Cephalopod
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| Cephalopod |
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| Scientific Classification |
| Orders |
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Subclass: Nautiloidea
Subclass: Ammonoidea Subclass: Coleoidea |
Contents |
Introduction
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Anatomy
The Class Cephalopoda has the most developed form in phylum mollusca. It is divided into 3 parts of the body; head, trunk, and the limbs. Also they can be cut in halves equally. The sizes of cephalopoda are various, usually 1" to 7". They have small head with sharp and beak-like mouth. Mostly behind its mouth, radula, tooth tongue is placed. Using both mouth and radula, they grasp, tear and bite the prey.[1] However, class cephalopoda mean ‘head-footed’ by its tentacles and arms, the most noticeable structures. Tentacles looks like long arms but shorter than arms. On the surface of each arm, there are suckers to have enough strength to catch the prey. Members of orders sepioidea and teuthoidea have eight arms and two tentacles while ocotopoidea and vampyromorpha have only eight arms. The body is supported by its mantle or shell. Especially only nautiloidea has an external shell while others have internal ones. [2]
Digestive and Excretory system
All members of cephalopoda are carnivorous. When the arms and tentacles catch the prey, cephalopds put the food into the beak-like mouth getting help from tentacles and arms. Before swallowing, the food goes into the buccal cavity imidiately and then it goes to the digestive tracts. Sometimes they excreted the digestive juices to disassemble the connection between the flesh and the bone of the prey to digest it effectively. At first, it passes through the esophagus and crop. The food is stored at the crop a moment and goes directly to the stomach and be broken down. In caecum, the most of digestion happens and the nutrients are absorbed. [3]
The excretion in cephalopods occurs by a pair of nephridia which has tubular looks. From the coelom, it gathers all fluids in its body and filters. Also it exchanges substances like salt with body tissues. The wastes are released into mantle cavity and finally excreted outside by pore. [4]
Locomotion
To move in water, cephalopods need a special structure that helps their locomotion. Order octopoids use their arms to walk on the sea floor, sepioids and teuthoids owns lateral fins to propel their body to move. However, the most common way cephalopods move is jet propulsion. [5] They are pumping water into the gills and through out the siphons or funnel called hyponome. Oxgenated water comes into the cephalopods' gills and provides oxgen all over the bodies. After giving oxgen, the water then expelled through the hyponome by muscular contraction. When water is expelled, they get energy to move to the opposite direction that the water went out. [6]
Circulatory and Respiratory system
Class cephalopoda has closed circulatory system which the blood is contained within vessels. A muscular enlarged portion of a vein that forces the blood into the gills is called branchial heart and cephalopods have two of it also called gill heart. [7] Their heart contribute in providing oxgen over the bodies from oxgenated water by contraction. Moreover they use hemocyanin, similar to hemoglobin but bluish protein, contains copper, and carries oxgen.
[8]
For respiratory system, the most important organ is gill. In the gill, cephalopods
Nervous system
Reproduction
Ecology
Other
Gallery
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References
- Class Cephalopoda Kristen Wheeler, Daphne G. Fautin, Animal Diversity Web, 2001.
- the anatomy of swimming in cephalopods Carl Howard, jrscience.wcp.muohio.edu, 2003.
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External links
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