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Zoology has brought to my attention some of the most interesting invertebrate animals on planet Earth. Every invertebrate animal usually has their own uniqueness about them as to why one might find them interesting to learn some. Therefore, one section of learning in specific did stand out to me the most. Order Octopoda stood out to me in so many interesting ways. I decided to write this paper on something I found interesting to not only deepen my knowledge of this animal, but hopefully help do the same for those reading.
Order Octopoda belongs to the Class Cephalopoda and Phylum Mollusca. Within the Phylum, there are multiple classes that contain different animals and the only reason they are separated the way that they are is because they receive some specific characteristics that can differ (Figure One). Within Class Gastropoda, there are conch shells, whelks, moon snails, and olive shells. Next, there is Class Bivaliva and this class contains things such as mussels and clams. The most interesting to learn is Class Cephalopoda where one would find the octopus under this division along with cuttlefish, squid, and chambered nautilus. According to the Grecian language, “kephale” means head and “pod” means foot (Greek Latin 1). Meaning anything that ends in “pod” means there is some type of foot to it, hence Octopoda. This Class doesn’t have only Octopoda, it also possesses three other parts of this taxonomy. These animals are more or less closely related to each other, especially the squid, cuttlefish, and octopus. The many defining characteristics of Order Octopoda is what sets them apart from many organisms. Their eight legs contain around 200 suctions per tentacle, and the males have one arm that is modified because of when they mate with females, they need a spoon-like arm to reach their spermatophores to the female (Octopodidea 1) (Octopus 1). The mantle on top is what houses all of the octopuses organs. They also have pigment sacs that let their skin change colors to help them hide from predators. Octopuses lack a, therefore, they are able to squeeze into small spaces to also help them hide from predators. the blue-ringed octopus is a species of Octopuses and they are also one of the only species that is poisonous. The venom in the blue-ringed octopus is within their saliva making it easier for the venom to be transferred to a predator or even a human. The bite often painless, the venom, however, is toxic and attacks your muscles and works its way up to your diaphragm and eventually stops your lungs if you don’t seek medical care. The Blue-ringed octopus carries enough venom to kill twenty-six adults (Small but Deadly). Blue-ringed octopus feed on crabs, and shrimps and hunt normally during the day. Their species is called Hapalochlaena maculosa. Another species is called Octopus bimaculoides but the generic name is the California Two-Spot octopus. They are more of a friendlier type of octopus and spends most of its time isolating themselves. When these octopuses mate, they tend to avoid it until its time and when they do mate, they do it as quick as possible. This species has a lot of human interaction because they live in shallow waters. Also, there is a species called the mimic octopus and its scientific name is Thaumoctopus mimicus. The reason they are called mimic octopus is that they can transform themselves to look like almost anything. They can look like sea snakes, crabs, shrimp, and even jellyfish. They are black and white just like you would see on a human mime (Its World Octopus Day 1). octopus has their own characteristics, yet they are shared with squids and cuttlefishes. Squids belong to Order Teuthoidea and their Family is called Loliginidae and the cuttlefish belong to the order of Sepiidae and their Family is called Sepiidae. Cuttlefish and Squids are in same Phylum as the Octopus because they share similarities such as being very intelligent, having no cuttlebone, complex eyes, being able to change their skin and to squeeze into smaller areas. Sometimes some of the organisms use their tentacles and use large stones to barricade themselves. Squids, Cuttlefish, and Octopus are all bottom feeders.
