Radiate Phyla Chapter 7 Chordata Arthropoda Annelida Mollusca Protostomes † Triploblasts * Diploblasts Hemichordata Echinodermata Deuterostomes Coelomates Pseudocoelomates Acoelomates Bilateria† Radiata* Eumetazoa Mesozoa Metazoa Protozoa Monera (Bacteria) Cnidaria Ctenophora Parazoa The Basics • Radial symmetry • Diploblastic • Dimorphic life cycle – Polyps – medusae • Gastrovascular cavity – Blind sac Radial Symmetry CNIDARIA: HYDROZOA HYDRA SP. BUDDING FROM LINCOLN NEBRASKA: POLYP FORM HYDRA SP. TOP VIEW MEDITERANIAN JELLYFISH: MEDUSA FORM Cassiopea frondosa Tissue Layers Diploblastic = 2 germ layers • endoderm gastrodermis • ectoderm epidermis mesoglea • gelatinous matrix between the 2 layers epidermis gastrovascular cavity mesoglea gastrodermis General Body Plan • sac-like body (only 1 opening) • Food and waste go in/out the same opening no anus! • water within GVC acts as a hydrostatic skeleton oral surface gastrodermis mesoglea epidermis aboral surface mouth Gastrovascular cavity Dimorphic life cycle Tentacle Gastrovascular cavity Tentacle Polyp Medusa Radiate Phyla p. Cnidaria c. Hydrozoa c. Scypozoa c. Cubozoa c. Anthozoa p. Ctenophora HYDRA SP. FEEDING A B C D Nematocysts • specialized stinging organelles • found within cnidocytes (cells) • cnidocytes are located in epidermis A cnidocyte with a nematocyst within it Nematocysts • nematocysts are like “mini-harpoons” • cnidocil senses movement & acts like a “trigger” • can inject poison, coil around prey, or be adhesive • functions: - prey capture; defense nematocyst cnidocil cnidocyte Undischarged Discharged HYDRA SP. UNDISCHARGED STENOTELE NEMATOCYSTS DS DS HYDRA SP. UNDISCHARGED AND DISCHARGED STENOTELE NEMATOCYSTS A S HYDRA SP. UNDISCHARGED STENOTELE AND ATRICHOUS ISORHIZA NEMATOCYSTS A S HYDRA SP. DISCHARGED STENOTELE AND ATRICHOUS ISORHIZA NEMATOCYSTS Biology Feeding – nematocysts within cnidocytes – tentacles Digestion – extracellular (in GVC) – intracellular (by gastrodermal cells) – incomplete system (no anus) Gas exchange & Excretion – these systems are absent Structure Nervous System – nerve net (no central nervous system= no brain) – sense organs – statocysts (equilibrium organs) – ocelli (photosensitive organs) Skeletal System – Mesoglea, water in GVC acts as a hydrostatic skeleton, and some external skeletal system. Reproduction Reproduction Asexual – budding – longitudinal fission Reproduction Reproduction Sexual – usually dioecious (separate sexes e.g. humans) – monoecious (both male + female gonads in 1 individual) – results in Planula larva General Life Cycle Phylum Cnidaria Class Hydrozoa: Freshwater (Hydra) and marine (Fire Corals). Class Scyphozoa: Jellyfish, all marine. Class Anthozoa: Corals and Anemones, all marine. Class Cubozoa: Box jellyfish and sea wasps, all marine. Class Hydrozoa • medusa & polyp body forms • mostly marine but some fresh water Fire coral Millepora Class Hydrozoa • medusa & polyp body forms (medusa with velum) • most are colonial colonies are formed of individual zooids a single zooid Class Hydrozoa • many of these colonies show polymorphism this is where there are several different types of polyps/zooid and each type is specialized for a different function e.g. gastrozooids = feeding polyps e.g. dactylzooids = defense polyps all the zooids within a colony are genetically identical these different zooids work together in the colony Class Hydrozoa Obelia - a sessile colony showing polymorphism gonozooid entire colony gastrozooid Class Hydrozoa - a Portugese Man-o-war (Physalia) is a floating hydrozoan colony showing polymorphism Float entire colony gastrozooid dactylzooid Fire coral Millepora Fire coral Millepora victim! Class Hydrozoa- life cycle Obelia sexual reproduction asexual reproduction Class Hydrozoa • Hydra is an example of a solitary, freshwater hydrozoan sexual reproduction gonads asexual No Medusa Stage reproduction bud Class Hydrozoa • Hydra is an example of a solitary, freshwater hydrozoan asexual reproduction bud Oklahoma Hydrozoans Chlorohydra viridissima: The Green Hydra The green color arises from Chlorella-like unicellular algae each occupying a vacuole in the endodermal cells. Hydra vulgaris The common Hydra Craspedacusta sowerbii Velum Lives predominantly as a polyp in small lakes, ponds, and old water filled quarries the medusa stage occurs during July-October. Polypodium hydriforme The most bizarre of the freshwater cnidarians and one of the most unusual species of ALL Cnidarians!! Polypodium spends almost all of its pre-adult life as a parasite of Acipenseriform fishes. LIFE CYCLE Class Scyphozoa • “true” jellyfish • medusa & polyp body forms • thick mesoglea Class Scyphozoa- life cycle sperm ephyra strobila egg Adult medusa Scyphistoma Polyp Larva Planula (Ciliated) Jellyfish Diversity Primitive jellyfish: Stauromedusae Jellyfish Diversity Primitive jellyfish: Stauromedusae; small sessile individuals that develop directly from benthic planula larvae. Can change locations, but normally attached with stalk and adhesive pad to solid objects like kelp and rocks. Rhizostomae jellyfish: lack a central mouth, instead they have many suctorial “mouths” Rhizostomae jellyfish: lack a central mouth, instead they have many suctorial “mouths” Cassiopea: a small tropical jellyfish is unusual among jellyfish. It lies on the bottom in shallow waters, with its mouth at tentacles oriented upwards. Its mouth is much reduced, and is not much used. Instead, the jellyfish gets most of the nutrition it needs from symbiotic dinoflagellates which live inside its body tissues. Rhizostoma octopus Semaeostomae the typical jellyfish: corner of mouth drawn out into four broad gelatinous frilly lobes. Aurelia sp. Semaeostomae the typical jellyfish Cyanea capillata the Giant Jellyfish or Lion's Mane Jellyfish Can be over 1 meter across and its trailing tentacles can reach more than 10 meters in length.