LSM1303 Animal Behaviour Student Blog : defence mechanism

Is it a Water Balloon?! - Pufferfish

U0609533 — Fri, 21 Mar 2008 21:17:00 GMT

The Water Balloon = Pufferfish...
When we think about pufferfish, we would normally associate it with its ability to puff itself up and make itself look really bloated and big. But have you ever wondered how it actually happens? Get to know some of the facts, find out some other interesting behaviours and witness for yourself how the pufferfish defends itself from its predator by inflating itself up!

Introduction:
The pufferfish, also called blowfish, swellfish, globefish and balloonfish, make up the family Tetraodontidae, in the order Tetraodontiformes. They are named for their ability to inflate themselves to several times their normal size by swallowing water or air when threatened. The scientific name, Tetraodon, refers to the fact that they have four large teeth, fused into an upper and lower plate, which are used for crushing the shells of crustaceans and mollusks, their natural prey.

Puffed up pride:
The pufferfish's unique and distinctive natural defenses are necessary due to its slow speed. Pufferfish use a combination of pectoral, dorsal, anal, and caudal fins for propulsion, making it unmaneuverable and an easy target for predators. As a defense mechanism, pufferfish have the ability to inflate rapidly, filling their extremely elastic stomachs with water (or air when outside the water) until they are almost spherical in shape. They turn themselves into a virtually inedible ball several times their normal size. Thus, a hungry predator stalking the pufferfish may suddenly find itself facing what seems to be a much larger fish and pause, giving the pufferfish an opportunity to retreat to safety.

One particular pufferfish, spiny puffer (Diodon holocanthus) combines inflation and pointy spikes in one spectacular defense mechanism. Compared with creatures like these, the spiny puffer seems relatively normal when relaxed. But when threatened, the puffer undergoes a remarkable transformation, its body swelling until the fish is three times its usual size and has become a rigid, near-perfect sphere covered in spiky armor-not a good design for swimming but decidedly discouraging to attackers.

An Uninflated Spiny Puffer

A more accurate name for this fish would be "pumper," because it inflates not by puffing itself up but by pumping water into its stomach (which has ceded its digestive function entirely to the intestine). The stomach expands to nearly a hundred times its original volume, an astonishing increase made possible by the stomach's being pleated, like a skirt. An amazing amount of material can be hidden away in pleats.

As the puffer fills with water, the fish's spine, already slightly curved, bends into an upside-down U shape, and the liver, intestines, and other internal organs become squeezed between the fish's backbone and its rapidly expanding stomach.

Meanwhile, the fish's skin is pushed out, obscuring most of the puffer's features. Only the mouth-a cartoonish orifice containing heavy, crushing plates capable of pinching a human finger to the bone-remains unaffected.The skin of a fully inflated puffer is stretched to one and a half times its resting length.

"As a spiny puffer pumps water into its stomach, the stomach inflates and the spine arches to accommodate the organ's expansion. Pockets of the stomach soon get shoved above and around the spine, making the fish nearly spherical."

An Inflated Spiny Puffer

The skin also helps deploy the puffer's armor. The scales of this fish have been modified into slender spikes, each on a tripod-shaped, bony base embedded in the skin. Normally the tripod lies on its side, with the spike flat against the skin, pointing backward. But when the fish puffs up, the stretched skin pulls two of the tripod's legs backward and one leg forward, snapping the spike upright. The three legs provide a secure base that blunts the force of anything pushing against the spike's sharp tip.

Last Line of Defense:
A predator that manages to snag a puffer before it inflates won’t feel lucky for long. Almost all pufferfish contain tetrodotoxin, a substance that makes them foul tasting and often lethal to fish. This extremely strong, paralyzing poison is found in many parts of the pufferfish (including the liver, muscles, skin, and ovaries).To humans, tetrodotoxin is deadly, up to 1,200 times more poisonous than cyanide. There is enough toxin in one pufferfish to kill 30 adult humans, and there is no known antidote.

