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Animal Diversity Non-Chordate Animals: Supplementary Material STRUCTURAL ORGANIZATION In today’s lab, we will review microscope slides and demonstrations on: 1. Body Symmetry and Bauplan 2. Cell and tissue organization: germ layers 3. Body organization: nature of tissue layers and body cavity 4. Developmental Patterns: Protostomate and Deuterostomate LABORATORY OBJECTIVES: The purpose of this set of laboratory exercises is to introduce you to the structure, and anatomy of basic animal groups that underlie classification: • The differences between asymmetric, radial and bilateral symmetry, as well as spheroid and bi-radial symmetry, and metameric design in a variety of animals. • To recognize germ layers (endoderm, mesoderm and ectoderm) and identify cell types within them (epithelial, muscle, digestive, etc.). • Differences between acoelomate, pseudocoelomate and coelomate body organization. Body Plans 1. Hydra xs – These small tubular creatures are diploblastic, organisms that have only two distinct germ layers. The outer layer is ectoderm (ecto-outer, derm-skin). This cell layer gives rise to the epidermis, ectodermal muscles, nervous system, etc., during development. The inner layer is endoderm (endo- inner). This cell layer gives rise to the gastrovascular cavity (the digestive system) and associated organs and structures during development. Only two of the phyla that we cover are considered diploblastic - the Cnidarians, which include sea anemones, coral, and jellyfish, and the Ctenophora, the comb jellies. 1 Body Organization: Tissue Layers and Body Cavity 2 Most animals are triploblastic, with body layers composed of ectoderm, endoderm and a third tissue layer between them. This middle layer is the mesoderm, a tissue from which muscle and many organ systems arise during development. Triploblastic animals can be further classified into three basic plans of body construction, based on whether an organism has an internal body cavity independent of the gut and on how this cavity (if present) is formed during embryogenesis. a. Acoelomate – These animals lack an internal body cavity, that is, the space between the gut (endoderm) and the outer body wall (ectoderm) is filled with tissue derived from the embryonic mesoderm. b. Pseudocoelomate – These animals have a true, fluid filled body cavity, however the cavity derives from the blastocoel (a space formed during gastrulation in a developing embryo) and is not lined with mesoderm. c. Coelomate – These animals have a fluid filled body cavity between the gut and the musculature of the outer body wall that is completely lined with mesoderm. 2. Dugesia xs – Flatworms, like most animals, are triploblastic. The most primitive, represented by Dugesia, are acoelomate - there is no body cavity between the gut and the outer body wall. Characteristically, the area lying 3 between the outer body wall and the gut of acoelomates is solid mesoderm tissue. In Dugesia this tissue is referred to as parenchyma. 3. Ascaris x.s. – is a pseudocoelomate, an example of the worm-like animals with a “false” body cavity derived from the blastocoel, and a tubular digestive system. Most of the more complex invertebrates have a true coelom, which is an internal fluid-filled space completely surrounded by mesoderm, and lined with a thin membrane called a mesentery. 4. Lumbricus xs – is a coelomate, and illustrates the basic body design of most ‘higher’ invertebrates, with three cell layers, a tubular digestive system and a variety of complex organs. 4 We will also look at invertebrate development - The true coelomates are subdivided into two types, based on embryological development. Protostomes and deuterostomes are distinguished by cell division or cleavage type, coelom formation and origin of the mouth and anus. The word protostome means “first mouth” and comes from the fact that these animals have the first opening of the blastocoel (the blastopore into the archenteron) give rise to the mouth. The deuterostome “second mouth” never has the mouth originate from the blastopore. Usually it is the anus that arises from this opening. DEMONSTRATIONS We will also have on display a variety of invertebrate phyla for you to see. 5 PORIFERA TAXONOMY: Phylum Porifera The sponges Class Calcarea Spicules composed of calcium carbonate. Class Hexactinellida Spicules composed of silica. Class Demospongiae Spicules composed of silica or spongin fibers or both. In addition to their taxonomic classes, the sponges are organized into three structural grades of increasing complexity: Asconoid The simplest structural grade, comprised of a single chamber lined with flagellated choanocytes and single exit pore or osculum (e.g. Leucosolenia). Syconoid Sponges with many flagellated canals, but a single osculum (e.g. Grantia or Scypha). Leuconoid Complex sponges with flagellated chambers and