1500_4_Cnidaria - Cnidaria: third oldest phylum of the...

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Unformatted text preview: Cnidaria: third oldest phylum of the kingdom Animalia? BIO1500 W07 Cnidaria Delaporta et al 2006 Cnidaria are considered the third oldest phylum of the kingdom Animalia Cnidarian key characteristics: two true tissue layers Fig. 31.1 !Ectodermal origin: outer covering of the body (epidermis) and the nervous system ! Endodermal origin: layer of digestive tissue (g a s t r o d e r m i s ) ! Between epidermis and gastrodermis is MESOGLEA, composed of gelatinous material (not conisered a true tissue layer) Cnidarian key characteristics: no true organs but specialized tissues Nutritive muscular cell Gland cell Cnidarian key characteristics: no true organs but specialized tissues Cnidocyte Epidermal nerve cell Epitheliomuscular cell ! TENTACLES around mouth for catching food ! CONTRACTILE CELLS for movement (epidermal) ! NERVE CELL NET to control movement (but NO central brain area) ! CNYDOCYTES, stinging cells (epidermal) ! SEXUAL tissues, ovaries and testis TENTACLES around mouth for catching food ! CONTRACTILE CELLS for movement (epidermal) ! NERVE CELL NET to control movement (but NO central brain area) ! CNYDOCYTES, stinging cells (epidermal) ! SEXUAL tissues, ovaries and testis Cnidarian key characteristics: no true organs but specialized tissues Cnidarian key characteristics: no true organs but specialized tissues Hydra with ovaries TENTACLES around mouth for catching food ! CONTRACTILE CELLS for movement (epidermal) ! NERVE CELL NET to control movement (but NO central brain area) ! CNYDOCYTES, stinging cells (epidermal) ! SEXUAL tissues, ovaries and testis TENTACLES around mouth for catching food ! CONTRACTILE CELLS for movement (epidermal) ! NERVE CELL NET to control movement (but NO central brain area) ! CNYDOCYTES, stinging cells (epidermal) ! SEXUAL tissues, ovaries and testis Cnidarian key characteristics: no true organs but specialized tissues Oral Cnidarian key characteristics: true radial symmetry in many species TENTACLES around mouth for catching food ! CONTRACTILE CELLS for movement (epidermal) ! NERVE CELL NET to control movement (but NO central brain area) ! CNYDOCYTES, stinging cells (epidermal) ! SEXUAL tissues, ovaries and testis Aboral Oral-aboral axis but no dorsoventral axis Cnidarian key characteristics: no true organs but specialized tissues Cnidocil Operculum Nematocyst capsule Cnidarian key characteristics: two life forms, that alternate in most species: Nematocyst discharge statistics in Hydra attenuata: ! Duration is ~3 milliseconds ! Maximum velocity of 2 meters per second ! Acceleration of 40,000g. ! One of the fastest cellular processes in nature. POLYP, attached to a substrate, with mouth facing up MEDUSA, free swimming, with mouth facing down Key characteristics of cindarian animals Cnidaria develop through a free swimming larva: the planula larva Planula Medusa xxx Strobila Fig. 32.5 Aurelia Reproduction in cnidarians Encapsulated embryo Classification in the phylum Cnidaria life forms Class. Hydrozoa POLYP+medusa +medusa Ovaries Spermaries Budding (eg.. Obelia, Hydra) eg Class. Scyphozoa polyp+MEDUSA Cubozoa Anthozoa polyp+MEDUSA POLYP only (jellyfish) Sexual cycle Asexual cycle Class. Asexual - by budding of polyps Sexual - both polyps and medusa forms can generate ovary and testis tissues (box jellies) Class. (sea anemone, corals) Cnidarian diversity: Corals are reef building Anthozoa Cnidarian diversity: Anthozoa and Hydrozoa include genomic model organisms Class. Hydrozoa: Nematostella vectensis Class. Anthozoa: Aquapora millepora Class. Anthozoa POLYP only (sea anemone, corals) Cnidarian diversity: Cubozoa include species with eyes Another note of caution: Beware the box jelly fish! Gehring 2002 box jelly fish burns Class. Cubozoa polyp+MEDUSA (box jellyfish) ...
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This note was uploaded on 08/03/2010 for the course BIO 1500 taught by Professor Pandolfi during the Winter '08 term at Wayne State University.

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