The dorsal epidermis contains numerous secretory vesicles and rod-shaped membrane enclosed secretions, the rhabdites (rhabd = rod). Rhabdites are synthesized by epidermal gland cells submerged below the basal lamina into the parenchyma. When expelled at the surface, rhabdites absorb water and expand to become sticky mucus which may help trap small invertebrate prey.
ANASTOMOSIS the union of parts or branches (as of streams, blood vessels, or leaf veins) so as to intercommunicate or interconnect
Dugesia is a genus of dugesiid triclad that contains some common representatives of the class Turbellaria . These common flatworms are found in freshwater habitats of Africa , Europe , Middle East , Asia and Australia . Dugesia is best known to non-specialists because of its regeneration capacities.
Three types of proglottids: immature, mature and gravid.
PhylumPlatyhelminthes The Flatworms
CHARACTERISTICS Acoelomate - Hey, where’s my cavity? Dorsoventrally flattened Triploblastic Embryo has 3 cell layers Ectoderm(cnidarians) Endoderm (cnidarians) AND NOW, introducing MESODERM!
Bilateral symmetry- with external and internal features arranged symmetrically on either side of a median or sagital plane Bilateral symmetry: active mode; Biradial symmetry: sedentary lifeADVANCEMENTS: Nervous system Anteriorbrain Paired ventral nerve cords Longitudinal Incomplete gut (Digestive system) No anus Food exits via mouth
Excretory system & osmoregulation Diffusion across body wall Protonephridia Specializedexcretory organs May also help osmoregulate Formed reproductive organ
Class Turbellaria Free living Freshwater Planarians such as Dugesia A few inhabit terrestrial (moist) habitats
STRUCTURE Dugesia is a thin, slender, soft worm about 15mm long, bluntly triangular anterior end, or “head,” and a tapered body patterned with dark pigment. Head region bears two black eyespots middorsally The mouth is on ventral surface near the middle of the body
Through it a tubular pharynx, or proboscis, with muscular walls can be extended to capture food. Excretory openings, present laterally on the dorsal surface but are difficult to see. Genital pore, mature worm has it on the ventral surface behind the mouth. Body covered by epidermis of single layer of cuboidal to columnar cells.
The epidermal cells contain small bodies called rhabdites, and many deep-lying unicellular glands that open the surface. Gland cells produce mucus. Ventral epidermis is covered with cilia for locomotion Beneath the basement membrane are the layers of muscle fibers, circular, longitudinal, and diagonal, also dorsoventral fibers.
Spaces between the muscles and internal organs are filled with parenchyma (mesenchyme) There is no body cavity In the parenchyma are scattered free formative cells, which by mitosis produce new parts in regeneration.
Class Turbellaria Marine species (beautiful colors) Significantmembers of coral reef ecosystems Some are major predators of colonial ascidians (sea squirts) Others are pests of commercial clams and oysters Some live symbiotically on a variety of reef invertebrates
Class Turbellaria Locomotion Usually by cilia Dugesia can move at about 1.5 mm/sec Peristaltic waves can achieve higher velocities Marine flatworms can use this to swim gracefully
Class Turbellaria Locomotion Terrestrial planarians Glide smoothly on the substrate by the action of powerful, closely spaced cilia in a special medial ventral strip (creeping sole), on a thin coat of mucus secreted on the substrate by glands opening into the creeping sole Planarians that migrate on plants or objects above the ground sometimes lower themselves to the ground on a string of mucus.
ORGAN SYSTEMS NO Respiratory System NO Skeletal System
Muscular System Below the epidermis are layers of circular and longitudinal muscle fibers; used in locomotion
Class Turbellaria Feeding Ecology Mostturbellarians are carnivorous predators or scavengers. Carnivores feed on organisms that they can fit into their mouths, such as protozoans, copepods, small worms, and minute mollusks. Some species use mucus that may have poisonous or narcotic chemicals to slow or entangle prey. Some have specific diets and feed on sponges, ectoprocts, barnacles, and tunicates. Several species have commensal relationships with various invertebrates
Feeding and Digestion The pharynx is protruded from the mouth and into the prey. The pharynx and gut cells produce digestive enzymes that breakdown food extracellularly. Because these worm lack a circulatory system, larger species have extensive anastomosing guts to aid in distribution. Since these worms have incomplete guts, all waste must pass back out of the mouth.
