The saying that "if humans go extinct, octopuses will rule the planet" has been around for a long time. Without discussing this statement, it is difficult to distinguish between squid, cuttlefish and octopus.
Squid, cuttlefish and octopus are all soft organisms belonging to the cephalopod order. Cephalopods were first present in the oceans in the late Cambrian period and were already at the top of the food chain in the Early Paleozoic. After a long evolutionary process, there are two suborders of cephalopods, one is the subclass Nautilus, known as the "living fossil", the famous Nautilus belongs to this subclass, and is the only surviving cephalopod with a shell; and the other is the suborder Scorpiopod, which includes squid, cuttlefish and octopus that make us unclear.
Squid: A domineering "hunter" who is fast and has good eyesight
Squid usually refers to open-eye and closed-eye species, which are the most "multi-offspring" offshoots in cephalopods, which in total include more than 300 species. From the mesonychoteuthis hamiltoni, the king who can fight the sperm whale, to the "Higashiyama Pipe", which makes diners everywhere linger. They generally have slender bodies, highly evolved eyes, a pair of fins, 4 pairs of wrists and a pair of specialized tentacles. Over the course of a long evolution, their exoskeletons gradually degenerated, leaving only a slender, long chitinoid inner skeleton wrapped in the mantle membrane.
In the sea, squid are very domineering predators. Their streamlined figure allows them to spray water through a funnel and swim as fast as a rocket in the water. When hunting, their two long tentacles can be used to catch prey, and the 8 wrists are controlled. The powerful beak can then cut the prey into appropriate sizes and swallow them piece by piece. Highly evolved eyeballs give them some of the best eyesight among marine life, so in the sea full of "myopic eyes", they can largely locate their prey through their eyes. They are one of the most intelligent invertebrates.
It has been observed that the American giant squid living in the eastern Pacific Ocean can even hunt cooperatively in groups. However, ferocious squid can still be a meal on the plate for carnivorous fish such as sharks, seabirds, seals and cetaceans, especially sperm whales.
Cuttlefish: A "chameleon in the sea" that can be transformed in just one second
Cuttlefish refers to the species in the order Cuttlefish, or squid. Their inner shell is famous in the field of Chinese medicine, which is called "cuttlefish bone" or "sea mantis".
For cuttlefish themselves, the inner shell is an important buoyancy regulatory organ. The body of cuttlefish is usually flattened and oval, but also has highly evolved eyes with w-shaped pupils. Most cuttlefish mantle membranes can grow up to 15 to 20 cm, and the largest Australian giant cuttlefish can reach up to 50 cm.
W-shaped pupil of cuttlefish Image source: Wikipedia
Cuttlefish have a unique ability to change color, and are known as "chameleons in the sea". This discoloration can occur even within a second. Cuttlefish change color and pattern (including the polarization of reflected light waves) to communicate with their peers and camouflage themselves, and warn and deter potential predators.
In some cases, humans can train cuttlefish to change color in response to stimuli, suggesting that their color changes are not entirely congenital. In addition, the ability to change color helps those "petite" males to successfully reproduce in the fierce reproductive competition. Although they cannot defeat their larger competitors head-on, they can disguise themselves as females by changing color, blatantly "inserting a foot" in the cuttlefish "couple", and handing their seminal vesicles to the real females.
Returnee cuttlefish/white-spotted squid in mate Credit: science photo library
Octopus: A "wise man" with 8 wrists who can "think independently"
Octopus, which is commonly known as "octopus" and "grub", belongs to the octopus order under the order Octopus. As the name suggests, the octopus has only 8 wrists, each of which is covered with suction cups. In males, one wrist is specialized as a hand-over wrist, which is specifically used for mating. Their bodies are ovoid in shape and are very different from species of the decalopod order. Soft bodies allow them to change their shape at will, even very small gaps—as long as the gaps are larger than their beaks, they can drill through. Of course, this also benefits from the complete disappearance of their bones.
What pushed them to the center of public opinion of "dominating the planet"? The answer is that they are highly developed and complex nervous systems and super vision. They have 2/3 of the nerve cells located in the wrist, which allows the wrist to react quickly without the need for instructions from the brain. It can be said that each wrist has "independent thinking ability".
Not only that, but the octopus's eyes are like a camera and can feel the polarized light. They also have opsins in their skin that respond to different wavelengths of light, which allows them to camouflage better, and pigment cells in the skin can respond to outside light independently of the eye. Such extraordinary "intelligence" and behavioral complexity make them a race among invertebrates.
Therefore, in the future, when discussing "octopus rules the earth", it is better to distinguish who is the real octopus.
Contributed by the Marine Science Popularization Professional Committee of the China Association of Popular Science Writers
Source: Popular Science Times
Author: Hu Juntong
Editor: Wu Tong
Review: Wang Fei
Final Judge: Chen Lei
< public number id: kepuing >