Table Of ContentAnimal 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.
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Body Organization: Tissue Layers and Body Cavity
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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
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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.
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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.
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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.
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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
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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
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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.
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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.
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