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Phylum Mollusca General Characteristics Pdf Phylum mollusca general characteristics pdf Continue The mollusk makes the second largest filum non-chordate of animals including snails, octopuses, sea slugs, squid and bivalve such as molluscs, oysters and mussels. This phylum contains about 100,000 described species. Of all known marine species, 23% are molluscs. But some species live in freshwater and terrestrial habitats. This group displays a wide range of morphological features such as muscle leg, mantle and visceral mass containing internal organs. Calcium carbonate is released from the mantle and forms the outer calciferic shell of the body in most molluscs. The size of molluscs ranges from less than one millimeter to 20 meters. They play an important role in people's lives because they are a source of food for many people as well as jewelry. Many molluscs are not good for human life. Some cause disease or acts as pests like snails and slugs. Typically, solid shell shells are used to create amazing jewelry. Some molluscs, such as bivalve and gastropods, produce valuable pearls. Natural pearls are produced when a small foreign object is trapped between the shell of the mollusc body and the mantle. In addition, many scientists use bivalve molluscs as bioindicators of freshwater and marine environments. They have a bilaterally symmetrical organ (exception: body gastropos asymmetrical) and show the organ of the organization's class system. They are mostly aquatic organisms. Most of them live in the marine environment, and only a few of them are freshwater. In addition, some live in ground wet soil. These are triplhoblated animals with non- segmented (exception: Neopilina) soft body. The mantle and shell cover the body, and the body has three areas, namely the head, abdominal foot, and visceral mass. In this case, the shell is a solid calcium structure, composed of calcium carbonate. They have an open circulatory system of blood group with heart (one or two morica and one ventricle) and aorta. The body cavity is known as hemocoel, which circulates blood. They have a well developed and complex digestive system. The mouth contains a rasping rainbow structure with chitinous teeth for scraping or cutting food. The nervous system consists of three pairs of ganglia (cerebral, visceral and pedals) with connective and nerves. In aquatic molluscs, breathing occurs through the gills or ctenidia that are located in the mantle cavity while in terrestrial forms, it occurs through the lungs (pulmonary bags) or the common surface of the body. They are methanefridi (kidneys) for excretion. The senses consist of eyes, osfrazium, tentacles and satocyst. The floors are usually separate, but some are monotonous. In this case, there is sexual reproduction. There is external or internal fertilization. They show a direct or development with trohophores or larvae stages of the velager. The gmichia larva is also found at the parasitic stage for some species and clams). They use the abdominal muscular leg to move around. The Phylum Molluska can be divided into the following classes: Pelecypoda or BivalviaGastropodaCephalopodaAplacophoraMonoplacophoraPolyplacophoraScaphopodaThis class includes more than 15,000 species, Including mussels, oysters, clams, scallops, etc. the largest living bivalve species is a giant mollusk (Tridacna gigas), which can grow up to 47 inches (1200 mm) in length and more than 200 kg in weight. They are characterized by a shell that is divided into left and right valves. They are mostly marine organisms and they burrow into the mud and sand. They have a two-way symmetrical and lateral compressed body. They don't have a separate head. They are a feeder filter, but some are scavengers. Examples: Mya arenaria (soft shell mollusk), Mercenaria mercenaria (hard mollusk) Mya arenaria (soft shell molluscs) Class Gastropoda contains more than 65,000 species that make the largest group in the phylum Molluska, consisting of more than 80% of all molluscs. Of the 65,000 species, about 30,000 are marine, 5,000 live in fresh water and 30,000 live on land. These are successful groups in the ocean, fresh water (ponds, streams, swamps and lakes) and land. They have a well-developed head. The head carries his eyes and a couple of tentacles. They have a large and flat muscular leg that is used for creeping, swimming or burying. They have a well-developed nervous and circulatory system with a concentration of nerve ganglia. They have a two-way symmetrical body with a spiral or spiral shell. Examples: Turritella cumberlandia, Diastoma insulaemaris, Epitonium charlestonensis, Pila globosa (Apple snail)Pila globosa (Apple snail)This class contains about 800 known living species, including octopus, squid and cuttlefish, which live only in the marine environment. They are carnivorous and their products consist of various fish, crustaceans and other molluscs. They