( Amazingly, the meat of some pufferfish is considered a delicacy. Called fugu in Japan, it is extremely expensive and only prepared by trained, licensed chefs who know that one bad cut means almost certain death for a customer. In fact, many such deaths occur annually.)

Other Interesting Behaviour:

Another type of pufferfish, Dogface Puffer, Arothron nigropunctatus, is renowned to have a charming personality, and it is a very individualistic fish. Some interesting facts has been observed when it is kept in captivity. It is reported that when a Black Dogface Puffer is young, it should only be kept with docile and non-aggressive species, since a young Black Dogface Puffer fish is easily frightened. If a young Black Dogface Puffer feels insecure or harassed in the aquarium it might refrain from eating and begin to starve. A Black Dogface Puffer can also loose its appetite if it feels stressed in the aquarium. Unsuitable aquarium companions can stress the Black Dogface Puffer fish tremendously, e.g. poor water quality and tiny space with no place to seek shelter.

What is so Interesting about that?!
If these boring facts are boring you, then how about watching this video? This would probably make you think: 'WOW! PUFFERFISH ARE SO COOL!' Their nature of defence against predators is indeed intriguing and amusing! Like what the narrator in the video says: "how tough can it be (to catch the pufferfish for a meal)?? .... no matter what the otters tries, the puffer refuses to deflate itself...... it sets out to get a fish dinner, instead it is finding itself playing a ball game!"

References:

"Pufferfish, Blowfish, Fugu or Globefish" by Enchantedlearning.com, 21 March 2008

"Tetraodontidae" by Wikipedia, 21 March 2008

"A Fish Story" by Adam Summers (Illustrations by Sally J. Bensusen) by American Museum of Natural History Biomechanics, 21 March 2008

"Pufferfish" by Sheppard Software, 21 March 2008

"Pufferfish" by National Geographic, 21 March 2008

"Freaks of Nature: Self Inflating Fish" by National Geographic, 21 March 2008

"Black Dogface Pufferfish" by Aquatic Community, 21 March 2008

"Arothron Dog Face Puffer" by Tropicalfishdata.com, 21 March 2008

Inhuman Doctors: Zoopharmacognosy and Self Medicating Animals

Vigneshwaran Shunmugam — Fri, 21 Mar 2008 15:15:00 GMT

Many major cultures around the globe have developed some form of medical science. The Indians have Ayurveda, the Chinese have TCM and of course there is Western medicine. What these fields have in common is that they are derived from the process of observing the effects of certain herbs or foods on the health of the imbiber and thus correlating cause and effect. While medical science and its practitioners have long been held to be at the forefront of human intellectual pursuits, we now realise that this was no great achievement at all. In fact, even monkeys do it.

Observe this Orang Utan for example.

Right. This is just a monkey opening a packet of powder. Nothing fancy. However, monkeys DO develop their own medical techniques to deal with their own health issues. This is known as Zoopharmacognosy which is basically the animal form of Medical Science. Many species of animals use various techniques to deal with their maladies.

If you have seen your dog or cat eating grass you may have been puzzled at their sudden vegetarianism. They do have good reason for doing so. Eating grass "stimulates either retching or the rapid expulsion of worms in diarrhea" (Hart and Hart 1985). Compare this with the Tamil proverb which claims that a Tiger would not eat grass, no matter how hungry.

Medicine is not a purely mammalian pursuit either.Snakes too have herbological knowledge! "According to Chinese folklore, many centuries ago a farmer in the Yunnan district found a snake near his hut. Fearful for his life, he beat it senseless with a hoe and left it for dead. A few days later, the same snake returned. Again he tried to kill it, but again it returned. After he had beaten it a third time, the farmer followed the severely wounded snake as it crawled into a clump of weeds, started feeding on them, and thereby rapidly cured the worst of its injuries. The plant in the story was Panex notoginseng, which now forms the main ingredient in the herbal formulation 'Yunnan bai yao', a white powder that cauterizes cuts and stems external bleeding immediately. It was standard issue in the Vietnam War, for use when soldiers were wounded far from conventional medical treatment. "(Reid 1987).

