Segmented Worms 6i3h4s

Segmented worms (Annelida) Basic Features:  

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Vermiform (worm-like!) Externally segmented which is reflected on the inside, internal segments separated by septa (walls) with identical copies of muscles, nerves and excretory structures. This division of the body into similar repeating segments is known as "metamerism" or "metameric segmentation" Each segment has 2 pairs of setae or hairs made of chitin, these are used for locomotion and may be developed into paddle-like appendages in aquatic forms Hydrostatic (liquid) skeleton comprises of body fluid that is contained within a segment Segments have longitudinal and circular muscles that work antagonistically (against each other) in locomotion Have blood, a simple circulatory system, blood vessels with valves and a heart. Reproduction is sexual, many species are hermaphrodite (both male and female at the same time) of the group may be land dwelling, in soil or sediments or aquatic Some show a high degree of encephalization (development of a head) Size from 1mm to up to 3m - typically in the region of 1-20cm

HABITAT Annelida is a group commonly referred to as segmented worms, and they are found worldwide from the deepest marine sediments to the soils in our city parks and yards. Through most of the 20th centuryAnnelida was split into three major groups; Polychaeta, Oligochaeta (earthworms etc.) and Hirudinea(leeches). Earthworms and leeches are the familiar annelids for most people, but polychaetes comprise the bulk of the diversity of Annelida and are found in nearly every marine habitat, from intertidal algal mats downwards. There are even pelagic polychaetes that swim or drift, preying on other plankton, and a few groups occurring in fresh water and moist terrestrial surroundings. Around 9000 species of polychaetes are currently recognized with several thousand more names in synonymy, and the overall systematics of the group remains unstable (Rouse and Pleijel, 2001). Reproduction Annelids can reproduce asexually or sexually. One type of asexual reproduction takes place through a method called fission. During fission, the rear end of the body splits from the rest of the body to form a new annelida. Many other taxa (such as most earthworms) cannot reproduce this way, though they will regrow the posterior most segments in most instances. Sexual reproduction takes place by species that are hermaphroditic or species that have separate females and males through cross-fertilization. During sexual reproduction, fluids are transferred from the male pore to the female ovipore. Annelids tend to mate when conditions are moist or following a rain, meaning they may mate quite frequently throughout the year. Hermaphrodite annelids like earthworms mate periodically throughout the year in favored environmental conditions. Annelids mate by copulation. Two worms which are attracted by each other's secretions lay their bodies together with their heads pointing opposite directions. Earthworms are hermaphrodites and can reproduce in three different ways. Although they will not undergo fission, they are capable of fragmentation regeneration and may also go through budding, which is a process where a creature will grow another copy of itself like a branch. This new copy will then be detached and continue to live and grow as an independent organism. Both of these processes are asexual. Earthworms will also undergo sexual cross-fertilization. Also most polychaete worms have separate males and females and external fertilization. The clitellum, a smooth girdle about each worm secretes mucus, after which the sperm leave the sperm ducts and travel to the seminal receptacles of the partner. The clitellum later produces a slime tube, which is move along over the head of the worm by muscular contractions. Into this tube are deposited eggs from the oviducts and

sperm from the seminal receptacles. The slime tube forms a cocoon within which the miniature worms develop. There is no larval stage.[2]

A earthworm has both sperm and eggs within its body and reproduces sexually. However, the eggs must be fertilized by the sperm of another worm. An earthworm lays a batch of eggs at one time. They do not spend time raising their young once they are hatched.

Body Parts in Sections They are special. The whole segmentation thing is the big one. They actually have loads of body parts that are duplicated in each segment. If one segment is damaged, some annelids can go on living. You are not segmented. You have one of everything. If you lose something... Too bad. They also have something called a closed circulatory system. It doesn't seem that amazing because you have one. However, as far as developed creatures, annelids were one of the first. They circulate nutrients and compounds through their segments using tubes. Other creatures with open systems just let everything move around on its own. Closed circulatory systems are more efficient.

Characteristics of Segmented Worms

Annelid worms are characterised by a linear series of external ringlike segments which coincide with internal compartments containing repeated nervous, muscle, end excretory systems. Polychaetes, earthworms and leeches belong into this group. Bristles made from chitin (= setae) which are on each segment of most annelid worms, but not the leeches, are used for locomotion. They can have a stripe or spot pattern and can be colourful, e.g. pink to brown and purple, and luminescent. They vary in length from 0.5 mm to 3 m. Their feeding mode is variable, but often segmented worms are predators or scavengers. Some polychaetes can reproduce by budding and generally annelids can regenerate very well. Annelids have iron-containing pigments, which help transport oxygen through the blood. Annelids have a closed circulatory system with the contractile dorsal blood vessel pumping blood through unidirectional valves (= simple “hearts”). Their nervous system consists of segmented ganglia, a simple brain and ventral nerve cord(s). Eyes and sensory organs are present.