Nutrition Planaria store food in digestive epithelium and can survive many weeks shrinking slowly in size without feeding. They are capable of utilizing their own tissues such as reproductive tissue for food when reserves are exhausted. Lab animals often tend to shrink in size when not fed properly
Digestive system Ventral mouth Muscular pharynx A blind intestine (details depend on order) Tricladida — 10-20 mm long Tripartite gut; one main anterior branch and two main posterior branches with numerous blind pockets off all three. Dugesia Polycladida — up to 5 cm long Gut has numerous branches ramifying throughout the body.
Excretory System Protonephridial System- comprises 2 longitudinal ducts connecting to a network of tubules that branch throughout the body and end in in many large flame cells. Flame cells- they collect excess water or fluid wastes Osmoregulation-removing excess fluids from the organism, although small amounts of ammonia are also removed.
Class Turbellaria Protonephridia One end of the tubule opens through a small pore to the exterior. The other end of the tube ends blindly within the body in a spherical structure containing long cilia - these are called flame cells Excess water (and possibly wastes) enters the flame cell system and is propelled through the tubules toward the outside by the beating of the cilia (the "flame").
Protonephridia Branches terminate in blind flame cells. Flame cells have slits that penetrate the cell Slits are crossed by filaments or a membrane that reduce the effective pore size Slits act as an ultrafilter to keep back large proteins Filtrate of mesenchymal intercellular fluid enters tubule. Inorganic and organic materials actively reabsorbed in tubule; remainder is excreted
Nervous System More organized Two cerebral ganglia= “brain” Short nerves extend to the anterior end and the eyes, and two longitudinal nerve cords pass back With many transverse connectives and peripheral nerves
Nervous system and sensory organs Dorsal, anterior eyes Ciliated pits behind auricles on head are probably chemosensors Dorsal, bilobed brain underlays eyes Primitively 3-4 pairs of longitudinal nerve cords Reduced to two longitudinal ventral nerve cords Run down length of body with numerous cross connections and branches in most groups.
Reproductive System and Reproduction Thereare two types of reproduction; asexual reproduction sexual reproduction
Asexual Reproduction They reproduce asexually by transverse fission (split into two) and have great regenerative capabilities. This means that if a part of their body is cut into half, they are able to grow the lost body part within a period of time.
Sexual Reproduction Most Turbellarians are hermaphroditic, meaning that they contain the male and the female sex organs. However, they are unable to self-fertilize and thus need the sperm of other turbellarians to fertilize the egg.
The MALE Reproductive System Several hundred small spherical testes along both sides of the body, each connected by, a minute ductus eferens to, A larger ductus deferens: the 2 ducts enter Median seminal vesicle for sperm storage, connects to, Muscular penis opening into. Genital atrium, just within the genital pore
The FEMALE Reproductive System 2 rounded ovaries, connecting to, Two oviducts Along each duct are: many yolk or vitelline glands, which supply yolk cells when eggs are produced the 2 oviducts join the median vagina opening into, The genital atrium, to the vagina is connected A bulbous copulatory sac that receives sperm at mating Soon the sperm move to the seminal receptacles which are slight enlargement between the ovaries and oviducts.