Our closest cousins, the Great Apes have various methods by which they keep themselves in the pink of health.

Above we see a chimpanzee(Pan troglodytes) chewing on the bitter pith of the Vernonia Amygdalina plant. Chewing on the pith allows the chimp to extract the bitter juice that is within. THe chimpanzees use this method to kill parasites in their intestinal tracts. Interestingly, chimps do not usually eat this leaf due to it being slightly toxic to them. Thus, they only eat this leaf for medicinal purposes! This paper has extensive information on this phenomenon, complete with graphs. The author Michael Huffman is an eminent figure in the field of Zoopharmacognosy.

Chimps sometimes consume the leaves of the Aspilia plant, which they got to great lengths to obtain. The leaves are covered in stiff hairs and are swallowed whole, despite the difficulty of doing so. "Huffman doesn't doubt that there is a medicative function behind leaf swallowing behavior. His theory about how it gets rid of worms revolves around the hairiness of the leaves. Huffman found live worms in chimp *** stuck "like Velcro" to leaf hairs and trapped within the folds. He speculates that worms may become attached to the leaves or somehow enticed into the folds during digestion, taking a "magic carpet ride" through the gastrointestinal tract, eventually to be excreted from the body. Chemicals in the plant may also decrease the ability of the parasites to adhere to the intestine, making it easier for them to be swept out by the leaves."

Perhaps the animal use of medicines to treat themselves is not such a surprising phenomenon. In fact post-Darwinists should have predicted it regardless of evidence. Using medical methods enables an animal to prevent its death,prolong its life, to heal faster and have a survival advantage. This is an advantage that would allow those animals who use it to be more successful than those who dont. In the abscence of a consequent negative selection pressure, animals who self-medicate would definitely outsurvive those who do not. Thus, Zoopharmacognosy is not surprisingly prevalent in the animal kingdom.

Not only do animals consume herbs and plants as medicines, but they also consume certain types of soil(geophagy) and insects for the same purpose.

Even more interesting than the fact that animals employ medical science is the fact that many of the herbs and techniques employed by animals are similarly employed by humans. This highlights the cross pollination of medical knowledge from the animal kingdom to ours.

To learn more on the exciting field of Zoopharmacognosy, this book might help.

"Really Wild Remedies—Medicinal Plant Use by Animals" by Jennifer A. Biser. Zoogoer, January/February 1998

Huffman, M.A. 2001. Self-Medicative Behavior in the African Great Apes: An Evolutionary Perspective into the Origins of Human Traditional Medicine. Bioscience, 51(8):651-661.

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Is it a Water Balloon?! - Pufferfish

U0609533 — Fri, 21 Mar 2008 13:18:00 GMT

An Inflated Spiny Puffer

Last Line of Defense:
A predator that manages to snag a puffer before it inflates won’t feel lucky for long. Almost all pufferfish contain tetrodotoxin, a substance that makes them foul tasting and often lethal to fish. To humans, tetrodotoxin is deadly, up to 1,200 times more poisonous than cyanide. There is enough toxin in one pufferfish to kill 30 adult humans, and there is no known antidote.

Other Interesting Behaviour:

Another type of pufferfish, Dogface Puffer, Arothron nigropunctatus, is renowned to have a charming personality, and it is a very individualistic fish. Some interesting facts has been observed when it is kept in captivity. It is reported that when a Black Dogface Puffer is young, it should only be kept with docile and non-aggressive species, since a young Black Dogface Puffer fish is easily frightened. If a young Black Dogface Puffer feels insecure or harassed in the aquarium it might refrain from eating and begin to starve. A Black Dogface Puffer can also loose its appetite if it feels stressed in the aquarium. Unsuitable aquarium companions can stress the Black Dogface Puffer fish tremendously, e.g. poor water quality and tiny space with no place to seek shelter.

