Invertebrate Zoology (Z 101) Lecture 3 PDF

Invertebrate Zoology (Z 101) For First year students Invertebrates Lecture Three Dr. Mona Fathi Fol  (II)- Phylum: Apicomplexa Class: Sporozoa Levine (1970) They are protozoan parasites which live as internal parasites (endopara...

Invertebrate Zoology (Z 101) For First year students Invertebrates Lecture Three Dr. Mona Fathi Fol  (II)- Phylum: Apicomplexa Class: Sporozoa Levine (1970) They are protozoan parasites which live as internal parasites (endoparasites) in higher animals. It comprised of organisms that possessed the apical complex which include polar ring, micronemes, rhoptries, subpellicular microtubules, micropore(s) and conoid which help in penetrating host. Respiration and excretion are takes place by simple diffusion. Nutrition takes place by absorbing food directly from the host through saprozoic nutrition.  The life cycle of each organism in this phylum involves: 1- Asexual cycles I. Schizogony or Merogony (Multiple fission), means formation of merozoites which acts as the feeding stage. II. Sporogony (Multiple fission), means formation of sporozoites which acts as the infecting stage. 2- Sexual cycle I. Gametogony or gamogony, where male and female gametes unite resulting in the formation of zygotes.  Plasmodium sp. They are intracellular blood parasites of blood cells and tissues of birds and mammals. They causes to human several diseases, which transmitted by blood sucking arthropods acts as intermediate hosts.  Life cycle of Plasmodium sp. Female Anopheles mosquito (Final Man (Intermediate host) host) 1.Schizogony in liver cells (Exo-erythrocytic cycle) 1. Gamogony (Sexual cycle A.Primary tissue phase inside the stomach of B.Secondary tissue phase or mosquitoes). Re-infection 2. Sporogony (Asexual cycle in 2.Schizogony in RBCS haemolymph of mosquitoes) (Erythrocytic cycle)  (III)- Phylum Ciliophora Ex. Paramecium caudatum A group of protozoans which are characterized by the presence of hair-like organelles called cilia used for locomotion & feeding. Ciliates have two different types of nuclei which are: 1. Small diploid micronucleus (for reproduction only) 2. Large polyploid macronucleus (for all the vegetative functions except the reproduction). Ciliates can undergo both asexual and sexual reproduction. i- Asexual reproduction occurs by transverse binary fission.. ii- Sexual reproduction occurs by conjugation.  i- Asexual reproduction in Paramecium - By transverse binary fission & yields two identical new individuals.  Meioti Mitotic c divisio divisio n n ii- Sexual reproduction in Paramecium - It occurs by conjugation. division Mitotic division Mitotic Daughter Paramecia 3 Mitotic divisions  Kingdom Animalia Subkingdom Metazoa Branch Parazoa Phylum Porifera (Sponges) (Pore bearers) They are stationary and rooted in their places, and so they were considered as plants for centuries, but eventually their animal nature was discovered. The Porifera (15,000 species) represent Metazoa at the cellular level of organization. Sponges are usually found in relatively shallow water, but some groups live at great depths. Few species live in freshwater. General characters of Sponges 1. They are radially symmetrical. 2. Body with many pores or ostia through which water flows. 3. The internal cavity is known as spongocoel lined with choanocytes (collared flagellated cells). 4. They are holozoic with no mouth, no digestive system and digestion is intracellular. 5. They respire and excrete by simple diffusion.  Structure of the body wall The body wall in sponges is made up of: (1)- Outer layer, epidermis of thin flat cells called pinacocytes. (2)- Middle layer, gelatinous layer is mesenchyme (mesoglea), containing: A- Skeletal components may be spicules (calcareous or siliceous spicules), and also it may be spongin fibers. B- Amoebocytes in different kinds: 1- Archaeocytes, which receive, digest, circulate food and can produce other types of cells particularly reproductive elements (ova, sperms, gemmules). 2- Scleroblasts, which synthesis spicules to constitute the skeleton, it present in two types calcoblasts and spongioblasts. (3)- Inner layer, gastral layer, consisting of collared flagellated cells or choanocytes.  Skeleton of Sponges used in taxonomic identification of the different types of sponges Spicules Spongin fibers Combination (Calcareous or silicious) (network branched) between Spicules and spongin fibers According to No. of axes and rays According to size may be Megasclera or microsclera Monoaxon Triradiate Triaxonic Amphidiscs (Needle like) (Triactinal) (Hexactinal) Tetraxon Polyaxon Spheres (4 rays not in the same plane)  Types of Sponges referring to water circulation According to the types of water canal system, there are three types of sponges which are: (1)- Ascon, Ex. Leucosolenia, Ascetta This is the simplest type of sponge. The body is tube or vase-shaped. The body wall is thin, the inhalant pores lead directly into the spongocoel which is lined with choanocytes. Pores Osculum Water Paragastric cavity Outside (2)- Sycon, Ex. Sycon, Grantia The body wall has been folded horizontally and as a result two types of canals are found which communicate with each other through pores called