Lab 2 Phylum Porifera and phylum Cnidaria. Grantia. Phylum Porifera. Kingdom :- Animalia. Phylum:- Porifera. Class:- Calcarea. Order:- Leucosolenida

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1 Lab 2 Phylum Porifera and phylum Cnidaria Phylum Porifera Adults sessile and attached Radial symmetry or asymmetrical Multi-cellular ; loose aggregation of cells Skeleton made of collagen and spicules (calcareous or siliceous) No organs or true tissue Specialized for filter-feeding Digestion is intracellular (no mouth, anus or digestive system) Excretion and respiration by diffusion No nervous system Asexual (budding or formation of gem mules) Sexual (eggs and sperm produce ciliated larvae) Dioecious Mostly marine; few are freshwater Grantia Kingdom :- Animalia Phylum:- Porifera Class:- Calcarea Order:- Leucosolenida Genus:- Grantia Tubular or syconoid-shaped Water enters via small pores (incurrent pores)and exists via large pore (osculum) Outer surface covered in flat cells (pinacocytes),inner choanocyte layer and the middle is mesohyl (gelatinous protein matrix) Pinacocoytes at base of sponge secrete a substance that attached sponge to its substrate Water flow;incurrent pores> incurrent canals >radial canal (flagellated choanocytes)>central cavity/spongocoel > osculum Choanocytes generate feeding current Skeletal components (non-living)-spongin fibers,spicules of calcium carbonate/silicon dioxide. 1

2 Phylum Cnidaria Sedentary or free-swimming metazoan Radial symmetry Body wall composed of two cell layers; o Outer ectoderm o Inner endoderm o Structure-less layer between them(mesoglea)- contains cells derived from primary cells Nervous system is a network of cells No specialized organs for excretion(its by diffusion) Asexual (budding) Sexual (planula larva- ovoidal and uniformlyciliated is produced) 2 body forms (polyp or medusa) Nematocysts (stinging threads)- for capturing prey Class Hydrozoa :-Polyp and medusoid body forms occur in successive stages of life cycle -polyps(colonies) have 2 types ;gastrozooids(feeding) and gonozooids (asexual reproduction) - Medusoid reproduces sexually to produce a planula larva 2

3 Order Hydroida : well developed polyploidy generation.(solitary or colonial). Usually buds off as free medusa. Eg. Hydra (solitary with no medusoid stage ), Velella and Porpita(free-floating polymorphic colonies), Obelia Order Siphonophora:- swimming colonies. Consisting of many kinds of polyp and medusae (polymorphic).medusae attached to stem. marine. Eg. Physalia (Portuguese man of war). Class Scyphozoa :- Medusoid stage as main stage of life-cycle -polypoid form only in larva. -Eg. Aurelia (common jelly-fish) Class Anthozoa:- corals, sea anemones - attached polyps - NO medusa - Some members posses a skeleton -gonads found in septa - all marine - Soliatry or colonial -Eg. Gorgonia (sea fan), Pennatual (feather-like sea pen), Metridium (sea anemone with no skeleton), Meandria (brain coral with big external calcareous skeleton) Hydra Kingdom :- animalia Phylum:- Cnidaria Class:- Hydrozoa Order:- Hydroida- Anthomedusa Genus:- Pelmatohydra (brown hydra) Batteries of intact nematocytes are located in cnidocyte Epidermis of hydra possesses epitheliomuscle cells and interstitial cells Gastrodermis possesses flagellated nutritive muscle cell and gland cells Food vacuoles are present in gastrodermal cells Space in the centre of the cross section is the gastrovascular cavity (enteron) Mesoglea thin layer between epidermis and gastrodermis 3

4 Obelia Kingdom :- animalia Phylum:- Cnidaria Class:- Hydrozoa Order:- Hydroida- leptomoedusae Genus:- Obelia Gastrozooid (feeding polyp)- comprises the tentacles,mouth and hypostome Chitinous sheath covers the living tissue of the central stalk and branches and extends over the base of the polyps Gonozooid (reproductive polyp) Obelia medusa is bell-shaped Ventral surface of bell has manubrium that hangs from centre and contains the mouth Mouth leadsto 4 radial canals and ring canal(circles the margin of the bell and connects with the hollow tentacles) Canals are lines with gastrodermal cells (intracellular digestion occurs) Statocysts (balancing organs)- found between tentacles Mesoglea is thick in all medusa and takes up the volume of organism 4

5 Mature gonads are noticeable (4 dark structures in the region of the radial canals) Alteration between sexual and asexual generations is call metagenisis Obelia life-cycle The polyp colony reproduces asexually. During this stage of life, Obelia are confined to substrate surfaces. On this mature colony there are individual hydranths called gastrozooids, which can be found expanded or contracted, to aid in the growth of this organism by feeding; the reproductive polyp gonozooids has medusa buds. Other hydranths are specialized for defense. 5

6 The next generation of the life cycle begins when the medusae are released from these gonozooids, producing free swimming only male medusae velum with gonads, a mouth, and tentacles. The physical appearance of the male and female medusae velum, including their gonads, are indistinguishable, and the sex can only be determined by observing the inside of the gonads, which will either contain sperm or eggs. The medusae reproduce sexually, releasing sperm and eggs that fertilize to form a zygote, which later morphs into a blastula, then a ciliated swimming larva called a planula. The planulae live free-swimming for a while but eventually attach themselves to some solid surface, where they begin their reproductive phase of life. Once attached to a substrate, a planula quickly develops into one feeding polyp. As the polyp grows, it begins developing branches of other feeding individuals, thus forming a new generation of polyps by asexual budding. Why does Obelia represent a more typical cnidarian than Hydra? The "typical" Cnidarian life cycle has two stages: one as a medusa (like a jellyfish), the other as a polyp (like Hydra). Obelia goes through both stages, but Hydra does not have a medusa stage. 6

7 Aurelia (true jellyfish) Kingdom :- animalia Phylum:- Cnidaria Class:- Scyohozoa Order:- Semaeostomeae Genus:- Aurelia Horseshoe-shaped gonads are contained inside gastric pouches 7

8 Metridium (sea anemone) Kingdom :- animalia Phylum:- Cnidaria Class:- Anthozoa-Hexacorallia Order:- Actiniaria Genus:- Metridium Animal rests of pedal disc Has stout polyp form with tentacles surrounding the mouth Thick body wall because of mesoglea Pharynx has ciliated tracts (siphonoglyphs) Space below pharynx is gastrovascular cavity- 6 septa project here Gonads resemble a string of beads along the free edge of each septum No anus in all cnidarians (all undigested food exists via mouth) 8

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