What is so Interesting about that?!
If these boring facts are boring you, then how about watching this video? This would probably make you think: 'WOW! PUFFERFISH ARE SO COOL!' Their nature of defence against predators is indeed intriguing and amusing!

References:

"Pufferfish, Blowfish, Fugu or Globefish" by Enchantedlearning.com, 21 March 2008

"Tetraodontidae" by Wikipedia, 21 March 2008

"A Fish Story" by Adam Summers (Illustrations by Sally J. Bensusen) by American Museum of Natural History Biomechanics, 21 March 2008

"Pufferfish" by Sheppard Software, 21 March 2008

"Pufferfish" by National Geographic, 21 March 2008

"Freaks of Nature: Self Inflating Fish" by National Geographic, 21 March 2008

"Black Dogface Pufferfish" by Aquatic Community, 21 March 2008

"Arothron Dog Face Puffer" by Tropicalfishdata.com, 21 March 2008

Octopus - The devil fish capable of dragging down ships??

LIN WANHUA — Mon, 17 Mar 2008 18:33:00 GMT

With it's 8 menancing looking arms, it's not surprising that sailors of the past used to fear the Octopus and called it the Devil Fish.

Why did i choose to blog about the octopus out of all the many other interesting animals out there? My interest in them can be attributed to my favourite show, the "Pirates of the Caribbean". Perhaps it is a coincidence that the "villain" of the show, Davy Jones, had facial features that resembled an octopus. Or yet by chance that the monsterous sea creature, the Kraken, really looked like an oversized octopus. That really sparked off my interest in this mysterious underwater creature...

Image (Above) of Captain Davy Jones, taken from http://www.sfgate.com

Image (Above) of the Kraken sinking a ship, taken from http://en.wikipedia.org/wiki/Kraken_%28Pirates_of_the_Caribbean%29

But yet, was it really an Octopus that Davy Jones and the Kraken resembled? Perhaps it was a squid instead of an octopus! So what is the difference between Octopus and Squids? While they may appear to be similar, there are some fundamental differences. The major distinction would be that the suckers of squid are armed with hooks or sucker rings, sometimes both; while octopuses have simple suckers without secondary armature. However, today I would be concentrating on the Octopus instead of the squid.

The Octopus, refers to creatures belonging to the genus, Octopus. To date, there are around 300 recognized octopus species in the world.

Image (Above) of the Common Octopus, Octopus vulgaris, taken from http://en.wikipedia.org/wiki/Octopus.

So... are Octopuses as scary and terrifying as the old sailors made them out to be?

Unlike sharks, they do not have razor sharp teeth. In fact, octopus do not even have a protective outer shell to protect if from predators. Majority of octopuses have almost entirely soft bodies with no internal skeleton. This sure makes it seem like an easy meal to swallow!!

Yet, how have these sea creatures eluded their predators and instead become excellent hunting machines?

Certainly, their mascular eight arms allow them to put up a tough fight against predators. However, not all battles can be won and when you can't beat them, run! And that's certainly an easy task for the Octopus whose body structure allows them to escape to safety by squeezing through very narrow cracks between underwater rocks where predators cannot follow. Even a 600 pound Octopus can pass through a tight passageway no larger than the size of a quarter coin.

Exactly how flexible are these creatures? You'd have to see it to believe it.

Watch how the octopus gets out of a tight situation.

Watch the Octopus escape through an one-inch hole!!

Other defensive mechanisms employed by the Octopuses include the usage of camouflage, mimicry, ink sacs and autotomising limbs.

