PRINCIPLES OF ZOOLOGY
LAB # 2-A (Supplement)
(Written and provided by Dr. Olson, Professor Emeritus)
PHYLUM: PORIFERA ("sponges")
LAB. MAN.: EXERCISE # 7-A; Pages 107-111
TEXT: CHAPTER # 12; Pages 243-251
The Phylum: Porifera (translation: "pore-bearing") is an ancient group that is believed to have evolved from flagellated protozoans. However, poriferans themselves are thought to be an "evolutionary dead end" because they apparently have not given origin to any other animal group. As a result, sponges possess several unique, or one-of-a-kind, features.
GENERAL PORIFERAN CHARACTERISTICS:
1. Sponges are among the simplest of the metazoans (many-celled animals). They represent the cellular level of body organization and they are little more than a "loose grouping of cells" embedded in a gelatinous matrix known as the mesohyl. Although there is some division-of-labor among their various cell types, no true tissues are present in sponges.
2. As adults, most sponge species lack a set or distinct shape and, thus, exhibit asymmetry.
3. Habitat:
Most sponge species are marine while relatively few are freshwater. All adult sponges are sessile (attached or non-moving) and are classified as "filter feeders" because they filter or strain food items from water flowing through their bodies.
4. Water-Vascular System:
The bodies of most sponges are composed of a series of interconnected ostia (pores), canals, and chambers through which water containing nutrients, oxygen, and metabolic wastes is circulated. Based on relative complexity, there are 3 canal-system types:
Asconoid = The simplest type of sponge-body design. Water Path: Ostia, FLAGELLATED SPONGOCOEL, Osculum.
Syconoid = The intermediate type of sponge- body design.
Water Path: Ostia, Incurrent canals, FLAGELLATED RADIAL CANALS, Spongocoel, Osculum.
Leuconoid = The most-common and complex type of sponge-body design.
Water Path: Ostia, Incurrent canals, FLAGELLATED CHAMBERS, Excurrent canals, Oscula.
5. Major Cell Types:
Choanocytes
Commonly called "collar cells". Are special flagellated cells which line either the spongocoel, radial canals, or internal chambers. Their "flagellum" creates a water current through the canal system while the "collar" portion traps/filters food particles which then are passed to the "cell body" for digestion.
Pinacocytes
Thin, flat cells that cover the sponge surface and which line the incurrent canals and the spongocoel of most sponges.
Archaeocytes/Amoebocytes
A mixed group of mobile, amoeboid cells with varied functions that occur in the mesohyl. Includes Sclerocytes (secrete spicules) and Spongocytes (secrete spongin fibers).
6. Reproduction:
Sexual:
Most sponges (including Sycon/Grantia) are monoecious (produce both eggs and sperm). In Sycon (=Grantia), a fertilized egg becomes a flagellated, free-swimming larva called the amphiblastula larva. These larvae often can be seen in the mesohyl.
Asexual:
Many sponges (including Sycon/Grantia) also can reproduce by asexual budding in which new individuals develop as external "outgrowths" from the base of the "parent" sponge. In freshwater sponges, internal buds known as gemmules are produced. Each gemmule is a cluster of amoebocytes/archaeocytes surrounded by a spongin coat with embedded spicules. Gemmules (like zygotes of Volvox) can withstand harsh conditions and thus help promote freshwater sponge survival.
7. Skeleton:
The loosely-organized sponge body is supported by a skeleton composed of one, or both, of the following:
Spicules (secreted by "sclerocytes")
Hard skeletal subunits composed either of lime (calcium carbonate) or glass-like silica. Spicule types include needle-like, unbranched monaxons, 3-branched tri-radiates, and complex polyaxons.
Spongin (secreted by "spongocytes")
A loosely interwoven network of scleroprotein fibers.
GENERAL PORIFERA TAXONOMY: (Condensed for this lab)
KINGDOM: ANIMALIA
PHYLUM: PORIFERA ("pore-bearing")
CLASS: CALCAREA ("lime")
-Some texts still use the older class name Calcispongiae.
