Porifera (sponges) and Cnidarians Lab
Porifera (sponges) and Cnidarians Lab Bio 106-016
Kutztown University of Pennsylvania
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This 11 page Class Notes was uploaded by Dallas Bowe on Tuesday March 1, 2016. The Class Notes belongs to Bio 106-016 at Kutztown University of Pennsylvania taught by Dr. Nancy Butler in Spring 2016. Since its upload, it has received 39 views. For similar materials see Zoology Lab in Biology at Kutztown University of Pennsylvania.
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Date Created: 03/01/16
Chapter 6 - Sponges Kingdom: Animalia o Phylum: Porifera Grantia and Scypha - types of sycon sponges All major physiological function occur at a cellular level Entirely aquatic, mostly marine animals with some found in freshwater lakes/streams Size range: mm - meters Some species display low, encrusting body forms or tall upright forms Have natural selection favored body planes with increasing surface area; body planes rises over time Intermediate level of cellular organization suggests an evolutionary link between unicellular protists and higher multicellular animals Some biologist speculate sponges arose from assemblages of choanoflagellates which lead to the rise of other animal groups → one- ancestral theory Sponges share anatomical similarities that tie in to their common lifestyle… 1. Sedentary with NO body symmetry. Lack tissues, organs/ organ systems. Result: all major biological functions occur at a cellular level. 2. Simple bodies consist of four primary cell types arranged around a system of pores and canals 3. Feed by filtration 4. Possess an internal meshwork of microscopic spicules or collagen fibers, which serves as the internal skeleton Filtration- collar cells create water currents that pull in organic particles Choanoflagellates- type of colonial protist Most likely the ancestor of sponges Nearest living protist relative; supports one-ancestral theory One-ancestral theory- animals arose from one single-celled organism Multiple-origins theory- animals arose from 2 or 3 different single-celled organisms Sponges are categorized into 3 principal body types based on the degree of convolution ( folding of body walls) 1. Ascon sponge has no foldings in its body wall. It is a hollow tube; a few cells with a prominent osculum at the top. Quite small due to constraints of small surface to volume ratio 2. Sycon sponges have simple infoldings to their body walls. Larger than ascon sponge because they have an increased surface to volume ratio. 3. Vast majority of sponges are organized by leucon body type Leucon body type -body folds that themselves folded, resulting in a series of chambers connected by canals (i.e. bath sponges) Water flow allows every aspect of sponge’s existence (i.e. feeding, respiration, excretion, reproduction) to function Filter- feeding process Process strips food particle of oxygen when water passes through the series of chambers and canals Summary: flagella on choanocytes creates currents that pull in water carrying suspended food particles 1. Water enters the sponge through ostia 2. Ostia channels water down the incurrent canals to porocytes 3. Porocytes channel water into radial canals, which is lined with choanocytes 4. Choanocytes trap food particles with their flagella and engulf them through phagocytosis 5. Choanocytes’ flagella create a water current and passes food particles to amoebocyte 6. Amoebocyte carries food to other cells within sponge body and undergoes developmental changes when the sponge needs a certain cell to function properly 7. The water (now pure of food particles and water) passes out of each radial canal, through apopyle and into the spongocoel 8. Water is pushed out of the osculum Spongocoel- large central cavity that passes through the center of the sponge Ostia- pores on the body surface of the sponge; allows water to enter sponge Incurrent canal- location where ostia channels water during filter-feeding process Porocytes- tiny pores that are scattered along the folds of the incurrent canal Description: elongated, donut-shaped cells Radial canals- flagellated chambers; location where porocytes channel water Choanocytes - collar cells; virtually identical to one type of colonial protist (choanoflagellates); lining of the interior surface of the radial canals Function: Traps food particles with their flagella and engulf them through phagocytosis Amoebocytes- mobile cells that reside in the gelatinous matrix between choanocytes and pinacocytes. Function: Carries food to other cells within sponge body and can undergo developmental changes to transform into any type of cell type that is required for the sponge to function properly Pinacocytes- cells that make the outer layer of the sponge Apopyle- large opening in radial canal used to transfer the water left from the filter feeding process from the choanocytes to the exit (osculum) Respiration process 1. Oxygen-rich water passes through sponge. 