Camouflage:

A very important tactic to avoid detection by predators, is the use of certain specialized skin cells which can change the apparent color, opacity, and reflectiveness of the epidermis. When possible, Octopuses prefer to aviod head-on confrontation with their enemies and prefer to remain unnoticable. They been observed to have the ability to adopt different textures, (such as those of a seaweed, uneven coral reef, bumpy rocks) of their mantle in order to reach the highest stage of blending in with the environment.

Image (Above) of an Octopus blending into it's surroundings, taken from http://hmpadventures.dk

Watch this video to see the shape-shifter and colour-changer perform its magic.

Mimicry: Certain species of Octopus, go a further step to combine their highly flexible bodies with their color changing ability to allow for the accurate immitating of some of the most dangerous sea creatures such as the lionfish, sea snakes and eels. By adopting the posture or movements of the lionfish or sea snakes, the mimic octopus deters enemise from eating it as fishes do not want take the risk of eating the wrong thing.

Image (Left) of a Mimic Octopus imitating a Lionfish, taken from http://www.michaelaw.com

Image (Right) of a Lionfish, taken from http://www.amnh.org

Are they successful at imitating other sea creatures? You be the judge.

Ink sacs: If spotted by their enemies, most octopuses eject a jet of thick blackish ink to allow for their escape by blinding and confusing their enemies. This ejected ink goes a further step to dull smells which is very useful for evading hunters that rely on their sense of smell, like sharks.

Image (Above) of an Octopus ejecting ink, taken from http://encarta.msn.com/media_461532742/octopus_ejecting_ink.html

Autotomising limbs: If everything fails and an octopus is unable to break free from a predator's attack, some octopuses can detach their own limbs at their own will, similar to how lizards drop their tail to escape from predators. The Ameloctopus is one such species who employ such evasive tactics.

Watch the video to have a better look at the Ameloctopus in action!

http://video.nationalgeographic.com/video/player/animals/invertebrates-animals/octopus-and-squid/octopus_amel.html

Please do not be fooled into thinking that an Octopus is only capable of elaborate defensive techniques. Instead, the Octopus is able to leverage on such capabilities to change its status from the hunted to the hunter.

Their flexible body structure allows for them to explore tight corners and deep crevices to look for food. Not only can their colour-changing, shape shifting ability be used for predator evasion, it can also be used to sneak up on unsuspecting prey. The squirting of ink can also be used to confused their prey and prevent them from escaping. This speaks volume of the versatile nature of this sea creature.

AVP? Not exactly. In the battle of the Shark versus the Octopus, who would emerge victorious?

Can the defense tactics of the Octopus protect it from the prowling Shark?

Find out here!

Ever wondered how intelligent Octopus are?

It has been argued that they are probably the most intelligent invertebrates around. Although unable to tell the depth of their intelligence and learning capability, the usage of mazes and problem-solving experiments has revealed that Octopus do have both short and long- term memory. Laboratory experiments also observed that Octopus are possibly capable of observational learning. An experiment in 1992 by Graziano Fiorito and Pietro Scotto highlighted the possibility that Octopus had the potential to learn by watching. Although strongly this theory was contested by many, it does remind us of the endless possibilities of the true intelligence of the Octopus.

"An octopus in a German zoo has learned to open jars of shrimps by copying staff - and is now showing off her skills to visitors."

Read the full articule here: http://news.bbc.co.uk/2/hi/europe/2796607.stm

References:

"Armed But Not Dangerous," by Doug Stewart. National Wilflife, Vol. 35 No. 2. Feb/Mar 1997.

http://animals.nationalgeographic.com/animals/invertebrates/common-octopus.html

http://en.wikipedia.org/wiki/Octopus

http://encarta.msn.com/media_461532742/octopus_ejecting_ink.html

http://hmpadventures.dk

http://news.bbc.co.uk/2/hi/europe/2796607.stm

http://video.nationalgeographic.com/

http://www.amnh.org

http://www.lookandlearn.com

http://www.sfgate.com

http://www.tonmo.com/science/public/giantsquidfacts.php

http://www.youtube.com

Smelly ground squirrels fool hungry rattlesnakes

CHAN JINGWEN, JANE — Sun, 16 Mar 2008 04:23:00 GMT

Predators have a remarkable evolutionary effect on the morphologyand behaviour of their prey. In their attempt to reduce thelikelihood of being killed, prey species have evolved a varietyof counterstrategies, including the ability to smell like their predators to discourage pursuit or attack.