Viewing an octopus without studying it, you can see that it has eight tentacles, suctions on the tentacles, eyes and a larger head. Beginning with the arms, there are a few specific reasons as to why they are developed the way they are. For starters, the eight legs are used for transportation to be able to move from place to place. Typically, when one leg is injured it can grow back and become normal and useful again. When it comes to male octopuses, they still have the eight arms you would find in a female, however, one is now modified. This modified arm is called a Hectocotylus. In order for mating between octopuses to happen, the male has to give off a spermatophore, and since the male has a modified arm, the male is able to reach the spermatophore into the females’ ovaries and fertilize the eggs. Now onto a very complex part of the octopus, the eye. Their eyes are considered a camera-type eye because it contains an iris, circular lens, pigment cells, vitreous cavity, and photoreceptor cells (Figure 6). The cephalopod eye is commonly compared to a vertebrate eye through convergent evolution however, the vertebrate eye bases its movement off of motion and the cephalopod eye bases its movement off of invaginations (Cephalopod Eye 1). Octopus also has what is referred to as a beak and a radula in the mouth. The beak is used for when an octopus is lurking for food. Whenever they come across a crab, they can use the beak to break the crab’s shell and proceed to eat the meat that is inside. The radula is used for drilling into the food that they bring in. It is a row of very sharp tiny teeth so it protrudes any hard shell and breaks it just like the beak (Figure Two). The siphon is also a huge part of the respiration for the octopus, this is found at the very base of the mantle. This is an important feature as water flows in through the gill slits, moves past the gill slits and out through the siphon, being able to shoot out water rapidly, this helps the octopus zoom away from predators very quickly. Located near the siphon, another interesting feature called the ink sac. Octopus produce ink when they are feared by a predator. Octopus does not have an external shell at all so, they are able to squeeze themselves into smaller areas to run away from predators, which is considered a huge advantage. This is a very useful thing for them because it keeps them alive. Going on up from the eye to the head of the octopus which is referred to as the mantle. This is the home to all of the organs the octopus needs. The digestive system, gills, hearts, and reproductive system are all formed in the head of the octopus. The gills are used for the respiratory reasons and help pump in the oxygen that they need. As humans, we have one heart that does the job with different pathways for the blood to circulate to the rest of the body. Whereas the octopus has three hearts that are used. They have two branchial hearts and a systematic heart that are utilized. The two branchial hearts pump blood through each of the gills and the systematic pumps blood through the whole body of the octopus (The Giant Pacific Octopus 1). Pulmonary circulation pumps blood from the right side of the heart to the lungs and in systematic circulation, it pumps blood from the left side of the body and transports it to tissues of the body (Cardiovascular System 1). The octopuses nervous system is separated into three different sections: the central brain which houses 40 to 45 million cells can be found within the cartilaginous capsule. The other two parts being the optic lobe and the nervous system of the arms. The optic lobe contains 120 to 180 million cells (3.3 Octopus nervous system). The amazing thing about octopus is that they have about two-thirds of their neurons found in their arms, around 350 million cells. Their nervous system is extremely complex, and the neurons found here to give their arms their ability to multitask (Voight 1). Each individual sucker on their arm works independently. they change the suckers shape to form a tight seal and contracts their muscles to form a powerful suction when it touches something. They are able to control their arms whatever way they prefer. Octopus are able to sense their own body from other objects as well as a specific chemical which allows them to not get stuck to each other or themselves (Why Octopus Arms Don’t Get Tangled 1).
The octopus has eight legs for a reason and they are certainly used most of the time. In the previous category, the characteristics of the eight arms were discussed. Giving a little bit of insight on what they did, however, now we will dig deeper into other things for example – what the arms are capable of. Recall the siphon that was discussed earlier that is used to pump water out and jet away from predators – that’s not its only job. When an Octopus is in search of shelter, they aim to make it as fitting for them as possible. That being said, when an area is congested with sand and/or rocks and it is difficult for them to make the home, the octopus gathers the sand and/or small rocks that is in the area and puts them underneath one of the arms and jets water out of its siphon and by doing so it will clear some of the obstruction. The octopus will continuously do this until the area is clear and is fitting for a home. Focusing on the behavior of octopus, I have read that they can have different personalities. Their personalities can range just like humans from a friendly octopus who enjoys playing while others are aggressive, always annoyed, and easy to anger. Time to time one will see an octopus even break out of their own tanks. Most of the time this is to attempt to make their way over to a tank that they have been eyeing up after they eat all the crabs and clams that were in that tank they will then make their way back to their old tank (Stankus 1). Every octopus that is in the order Octopoda are considered to be active predators. Octopus feed mainly during the night since they can see in the murky waters. They also have pigmented sacs, which allows them to be able to change the color of their skin (Octopus Feeding 1). There a few ways that an octopus can attack, some are by their ink sac, poisonous venom, or simply by surprise. The act of trying to hunt for their food by using their ink sac is a very simple yet useful way. When they approach a prey, they spray them with some of the ink to disorient the prey and then the octopus will take action (How do octopus attack? 1). Their poisonous venom is enough to inject into their prey and immobilize them which makes it easier on the octopus to handle the food and eat it better. Good news is that their venom it is not enough to kill a human (Figure Four). Although beware as the blue-ringed octopus does indeed have venom strong enough to kill a human. Another interesting fact about octopus is how they mate with one another. As previously stated, for a male octopus, they have a modified arm called hectocotylus and it carries rows of sperm. The male octopus will then usually reach into the female’s oviduct and fertilizes the eggs, but the interesting part of this is that the male can detach that part of the arm and the female can save the arm for later when she is ready to be fertilized (Horton 1).