-Are often called the "lime sponges" because their skeletal spicules are composed of calcium carbonate.
Examples:
**Sycon/Grantia
*Leucosolenia
CLASS: HEXACTINELLIDA ("6-rayed")
-Some texts still use the older class name Hyalospongiae.
-In members of this class, most spicules are either unbranched monaxons or are 3-branched tri-radiates.
-Class members are marine, shallow-water, small, and vase-shaped.
-Are often called the "glass sponges" because their skeletal spicules are composed of glass-like silica.
-In members of this class, most spicules are 6-branched polyaxons which are interconnected to form an intricate lattice-like network.
-Class members are marine, deep water, large, and usually cylindrical or funnel-shaped.
Example:
*Euplectella ("Venus’ flower basket")
CLASS: DEMOSPONGIAE ("people sponges")
-95% of all living sponges belong to this class!
-Are often called the "bath sponges" because their skeleton is composed mainly of an interwoven network of relatively soft spongin-protein fibers. Some are used by man for bathing. If present, skeletal spicules are composed of glass-like silica but they are not 6-rayed.
-Class members are marine (except the freshwater family Spongillidae) and are relatively large-sized.
-Freshwater sponges typically appear as a "scummy mass" encrusting stems of aquatic plants and pieces of submerged wood.
Examples:
*Spongilla ("common freshwater sponge")
*Other common marine sponges including:
"Hardhead sponge"
"Basket sponge"
"Grass sponge"
_____________________________________________________________________________
NOTE: ** = Study this organism from slides provided in regular slide boxes.
* = See demonstration microscope or materials.
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BY READING IN YOUR LABORATORY MANUAL OR TEXTBOOK, YOU SHOULD BE ABLE TO ANSWER THE FOLLOWING QUESTIONS CONCERNING THE ORGANISMS LISTED BELOW:
1. Sycon/Grantia
Phylum?
Class?
Where does Sycon/Grantia normally live?
What water-vascular-system type does it represent? Can you accurately trace (name the parts of) the water pathway through this sponge in the correct sequence?
What spicule type(s) does Sycon/Grantia possess?
What are the functions of choanocytes and where are they located in this sponge?
What is the larval stage of Sycon/Grantia called? Is it ciliated or flagellated?
*STUDY SLIDES of a transverse section (c.s. or x.s.) of Sycon/Grantia and KNOW the structures/terms found in heavy print on pages 108-111 of your laboratory manual.
*OBSERVE PRESERVED DEMONSTRATION SPECIMENS of Sycon/Grantia.
*VIEW DEMONSTRATION SLIDE of spicules.
2. Other Sponge Materials
*OBSERVE PRESERVED DEMONSTRATION SPECIMENS representing the various classes of sponges.
*VIEW DEMONSTRATION SLIDE of freshwater-sponge gemmules. When are gemmules produced and how do they contribute to the success of freshwater sponges?
PRINCIPLES OF ZOOLOGY
LAB # 2-B (Supplement)
(Written and provided by Dr. Olson, Professor Emeritus)
PHYLUM: CNIDARIA ("cnidarians")
LAB. MAN.: EXERCISE #8-A/B/C; Pages 117-133
TEXT: CHAPTER # 13; Pages 253-275
Most zoologists believe the Phylum: Cnidaria (translation: "to nettle or sting") evolved from ciliated protozoans and not the "dead-end" sponges. The most-likely "link" connecting the cnidarians and ciliated protozoans is the ciliated, somewhat Paramecium-like, planula larva of cnidarians which occurs throughout the phylum.
GENERAL CNIDARIAN CHARACTERISTICS:
1. Cnidarians exhibit considerably better body organization than sponges in that they possess the tissue level of development with groups of similar cells united as "teams" (tissues). The true tissues found in cnidarians include the outermost epidermis (ectoderm origin), the innermost gastrodermis (endoderm origin), and nervous tissue (ectoderm origin). The diffuse nerve net of cnidarians represents the first nervous system in the animal kingdom! A non-cellular, gelatinous layer called the mesoglea lies between the epidermis and gastrodermis tissues. In the sessile polyp stage, the thin mesoglea serves as a supportive "skeleton". In the free-swimming medusa stage, the much thicker mesoglea aids buoyancy.