Importance of Segmented Worms

Annelids can be found in freshwater, marine and terrestrial habitats. The medicated leech is used to control swelling, e.g. after reattachment of fingers, for his salvia contains hirudin which prevents coagulation and an anaesthetic. In addition the leech is host to a bacterium which congests blood and produces an antibiotic which kills other bacteria. Aquatic annelids pump water through their burrow to bring food and oxygen and remove waste products. There are about 15500 species of annelids in three classes: Polychaeta, mostly marine, but some soil and freshwater bristle worms form the largest class with about 9000 species, Oligochaeta, about 6000 freshwater or terrestrial bristle worms and Hirudinea (= leeches) with about 500 species. The three classes differ in their reproduction. While polychaetes are

dioecious and often develop via a free-living larval state, oligochaetes and leeches are monoecious and develop in cocoons to little adults.

Tapeworm This flat, segmented worm usually infects animals that drink from contaminated water sources but can also invade humans who eat undercooked meat of infected animals, or from improper handling of food by an infected person. The worms are normally ed through bowel movements and if the infection is severe enough, will cause blockage in the intestines. If left untreated, the worms can be ed to the liver, heart, eyes, and brain and become fatal. Tapeworm Causes Six types of tapeworms are known to infect people. They are usually identified by the animals they come from -- for example Taenia saginata from beef, Taenia solium from pork, and Diphyllobothrium latum from fish. Tapeworms have a three-stage lifecycle: egg; an immature stage called a larva; and an adult stage at which the worm can produce more eggs. Because larvae can get into the muscles of their hosts, infection can occur when you eat raw or undercooked meat from an infected animal. It is also possible to contract pork tapeworms from foods prepared by an infected person. Because tapeworm eggs are ed with bowel movements, a person who doesn't wash hands well after wiping and then prepares food can contaminate the food. Tapeworms Symptoms Sometimes tapeworms cause signs and symptoms such as: 

Nausea

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Weakness

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Diarrhea

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Abdominal pain

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Hunger or loss of appetite

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Fatigue

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Weight loss

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Vitamin and mineral deficiencies However, often having tapeworms does not cause symptoms. The only sign of tapeworm infection may be segments of the worms, possibly moving, in a bowel movement. In rare cases, tapeworms can lead to serious complications, including blocking the intestine. If pork tapeworm eggs are accidentally swallowed, they can migrate to other parts of the body and cause damage to the liver, eyes, heart, and brain. These infections can be life-threatening.

Treatment for Tapeworms If you suspect you have tapeworms, you should see your doctor. Because there are different types of worms and tapeworms that can infect people, diagnosing a tapeworm infection may require a stool sample to identify the type of worm. If worms are not detected in the stool, your doctor may order a bloodtest to check for antibodies produced to fight tapeworm infection. For serious cases, your doctor may use imaging tests such as computed tomography (CT) or magnetic resonance imaging (MRI) to check for damage outside the digestive tract. Earthworms are hermaphrodites—each individual carries both male and female sex organs. As an invertebrate, it lacks a skeleton, but it maintains its structure with fluid-filled coelom chambers that function as a hydrostatic skeleton. Why Are Earthworms Important? Soil structure Earthworms have been called ‘ecosystem engineers’. Much like human engineers, earthworms change the structure of their environments. Different types of earthworms can make both horizontal and vertical burrows, some of which can be very deep in soils. These burrows create pores through which oxygen and water can enter and carbon dioxide can leave the soil.Earthworm casts (their faeces) are also very important in soils and are responsible for some of the fine crumb structure of soils. Image right: An earthworm in its burrow.

Decomposition and soil organic matter Earthworms play an important role in breaking down dead organic matter in a process known as decomposition. This is what the earthworms living in your compost bin are doing and earthworms living in soils also decompose organic matter. Decomposition releases nutrients locked up in dead plants and animals and makes them available for use by living plants. Earthworms do this by eating organic matter and breaking it down into smaller pieces allowing bacteria and fungi to feed on it and release the nutrients. Earthworms are also responsible for mixing soil layers and incorporating organic matter into the soil. Charles Darwin referred to earthworms as ‘nature’s ploughs’ because of this mixing of soil and organic matter. This mixing improves the fertility of the soil by allowing the organic matter to be dispersed through the soil and the nutrients held in it to become available to bacteria, fungi and plants.