It seems like an uneven match. In one corner, the unassuming California ground squirrel (Spermophilus beechyi) or rock squirrel (Spermophilus variegatus), 30cm in length. In the other, the rattlesnake (Crotalus spp.), more than twice the length of the squirrel, and armed with hinged fangs that pack a lethal venom. But thanks to a cunning adaptation, the squirrel often gets an unexpected upper hand in this bout.

Chemical substances unique to one species are occasionally found on the body of a different species. Animals often ingest such foreign substances and sequester them into their integument, but here is a case of direct application of heterospecific substances to the body. Female California ground squirrels and rock squirrels chew on skins shed by rattlesnakes then lick themselves and their pups. This "snake scent application" (SSA) to their fur apparently anoints the squirrels with the odour of their enemy, most likely premeditated for antipredator shield.

To find out the function of this olfactory disguise, Barbara Clucas and company of the University of California in Davis captured 30 California ground squirrels (14 adult females, 9 adult males, and 7 juveniles) and 41 rock squirrels (16 adult females, 14 adult males, and 11 juveniles) and offered them frozen shed skins from different rattlesnakes. Their results ruled out ectoparasite defence and conspecific deterrence, and indicated that SSA most likely serves an antipredator function for ground squirrels.

This intriguing form of adaptive behaviour is a wonderful illustration of the many evolutionary arms races between predator and prey. Wild, snake-scented ground squirrels may evade attack because they no longer smell tasty. Fascinatingly, the weaker adult females and juveniles are known to spend more time applying scent than did adult males. Adult ground squirrels have essentially developed a certain degree of immunity to snake venom and their agility helps them avoid strikes. But their pups are still vulnerable and due to maternal instinct, adults disguise their scents by chewing on the discarded skins of rattlers and licking them.

The abovementioned study has established one of a remarkable package of defences that squirrels use against rattlesnakes and could very well be an onset to prove SSA as a novel form of defence behaviour in vertebrates!

Reference:

Clucas B., M. P. Rowe & D. H. Owings, 2008. Snake scent application in ground squirrels, Spermophilus spp.: a novel antipredator behaviour? Animal Behaviour, 75(1): 299-307.

Image of California ground squirrel taken from here;

Video clip of California ground squirrel chewing on shed rattlesnake skin taken from here;

Image of Southern Pacific rattlesnake (Crotalus oreganus helleri) taken from here. Photo credit: Russ Smith.

Related stories on ground squirrels and SSA:

Clucas, B., D. H. Owings & M. P. Rowe, 2008. Donning your enemy’s cloak: ground squirrels exploit rattlesnake scent to reduce predation risk. Proceedings of the Royal Society: Biological Sciences, 275(1636): 847-852.

“Smelly squirrels fool hungry snake.” 2006. The New Scientist, 191(2565): 17.

“Squirrels use snake scent.” UC Davis News Services, 19 Dec 2007.

More about ground squirrels and antipredator tactics:

Rundus, A. S., D. H. Owings, S. S. Joshi, E. Chinn & N. Giannini, 2007. Ground squirrels use an infrared signal to deter rattlesnake predation. Proceedings of the National Academy of Sciences of the United States of America, 104: 14372-14376.

Swaisgood R. R., D. H. Owings & M. P. Rowe, 1999. Conflict and assessment in a predator-prey system: ground squirrels versus rattlesnakes. Animal Behaviour, 57(5): 1033-1044.