Chapter 12 - Sponges (1) PDF

Because learning changes everything. ® Integrated Principles of Zoology Nineteenth Edition Chapter 12 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC.  Chapter 12: Sponges...

Because learning changes everything. ® Integrated Principles of Zoology Nineteenth Edition Chapter 12 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC.  Chapter 12: Sponges only ©William C. Ober/Medical Scientific Illustration © McGraw Hill LLC. 2  The Origins of Multicellularity Cells are the elementary units of life. Increasing the size of a cell causes problems in exchanging molecules with the environment. Multicellularity prevents surface-to-mass problems as smaller units greatly increase surface area for metabolic activities. Highly adaptive toward larger body size. © McGraw Hill LLC. 3 © McGraw Hill LLC. 4  Multicellular Sponges Sponges are the simplest multicellular animals but their cell assemblages are distinct from other metazoans. Sponges have cells embedded in an extracellular matrix supported by a skeleton with needle-like spicules and protein. Sponges neither look like nor behave as animals but molecular evidence demonstrates that they are phylogenetically grouped with animals. © McGraw Hill LLC. 5  Growth Habits and Forms of Sponges Figure 12.1 Some growth habits and forms of sponges. Access the text alternative for slide images. © McGraw Hill LLC. 6 © McGraw Hill LLC. 7  Phylum Porifera: Sponges General features of sponges. Mostly sessile. Body designed for efficient aquatic filter feeding. Porifera means “pore‑bearing”; sac-like bodies are perforated by many pores. Use flagellated “collar cells”, or choanocytes, to move water to bring food and oxygen while removing wastes. Most of the 8600 sponges are marine, found in all seas and all depths, while few live in brackish water and 150 live in fresh water. © McGraw Hill LLC. 8  Sponge Collar Cells Figure 12.2 Sponge choanocytes have a collar of microvilli surrounding a flagellum. Access the text alternative for slide images. © McGraw Hill LLC. 9  More Sponge Features Sponges vary in size from a few millimeters to over 2 meters in diameter. Many species are brightly colored because of pigments in dermal cells. Embryos are free-swimming while adult sponges always attached. Growth form varies. Some appear radially symmetrical but many are irregular in shape. Some stand erect, some are branched, and others are encrusting. Growth patterns depend on shape of substratum, direction of water, speed of flow, and availability of space. © McGraw Hill LLC. 10  Interactions Many animals such as crabs, nudibranchs, fish, and other species live as commensals or parasites in or on sponges. Sponges can also grow on a variety of other living organisms with some crabs using sponges for camouflage and protection. Sponges and microorganisms living on them often have a noxious odor and produce a variety of bioactive compounds. Certain sponge extracts have manifested medical and pharmaceutical effectiveness. © McGraw Hill LLC. 11  https://www.youtube.com/watch?v=uZglGXT4IXk © McGraw Hill LLC. 12  Skeletal Structure Skeletal structure of a sponge can be fibrous and/or rigid consisting of calcareous or siliceous spicules. Fibrous portion comes from collagen protein fibrils in intercellular matrix. There are several types of collagen, which vary in chemical composition; sponges contain spongin. Composition and shape of spicules are the basis of classification. © McGraw Hill LLC. 13  Spicule Forms Figure 12.3 Diverse forms of spicules that support a sponge body. Access the text alternative for slide images. © McGraw Hill LLC. 14  Poriferan Classification Sponges date to early Cambrian, maybe even Precambrian. Traditionally grouped in three classes based on spicules and chemical composition. Calcispongiae: calcium carbonate spicules with one, three, or four rays. Hexactinellida: glass sponges with six-rayed siliceous spicules. Demospongiae: siliceous spicules around an axial filament, spongin fibers, or both. Class Homoscleromorpha identified as sponges without a skeleton, or with siliceous spicules without an axial filament. © McGraw Hill LLC. 15  Cladogram of Poriferans Figure 12.4 Cladogram depicting evolutionary relationships among the four classes of sponges. Access the