2. Because cnidarians possess both ectoderm (epidermis) and endoderm (gastrodermis) germ layers, they are categorized as being diploblastic. Note that a third germ layer, mesoderm, is not found in cnidarians.
3. Cnidarians exhibit radial symmetry around their oral-aboral (mouth-to-base) axis and their internal "digestive cavity" is known as the gastrovascular cavity (g.v.c.) The g.v.c. represents the "blind-sac" type of digestive system in which one opening serves as both mouth and anus.
4. All cnidarians are aquatic with the most being marine. However, the freshwater "hydra" remains the most-commonly studied cnidarian because of its accessability and simple/basic design.
5. Dimorphism:
Most cnidarian species exhibit 2 distinct body forms during their life cycle:
Polyp ("hydroid")
-A tubular body form; Usually sessile.
-Aboral end attaches to a substrate; Oral end bears the mouth/anus surrounded by tentacles.
-Polyps reproduce only by asexual budding (exception: hydra).
Medusa ("jellyfish")
-An umbrella-shaped body form; Usually floating or free-swimming.
-The mouth/anus is located on a short stalk-like manubrium and tentacles are located along the medusa margin.
-Medusae reproduce only by sexual means (egg + sperm).
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6. Nematocysts:
Cnidarians possess distinctive cells called cnidocytes in both their epidermis and gastrodermis tissues. Within these cnidocyte cells are specialized organelles called nematocysts whose functions include food capture, locomotion and defense. The 3 general nematocyst types are harpoon-like penetrants, thread-like entangling volvents, and sticky glutinants. The painful "stinging action" of some of the penetrant types is the basis for the phylum name Cnidaria ("to nettle or sting").
7. Reproduction:
Asexual:
The tubular, sessile polyp reproduces only by budding. "Buds" typically mature to form the umbrella-like free-swimming medusa stage (exception: "hydra").
Sexual:
The sexually-reproducing medusae generally are dioecious (produce either eggs or sperm; not both) and shed their gametes into the water. When the sperm of a male medusa fertilizes the egg of a female medusa, the resulting zygote develops into a ciliated, free-swimming larva called the planula larva. After a brief existence, the planula "settles" and develops into a sessile polyp (see Fig. 8-4 on page 122 of your laboratory manual).
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GENERAL CNIDARIAN TAXONOMY (condensed for this lab)
KINGDOM: ANIMALIA
PHYLUM: CNIDARIA ("to nettle or sting")
CLASS: HYDROZOA ("water animal")
-Class members typically feature both polyp and medusa stages in their life cycle (exception: "hydra" which lacks the medusa stage).
-The medusa in this class possesses a unique structure called the velum, a "shelf-like" membrane inside the lower margin of the "umbrella" that is used to aid locomotion (swimming). In the "true jellyfishes" (Class: Scyphozoa), the medusa stage lacks a velum.
Examples:
**Hydra **Obelia
*Gonionemus
*Craspedacusta ("freshwater jellyfish")
* Physalia ("Portuguese man-o-war")
CLASS: SCYPHOZOA ("cup animal")
-In this class, the medusa stage dominates the life cycle. A polyp stage does occur but it is small, short-lived, and seldom seen.
-Class members are known as the "true jellyfishes" because the buoyancy-aiding mesoglea layer in the body wall is very thick and gelatinous.
-There is no velum in the medusa stage of true jellyfishes (scyphozoans).
Examples:
*Aurelia
*Other scyphozoan medusa types including:
Polyorchis, Synchorine, Cassiopeia, etc.
CLASS: ANTHOZOA ("flower animal")
-In this class, only the polyp stage occurs in the life cycle. There is no medusa stage.