Bacteria and fungi Earthworms have a positive effect on bacteria and fungi in soils. Where earthworms are present there are more bacteria and fungi and they are more active. This is important as bacteria and fungi are key in releasing nutrients from organic matter and making them available to plants. They are also an important source of food in their own right for many other animals that live in soils.

BODY SYSTEMS OF A SEGMENTED WORM Nervous system has a nervous system with a simple brain and nerve cord. Respiratory system has no respiratory organ. It takes in oxygen directly through its skin and gives off carbon dioxide. Its skin is always moist. Excretion Their waste help to fertilize the soil. It gets rid of its wastes through tubes called nephridin that lead to pores that allow the wastes out. Circulation has blood and blood vessels with multiple (5) hearts. Digestion has a digestive system. It eats dirt, digesting the plant and animal matter in the dirt and then eliminates the rest. It has an esophagus for the food to go down, a crop to store the food in, a gizzard that grinds the food down, intestines for the food to through and take out nutrients and an anus for the food to come out. Muscular-Skeletal A earthworm does not have a skeleton. It has bristles on each segment called setae that help the earthworm move. Earthworms have no limbs. The earthworm has two sets of muscles; one that makes it long and thin and one that makes it fat. FLATWORMS GENERAL CHARACTERISTICS OF FLATWORMS Flatworms have amazingly interesting characteristics. Flatworms, like all worms, are invertebrates with bilateral symmetry, meaning they have fronts and backs. Flatworms are soft and paper thin (The most defining characteristic, hence their name). Their brains are not much more than small clusters of nerves placed near the sensory organs to improve response time. Flatworms are either parasites or free-living (called Tubellarians)

Characteristics: Flatworms are unsegmented worms with a tail and a head end. They are bilaterally symmetrical with a definite upper and lower surface. They have no body cavity or and no specialized respiratory or circulatory organs. This is the reason behind the flat shape, common to all flatworms. They depend on a large surface to allow oxygen and nutrition to diffuse into their bodies. Most species are hermaphrodites, having both female and male reproduction organs.

Taxonomy: Many flatworms are parasites, but most flatworms encountered by divers are of the order Polycladida, a group of free-living flatworms, mainly found in tropical waters. A few species though, are relatively common along the coast of Norway. 1)Bilaterally symmetrical. 2)Body having 3 layers of tissues with organs and organelles. 3)Body contains no internal cavity. 4)Possesses a blind gut (i.e. it has a mouth but no anus) 5)Has Protonephridial excretory organs instead of an anus. 6)Has normally a nervous system of longitudinal fibres rather than a net. 7)Generally dorsoventrally flattened. 8)Reproduction mostly sexual as hermaphrodites. 9)Mostly they feed on animals and other smaller life forms. 10)Some species occur in all major habitats, including many as parasites of other animals. The Habitat of a Flatworm!

These animals can be found in the sand of ponds and rivers. They also live in the spaces betwee move, feed, and reproduce. Flatworms are confined to watery environments, either in actual wate found inside larger animals. But exceptions still require a lot of moisture! Flatworms in this class are photonegative (they avoid light) and are found under rocks and debris during the day. Unlike most flatworms, those in this class live in freshwater aquatic systems such as ponds, lakes, ditches, rivers and streams. REPRODUCTION With very few exceptions, platyhelminthes are hermaphroditic, and their reproductive systems are generally complex. Numerous testes but only one or two ovaries are usually present in these flatworms. The female system is unusual in that it is separated into two structures: the ovaries and the vitellaria, often known as thevitelline glands or yolk glands. The cells of the vitellaria form yolk and eggshell components. In some groups, particularly those that live primarily in water or have an aqueous phase in the life cycle, the eggshell consists of a hardened proteinknown as sclerotin, or tanned protein. Most of this protein comes from the vitellaria. In other groups, especially those that are primarily terrestrial or have a terrestrial phase in their life cycle, the eggshells are composed of another protein, keratin, a tougher material that is more resistant to adverse environmental conditions. In the tapeworms, the tapelike body is generally divided into a series of segments, or proglottids, each of which develops a complete set of male and female genitalia. A rather complex copulatory apparatus consists of an evertible (capable of turning outward) penis, or cirrus, in the male and a canal, or vagina, in the female. Near its opening the female canal may differentiate into a variety of tubular organs. Fertilized eggs are often stored in a saclike uterus, which may become greatly distended; in tapeworms, it may fill a whole segment. Each male and female reproductive system may have its own external opening, or gonopore, or the terminal regions of each system may to form a common genital atrium, or age, and a genital pore.