text alternative for slide images. © McGraw Hill LLC. 16  Feeding in Sponges Sponges feed by collecting suspended particles from the water pumped through internal canal systems. Many small incurrent pores (dermal ostia) in pinacoderm (outer layer of cells). Water is directed past the choanocytes, which are flagellated collar cells that keep the current flowing via beating of flagella. Microvilli in the collar trap and phagocytize food particles that pass by. Efficiency of food capture is dependent on water movement through the sponge body. © McGraw Hill LLC. 17  Food Particle Consumption Sponges non-selectively consume food particles (detritus, plankton, and bacteria). The smallest particles (80%) are taken into choanocytes by phagocytosis. Protein molecules may be taken in by pinocytosis. Two other cell types, pinacocytes and archaeocytes, facilitate feeding. Dissolved nutrients can also be absorbed by sponges. © McGraw Hill LLC. 18  Sponge Body Structures Figure 12.5 Three types of sponge structure. Access the text alternative for slide images. © McGraw Hill LLC. 19  Asconoid Sponge Body Simplest body organization. Small and tube-shaped to allow water to flow directly across cells so no “dead space.” Choanocytes are in a large internal chamber, the spongocoel. Choanocyte flagella pull water through the pores and extract food particles. Used water is expelled through a large single osculum. All asconoids are in class Calcispongiae. For example, Leucosolenia sp. and Clathrina sp. © McGraw Hill LLC. 20  Asconoid Sponge Figure 12.6 Clathrina canariensis (class Calcispongiae) is common on Caribbean reefs in caves and under ledges. ©Larry Roberts/McGraw-Hill Education © McGraw Hill LLC. 21  Syconoid Sponge Body Syconoids resemble asconoids, but larger with a thicker, more complex body wall. Body wall is folded outwards with choanocyte-lined radial canals that empty into spongocoel. Water enters through dermal ostia and move through tiny openings (prosopyles) into the radial canals. Food is ingested by choanocytes and used water is pumped through internal pores called apopyles then outwards via osculum. Spongocoel is lined with epithelial cells rather than choanocytes as in asconoids. © McGraw Hill LLC. 22  Syconoid Body Wall Figure 12.7 Cross section through wall of sponge Sycon sp., showing choanocytes in canals within the wall but do not line spongocoel. Access the text alternative for slide images. © McGraw Hill LLC. 23  Leuconoid Sponge Body Most complex and largest, with more food-collecting regions. These regions have choanocytes lining in small chambers that effectively filter all water present. Clusters of flagellated chambers are filled from incurrent canals and discharge to excurrent canals which lead to osculum. After food is removed, used water is pooled to form an exit stream that leaves through an exit pore at very high velocity. This high rate of exit flow prevents the sponge from re-filtering used water and wastes. Most sponges are leuconoid type. © McGraw Hill LLC. 24  Leuconoid Evolution and Distribution The leuconoid system has high adaptive value to efficiently meet high food demands of larger body size. Highest proportion of flagellated surface per volume of cell tissue. More collar cells can filter more particles. Water flow slows inside due to greater surface area in the chambers. Large sponges filter 1500 liters of water per day for maximum food collection. The leuconoid system has evolved independently many times in sponges. © McGraw Hill LLC. 25  Leuconoid Sponge ©William C. Ober/Medical Scientific Illustration Figure 12.8 This orange demosponge, Mycale laevis, often grows beneath plate-like colonies of the stony coral Montastrea annularis. © McGraw Hill LLC. 26  Types of Cells in the Sponge Body Sponge cells are arranged in a gelatinous extracellular matrix called mesohyl or mesenchyme. The connective “tissue” of sponges found in fibrils, skeletal elements, and amoeboid cells. Absence of organs requires that all fundamental processes occur at the individual cell level. Respiration and excretion via diffusion and water regulation via contractile vacuoles in the archaeocytes and choanocytes. © McGraw Hill LLC. 27  Sponge Activity and Response Visible activities seen in sponges include. Slight alterations