2. Diffusion of oxygen into a sponge cell; Carbon dioxide diffuses out to surrounding water Excretion process 1. Water enters the sponge 2. Diffusion of metabolic waste for individual cells into surrounding waters Reproduction processes Regeneration by fragmentation/budding (asexual)- fragments of sponge break off, break away, and settle to start new colonies Formation of gemmules (asexual)- adverse weather conditions causes sponge to disintegrate, leaving gemmules behind. Survive winter to form new adult sponge in spring (common in freshwater sponges; rare for marine) Occasionally reproduce sexually through meiosis in favorable environments o Sponge divides through meiosis to become haploid sperm; released in water; enters different sponge; sperm travels to embedded haploid egg; egg develops into a simple ciliated larva; breaks free to settle in a new area Regenerating- possible due to interchangeability of their cells and lack of specialized tissue; wounded sponges can regenerate tissue and skeleton to replace wounded ones Gemmules- densely-matted, harden ball containing amoebocytes, surrounded by a coating of collagen and spicule Spicules- skeletal elements of sponges that are secreted by amoebocytes; used by zoologists to classify sponges into taxonomic groups Skeleton is composed of hard,crystalline spicules formed by calcium carbonate or silicon Other sponges secrete spongin (more flexible) Spongin- flexible proteinaceous material used by some sponges as a skeleton opposed to spicules Chapter 7 - Cnidarians Kingdom: Animalia o Phylum: Cnidaria o Class: Hydrozoa, Anthozoa, Scyphozoa Cnidarians- simplest living animals with tissues and no specialized organs; nearly all marine Derived from cnidocytes Diploblastic arrangement consisting of an outer epidermis layer and inner gastrodermis layer Mesoglea resides b/n 2 layers Gastrodermis lines central digestive cavity; gastrovascular cavity Have radial symmetry Lack definite concentrations of nervous tissue/ sensory organs Posses a nerve net Nearly all carnivorous; rely on passing prey to make contact with their tentacles for capture No blood vessels, respiratory organs, excretory organs Depend on diffusion for gas exchange across their tissues and the elimination of metabolic waste Thin body walls so that all the cells in layers have effective diffusion Cnidocytes- unique stringy cells present on the body and tentacles of members of the phylum Cnidaria Diploblastic- Body arranged into 2 discrete tissue layers Mesoglea- inert, gelatinous layer b/n epidermis and gastrodermis Gastrovascular cavity- central digestive cavity in cnidarians with a single opening (mouth - protostome) that is used to ingest food and expel indigestible waste Nerve net- connects uniformly distributed sensory cells and motor neurons to provide for some coordinated movements and behaviors 2 basic body forms Polyps - represented by a cylinder organism that remains attached to the substrate by a short stalk and has a mouth that faces away from the substrate. Medusa - circular, umbrella shaped form with a mouth on the underside; free-floating with tentacles that hang downward and surround the mouth; body shape maintained by mesoglea and the regulation of fluid in the gastrovascular cavity (i.e. jellyfish) ---( this is an ex. of hydrostatic skeleton) Evolutionary History Emergence of discrete tissue layers, limited mobility, and precursors to organ system (digestive tissues, reproductive tissues, nervous tissues and sensory cells) ability to digest food extracellularly within the gastrovascular cavity o digestive enzymes are released from gastrodermal cells partially break down food then phagocytosis takes place and intracellular digestion. allows all cnidarians to obtain the ability to digest large animals than sponges or protists, and expands their ecological niche Classes Hydrozoa and Anthozoa distinguished by dominance of polyps/medusa Hydrozoa- polyp is predominant; alteration of polyps and medusa stages; medusa has velum; mostly marine few freshwater; colonial or solitary Scyphozoa - mesdusa is predominant; solitary; free-floating medusa w/o velum; thick mesogleal layer Anthozoa - exists only as polyps; medusa stage is completely lost; entirely marine; colonial or solitary; gastrovascular cavity divided by septa into chambers to increase digestive surface area Hydrozoans (Class Hydrozoa) (Genus: Obelia, Hydra) (Species: littoralis) Asexual reproduction in polyps form Sexual reproduction in medusa form Obelia assemble into colonies-- polyps Hydra do not produce mesduae, exists as single, mobile polyps, that reproduce either sexually (through production of sperm and egg) or asexually (through budding) Hydra littoralis small hydrozoans as polyps in shallow, freshwater ponds, and streams predators of small aquatic vertebrates solitary settle in submerged rocks, twigs, and vegetation with their tentacles outstretched waiting for prey Structure Function Tentacles Defense and prey capture Mouth Ingestion of food and elimination of indigestible particles (egestion) Hypostome Elevated mound of tissue that expands or contracts to regulate size of mouth opening Cnidocytes Specialized stinging cells located in the epidermal layer of the tentacles and body wall Gastrovascular Chamber within which extracellular digestion of prey cavity occurs; only opening is through the mouth Bud Product of asexual reproduction; will fall off when mature and becomes self-sufficient organism Gonads (testes Organs for sexual reproduction; Hydra are dioecious, and