REPRODUCTION Cross-fertilization- exchange of sex products between separate individual Internal fertilization- direct transfer of sperm from male to female organ Development is direct
Ecology and Evolution Many flatworms are brightly coloured Warning coloration (aposomatic coloration) These flatworms are believed to be toxic or distasteful Other species are mimics of toxic nudibranchs (sea slugs)
Other Turbellaria ACOELA Have mouth but without digestive cavity Lacks excretory organ Have no distinct gonads Nervous system is an epidermal net system Free living and others live in the intestines of sea urchins and sea cucumbers
Characteristics All parasitic, mostly in vertebrates Covered externally by a non-ciliated syncytium (tegument) Oral sucker surrounds mouth Ventral sucker used for attachment Mouth is anterior Digestive tract is -shaped,, with 2 main trunks and smaller branches Complex life cycles (involving at least one intermediate host)
The food consists of the tissues or body fluids of the host, which are sucked in by action of the muscular pharynx Are more like turbellarians Complex muscle layers, excretory organs, and a nervous system Parasitic life, the development of a resistant cuticle, suckers, and hooks and general lack of sense organs. Sensory organs, such as dorsal eyespots occur in some larve and in some flukes that are ectoparasites.
Subclass Monogenea Inhabit only one host Ectoparasites of fishes, amphibians, and reptiles, but some inhabit the mouth cavities or urinary bladders. At the posterior end is a well-developed adhesive organ with one or more suckers and chitinous hooks or anchors Cross-fertilization Development is direct adult form
Subclass Aspidobothrea Internal parasite of lower vertebrates and mollusks and have but a single host Characterized by huge adhesive structure (sucker) covering the whole ventral part of the body They show features of both Monogenea and Digenea and may have one or two hosts.
Subclass Digenea Largest group of trematodes All internal parasites Must live in two or more host species to complete the life cycle, larvae in a certain snail (intermediate host) and the adult in some vertebrate (primary host) Live in the parts of digestive tract, lungs, urinary bladder, blood vessels, or other organs
Sheep liver fluke Common liver fluke or Fasciola hepatica Inhabits the bile ducts and sometimes invades other organs Commonest in sheep and cattle but is sometimes found in other mammals and occasionally in humans, producing the disease known as liver rot or fasciolosis
One of the largest flukes of the world, reaching a length of 30mm and a width of 13mm It is leaf shaped, pointed posteriorly and wide interiorly The anterior sucker is terminal surrounding the mouth, and close behind is the ventral (posterior) sucker for attachment in host Between them the genital opening Digestive system: mouth, muscular pharynx, short esophagus, and two branched enteron.
Muscles are complex Excretory has many flame cells Nervous system: double ganglion, 2 lengthwise nerve cords, and various nerves Hermaphroditic
The testes are large and greatly branched, arranged in tandem behind the ovary. The smaller, dendritic ovary lies on the right side, coiling between the ovary and the preacetabular cirrus pouch. Vitelline follicles are extensive, filling most of the lateral body and becoming confluent behind the testes.
Fasciola hepatica Commonly known as the sheep liver fluke Important parasite of sheep and cattle (other grazers) can be found in humans. Morphology Large size, frequently over 30 mm long Characteristic cone-shaped projection at anterior end followed by wide shoulders
Fasciola hepatica: Trematode Life Cycle Representative Ova or egg Miracidium Sporocyst (Daughter sporocyst, or redia) Cercaria Metacercaria Adult
Stages of Trematode Life Cycle Ova or egg - shelled embryo. Contains miracidium inside shell Under appropriate conditions, the operculum (cap on shell) opens to allow miracidium to escape. Many of flukes have very distinctive eggs.
Stages of Trematode Life Cycle Miracidium Ciliated organism that can be mistaken for a ciliated protozoan. In species that hatch in water, it contains penetration glands that release histolytic or proteolytic enzymes to help penetrate snail Some species do not hatch until eaten by snail host.
Stages of Trematode Life Cycle Sporocyst The miracidium develops into sporocyst often in the digestive gland of the snail. The sporocyst is an embryonic bag or germinal sac. The sporocyst will produce many daughter stages called rediae or in some cases daughter sporocysts.
