Differences between squid and octopus

There is a common misconception regarding which animal is which, many mistaking octopuses for squids and vice versa. In order to help differentiate them, four essential elements are to be discussed: their appearance, their anatomy, their locomotion, and their hunting methods. Cephalopods are a diverse and versatile bunch of animals. The many kinds of octopi, squid, nautilus, and cuttlefish that make up the class Cephalopoda are clever predators and scavengers that can live in many different depths and environments in the world’s oceans. All cephalopods are soft-bodied, with arms around a central mouth; highly developed, image-forming eyes; and a tube-shaped organ called a funnel, or siphon, near the head. Cephalopods have evolved a remarkable variety of modes to get from one place to another. Some swim using all their arms, some wave small fins along their body, and others can actually walk from place to place along the seafloor. According to What's the Difference? Octopus vs. Squid. (2020, January 22), “They are cousins—both part of the group Cephalopoda—a group of marine mollusks that include squid, octopus, nautilus, and snails”. The biggest of their species is the giant squid and the smallest, the pygmy squid. All these animals are characterized by having symmetrical bodies, lacking vertebrae, gargantuan heads, and arms or tentacles that extend from their bodies. Being pretty different from the nautilus and snails, octopuses and squids have chosen to evolve in a quite opposed direction: while the first require the use of a hard shell to protect themselves, the latter traded it for other abilities, including but not limited to camouflaging, heightened intelligence, and strong, flexible arms. At the moment of speaking, there are supposed to be almost 300 species of octopuses and other 300 species of squids. Maintained by What’s the difference between Squid and octopus? (2020, July 13), “Squids and octopuses are built similarly, but you can tell they’re different creatures just from their appearance. ” Aesthetically speaking, while the octopus has a round head and eight arms, the squid’s head is triangular and its eight arms reside in the rear, including 2 extra long tentacles and body, and a bony plate called “pen” that is a vestigial remnant of its mollusk shell. It is worth mentioning that a squid has 2 fins on their head, whilst only some rare species of octopus possess them as well. Both have suckers on their tentacles, but the 2 extra ones that the squid has are equipped with specialized hooks and sucker rings with teeth attached. Intriguingly, both squid and octopus have blue blood because of the copper and squirt ink they have in their bodies. D. (n. d. ). Squid vs Octopus lists some important anatomical differences: “Both squids and octopus have three hearts each. Two pump blood through the gills, while the third heart is dedicated blood circulation through the body. The blood in both creatures contains a copper-rich protein known as hemocyanin. Both creatures have similar, though not identical, organ systems. ” It is also mentioned that due to lacking an internal skeleton, the bodies of octopi are very soft, the only hard part being its beak, which is made of chitin, a fibrous substance consisting of polysaccharides and forming the major constituent in the exoskeleton of arthropods and the cell walls of fungi. While the body of an octopus makes it look like a delicate and fine animal rather than a predator, the squid’s is encapsulated in a hard mantle, which has a pair of swimming fins on each side. A squid also possesses chameleonic features thanks to its body being covered in chromatophores, cells that produce color, of which many types are pigment-containing cells, or groups of cells, found in a wide range of animals including amphibians, fish, reptiles, crustaceans, and cephalopods. The underside of the squid is also found to be lighter than the topside, in order to provide camouflage from both prey and predators. The size ranges of both animals are disparate as well: while an average squid can grow up to 60 centimeters on average and end up being almost 20 meters long, octopi can start from as short as 1 centimeter to more than 5 meters. As stated by Locomotion-elementary [PDF]. (2018). New England Aquarium, “Perhaps the most common type of locomotion used by cephalopods is jet propulsion. To travel by jet propulsion, a cephalopod such as a squid or octopus will fill its muscular mantle cavity, which is used to get oxygenated-water to their gills, with water and then quickly expel the water out of the siphon. The force of the water jet coming out of the siphon is opposed in equal magnitude by the force of the cephalopod’s body as it moves in the opposite direction (Newton’s third law of motion: for every action, there is an equal and opposite reaction). These equal, opposing forces send the cephalopod jetting away from its water stream, much in the same way that a rocket ship is sent in the opposite direction of the exploding rocket fuel coming out of its engines. This type of locomotion is a great way for an octopus to accelerate away from danger quickly or for a squid to jump onto unsuspecting prey. ”. The cephalopods are able to point the siphon in different directions, change the amount of water drawn, and the force applied to push it out. Therefore, they have the ability to modify the direction and speed of their jet propulsion. Some of them choose to use their tentacles to help steer, while others possess stabilizing fins on their mantle that aids them in controlling the jet-propelled movements. Between squids and octopi, the first are the fastest due to having long, slender bodies that make it easier to suddenly accelerate toward prey, and stabilizing fins that help with steering and staying on target. While the squid lives more than an octopus with a life span from 9 months to 5 years, respectively 1 to 3 years, the octopus compensates with its hunting behavior. On the report of W, K. (2021, June 15). Squid vs Octopus: What's the Difference? , “Very much like their cousins, the squid, octopuses also use their tentacles to grab and hold onto prey, but that’s about as far as their similarities go. The biggest difference is that instead of using sucker rings and teeth (which they don’t have), they grab and inject their prey with poison, paralyzing the prey. Once completely helpless, octopuses slather their prey with saliva, which dissolves and loosens the meat before using their mouths and beaks to rip and tear the meat from said prey. They prefer to hunt for bottom-dwelling crustaceans because their soft bodies are vulnerable to predation. ” In conclusion, it can be observed that despite coming from the same family, squid, and octopi pack quite a few differences that make each of them unique, starting with their looks and anatomical variance, and ending with specific hunting methods and matters of locomotion.