carry tight beaks to burst and devour their prey. They have a symmetrical body. The left and right sides of the body are equal or identical. They have a well-developed vision to discover their praying or potential enemies. They have the ability to inject ink during the threat. Their leg is modified by eight hands or two tentacles in the head area. In this case, tentacles are used to capture prey, while weapons force prey into the mouth. They have a big pair of vertebrates, like eyes. They are able to detect the polarization of light. Their brain is large and well developed unlike any other molluscs. They have a very complex nervous system. The shell is either external, internal or absent. Examples: Octopus abaculus, Loligo vulgaris, Sepia dubiaLoligo vulgarisThere - these are about 25 living species that live in the deep sea between the ranges of depths of 175- 6400 m. These are sea molluscs characterized by a single shell in the form of a lid. They have a two-way symmetrical with a curved front top and an abdominal leg and mouth. The mouth is located in front of the foot, and the anus is located in a pale groove on the back of the body, behind the leg. They don't have a head without eyes and eyes. Jills are external, which grow in the abdominal palliative cavity on either side of the foot. They have a looped digestive system where the stomach is cone-shaped with a long intestine, making four to six loops before reaching the back position of the anus. They have several pairs of excretion organs (jade) that are arranged sequentially. Examples: Laevipilina antarcticaThey is a small group of molluscs that contains about 320 species. They are exclusively deep-sea molluscs and are found in all oceans of the world. They have a worm-like appearance without projectiles. They are very small clams and their length ranges from 5-30 cm. Mantle secrets are tiny calcareous spicules that make their body a beautiful shine. They have no eyes, tentacles and jade, but the rainbow is present. Example: Neomenia yamamotoiNeomenia yamamotoiAnimals of this class is widely known as chitons. They are exclusively marine organisms and have worldwide distribution. This is a familiar group of organisms with eight valves on the shell. Most animals of this class live in rocky intertical or shallow subtical zones, but few live at a depth of more than 7,000 meters. They have a wide ventral leg that is used to suction rocks and other substrates. They have an elongated oval and flattened body. The body contains eight overlapping dorsal plates. The pallial cavity carries many pairs of small gills that surround the legs. They are usually small in size and their length ranges from 0.5-5 cm, but one species over 30 cm. The blood system is open with the heart and for secretion, a pair of kidneys are present that are open to a palliative cavity. The nervous system is simple, which contains two pairs of lateral nerve cords with several special tiny senses. A simple velour is present that surrounds the mouth and the head does not carry tentacles or eyes. Cryptochiton stelleri (Gumboot or Gumshoe chiton) This class contains about 350 species. Most species live in fairly deep waters within about 4,000 meters of depth. Among them, many species are cosmopolitan in their distribution. Typically, their products consist of small organisms such as foraminiferans and young bivalve. They are also known as a tusk shell, elephant tusk, elephant tooth or dental shells. They live their adult life buried in sand or mud. They have an elongated and two-sided symmetrical organ. They have both ends of the open one conical shell. They have no eyes, but they have radials. The leg is reduced and modified into tentacles. The tentacles have an onion end, which is known as captaculae. Captacula are used to capture and Production. They don't ctenidia and there are a couple of kidneys. The floors are separated and they show stage larvae (trocophor larvae) in their life cycle. Examples: Cadulus delicatulus, Dentalium americanumDentalium americanumMollusca is the second largest filum, which contains more than 75,000 described species. Of all known marine species, 23% are molluscs. But some species live in freshwater and terrestrial habitats. They play an important role in people's lives because they are a food source for many people. Solid shell shells are used to create amazing jewelry. Some molluscs, such as bivalve and gastropods, produce valuable pearls. In addition, many scientists use bivalve molluscs as bioindicators of freshwater and marine environments. In animals belonging to the philosophy of Mollusk, soft bodies, triple-regional and bilateral symmetrical and chelomat. The study of Molluski is called malacology. They are sluggish invertebrates, with a thin fleshy envelope or mantle covering the visceral organs. The term Molluska was derived from the term given by Aristotle cuttlefish.
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