Either cross-fertilization (i.e., involving two individuals) or self-fertilization may occur; self-fertilization is probably more common. Some free-living flatworms perform a type of copulation known as hypodermic impregnation, whereby the penis of one animal pierces the epidermis of another and injects sperm into the tissues. Some forms reproduce asvexually through budding.

A flatworm reproduces by splitting in two. When a flatworm is split up it immediately forms a new flatworm. Generally all flatworms are hermaphroditic, meaning an individual flatworm has both male and female reproductive components. They engage in sexual and asexual reproduction, with the dominant mode of reproduction varying among species. Asexually, flatworms procreate via fragmentation and budding. Fragmentation, also called cloning, occurs when a flatworm splits off a part of its body, allowing the separated portion to regenerate into a new worm. With budding, a flatworm grows an extension from its body. This extension, or bud, becomes a new worm and separates from the original flatworm. There are also multiple methods of flatworm sexual reproduction. Because a flatworm is hermaphroditic, it can produce eggs within its body and also fertilize them with sperm, also generated in its body. Another method of reproduction involves physical between two flatworms, where the sperm of one flatworm is absorbed into the skin of another. With some species, this occurs through penis fencing, where flatworms use their penis to compete in trying to pierce the skin of a potential mother. Ultimately, fertilized eggs are encased in a cocoon within a flatworm's body. The cocoon is released into environments such as amid water weeds. The cocoon nourishes the eggs, which develop and later hatch. harmfulness Tapeworms are flat segmented worms that live in the intestines of some animals. Animals can become infected with these parasites when grazing in pastures or drinking contaminated water. Eating undercooked meat from infected animals is the main cause of tapeworm infection in people. Although tapeworms in humans usually cause few symptoms and are easily treated, they can sometimes cause serious, life-threatening problems. That's why it's important to recognize the symptoms and know how to protect yourself and your family.

INTERESTINGFACTS

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If a flatworm is cut through the middle of the body (as it is in normal transverse fission), each half will regenerate the corresponding lost part. However, if the animal is cut transversely near one end, say, separating a small piece of the tail from the rest of the body, the larger piece will grow a new posterior end, but the piece of tail lacks the capability to produce an entire new anterior end. Flatworms usually have one pair of direct or inverted cup eyes for detecting movement.

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Scientists can train flatworms to do simple tasks, such as finding water in a maze. When these flatworms are then cut in half, the new halves learn faster than the original.

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Small flatworms use waves of ciliary action for locomotion to glide over surfaces, whereas larger species use muscular movements of their entire body to creep, swim, twist or somersault along the substrate.

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If a flatworm is starved it is capable of shrinking to hatching size and when fed it has the ability to grow back to its original size.

Sources USEFULNESS They play important roles for healthy streams, ponds, and lakes. They increase the chances for organic farming. They increased the popularity of raw cooked foods, such as the imports of meat, seafood, and vegetables BODY SYSTEMS OF A FLATWORM, Nervous System A flatworm has a very simple nervous system with two nerve cords running down either side. It has two simple brains called ganglia, which are simple bundles of nerves. . It has two eyespots that help it sense light. Circulatory System A flatworm has a gastrovascular cavity with one opening. It eats small worms, insects and microscopic matter. Respiratory System They take in oxygen but have no formal respiratory system. This is because they are very simple animals. They went through such small evolution that they never developed a complex respiratory system. They breathe through their skin which they have to keep moist which is why most live in water or watery environments. Reproductive System A flatworm reproduces by splitting in two. When a flatworm is split up it immediately forms a new flatworm. Sexuality In the asexual race, they reproduce by fission without sexual organs. In the sexual race, flatworms have hermaphroditic sexual organs, and copulate and then lay cocoons filled with several fertilized eggs. They are not likely to fission. In the physiological race, worms convert between asexual and sexual reproduction seasonally. In these planarians, the asexual race can switch from asexual to sexual reproduction by being fed with sexually mature worms of the same, as well as different, species. It is supposed that there is a non-species-specific substance involved here. In one experiment, the clone of Dugesia ryukyuensis used was one of the Japanese species established in Hirosaki University in 1986, and they were fed Bdellocephala, a totally sexual species in order to make them into "acquired sexuals." – Muscular-Skeletal A flatworm has no skeleton. It has tiny bristles called cilia that help it move as well as two layers of muscles under its skin. It has three cell layers called the endoderm, the mesoderm and the ectoderm. They also have the beginnings of a head region. Digestion A flatworm has a combination digestive/excretory system. It takes food in and gets rid of wastes through the same opening.

Excretion A flatworm gets rid of wastes through the same opening it takes in food.