Examples:
*Metridium ("sea anemone")
*Miscellaneous "corals" including:
"Sea fan" (Gorgonia)
"Sea pansy" (Renilla)
"Brain coral"
"Staghorn coral"
etc.
_____________________________________________________________________________
NOTE: ** = Study this organism from slides provided in regular slide boxes.
* = See demonstration microscope or materials.
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BY READING IN YOUR LABORATORY MANUAL OR TEXTBOOK, YOU SHOULD BE ABLE TO ANSWER THE FOLLOWING QUESTIONS CONCERNING THE ORGANISMS LISTED BELOW:
1. "Hydra"
Phylum?
Class?
Where does hydra normally live? (Where could you collect living specimens?)
How does hydra capture its prey/food?
Does a medusa stage occur in the hydra life cycle?
STUDY SLIDES of preserved/stained specimens:
(1) Whole mount (w.m.) showing asexual budding.
(2) Transverse section (c.s. or x.s.) showing body wall structure.
KNOW the structures/terms found in heavy print on pages 118-121 of your laboratory manual.
OBSERVE "living" hydra specimens (if they are available).
BRIEFLY VIEW any hydra-related demonstration slides or materials.
2. Obelia
Phylum?
Class?
Where do Obelia colonies normally occur?
What are the 2 distinctly-different polyp types found on a branched "plant-like" Obelia colony? For what main purpose is each of these polyp types specialized?
STUDY SLIDE of a preserved/stained Obelia colony and KNOW the structures/terms found in heavy print on pages 121-123 of your laboratory manual.
BRIEFLY VIEW DEMONSTRATION SLIDE of the Obelia medusa stage.
FAMILIARIZE YOURSELF with the general life cycle of Obelia as seen in Fig. 8-4 on page 122 of your laboratory manual.
BRIEFLY VIEW DEMONSTRATION SPECIMENS of an Obelia colony and other typical cnidarian polyp types. There is no need to memorize the scientific names of these polyp forms!
3. Gonionemus
Phylum?
Class?
Where does Gonionemus normally live?
This is an good example of a "typical" hydrozoan medusa stage. You should, therefore, be generally familiar with its structure. Does it possess a velum?
OBSERVE DEMONSTRATION SPECIMEN of a Gonionemus medusa and read about its general structure on pages 123-125 of your laboratory manual. Can you correctly label the diagram on page 127 of your laboratory manual?
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4. Craspedacusta ("freshwater jellyfish")
Phylum?
Class?
*See demonstration specimen of the medusa stage of this organism.
5. Physalia ("Portuguese man-o-war")
Phylum?
Class?
This cnidarian exhibits polymorphism. What does this mean?
What is the pneumatophore and what is its function? (See page 125 in lab. manual).
How and when is this organism dangerous for man?
*See demonstration specimen.
6. Aurelia
Phylum?
Class?
Where does Aurelia normally live?
Which one of the two body forms dominates the life cycle?
What part of the medusa body wall is thicker and more "jelly-like" than in the medusa of a hydrozoan?
*Observe demonstration specimens of the Aurelia medusa and other representative medusa forms. Do these "true jellyfish" medusae possess a velum?
*Are you generally familiar with:
(1) The structure of Aurelia’s medusa stage? (See Fig. 8-7 on page 129 of lab. manual)
(2) The life cycle of Aurelia as diagramed in Fig. 8-7? What is the larva called?
7. Metridium ("sea anemone")
Phylum?
Class?
Where does Metridium normally live?
Do both the polyp and the medusa stage occur in the life cycle of members of this class?
*Observe demonstration specimens of sea "anemones".
*Be generally familiar with anemone structures described on pages 131-132 and diagramed in Fig. 8-8 on page 131 of your laboratory manual.
8. Misc. Corals
Phylum?
Class?
Where do most coral organisms occur?
*Observe preserved "bits and pieces" of several different coral specimens. What are the theca, basal plate, and the sclerosepta of a coral’s skeleton? (See page 133)