Stages of Trematode Life Cycle Rediae or Daughter Sporocyst Infunction they are very similar to sporocysts. Contain digestive tract and are more active Asexually reproduce to yield many cercariae. Some species they can live for many years.
Stages of Trematode Life Cycle Cercariae Usually escape snail and often swim by some means of tail structure. Responsible for transmission from snail to the next host.
Stages of Trematode Life Cycle Metacercaria Resistant stage that is formed in many species Cercaria that have this stage contain cystogenic glands that helps the organism encyst on vegetation. Cercaria that form metacercaria in second intermediate hosts, often have penetration glands that enable them to penetrate the second intermediate host.
Stages of Trematode Life Cycle Adult Always found in the definitive host Responsible for sexual reproduction Often restricted to specific region of host. Often very host specific.
Fasciola hepatica Adult in bile duct of definitive host passes eggs in feces. If eggs land in water, they hatch into miracidium that actively swims until it finds an appropriate snail. (Galba truncatula) Penetrates snail, develops into germinal sac (sporocyst), asexual stages of rediae and cercariae formed.
Fasciola hepatica Cercariae leave snail, encyst on vegetation, and form metacercaria. Herbivore infected when it ingests vegetation with metacercaria. Metacercaria develop into adult penetrates gut wall, moves to the liver. Humans infected by eating watercress that has metacercaria on it.
Schistosoma sp. Adult worms are found in blood vessels of digestive tract or urinary bladder thus called blood flukes male worm has a split body called the gynecophoral canal. The female is usually found within this canal “safe in the arms of her lover.” She leaves only during the egg laying period.
Schistosomiasis Migratory phase - 4-10 weeks after infection. Is characterized by fever and toxic or allergic reactions resulting from migration of immature organisms. Often results in bronchitis, hepatomegaly, splenomegaly, and diarrhea.
Schistosomiasis Acute phase - 10 weeks to years. Eggs can become trapped and produce granulomas and scar tissue. Form fibrous nodules called pseudotubules. Eggs may lodge in gastrointestinal, renal, neural, and other systems. A person infected with 50 mating pairs would be exposed to about 15,000 eggs per day for several years. ½ of eggs might remain trapped in tissues.
Schistosomiasis Chronic phase - persons living in endemic regions are often asymptotic. May have mild, chronic bloody stools or urine. Often have formation of granulomas. Hepatomegaly, Spleenomegaly, Ascites (accumulation of fluid in abdominal cavity fig 16.17, page 245.
Epidemiology Human waste into water. Moslem religious practice of ablution Agricultural projects Irrigation extends snail habitats Use of night soil (human feces) Planting and harvesting of water crops Dependence of people on rivers.
Epidemiology Before the Aswan Dam was built, the region between Cairo and Aswan was subject to annual floods. The prevalence of Schistosomiasis was only about 5%. Four years after completion of the dam the prevalence ranged from 19%-75% (average 35%) or a 7 fold increase.
Schistosoma sp. Important parasites of man and some domesticated animals Three species infect man Schistosoma mansoni Schistosoma japonicum Schistosoma haematobium similar see table 16.1 pg 237 for differences
Schistosoma japonicum. Common in parts of Japan, China, Taiwan, Philippines, Thailand, and other parts of Southeast Asia. Most pathogenic and most difficult to control Located in blood vessels of small intestine. Eggs may lodge in brain causing CNS damage, coma, and paralysis.
Schistosoma mansoni Common in Egypt, the Middle East, parts of Africa, and parts of South and Central America. Found in portal veins draining large intestine The sharp lateral spine is distinctive Primary pathological effects come from the damage done by eggs.