in shape, local contraction, and propagating contractions. Closing and opening of incurrent and excurrent pores. Sponges can close their osculum due to heavy sediment load. Movements occur very slowly but they suggest a whole body response in organisms lacking complex organization above the cellular level. Apparently excitation spreads from cell to cell by mechanical stimuli and signaling molecules such as hormones or via electrical impulses. © McGraw Hill LLC. 28  Types of Sponge Cells Figure 12.9 Small section through sponge wall, showing four types of sponge cells. Access the text alternative for slide images. © McGraw Hill LLC. 29  Choanocytes One end embedded in mesohyl; exposed end has flagellum surrounded by a collar. Collar consists of microvilli connected to each other by fine microfibrils. Forms a fine filtering device to strain food. Particles too large to enter collar are trapped in mucous and slide down to base to be phagocytized. Food is passed to archaeocytes for intracellular digestion with no need for gut cavity. © McGraw Hill LLC. 30  Sponge Cells Trapping Food Figure 12.10 Food trapping by sponge cells. (A) Cutaway section of canals showing direction of water flow. (B) Two choanocytes, and (C) Structure of the collar. Access the text alternative for slide images. © McGraw Hill LLC. 31  Archaeocytes Archaeocytes are amoeboid cells with many functions that move about in the mesohyl. Phagocytize particles in the pinacoderm. Receive particles for digestion from choanocytes. Can differentiate into many other more specialized cell types. Sclerocytes: secrete spicules. Spongocytes: secrete sponging. Collencytes: secrete fibrillar collagen. Lophocytes: secrete large amounts of collagen. © McGraw Hill LLC. 32  Pinacocytes Pinacocytes are thin, flat, and epithelial-like cells. Cover the exterior and interior surfaces of sponges almost like real tissues. Form pinacoderm with a variety of intercellular junctions but no basal membrane in most sponges. Ingest food by phagocytosis and are contractile to regulate surface area of sponge. Form myocytes, circular bands around oscula, that help regulate flow of water. © McGraw Hill LLC. 33  Cell Independence: Regeneration and Somatic Embryogenesis Sponges have a great ability to regenerate lost parts and repair injuries. Process of reorganization differs in sponges of differing complexity. Regeneration following fragmentation is one means of asexual reproduction. © McGraw Hill LLC. 34  Asexual Reproduction Fragmentation. Sponge breaks into parts that are capable of forming a completely new sponge. Bud formation. External buds. Small individuals that break off from parents that have reached a certain size. Internal buds or gemmules. Formed by archaeocytes that collect in mesohyl. Coated with tough spongin and spicules that can survive harsh environmental conditions. © McGraw Hill LLC. 35 © McGraw Hill LLC. 36  Gemmulation When parent sponge dies, gemmules survive and remain dormant during the harsh situations. Live cells within gemmules escape through special opening called micropyles and develop into new sponges. Gemmulation is a adaptation to changing seasons and for colonization of new habitats. Gemmules are controlled by weather, internal chemicals, and by remaining inside the parent sponge. © McGraw Hill LLC. 37  Gemmule Cross Section Figure 12.11 Section through a gemmule of a freshwater sponge (Spongillidae). Access the text alternative for slide images. © McGraw Hill LLC. 38  Sexual Reproduction Most sponges are monoecious (both male and female sex cells in one body). Gametes develop from choanocytes or archaeocytes. Most sponges are viviparous (live birth i.e mammals). Zygote is retained within parent and provided with nourishment until it is released as a ciliated larva. One sponge releases sperm which enter the pores of another sponge. Choanocytes that phagocytize the sperm and transport it through mesohyl to oocytes to form zygotes. © McGraw Hill LLC. 39 © McGraw Hill LLC. 40 © McGraw Hill LLC. 41  Poriferan Larvae Some sponges are oviparous. Oviparous sponges release both sperm and oocytes into water for external fertilization. The free-swimming larva of most sponges is a solid-bodied parenchymula larvae. Six other larval forms also exist. Outwardly directed