ovaries) meaning that an organism has either testes or ovaries (male or female), but not both Basal disc Specialized region for attachment to the substrate Epidermis Outer tissue layer; specialized for protection Gastrodermis Inner tissue layer; specialized for digestion Mesoglea Inert, acellular, jelly-like substance that aids in supporting the body Hydrozoans may be either monoecious (having both testes and ovaries) or dioecious (having separate and female sexes) depending on the species Reproduce asexually by budding in optimal environment conditions Unfavorable environments rely on sexual reproduction o Females develop an ovary that produces a single egg and males from a testis the produces sperm. After fertilization the zygote leaves the parents with a protective shell before developing into an individual Cnidocytes Use tiny cells for capturing prey and deterrent to predators line the tentacles and outer surface of the cnidarian body. Contains nematocyst- stinging capsule o when a small trigger is simulated, a rapid increase in osmotic pressure within the cnidocyte causing the nematocyst to violently discharge, releasing a long, hollow, thread-like filament outside the cell driving its poisonous barbs into the flesh of the victim. Colonial Hydrozoans Genus: Obelia colonial hydrozoans connected by coenosarc life cycle is sexual (medusa) or asexual (polyp) o Asexual- a colony composed of feeding and reproductive polyp o Medusa cycle is short lived stage devoted to reproduction o Female medusa bud off reproductive polyp and and release haploid sperm and egg that fuse to form diploid zygote. Zygote develops planulna larva which settles on ocean floor, attaches to substrate and begins to form a new generation of polyps through asexual budding. Anatomy of Obelia Body Structure Function form Polyp Hydranth (feeding Polyp specialized for food acquistion polyp) Tentacles defense and prey capture Gonangium polyp specialized for reproduction (reproductive polyp) Medusa buds product of asexual reproduction; medusae will be released from the gonangium when mature and will produce either sperm or eggs, which fuse with the respective gamete forming a zygote that will develop int a new polyp Coenosarc Common chamber within extracellular digestion occurs; nutrients are distributed throughout organism; connects Obelia by branching from gastrovascular cavity Perisarc Translucent outer covering of organism; serves protective function Medus Manubrium Stalk of fleshy tissue that supports the mouth a Mouth ingestion of food and egestion of indigestible particles Gonads organs for sexual reproduction; either testes or ovaries Tentacles defense and prey capture True Jellyfish Kingdom: Animalia o Phylum: Cnidaria o Class: Scyphozoa o Genus: Cyanea (largest scyphozoans belong here) o Genus: Aurelia (moon jellyfish) Scyphozoans are jellyfish b/c they possess a thick gelatinous mesoglea Medusa stage dominates life cycle Anatomy of Aurelia Structure Function Marginal provide sensory information and used in defense and tentacles locomotion Mouth ingestion of food and elimination of indigestible particles (egestion) Oral arms Defense and prey capture Gonads (testes sexual reproduction organs; gametes are released into and ovaries) the gastric pouches and exit the body through the mouth Gastric pouch one of four divisions of the gastrovascular cavity for the digestion of food Radial canals extensions of the gastric pouches that radiate outward from the pouches and distribute nutrients throughout the body Circular canal circular extension of the gastric pouches that distribute nutrients to outer rim of jellyfish Sea Anemones and Corals Kingdom: Animalia o Class: Anthozoa o Genus: Metridium represented by sessile organisms in polyp stage Solitary (sea anemones) Colonies (coral) Life cycle does not include free swimming medusa Most numerous and specialized Metridium - common North Atlantic sea anemone Anatomy of Metridium Structure Function Tentacles defense and prey capture Mouth ingestion of food and elimination of indigestible particles (egestion) Oral disc raised portion of the mouth (equivalent to the hypostome in hydrozoans) Ostium pore that allows circulation of fluids between adjacent body sections Gonads (testes sexual reproduction organs; gametes are released into and ovaries) the gastric pouches and exit the body through the mouth Pharynx Muscular portion of the gastrovascular cavity for pulling prey inward and expelling indigestible particles Retractor expand and contract body muscles Gastrovascular specialized chamber for extracellular digestion of prey cavity Primary septum one of six thin vertical walls that divides the body into sections, providing support and increased surface area for digestion Secondary one of several incomplete vertical walls that further septum subdivides body, providing support and increased surface area for digestion Pedal disc tough, fleshy base that attaches organisms to rocks or sandy ocean floor; most anemones can use their pedal discs to move slowly, gliding along the ocean floor Acontia contains cnidocytes and may be extended through the mouth to aid in subduing live prey or to provide additional defense against predators
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