Schistosoma mansoni In heavy infections eggs become trapped in the mucous and submucosa of the gut and cause granuloma formation If extensive, they can cause colon blockage and significant blood loss. In liver can cause hepatomegaly. Destruction of lungs and heart tissue. Reservoir hosts are of limited or no importance
Schistosoma haematobium often referred to as Bilharzia after Theodore Bilharz who discovered it. found in parts of Africa, and parts of the Middle East, southern Europe and some parts of Asia. Found primarily in the veins of the urinary bladder. Eggs released in urine. They are least pathogenic
Diagnosis, Treatment, andControl Finding eggs in feces or urine Biopsy - in chronic cases if eggs not passed Treatment - very difficult - page 245-246. Control is very difficult Customs and traditions Agricultural practices Socioeconomics
Schistosome cercarialdermatitis or swimmers itch Schistosomes of animals other than man (usually rodents and birds) try to penetrate the skin of man, they can not establish themselves in the blood vascular system of man. Often cause a dermatitis which can be severe and in some cases life threatening. Allergic reaction
Fasciolopsis buski -Intestinal fluke of man large fluke infects man when he ingests metacercaria found on vegetation including water chestnuts, bamboo, and water caltrop. eat these raw or peel or crack with teeth. elimination of feces (human and animal) into water and use of night soil for farming
Fasciolopsis buski - Pathology Blockage of food passage or interference with normal digestive processes Destruction of intestinal tissue resulting in ulcers, hemorrhages, and abscesses formation Chronic diarrhea Verminous intoxication - result of absorption of parasite metabolites (waste products), can lead to death.
Dicrocoelium dendriticum Common parasite of herbivores, rare in man Not dependent upon aquatic environment Eggs eaten by land snail (asexual reproduction occurs producing cercariae. Cercariae surrounded forming slime balls. Ant eats slime ball and metacercaria develop. Herbivore infected by ingesting ant.
Dicrocoelium dendriticum Modification of host behavior Causes ant to climb to tips of grasses early morning and late evenings. Increases odds of ant being eaten.
Paragonimus westermani the human lung fluke, it is found in the Orient including India and Philippines Definitive host becomes infected by eating improperly cooked crustacean. Adult infections become established in lungs but larval forms may wander into brain, pleura, mesentery, etc.(ectopic infection).
Paragonimus westermani Reservoir hosts include - dogs, cats, pigs, rodents, and other animals Man becomes infected by eating improperly cooked crabs, ingestion of metacercaria from cutting boards where salads are fixed, medicinal use of crab juices) Smoked or pickled crab do not kill
Paragonimus westermaniPathology Early invasive stages usually asymptomatic. In the lung or ectopic site, connective tissue forms pseudotubertules. In the CNS, they can cause paralysis and in rare cases can be fatal. In the heart they can cause severe damage and can be fatal. Lung infections cause chronic cough, bloody sputum, pneumonia -like conditions.
Paragonimus westermani Prevention includes Cooking of crabs, crayfish Care when eating salads, no crab juice. Proper disposal of feces and sputum.
Clonorchis sinensis(Opistochonorchis sinensis) Commonly called the Chinese liver fluke, Asian liver fluke, Oriental liver fluke, and Human liver fluke Common in Orient including Japan, China, Korea, Taiwan, Viet Nam. Many immigrants from Orient living in the United States are infected.
Clonorchis sinensis Man becomes infected by eating improperly cooked fish containing metacercaria. Metacercaria may contaminate other foods such as salads, etc. Smoking, drying, pickling fish often fails to kill the metacercaria.
Characteristics Mostly slender and elongate With flat body usually of many short similar sections Complete lack of Digestive system They lack cilia Covered with tegument Have complex muscle layers, parenchyma, paired excretory ducts with flame cells, and nerve ring with 3 pairs of nerve cords.
Food is absorbed directly through body wall All are endoparasites, the adult worms is in the intestines of vertebrates and the larvae in tissues of some alternate host. Defining characteristics Scolex Proglottids
Subclass CESTODARIA Small worms lacking a scolex each with sucker for attachment the body undivided one set of reproductive organs Similar in outward appearance to trematodes But the larva is like tapeworm and LACK digestive tract.
