Phylum Platyhelminthes & Nematodes Lecture 7 PDF

Phylum Platyhelminthes (Z 101) For First year students (Chemistry/Zoology) Prof. Dr. Sayed Abd El- Monem  Kingdom Animalia Subkingdom Metazoa Branch Eumetazoa (Enterozoa) Divis...

Phylum Platyhelminthes (Z 101) For First year students (Chemistry/Zoology) Prof. Dr. Sayed Abd El- Monem  Kingdom Animalia Subkingdom Metazoa Branch Eumetazoa (Enterozoa) Division Bilateria (Triploblastica) Section Acoelomata Phylum Platyhelminthes (Flatworms) General characters 1- Body dorso-ventrally compressed with bilateral symmetry. 2- Triploblastic animals. 3- Epidermis is soft and ciliated as in Turbellaria or covered by tegument and with external suckers or hooks or both for attachment to host as in Monogenea, Digenea and Cestoda. 4- There is no secondary body cavity (acoelomate). 5- The muscular system is well developed. 6- Incomplete digestive system (with mouth, no anus). 7- Excretory system represented by flame cells or solenocytes. 8- It is the first phylum possesses some sense organs and central nervous system. 9- Sexes usually monoecious or hermaphrodite (except Schistosoma) with a complicated reproductive system. 10- No skeletal, circulatory or respiratory systems. Classification of Phylum Platyhelminthes: - Five classes of Phylum Platyhelminthes are recently recognized: 1- Class: Turbellaria, mostly free living. 2- Class: Monogenea, typically ectoparasitic. 3- Class: Aspidogastrea (Aspidobothrea) 4- Class: Digenea, endoparasitic. 5- Class: Cestoda (Tape worms), endoparasitic & segmented. Class Turbellaria Order Tricladida EX. Dugesia (Planaria) Rod like small bodies when discharged into water swell and form a protective gelatinous sheath around the body which serves in adhesion, capturing the prey and in protection against enemies. Muscular system composed of Three layers: 1- Circular muscle layer 2- Longitudinal muscle layer 3- Vertical muscle layer = Parenchyma (no body cavity) (acoelomata) Nervous system and Sense organs of Dugesia Nervous system (Ladder-shape) consists of: Anterior nerves Eye Brain, gives Two cerebral ganglia, joined to form Two longitudinal ventro-lateral nerve cords, connected by Transverse nerves, gives Peripheral nerves Sense organs are two rounded black spots termed as eyespots, each one consist of: 1- Cup-like structure 2- Black pigmented cells 3- Retinal cells 4- Photosensitive ends 5- Nerves connected to brain Planarians respond negatively to light as they mostly active at night General characters Class Digenea 1- All endoparasitic 2- Body is flattened and unsegmented 3- Attach to their hosts by suckers 4- Alimentary canal with mouth and no anus 5- Complex muscle layers 6- Excretory organs and nervous system are present The adult worms are found in different tissues of the primary host (vertebrate). According to their location in the body of the host, digenetic trematodes are grouped as follows: 1- Hepatic or liver flukes, e.g. Fasciola 2- Blood flukes, e.g. Schistosoma 3- Intestinal flukes, e.g. Heterophyes  Liver Flukes (Fasciola spp.) - The adult worms live in the bile ducts of the liver of cattle, sheep and pigs. - It produces the disease known as Fascioliasis (liver rot). - Fasciola gigantica is the common liver fluke in Egypt, while Fasciola hepatica (human liver fluke) is more common in Europe and Australia. - Mode of infection: When man eats vegetables or animals ingest the aquatic plants which contain the encysted metacercariae (infective stage). Morphology Body wall Digestive system in Fasciola Nervous system in Fasciola Respiration: Fasciola lives under anaerobic conditions as when the oxygen is not abundantly present Excretory system in Fasciola It consists of: 1- Main excretory canal 2- Excretory trunks 3- Excretory vessels 4- Twigs 5- Collecting tubules 6- Capillary ducts 7- Flame cells/ Protonephridia Flame cells consists of: 1- Thin elastic wall with pseudopodia 2- Nucleus 3- Intracellular cavity having long cilia (flickering movement) All structures are ciliated except the Main excretory canal which opened exteriorly by excretory pore through hydrostatic pressure excretory wastes. It concerned with excretion as well as osmoregulation.  Reproduction in Fasciola Female reproductive system Male reproductive system Single branched ovary, Two branched testes, form form ova to be collected by sperms to be collected by Oviduct Vas efferentia OOtype Vas deferens, dilates posteriorly to form Uterus Vesicula seminalis Genital atrium From it arise Laurer’s canal Ejaculatory duct, surrounded by opens on dorsal side to act prostate glands of alkaline secretion as vestigial vagina helps in free movement of sperms during copulation Mehlis’s gland surround ootype, its secretion Cirrus pouch (Penis) lubricates passage of eggs in uterus and hardens egg shells Genital atrium Vitelline glands extens in lateral fields and pour on longitudinal ducts NOTE: Fasciola is monoecious then connect by transverse ducts (Hermaphrodite), reproduction is sexual swollen into yolk reservoir forming median duct to open in ootype  Infective stage Life cycle of Fasciola Mode of transmission Final host Intermediate host  Blood Flukes (Schistosoma spp. or Bilharzia) - Schistosomes cause serious disease called Schistosomiasis or Bilharziasis. - Mode of infection: Cercariae (infective stage) penetrate the skin of man when drinking, washing, walking or bathing in infected water. Infective stage Final host Intermediate host  Class Cestoda (Tape worms or Gutless flatworms) General characters 1- Elongated ribbon like 2- Composed of head/scolex carries sucker, hooks, bothria, rostellum for attachment 3- Neck having activity dividing cells from