Phylum Porifera.pptx
- 1. Dr. Muhammad Moosa Abro Phylum Porifera Phylum Porifera Cell Types, Body Wall, and Skeletons Water Currents and Body Forms Maintenance Functions Reproduction
- 2. GC University Hyderabad Muhammad Moosa Abro Department of Zoology
- 3. The porifera or sponges, are primarily marine animals consisting of loosely organized cells The approximately 9,000 species of sponges vary in size from less than a centimeter to a mass that would more than fill your arms. Characteristics of the phylum porifera include: 1. Asymmetrical or superficially radially symmetrical 2. Three cell types: pinacocytes, mesenchyme cells, and choanocytes 3. Central cavity, or a series of branching chambers, through which water circulates during filter feeding 4. No tissues or organs Dr. Muhammad Moosa Abro Phylum Porifera
- 4. CELL TYPES, BODY WALL, AND SKELETONS In spite of their relative simplicity, sponges are more than colonies of independent cells. As in all animals, sponge cells are specialized for particular functions. This organization is often referred to as division of labor. Dr. Muhammad Moosa Abro Phylum Porifera
- 5. CELL TYPES, BODY WALL, AND SKELETONS Thin, flat cells, called pinacocytes, line the outer surface of a sponge. Pinacocytes may be mildly contractile, and their contraction may change the shape of some sponges. In a number of sponges, some pinacocytes are specialized into tubelike, contractile porocytes, which can regulate water circulation . Openings through porocytes are pathways for water moving through the body wall. Dr. Muhammad Moosa Abro Phylum Porifera
- 6. Just below the pinacocyte layer of a sponge is a jellylike layer called the mesohyl Amoeboid cells called mesenchyme cells move about in the mesohyl and are specialized for reproduction, secreting skeletal elements, transporting and storing food, and forming contractile rings around openings in the sponge wall. Below the mesohyl and lining the inner chamber(s) are choanocytes, or collar cells. Dr. Muhammad Moosa Abro Phylum Porifera
- 7. Dr. Muhammad Moosa Abro Phylum Porifera Choanocytes (gr. Choane, funnel 1 cyte, cell) are flagellated cells that have a collarlike ring of microvilli surrounding a flagellum. Microfilaments connect the microvilli, forming a netlike mesh within the collar. The flagellum creates water currents through the sponge, and the collar filters microscopic food particles from the water. the presence of choanocytes in sponges suggests an evolutionary link between the sponges and choanoflagellates.
- 8. SKELETON Sponges are supported by a skeleton that may consist of microscopic needlelike spikes called spicules. Spicules are formed by amoeboid cells, are made of calcium carbonate or silica, and may take on a variety of shapes (figure 9.5). Alternatively, the skeleton may be made of spongin (a fibrous protein made of collagen). A commercial sponge is prepared by drying, beating, and washing a spongin-supported sponge until all cells are removed. The nature of the skeleton is an important characteristic in sponge taxonomy. Dr. Muhammad Moosa Abro Phylum Porifera
- 9. WATER CURRENTS AND BODY FORMS The life of a sponge depends on the water currents that choanocytes create. Water currents bring food and oxygen to a sponge and carry away metabolic and digestive wastes. Methods of food filtration and circulation reflect the body forms in the phylum. Zoologists have described three sponge body forms. Dr. Muhammad Moosa Abro Phylum Porifera
- 10. ASCON BODY FORM The simplest and least common sponge body form is the ascon (figure 9.6a). Ascon sponges are vaselike. Ostia are the outer openings of porocytes and lead directly to a chamber called the spongocoel. Choanocytes line the spongocoel, and their flagellar movements draw water into the spongocoel through the ostia. Water exits the sponge through the osculum, which is a single, large opening at the top of the sponge. Dr. Muhammad Moosa Abro Phylum Porifera
- 11. SYCON BODY FORM In the sycon body form, the sponge wall appears folded ( figure 9.6b). Water enters a sycon sponge through openings*called dermal pores. Dermal pores are the openings of invaginations of the body wall, called incurrent canals. Pores in the body wall connect incurrent canals to radial canals, and the radial canals lead to the spongocoel. Choanocytes line radial canals (rather than the spongocoel), and the beating of choanocyte flagella moves water from the ostia, through incurren and radial canals, to the spongocoel, and out the osculum. Dr. Muhammad Moosa Abro Phylum Porifera
- 12. LEUCON Leucon sponges have an extensively branched canal system (figure 9.6c). Water enters the sponge through ostia and moves through branched incurrent canals, which lead to choanocyte- lined chambers. Canals leading away from the chambers are called excurrent canals. Proliferation of chambers and canals has resulted in the absence of a spongocoel, and often, multiple exit points (oscula) for water leaving the sponge. In complex sponges, an increased surface area for choanocytes results in large volumes of water being moved through the sponge and greater filtering capabilities. Although the evolutionary pathways in the phylum are complex and incompletely described, Dr. Muhammad Moosa Abro Phylum Porifera