Subclass EUCESTODA Have scolex Ex: Taenia solium (pork tapeworm of humans) SCOLEX “head” - a minute knoblike with four muscular suckers or sucker disc on the side and a circle of hooks on the elevated tip, or rostellum. A short “neck”, or budding zone, joins the scolex to the body, or strobila, which consist s of a series of up to 1000 proglottids.
Scolex, anterior holdfast organ Neck, region of growth Strobila made up of individual proglottids.
The suckers and the hooks serve to fasten the scolex to the intestinal wall of the host. Scolex contain nerve ring Each proglottid contains muscle, parenchyma, sections of the excretory canals connected by a cross canal, many flame cells in the nerves Complete set of both male and female sex organs develops in every prolottids
Since individual prolottid has acomplete set of both male andfemale sex organs…DO YOU THINK IT IS POSSIBLE FOR EVERY PROGLOTTID TO FERTILIZE ANOTHER PROGLOTTID????
Fact. Self-fertilization between the systems in one proglottid or in sepatarete proglottids or cross-fertilization between parts in two worms in one host are all possible.
Life cycle of the pork tapeworm.Taenia solium Feces Oncosphere Eggs eaten by pigs Eggs encyst in intestine Cysticercus- bladder worm Hollow papilla projecting in the sac In the cavity of papilla, scolex develop Eaten imperfectly cooked pork The papilla everts to form a scolex and neck Scolex attaches to the host intestine A new tapeworm begins to form
Beef Tapeworm,Taeniarhynchus saginatus• Definitive host humans; intermediate host cattle• Eggs are shed with human feces; infected persons defecate in apasture and the eggs are ingested by cattle• Eggs hatch giving rise to oncosphere larvae that bore into theintestinal wall and get into the circulatory system to betransported to muscle• Here the larvae develop into the cysticercus stage (=thebladder worm) with the inverted scolex• If uncooked beef is consumed the cysticercus is freed and thescolex everts, forming the adult• Symptoms include loss of weight, chronic indigestion, diarrhea
The free swimming coracidium is eatenby 1st intermediate host usually anaquatic arthropod! Copepod
In the copepod the second larval stage(PROCERCOID) Frontal glands Cercomer posterior end
2nd IH is a vertebrate of some kind(usually cold blooded)
The 3rd type of larva that develops in the2nd IH is the PLEROCERCOIDThe cercomere is lost and a scolex develops (no proglottids)!
Human Infections of Spirometra(Diphyllobothrium) mansonoides A few cases in the US have involved finding plerocercoids in the eyes.
Sparganosis Disease Humans infected with plerocercoid Ingestcopepod Eating raw meat with plerocercoids Plerocercoid transfers to human Frogor snake flesh poultice Pluerocercoid moves into human tissue
Human Infections of Spirometra(Diphyllobothrium) mansonoides Parasite is rare - only about 40 cases of human sparganosis have been reported in the U.S.
Sparganosis Seriousness depends on Where plerocercoid establishes Number If reproduction occurs Removed by surgery
ADJUSTMENT TO PARASITIC LIFE1. The integument protects against digestion by host alkaline digestive juices but is freely permeable to water and nutrients. o Nutrients—mostly amino acids and simple sugars broken down from complex molecules by the host o Adults—resistant to alkaline pancreatic juice
2. The internal osmotic pressure is lower than that of the surrounding host fluid or tissue.3. The pH tolerance is high, 4 to 11.4. The tissues have high glycogen content (to 60% of dry weight) and much lipid but far less protein. Fatty acid are derived from anaerobic metabolism of glycogen Carbohydrates in the host diet induces growth , longevity , and production
5. Oxygen is used in respiration if available, but anaerobic predominates.6. Eggs eaten by the intermediate host must experience both acid and alkali. Hence are released only in the intestine.
Adaptations of parasites in general:1. Sense organs are usually much reduced or absent2. Some mechanism of attachment to the host tissue is developed (hooks, suckers)3. There is increased egg production coupled with a larval stage to facilitate survival and infection of new host.