Octopuses are strictly aquatic animals. they generally live in the Mediterranean Sea and the Atlantic Ocean but in all actuality, they live and can be found anywhere that is 100 to 150 meters below the surface of the water. They normally can be found in dens that are typically under rocks or they go and make their own shelter out of the debris in the oceans. They can also live in corals as well as the burrows they make for themselves (Habitat 1). Their stay in the dens ranges between 10 to 14 days. They do this to eliminate themselves being hunted easily. Octopuses have a short lifespan, so if the octopus is caught and held in captivity they tend not to do well. This is because when held in captivity it can cause severe nervous system issues and can cause their stress levels to skyrocket (Octopus Habitat 1). During migrating periods, they usually have a certain place to go it just depends on the time of year. during the warmer times of the year, octopuses migrate towards the deeper ends of the waters during the colder times of the year, octopuses migrate towards the shallower waters – meaning they are able to live in different temperatures of water. The octopuses that live in warmer waters do tend to be smaller than the ones living in the colder waters. This is just one of the reasons as to why some of the species have been around for so long (Octopus Habitat 1). Even though octopuses are great predators for themselves, just like all animals they tend to be hunted by other animals in the ocean as well. Octopus are typically preyed on by sharks, large fish, eels, and even dolphins (What Preys On Octopi? 1). Octopuses enjoy hiding in their dens for most of the time. This is also why they hunt mostly at night. Luckily, they are able to defend themselves by using their defense mechanisms. Sometimes, eels have their own dens though and while octopus might be hunting or trying to find their own den, they wander into the wrong area and get attacked by eels. Although survival from the attack happens it is not all that common (Remarkable Giant Octopus 1).
Within the species, octopus range from all different sizes, and it depends on what kind of waters they live in. The largest octopus that was ever recorded is the Giant Pacific octopus. The measurements recorded were 30 feet across and weighed 600 pounds (Giant Pacific Octopus 1). the common octopus, however, can grow up to 39 inches in length and weighs as much as 25 pounds (How big is an octopus? 1). Octopus life cycle is quite intriguing. When octopuses eggs are hatched into a larval stage, the eggs float through clouds of plankton, where they feed on copepods and larval starfish and larval crabs until they are ready to sink down to the bottom of the ocean. Once they have reached their juvenile state, they start to grow at a more rapid rate. Their growth increases five percent each day and by the end, the octopus should weigh about one-third of all the food it has eaten. When the juvenile has survived this stage, they grow onto be an adult octopus. Around the age of one or two, the octopus is ready to begin mating. The males usually end up dying within a few months of the mating with a female. Once the female lays her eggs, she spends all her time watching over them and making sure the eggs get enough oxygen. During those months of development, the female octopus never eats as she has to watch over the eggs. By the time the eggs are ready to hatch and go into a separate state, the mother eventually dies (Divas 1). The common octopus can usually live up to one or two years whereas giant octopus lives up to be three to five years old (Lifespan of an octopus 1). When it comes to laying the eggs for the female octopus, it always varies as to how many she will actually lay. Females can lay up to anywhere near 20,000 to 100,000 eggs at a time (How does an octopus reproduce? 1).
Generalized phylogenetic tree explaining where octopuses fall under Cephalopods.
The external anatomy of an octopus.
The labeled internal anatomy of an octopus.
An octopus feeding on their prey.
An octopus being captured by their predator, a seal.
A diagram showing the complexity of a Cephalopods eye.
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