As divers, we know better than most that the ocean’s wonders come in all shapes and sizes, from the biggest whale to the smallest seahorse. There is one class of marine species in particular, however, that exemplifies the weird and the wonderful — the cephalopods. This class numbers approximately 800 extant species, and includes squid, octopuses, cuttlefish and nautiluses. They are found in all of the planet’s oceans, from the deepest abyss to the sea’s surface. Generally considered to include the most intelligent of all invertebrate species, some cephalopods are masters of disguise, while others are the stuff of maritime legend. Here we’ll take a look at five cephalopods that showcase the incredible diversity of this strange group of creatures.
Flamboyant Cuttlefish
In the natural world, beauty is often synonymous with danger. This is certainly true of the Pfeffer’s flamboyant cuttlefish, a species whose range includes Australia, the Philippines, Indonesia and Malaysia. Reaching lengths of up to 3 inches (8cm), the flamboyant cuttlefish can change color rapidly, exhibiting startling shades of yellow, brown, black, white and red at will. It is thought that the flamboyant cuttlefish uses this ability not only to camouflage itself when stalking prey, but also to warn predators of its highly toxic nature. This cuttlefish is one of only three toxic cephalopods, and is thought to be as poisonous as its distant relative, the blue-ringed octopus. It also moves in a unique way, and is the only cuttlefish species known to ‘”walk” upon the seafloor, using two of its front arms as legs. This may be because this species has an unusually small cuttlebone, making it difficult for it to remain buoyant for long periods of time.
Mimic Octopus
Although the ability to change color and even skin pattern is common to all octopus species, the mimic octopus takes its aptitude for camouflage to a whole new level. Growing up to 2 feet (60cm) in length, a mimic octopus’ natural coloration is beige. But when threatened or in predatory mode, this species can alter its appearance entirely so that it resembles a number of other animals. It does this not only by changing color via the chromatophores in its skin, but also by changing its shape. Although there are several species in the natural world that can mimic other animals, this octopus is the only one that has a whole repertoire of potential disguises, including the lionfish, whose splayed fins the octopus mimics by spreading out its tentacles, and the sea snake, whose sinewy body the octopus mimics by burying itself completely in the sand save for a striped tentacle or two. Because these animals are venomous, it’s likely that the mimic octopus copies them as a form of defense.
Nautilus
Of all the cephalopod species, the nautilus family is the oldest, having remained largely unchanged for millions of years. There are six extant species of nautilus, all of which are regarded as living fossils and are found only in the waters of the Indo-Pacific. Nautiluses are different from their other cephalopod cousins in several ways, most notably in that they are equipped with a hard shell into which they can fully withdraw if necessary. This hard shell is the nautilus’ only form of defense, as they cannot expel ink in the same way that other cephalopods can. Nautiluses spend the majority of their time hundreds of feet deep, ascending only to feed, mate and lay eggs. However, they must be careful not to exceed 2,600 feet (800m) — beyond that, the surrounding pressure becomes too great and their shells are likely to implode. Nautiluses use jet propulsion to move themselves through the water, and are among the longest lived of all cephalopod species, with a lifespan of over 20 years.
Southern Pygmy Squid
The smallest of all cephalopod species, this tiny squid is found in bays and inlets from southern Queensland to the mid-coast of Western Australia. It is one of seven pygmy squid species, and grows no bigger than 1 inch (2.5cm), and males are generally even smaller than females. Despite their size, pygmy squid are capable hunters. They feed on small crustaceans, which they kill after biting the spinal cord to induce paralysis. Southern pygmy squid are normally yellowish brown in color, and are therefore perfectly camouflaged for the seagrass beds that they call home. They have a sticky glue gland on their backs that allows them to adhere to the underside of the seagrass whenever they tire of swimming. Reproduction is an interesting affair for pygmy squid, with the male attaching sperm cells to the female’s body, which she then uses to fertilize her eggs. Once fertilization is achieved, the female pygmy squid uses her glue to attach the eggs to the seagrass as well.
Giant Squid
If the pygmy squid represents the smallest member of the cephalopod family, then the giant squid undoubtedly represents the largest. Amazingly, for a creature thought to reach up to 43 feet (13m) in length, it wasn’t until the 1870s that the giant squid transcended the boundaries of myth and became a scientific reality. Prior to that, mariners’ tales often included terrifying accounts of these colossal animals, but it wasn’t until specimens washed up in New Zealand and Newfoundland in the 1870s that they were officially recognized. Similarly, it was only as recently as 2012 that the giant squid was finally filmed alive in its natural habitat, meaning that this species is not only the largest cephalopod but also, ironically, one of the most elusive. It is believed that they spend much of their lives at depths of up to 3,300 feet (1,000m), where their only natural predator is the sperm whale. There have been various unsubstantiated reports of giant squid acting aggressively towards ships, and yet the diet of this species seems to consist primarily of deep-sea fish and other types of squid.
