the flesh of prey to allow the pieces to go through the narrow esophagus of the squid. Many beaks have been discovered in the stomachs of sperm whales, as the stomach juices dissolve the soft flesh of the squid but leave the hard beaks behind.^[3] The largest beak every discovered in this fashion had a LRL of 49 millimeters, which could mean that the specimen this beak came from was up to 600 or 700 kilograms.^[3]

Venom

All octopuses have venom for their intended prey, but few are fatally dangerous. However, the Greater Blue-ringed Octopus is considered to be one of the most venomous animals known to man. The venom of a single blue ringed octopus is enough to kill 10 grown men.^[4] The toxin that is in the venom of a blue ringed octopus is similar to the toxin in a pufferfish, called tetrodotoxin or TTX. These toxins cause very fast paralysis of the respiratory function of the individual, and there is no antivenom. The only treatment for poisonings by a blue ringed octopus is to get medical assistance as fast as possible and commence CPR if the victim loses respiratory function.^[5] Estimates of the number of fatalities reported for the blue ringed octopus vary, ranging from anywhere between 7 and 16 deaths, but most scholars agree that there are at least 11 recorded deaths by blue ringed octopus venom.^[6]

Attacks on humans

Octopus attacks

While squid and octopuses generally shun the presence of humans, there have been multiple accounts of attacks on humans by various species of squid and octopus for different reasons. One account is that of a diver who was attacked by an octopus while filming it. The rather confused octopus was attempting to mate with the cameraman. Male octopuses rarely differentiate between male and female octopuses when they mate, and sometimes they attempt to mate with other species entirely. They grapple onto their chosen target with all of their suckers and attempt to insert the hectocotylus, the special organ that contains an octopus’s sperm packet. This can be quite dangerous to the diver, as the grip of an octopus is not easy to break, and all octopus beaks inject venom, which while rarely deadly is mildly paralytic. However, in the 1960s, octopus wrestling was a popular sport in the coastal United States. There were world championships, held in Puget Sound, Washington, in which over 100 divers would attempt to catch the largest octopus by grappling with it. There were no casualties, and some divers even chose to allow the octopuses to grapple them as a strategy to catch the octopus.^{[citation needed]}

Humboldt squid aggression

Humboldt squid are large predatory squids found in the eastern Pacific Ocean. They can grow up to 5.7 ft (1.7 m). They have gained a notoriety for aggression. In Mexico, they are known as diablo rojo (Spanish for 'Red Devil') and local tales of fishermen claim that people who fell into the waters were devoured within tens of seconds by packs of Humboldt squid. Scott Cassell, filmed the documentary "Humboldt: The Man-Eating Squid" for the Dangerous Waters series of the Discovery Channel.^[2]

Although Humboldt squid have a reputation of being aggressive, there is some disagreement on this subject. Some scientists claim the only reports of aggression towards humans have occurred when reflective diving gear or flashing lights have been present as a provocation. Roger Uzun, a veteran scuba diver and amateur underwater videographer who swam with a swarm of the animals for about 20 minutes, said they seemed to be more curious than aggressive.^[7] In circumstances where these animals are not feeding or being hunted, they exhibit curious and intelligent behavior.^[8]

Giant squid attacks

Giant squids (Architeuthis) are some of the largest invertebrates, trumped tentatively by the colossal squid. Adult giant squids are estimated to reach up to 13 m in length.

In a recent BBC article, the crew of a yacht sailing in the round-the-world Jules Verne Trophy reported that they were attacked by a giant squid. The squid purportedly latched onto the ship and blocked the rudder with 2 tentacles, according to eyewitness reports. Olivier de Kersauson, a veteran yachtsman, was the captain of the yacht that was attacked several hours after leaving from Brittany. When faced with the dilemma of what to do with the beast, Captain Kersauson simply stopped the ship, and the squid lost interest. "We didn't have anything to scare off this beast, so I don't know what we would have done if it hadn't let go," Mr de Kersauson said.^[9]

Mythic attacks

Kraken

Legends of the kraken appeared as early as the 13th century in Icelandic and Norse literature. Reported by some to be the size of a small island and by others to merely be 40 to 50 feet long, the kraken was a symbol of destruction among almost all sailors. Although stories of the kraken whose tentacles could sink small ships and wreck devastation have been refuted, legends of gigantic squid attacking ships may be more believable than previously imagined.

Giant squids and sperm whales

The epic conflict between the giant squid and the sperm whale has been documented many times but never seen. Scars on the bodies of washed up sperm whales indicate that the toothed suckers of the giant squid had been used against them, and the beaks in the stomachs of the whales indicate that they eat the squids. There have been up to 30 beaks gathered from the stomach of a single sperm whale. It should be noted that sperm whales initiate these attacks, and they are never killed by the giant squid. The squid’s beak and tentacles cannot penetrate the thick skin and blubber of the whale enough to cause serious damage.

Notes

1. ^ Smith 1995.
2. ^ ^{a b} Cassell.
3. ^ ^{a b c} Te Papa.
4. ^ Williamson 1996, p. 332.
5. ^ Williamson 1996, p. 334.
6. ^ Williamson 1996, p. 336.
7. ^ Jumbo squid invade San Diego shores, spook divers, Associated Press, July 16, 2009
8. ^ Behold the Humboldt squid | Outside Online
9. ^ BBC News 2003.

References

• BBC News (15 January 2003), Giant Squid ‘attacks French boat’, http://news.bbc.co.uk/2/hi/science/nature/2661691.stm, retrieved 17 April 2011 
• Cassell, Scott Squidly, Humboldt: The Man-Eating Squid, http://diver.net/seahunt/fend/f_scottc.htm, retrieved 17 April 2011 
• Te Papa, The Beak of the Colossal Squid, Museum of New Zealand Te Papa Tongawera, http://squid.tepapa.govt.nz/anatomy/article/the-beak-of-the-colossal-squid, retrieved 17 April 2011 
• Smith, Andrew M. (12 December 1995), "Cephalopod Sucker Design and the Physical Limits to Negative Pressure", Journal of Experimental Biology (199): 949–958 
• Williamson, John A. (1996), Venomous and Poisonous Marine Animals: a Medical and Biological Handbook, UNSW Press