numerous oscula (this is the most common structural grade) (e.g. Rhabdodermella, commercial sponges). Sponges are the simplest of all metazoan animals. Neither true tissues nor organs are present, and the cells show considerable independence. All members of this phylum are sessile, and exhibit little detectable movement. Primitive sponges may appear radially symmetrical, but most sponges are asymmetrical in body shape, being shaped primarily by environmental factors. Except for a single family, the phylum is entirely marine. LABORATORY OBJECTIVES: The purpose of this set of laboratory exercises is to introduce you to the classification, structure, and anatomy of sponges. In this lab, you should learn: 1. To recognize the classes and structural grades of sponges. 2. The internal anatomy, including cell types, of sponges of each structural grade. 3. The organization and composition of the sponge skeleton. 6 EXERCISES: 1. Leucosolenia, a common asconoid sponge, will serve to illustrate some of the basic cell types found in sponges. Observe the diagram below, compare this to the structure and cell types you observe in Grantia, a syconoid sponge, in exercise 2. 2. Grantia (also called Scypha), a common syconoid sponge, will serve to illustrate additional cell types found in sponges. Look at the prepared slide of a cross section (cs), for the radial canals and their lining of flagellated choanocyte cells. The beating of the flagellae in these cells creates a water current that 7 brings in food particles through the canals from the incurrent pores or ostia. Each canal empties into the spongocoel in the center, which empties out through the single osculum. Look at the longitudinal section (ls) slide and see if you can figure out the overall body design of this sponge. 3. Spicules (the “skeleton”) - the skeleton of sponges may be made up of spicules (calcium carbonate or silica), spongin fibers (protein), or both. Refer to page 79 in your text for some basic spicule types. Examine the slide of Grantia spicules to see the different shapes and how they hold together. On the slide of 8 Spongilla gemmules, there can be seen characteristic amphidisc spicules. What is a gemmule? What role do gemmules play in the life cycle of sponges? 4. The three classes of sponges are distinguished by the makeup of their skeleton. “Unknown” pieces of sponge will be made available in the lab for you to test and identify. First, isolate the spicules by dissolving away proteins and other organic matter with bleach solution. If no spicules remain, what class does the sponge belong to? What shape are the spicules? Does this tell you what class they are? Add acetic acid, which dissolves calcium carbonate. Does this help you classify the sponge? DEMONSTRATIONS: We will have on display a variety of sponges for you to see. 9 CNIDARIA AND CTENOPHORA TAXONOMY: Phylum Ctenophora The comb jellies. Phylum Cnidaria Class Hydrozoa The hydrozoans, colonial or solitary coelenterates with the polyp as the predominant form. Class Scyphozoa The jelly fish, characterized by the mobile, floating medusoid form. Class Cubozoa The cubomedusae jellyfish, characterized by a cuboid swimming bell, with four tentacle clusters Class Anthozoa The anemones, corals, sea pens, etc., polypoid forms often with supporting skeletons. Subclass Octocorallia (or Alcyonaria) “soft corals” with 8 tentacles. Subclass Hexacorallia (or Zoantharia) “hard corals” with > 8 tentacles. Ctenophora is a small phylum of jellyfish-like marine animals, lacking the one unifying structure of the true jellyfish (cnidoblasts). They are characterized by possession of their own unique structures, “comb rows,” which are ciliated bands running along the length of the body, used for locomotion. They also possess two long tentacles, armed with explosive sticky cells called colloblasts, with which they capture plankton. The Cnidaria are the most primitive of all the eumetazoa (true multicellular animals). Except for a handful of species, the phylum is marine. They are generally radially symmetrical, and have tentacles armed with exploding cells (cnidoblasts). Cnidarians are diploblastic (two cell layers), and have a single body cavity with one opening (the coelenteron). There are two structural forms: the polyp and the medusa, which may alternate as vegetative and reproductive generations in the reproductive cycle. LABORATORY OBJECTIVES: The purpose of this part of the lab is to introduce you to the diversity, classification, anatomy, reproduction, and growth of Ctenophora and Cnidaria. Through this part of the laboratory, you should: 1. Learn to recognize members of the phyla Ctenophora and Cnidaria, the three main cnidarian classes (Hydrozoa, Scyphozoa, Anthozoa) and the cnidarian subclasses Octocorallia and Hexacorallia. 2. Learn the anatomy of Pleurobrachia, Hydra, Obelia, Aurelia, Metridium, and typical soft and hard corals. 10