- 13. Dr. Muhammad Moosa Abro Phylum Porifera
- 14. MAINTENANCE FUNCTIONS Sponges feed on particles that range in size from 0.1 to 50 um. Their food consists of bacteria, microscopic algae, protists, and other suspended organic matter. The prey areslowly drawn into the sponge and consumed. Large populations of sponges play an important role in reducing the turbidity of coastal waters. A single leucon sponge, 1 cm in diameter and 10 cm high, can filter in excess of 20 l of water every day! A few sponges are carnivorous. These deep-water sponges (asbestopluma) can capture small crustaceans using spicule- covered filaments. Dr. Muhammad Moosa Abro Phylum Porifera
- 16. Choanocytes filter small, suspended food particles. Water passes through their collar near the base of the cell and then moves into a sponge chamber at the open end of thecollar. Suspended food is trapped on the collar and moved along microvilli to the base of the collar, where it is incorporated into a food vacuole Digestion begins in the food vacuole by lysosomal enzymes and ph changes. Partially digested food is passed to amoeboid cells, which distribute it to other cells. Filtration is not the only way that sponges feed. Pinacocytes lining incurrent canals may phagocytize larger food particles (up to 50 m). Sponges also may absorb by active transport nutrients dissolved in seawater. MAINTENANCE FUNCTIONS Dr. Muhammad Moosa Abro Phylum Porifera
- 17. Because of extensive canal systems and the circulation of large volumes of water through sponges, all sponge cells are in close contact with water. Thus, nitrogenous waste (principally ammonia) removal and gas exchange occur by diffusion. Sponges do not have nerve cells to coordinate body functions. Most reactions result from individual cells responding to a stimulus. For example, water circulation through some sponges is at a minimum at sunrise and at a maximum just before sunset because light inhibits the constriction of porocytes and other Cells surrounding ostia, keeping incurrent canals open. Other reactions, however, suggest some communication among cells. Dr. Muhammad Moosa Abro Phylum Porifera
- 18. For example, the rate of water circulation through a sponge can drop suddenly without any apparent external cause. This reaction can be due only to choanocytes ceasing activities more Or less simultaneously, and this implies some form of internal communication. The nature of this communication is unknown. Amoeboid cells transmitting chemical messages and ion movement over cell surfaces are possible control mechanisms. Dr. Muhammad Moosa Abro Phylum Porifera
- 20. REPRODUCTION Most sponges are monoecious (both sexes occur in the same individual) but do not usually self- fertilize because individual sponges produce eggs and sperm at different times. Certain choanocytes lose their collars and flagella and undergo meiosis to form flagellated sperm. Other choanocytes (and amoeboid cells in some sponges) probably undergo meiosis to form eggs. Sperm and eggs are released from sponge oscula. Fertilization occurs in the ocean water, and planktonic larvae develop. In a few sponges, eggs are retained in the mesohyl of the parent. Sperm cells exit one sponge through the osculum and enter another sponge with the incurrent water. Sperm are trapped by choanocytes and incorporated into a vacuole. The choanocytes lose their collar and flagellum, become amoeboid, and transport sperm to the eggs. Dr. Muhammad Moosa Abro Phylum Porifera
- 21. In some sponges, early development occurs in the mesohyl. Cleavage of a zygote results in the formation of a flagellated larval stage. (A larva is an immature stage that may undergo a dramatic change in structure before attaining the adult body form.) The larva breaks free, and water currents carry the larva out of the parent sponge. After no more than two days of a free-swimming existence, the larva settles to the substrate and begins to develop into the adult body form (figure 9.7a and b). Dr. Muhammad Moosa Abro Phylum Porifera
- 22. Asexual reproduction of freshwater and some marine sponges involves the formation of resistant capsules, called gemmules, containing masses of amoeboid cells (figure 9.7c and d). When the parent freshwater sponge dies in the winter, it releases gemmules, which can survive both freezing and drying. When favorable conditions return in the spring, amoeboid cells stream out of a tiny opening, called the micropyle, and organize into a sponge. Some sponges possess remarkable powers of regeneration. Portions of a sponge that are cut or broken from one individual regenerate new individuals. Dr. Muhammad Moosa Abro Phylum Porifera
- 24. Dr. Muhammad Moosa Abro Phylum Porifera
- 25. REFERENCES 25 1. Miller, A.S. and Harley, J.B. ; 1999 , 2002., 2007, 2009, 2012 & 2016 Zoology, 4th , 5th, 6th, 7th, 8th , 9th& 10th Edition (International), Singapore : McGraw Hill. 2. Hickman, C.P., Roberts, L.C/, AND Larson, A., 2018. INTEGRATED PRINCIPLES OF ZOOLOGY, 15th Edition (International), Singapore: McGRAW-Hill