prosopyles. These canals are: (a) Inhalant canals which are lined with pinacocytes and open to the outside by ostia and end blindly inwards. (b) The flagellated chambers which are lined with choanocytes. They open at their inner ends into the paragastric cavity through pores called apopyles but end blindly towards the outer surface of the sponge. Prosopyles Water Pores Inhalant canals Flagellated Apopyles chambers Osculum (3)- Leucon, Ex. Bath sponge Euspongia The body wall is very thick and highly folded resulting in the formation of many small rounded flagellated chambers, while the paragastric cavity is very much reduced. Water Pores Subdermal Inhalant cavities canals Osculum Outside Exhalant Flagellated canals  Reproduction 1- Asexual Reproduction 2- Sexual Reproduction a. External budding b. Regeneration c. Internal budding (Gemmule formation)  Kingdom Animalia Subkingdom Metazoa Branch Eumetazoa (Enterozoa) Division Radiata (Diploblastica) Phylum Cnidaria (Coelenterata) Classification of Phylum Cnidaria: - Phylum Cnidaria is classified into 4 classes which are: 1- Class Hydrozoa (Gr., hydro, water + zoon, animal) = Water animals, Examples: Hydra, Obelia. 2- Class Scyphozoa (True jelly-fish), Example: Aurelia. 3- Class Cubozoa (Cube jelly-fish), Examples: Box jellies and Sea wasps. 4- Class Anthozoa (Actinozoa) (Gr., anthos, flower + zoon, animal) = Flower animals - Class Anthozoa is subdivided into two subclasses: a- Subclass: Alcyonaria (Soft corals), Examples: Alcyonium, Xenia. b- Subclass: Zoantharia (hard corals), Examples: Sea anemones & stony corals.  General characters of Cnidarians 1) They are solitary or colonial, sedentary or free swimming. 2) They are aquatic, mostly marine, some are fresh water. 3) The body is radially symmetrical. 4) Most cnidarians are carnivorous. 5) There is a central gastro-vascular cavity (coelenteron or enteron) which is communicated with the exterior by a single opening, the mouth. 6) The mouth is surrounded by tentacles arranged in one or more whorls. The tentacles help in food capture, ingestion and for defense. 7) Body wall has peculiar stinging cells called cnidocytes which are more abundant on the tentacles than elsewhere.  Structure of the body wall of Hydra (1)- Outer layer, Epidermis has several types of cells: A. Epithelio-muscular cells, they are collectively form the exterior surface of the body. B. Mucous-secreting cells, they are mainly cover the basal disc and hypostome. They secrete a sticky mucous for protection, prey capture and adhesion, also produce a gas bubble for floating. C. Interstitial cells, they found between the narrow bases of the epithelio- muscular cells, these cells capable of giving rise to other types of ectodermal cells, they serve for repairing any injured parts of the body and producing sperms and ova in breeding season. D. Sensory cells, they receive and transmit impulses, and they are sensitive to touch, temperature, chemical stimuli, light etc…. E. Nerve cells, has a small cell body containing nucleus and number of branching processes or nerve fibers which interact to form nerve net which extends over the entire body. F. Cnidocytes, they are specialized forming a nematocyst in the interior which act as organs of defence, food capture, locomotion. (2)- Middle layer, Mesoglea, this is non-cellular jelly–like, it is traversed by migrating cell and crossed by nerve fibers. This layer gives support and rigidity to the body and acts like an elastic skeleton. (3)- Inner layer, Gastrodermis, it lines the gastrovascular cavity and is made up of large columnar and irregular cells. This layer is mainly nutritive in function. It has several types of cells : A. Musculo-nutritive cells, they are function actively in the digestion of food and muscular function. When contracted the diameter of the body is reduced. Consequently, the length of the body is extended. They form pseudopodia, flagella, food vacuoles and others are filled with small secretory granules. B. Glandular cells, they secrete digestive enzymes inside the gastrovascular cavity for extracellular digestion. C. Mucous-secreting cells, they secrete mucous to facilitate the entrance of large food particles. D. Sensory cells and Nerve cells. 8. Digestion is extracellular in the gastro-vascular cavity and then intracellular inside the endodermal cells. 9. No respiratory, circulatory and excretory systems. 10. Sense organs are simple or complicated, e.g. ocelli and statocysts. 11. Nervous system consists of one or more nerve nets made up of nerve cells and nerve fibres. 12. Reproduction occurs by both asexual and sexual. Asexual reproduction by budding and regeneration; while, sexual reproduction by gametes to form a uniformly ciliated planula larva. Budding Regeneration in Hydra Planula larva 13.The individuals are of two types: the attached polyp and free- swimming medusa. 14. Life cycle exhibits metagenesis (alternation of generation) in which sexual medusoid generation alternates with asexual colonial polypoid generation. Life cycle of Obelia Blastula Gastrula  Locomotion Actual locomotion is achieved by the following various methods: (1)- Looping or walking (2)- Somersaulting (3)- Climbing (4)- Inverted movement (5)- Floating (6)- Gliding