Most intelligent invertebrates on the planet
Cuttlefishes, squids and octopuses belong all to the same class of animals, the Cephalopods. Cephalopod literally means head-feet and like their name indicates the feet of those animals are attached to their heads. Octopuses possess eight arms, whereas squids and cuttlefishes possess eight arms and two longer tentacles. Tentacles to catch prey, like jellyfishes? Yes, but they aren’t related to jellyfishes, though they do have brainless relatives. Surprisingly, those intelligent beings belong to the same group of animals as oysters, clams, sea slugs as well as snails. But unlike their brainless relatives (slugs and snails do have a very primitive form of brain though) cephalopods are highly intelligent beings. Their sensory capabilities and high brain-body ratio clearly separates them from their kin as well as the rest of the more than 1 million invertebrate animals on earth.
There are more than 800 species of cephalopods, most of them equipped with poisonous salvia. The strength of their venom varies, but some are extremely poisonous with some being able to kill human. The king of poison is the greater blue-ringed octopus (Hapalochlaena lunulata) and its venom is able to kill ten adult humans. Fortunately (for fans and observers “unfortunately”) octopuses, squids and cuttlefishes are very timid creatures and dash away with incredible speed whenever they feel threatened. They can do that because they possess a “jet-propulsion” system. The engine works as follows: Muscles within their mantle walls are able to contradict and suck in water into their torpedo-shaped bag-like bodies (refill period). When loaded they can squeeze their muscular body together forcing the water out through a small maneuverable pipe-like siphon. This jet-propulsion system let them dash away with incredible speed and precision (jet period). Through changing the position of their siphon they are able to shoot their body forward and attack prey or dash backwards to escape predators. For slower propulsion, squids and cuttlefishes additionally possess small fins along the sides and rear or their bodies. With their excellent propulsion skills, cephalopods are able to hunt a variety of live prey. Main food sources include crustaceans, small fishes, shellfishes and even other cephalopods. But cephalopods are not only attacked by their own kin, they are also a highly looked for food source for all kinds of carnivores. Beside humans as their main predators, they are hunted by seabirds, fishes, sharks, dolphins and whales. To be able to survive in a quite hostile environment they developed defense mechanisms which are unmatched in the animal kingdom.
Master of camouflage
Cephalopods are not only the most intelligent beings of all invertebrate animals; they are also the absolute masters of camouflage, probably the best in the whole animal kingdom. They can match the brightness, color, patter and textures of their skin to their surroundings in seconds and transform their body shape into odd positions to mimic the environment around them in 3-D. Cephalopods are able to display the full array of rainbow colors, vibrant hues of blues, purples, green or silver, the possibilities are nearly unlimited. To adapt their skin color and pattern, a complex nervous system connects their pigment organs with their exceptional large brain and complex eyes. But not only can they change the color of their skin, they can also change the textures of it, creating bumps, ridges and frills. Octopuses and cuttlefishes were observed to mimic rocks, sea weed and even copy the appearance of flounders and sea snakes. But their display skills aren’t just used for camouflage alone, they are also used for communication purposes and to confuse predators. In case their cover is blown they display a disco-like wild play of patterns, waves and colorful flashings which leave many predators baffled.
Ink defense and arm amputations
But cephalopods defense skills don’t stop there. In case their camouflage and disco skills fail, cephalopods possess a third defense mechanism: the ink bomb. Through an internal ink-sack they release ink and shoot it out through their siphon along with a burst of water. This ink cloud is able to distract predators, cause a burning sensation in their eyes and cause disorientation due to certain chemicals contained in the ink. Should all of the three mentioned defense mechanisms fail they got a last resort: The arm amputation. Any limb which was successfully caught by a predator is simply discharged and later regenerated and grown to its full length again.
Tool using invertebrates
The coconut octopus is famous for its use of coconut shells, shell fragments, shoes as well as plastic containers and other pieces of litter. It collects those things and use them as armors. They are able to totally encapsulate themselves in coconut shells or matching bivalves. As they move to other places, they carry those items with them. Once encapsulated in the bivalves of a clam, they hold the bivalves together with their strong sucker cups. Here a small video of a infant coconut octopus hiding in some clam bivalves (dive site: Pattaya, Huu Chang).