flagellated cells of the parenchymula become choanocytes. © McGraw Hill LLC. 42  Typical and Unique Development Patterns Figure 12.12 (A) Development of demosponges, and (B) Development of the calcareous syconoid sponge Sycon sp. Access the text alternative for slide images. © McGraw Hill LLC. 43  Unique Developmental Pattern Found in Calcispongiae and some Demospongiae. Hollow stomoblastula develops with flagellated cells oriented toward the interior. Blastula then turns inside out (inversion) and the flagellated cells now turn outside. Small flagellated cells or micromeres located at anterior end while larger non-flagellated macromeres located at posterior end. Macromeres overgrow invaginating micromeres during metamorphosis and settlement. Micromeres become choanocytes, archaeocytes, and collencytes while macromeres give rise to pinacoderm and sclerocytes. © McGraw Hill LLC. 44  Typical and Unique Development Patterns Figure 12.12 (A) Development of demosponges, and (B) Development of the calcareous syconoid sponge Sycon sp. Access the text alternative for slide images. © McGraw Hill LLC. 45  Class Calcispongiae Calcareous sponges with spicules of calcium carbonate. Spicules are straight (monaxons) or have three or four rays. Most are small with tubular or vase shapes. Many are drab in color, but some are bright yellow, green, red, or lavender. Leucosolenia and Sycon are commonly studied marine shallow-water genera. Asconoid, syconoid, and leuconoid body forms. © McGraw Hill LLC. 46  Class Hexactinellida Also known as Class Hyalospongiae. Glass sponges with six-rayed spicules of silica bound together to form network. Nearly all are deep-sea forms. Most are radially symmetrical with vase or funnel shaped bodies attached by stalks of root spicules onto the substrate. Have syncytial cell structure. Many nuclei within a large cell. Produced by the fusion of many cells or division of nuclei without dividing the cytoplasm. © McGraw Hill LLC. 47  A Glass Sponge ©Science Photo Library/Alamy Figure 12.13 The complex skeleton of a glass sponge (Hexactinellida) © McGraw Hill LLC. 48 © McGraw Hill LLC. 49 Hexactinellid Structure 12-50 © McGraw Hill LLC. 50  Class Demospongiae Contains 95% of living sponge species and most large sponges. Spicules are siliceous but not six rayed and may be absent or bound together by spongin. Leuconoid body form for all species. All marine except for Spongillidae, the freshwater sponges. Marine demosponges are highly varied in color and shape, with some growing to several meters in diameter. © McGraw Hill LLC. 51  Marine Demosponges (a,c): ©Larry Roberts/McGraw-Hill Education b:©William C. Ober/Medical Scientific Illustration Figure 12.15 Marine Demospongiae on Caribbean coral reefs. (A) Pseudoceratina crassa, (B) Aplysina fistularis, and (C) Monanchora unguifera Access the text alternative for slide images. © McGraw Hill LLC. 52 © McGraw Hill LLC. 53  Freshwater Demosponges Widely distributed in well-oxygenated ponds and streams. They encrust plant stems and submerged wood. Look like wrinkled scum, pitted and porous with brown and green colors. Flourish in summer and in early autumn. Reproduce sexually, but existing genotypes may also reappear annually from gemmules. Sponges die by late autumn and asexually release gemmules to prepare for next year’s population. © McGraw Hill LLC. 54 Freshwater Demosponges 12-55 © McGraw Hill LLC. 55  Unique Deep Water Sponges Many tiny hook-like spicules cover highly branched body. Spicule layer can entangle the legs of crustaceans that come near sponge. Filaments of the sponge body grow over prey, slowly enveloping it and later digesting it. Most of the group are carnivores and not suspension feeders. Some have symbiotic methanotrophic bacteria. Contain siliceous spicules, but lack choanocytes and internal canals making them very different than regular sponges. © McGraw Hill LLC. 56  Carnivorous Harp Sponge ©2012 MBARI Figure 12.16 The carnivorous sponge, Chondrocladia lyra, is commonly called a “harp sponge.” © McGraw Hill LLC. 57  Carnivorous Sponges https://www.youtube.com/watch?v=oJeyOU4 eSKw © McGraw Hill LLC. 58  Ecology Importance Structure to reef Filter water Food source © McGraw Hill LLC. 59  Tool Use Play Copyright 2024 Dr. S. Turnbull © McGraw Hill LLC. 60