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Download An Introduction to Invertebrates I Chapter 33A: 1. Porifera 2. Cnidaria
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Transcript
Chapter 33A: An Introduction to Invertebrates I 1. Porifera 2. Cnidaria Invertebrates Porifera Lophotrochozoa Bilateria Common ancestor of all animals Cnidaria Eumetazoa ANCESTRAL PROTIST Ecdysozoa Deuterostomia Animals without a backbone (vertebral column) are called invertebrates. • over 95% of known animal species are invertebrates 1. Porifera Porifera Cnidaria Lophotrochozoa Ecdysozoa Deuterostomia General Characteristics of Porifera All animals in the phylum Porifera are informally referred to as sponges which have the following characteristics: • sessile (non-motile, sedentary) filter-feeders • lack body symmetry • do not have any defined tissues • most are hermaphrodites (produce both eggs and sperm) The characteristics in RED are unique in the Animal Kingdom. The Structure of a Sponge Choanocytes Collar Food particles in mucus Choanocyte • choanocytes (or collar cells) draw water into the spongocoel through pores • choanocytes capture food to transfer to amoebocytes that distribute food to other cells Osculum Spongocoel Flagellum Phagocytosis of food particles Amoebocyte Pores Spicules Epidermis Water flow Mesohyl Amoebocytes Azure vase sponge (Callyspongia plicifera) 2. Cnidaria Porifera Lophotrochozoa Ecdysozoa Deuterostomia Eumetazoa Cnidaria General Characteristics of Cnidarians All animals besides the sponges belong to the clade Eumetazoa, animals with true tissues. One of the oldest groups of Eumetazoa is the phylum Cnidaria which has the following characteristics: • a diploblastic body plan with radial symmetry • some are sessile while others are free floating & motile • have single opening called a proctostome (“anal mouth”) through which food enters the gastrovascular cavity and waste passes out anemone jellyfish Two Cnidarian Body Types Cnidirians are either a sessile polyp (e.g., corals, anemones) or a motile medusa (e.g., jellyfish). Proctostome Polyp Tentacle Gastrovascular cavity Medusa Gastrodermis Body stalk Mesoglea Epidermis Tentacle Proctostome Cnidarian Feeding Tentacle Cnidarians are carnivores that use tentacles to capture prey. Cuticle of prey Thread Nematocyst “Trigger” Thread discharges Cnidocyte Thread (coiled) • each tentacle has multiple cnidocytes which contain a nematocyst, a specialized organelle that ejects a stinging thread when stimulated 2 Major Cnidarian Clades Medusozoans MEDUSOZOA • includes Scyphozoans (jellies), Cubozoans (box jellyfish), and Hydrozoans, all of which are medusae though some have a polyp stage in their life cycle (e.g., the Hydrozoans) Jellies Sea wasp Anthozoans ANTHOZOA • this clade includes the corals and anemones, all of which are polyps Sea anemones Star corals Life Cycle of the Hydrozoan Obelia Haploid (n) Diploid (2n) Feeding polyp Reproductive polyp Medusa bud Medusa MEIOSIS Gonad Egg ASEXUAL REPRODUCTION (BUDDING) Portion of a colony of polyps Sperm FERTILIZATION Developing polyp 1 mm SEXUAL REPRODUCTION Mature polyp Zygote Planula (larva)