which proglottid are formed 4- Three types of proglottid are found which are: [a] Immature (immature sexual organs) [b] Mature (mature sexual organs) [c] Gravid (uterus filled with eggs) 5- Digestive system absent and they absorb their food by tegument 6- Nervous system composed of nerve bundles and nerve cords 7- Excretory system composed of flame cells. They have specials ducts, collecting tubules unite to form main longitudinal excretory canals on each side of proglottid and connected by transverse excretory canal. They open to exterior by single excretory pore. 8- Hermaphrodite 9- Reproduction takes place by cross fertilization and self fertilization  EX. Taeniarhynchus saginatus (Taenia saginata) & T. solium Taenia saginata (beef tapeworm) Taenia solium (pork tapeworm) Measures 10-12 meters and composed of Measures 3-5 meters and composed of 1000-2000 proglottid 800-1000 proglottid Intermediate host is Sheep Intermediate host is Pig Final host is Man, they are intestinal parasites Mode of infection: When man eats raw or insufficiently cooked meat of cows or camel in case of Taenia saginata or meat of pig in case of T. solium which contain the bladder worms (infective stage) in their muscles. Disease it may cause: this is a human intestinal parasite causing Taeniasis which may result in mild anaemia, digestive & nervous disorders, and loss of weight. Muscular system Body wall  Life cycle of Taenia Reproductive system of Taenia  Kingdom Animalia Subkingdom Metazoa Branch Eumetazoa (Enterozoa) Division Bilateria (Triploblastica) Section Acoelomata Phylum Nematoda (Thread worms) General characters 1- They are bilaterally symmetrical, unsegmented triploblastic worms. 2- Pseudocoelomate animals with slender cylindrical bodies. 3- Alimentary canal is straight and complete with mouth and anus (or cloacal opening). 4- Respiratory and circulatory systems are absent. 5- Cuticle usually present and cilia are absent. 6- Body wall with longitudinal muscles only. 7- Excretory system of glandular organs or a system of canals or both. 8- Dioecious; male is smaller than female. 9- Fertilization is internal. 10-The nervous system is composed of a nerve ring around the oesophagus from which arise 6 short anterior and 6 long posterior nerve cords. 11- Eggs are shelled covering with a chitinous shell. 12- Development is usually direct and no asexual reproduction or regeneration occurs. Classification of Phylum Nematoda Phylum Nematoda is classified into 2 main classes: 1. Class: Secernentea (Phasmidea), It includes: a. Order: Ascaridida e.g. Ascaris lumbricoides (Eel worm) b. Order: Strongylida e.g. Ancylostoma duodenale (Hook worm) c. Order: Oxyurida e.g. Enterobius vermicularis ( Pin worm or seat worm) 2. Class: Aphasmidea, It includes: a. Order: Trichinellida e.g. Trichinella spiralis Ascaris lumbricoides (Eel worm) - This is a common intestinal parasite of man (children in particular) & other animals. - It causes to the human a disease known as Ascariasis: [a] In mild infections, it causes abdominal disorders [b] In severe cases, it causes general weakness, intestinal obstruction, hepatitis obstruction of biliary passages & further of the trachea, lead to suffocation - Mode of infection: When man eats vegetables & food or drinks water contaminated with the second rhabditiform larvae (infective stage). Morphology of Ascaris [A] Anterior end 1- Head has a terminal mouth, surrounded by three lips 2- Dorsal lip bear two double sensory papillae, and each latero-ventral lip has one double sensory papillae 3- Each latero-ventral lip has amphid which are olfactory chemoreceptors 4- Lips have fine teeth 5- Excretory pore behind lips [B] Cuticle of the body Smooth with Four longitudinal epidermal lines (one dorsal, one ventral, two lateral) [C] Posterior end 1- Male has cloacal aperture provided with number of anal papillae with two equal spicules project 2- Female has vulva on the anterior part Body wall of Ascaris 1- Cuticle (non-cellular) 2- Epidermis 3- Muscle layer, divided into 4 parts 4- Muscle cell, consists of [a] Contractile part [b] Cytoplasmic part 5- Between body wall and internal organs there is perivisceral cavity (pseudocoelom) Digestive system of Ascaris Alimentary canal consists of: 1- Foregut (mouth, pharynx) 2- Midgut (intestine) 3- Hindgut (rectum) Rectum opens into: 1- Male: by cloaca which receives ejaculatory duct 2- Female: by anus Extracellular digestion occurs in the gut, then soluble digested food absorbed by intestinal cells the pass by diffusion into pseudocoelomic fluid to different parts of the body  Reproductive system of Ascaris Male reproductive system Female reproductive system Single testis Two ovaries Vas deferens, dilates Oviduct posteriorly to form Seminal receptacles, to storage Vesicula seminalis sperms after copulation, and fertilization occurs Ejaculatory duct, opens into rectum to form cloaca to Uteri, to store fertilized eggs and opens out by cloacal aperture its cells produce yolk for egg shell Dorsal to cloaca is a pair of Vagina, opens by muscular sacs called penial sacs unite and join cloaca, Vulva they contain penial spicules Penial spicules serve in copulation to open female reproductive opening and help to transfer sperms Life cycle of Ascaris  Ancylostoma duodenale (Human hook-worm) - This is a common intestinal parasite of man (children in particular) & other animals. - It causes to severe anemia to man. - It known as hook-worms as the anterior end of both sexes is bent dorsally as hool- shape but rhe worms have no hooks. - Mode of infection: When man eats vegetables & food or drinks water contaminated with the filariform larvae (infective stage). Life cycle