Cephalopods are marine animals and it can be found in oceans all around the world. Some of this species live in caves or rocky areas. Smaller individuals dig dens in sand-shell substrates. All cephalopods have internal shells that have chambers connected by siphuncle. They also have a large brain formed by nerve ganglia and protected by cartilaginous cranium. All cephalopods have flexible tentacles. Cuttlefish and squids generally have two long tentacles. Octopus have eight and nautilus can have up to 90 tentacles! These organisms can range in size from a few centimeters up to more than 20 meters long. They are also known as head-foot because a cephalopod's head is connected with its foot. Some examples of exphalopods are octopus, squids, cuttlefish, and nautiluses.
Feeding :
All cephalopods are carnivores. They are predators with incredible senses to help them detect food. Octopus uses their acute vision to seek a prey. They grab on to the prey with their suckers, engulf the organism with its tentacles and draw the food into them. Some octopus and cuttlefish bite their food into smaller bite-size pieces before digesting it. They would inject their prey with saliva that paralyzes. Diet of bottom-dwelling octopus includes mollusks, crustaceans, and polychaete worms. Diet of open-ocean octopus and squid are fish, prawns, and cephalopods. Furthermore, squid catches its prey by shooting out its tentacles towards their prey and draw the prey inside. Cuttlefish and squids have long, sticky tentacles with suckers that aid them in capturing prey. Others would dangle their long arms down onto a school of fish or prawns and catches the food that goes through the arms. In addition, squid that lacks tentacles have suckers with hooks to lunge at their prey. Feeding patterns of cephalopods vary across different species. Like snails and clams, cephalopods also have a radula used for feeding purposes.
http://http://www.youtube.com/watch?v=3u_Vt_dyx4s <= CLICK HERE: EXCITING CLIP ON HOW SQUID FEEDS Respiration :
Like a typical aquatic animal, Cephalopods uses gills to breath and to filter food. Cephalopods use hemocyanin rather than hemoglobin to transport oxygen throughout its body. Because these animals use hemocyanin, their blood is colorless when deoxygenated and changes blue when it gets in contact with air.
Digestion :
Digestion in cephalopods is rapid. It starts with a strong beak which contains the radula. The radula is covered with teeth for digging and scraping food. There are two salivary glands (one of them is poisonous) that secrete alpha and beta cephalotoxins that aids them in digestion. Food enters the esophagus and goes through the crop where food can be stored until ready for digestion. The food then goes inside the stomach where food is mashed by digestive substances from the salivary glands, liver, and pancreas. Food is absorbed in the liver, pancreas and cecum. The intestine supplies the stomach and path to the anus with mucous.
Circulation/Internal Transport :
Cephalopods are the only mollusks with a closed circulatory system with three hearts. This is because open circulatory system is not efficient enough for octopi and squids to move quickly. Their coelom is like a bag that surrounds their hearts. The first two hearts, gill hearts (branchial hearts) moves blood through the gill's capillaries whereas, the reminding heart, systemic heart, provides the rest of the body with oxygenated blood.
Excretion :
Wastes are excreted through nephridia. They excrete in the form of urine which contains ammonium and feces.
Reproduction :Cephalopods are gonochoric which means their sexes are separate. Female possess a single oviduct, whereas, the male produces spermatophore. These are passed from male to the female's genital pore by using specialized arms which is the male's gonoduct. In some species, this specialized arm may tip off into the female's mantle cavity. The arm is called hectocoylus arm. However, in other species that doesn’t have hectocotylus, the male's reproductive organ (penis) is long and strong enough to transfer their spermatophores directly into the female. The eggs are then fertilized in the female as they leave the oviduct. As a result they lay a batch of fertilized eggs and are released into open water. Most cephalopod are semelparous, they die after they lay their eggs. This is different in Nautiloidea, this class produces a few large eggs in a batch and live afterwards. Cephalopods may mate by their color changes, body movements or both. They are spiral cleavage and protostomes.
Response to Environment : Cephalopods contains special pigments cells called chromatophores enables the organism to change color and patterns precisely and quickly to match a new environment. This can help the cephalopod camouflage and communicate when danger or emotion is detected. However, this is not the case for Nautilus. Furthermore, these organisms can defend themselves with the ability to release a large amount of "smoke screen" of ink when they sense danger. For cephalopods, they also have photophores as organs that produce light and make them bioluminescence. These help them to startle predators. Cephalopod can also tell the difference between brightness, size, shape, and horizontal or vertical orientation of things. When they try to camouflage themselves, they use their chromatophores from the background they see. In addition, they can match the correct color of a background from cells called iridophores and leucophores. These cells reflect light from the surrounding. Moreover, Cephalopods have a well developed nervous system as well as complex sensory organs and brain. They can recall memories and learn because they possess ganglia that can control their thinking.
http://youtube.com/watch?v=ckP8msIgMYE <= CLICK HERE: FASCINATING CLIP ON HOW OCTOPUS DEFENDS ITSELF
Movement :
This class of animals uses jet propulsion as a primary method to move. First, they draw in oxygenated water into their mantle cavity to the gills where the circular muscles contract around the mantle cavity and expels the water out of the tube like siphon or the hyponome. The Cephalopod can then aim their siphon in different directions and forces a jet of water that can propel them backwards. Some cephalopods can move by crawling along the ocean floor or sea bed with their arms. Squids and cuttlefish can move a short distance by moving a flap of their muscles around the mantle cavity.
Anatomy of Squid:
No comments:
Post a Comment