PRINCIPLES OF ZOOLOGY
LAB # 3-A (Supplement)
(Written and provided by Dr. Olson, Professor Emeritus)
PHYLUM: PLATYHELMINTHES ("flatworms")
LAB. MAN.: EXERCISE #9-A/B/C: Pages 135-152
TEXT: CHAPTER #14; Pages 281-302
Most zoologists believe the Phylum: Platyhelminthes evolved from a Cnidaria-like ancestor (possibly by way of the ciliated planula larva). Replacement of the non-cellular mesoglea of cnidarians with a cellular, mesodermal parenchyma in the flatworms made possible the development of more complex body organs and systems.
GENERAL PLATYHELMINTHES CHARACTERISTICS:
1. Platyhelminths (flatworms) exhibit the organ-system (organ) level of body design, a significant improvement over the tissue-level found in cnidarians. Improvements/advances can be most-clearly seen in the excretory, reproductive, and nervous systems of the flatworms.
2. The asymmetry of the poriferans (sponges) and the radial symmetry of the cnidarians is replaced with bilateral symmetry in the flatworms. This most-advanced symmetry type promotes active forward movement, development of anterior and posterior regions, and stimulates cephalization (specialization of the head end).
3. The diploblastic (ecto-, endoderm) condition seen in the cnidarians is improved in the flatworms with the addition of mesoderm, thus making them triploblastic. This mesoderm addition is "significant" in that it provides the foundation for development of many important new tissues, organs, and systems in the flatworms and in all "higher" animals.
4. Because flatworms lack a coelom (have no fluid-filled space between the body wall and the intestine wall), they are categorized as acoelomate organisms. Instead of a coelom, the would-be "space" between the body and intestine walls of flatworms is filled with a mesodermal tissue known as parenchyma.
5. Distinctive Flatworm Systems:
Digestive System
Is incomplete (mouth, intestine, no anus) in both "planarians" and "flukes". These flatworms thus have the same "blind-sac" style of digestive system that is found in the cindarians.
Is totally absent (no mouth no intestine, no anus) in "tapeworms". These flatworms feed by absorbing nutrients through their body surface.
Excretory System
Flatworms are the first (simplest) animals to possess an excretory system! It is known as the protonephridial ("first kidney") system and features specialized, ciliated cells called protonephridia or "flame cells" located at the ends of branched excretory ducts.
Reproductive System
Most flatworms are monoecious (each individual possess both ovaries and testes). However, nearly all exhibit "cross-fertilization" (are fertilized by a "mate") and do not self-fertilize.
Nervous System
The primitive, inefficient "nerve net" of cnidarians is improved upon in the flatworms in the form of a "ladder-type nervous system". This more-centralized arrangement features a pair of anterior ganglia, two longitudinal nerve cords, and numerous transverse connectives between the nerve cords. The primitive bipolar protoneurons of cnidarians are replaced by flatworm neurons that are unipolar and organized into motor, sensory, and association types......an important development in the evolution of the animal nervous system!
GENERAL PLATYHELMINTHES TAXONOMY (condensed for this lab)
KINGDOM: ANIMALIA
PHYLUM: PLATYHELMINTHES ("flatworms")
CLASS: TURBELLARIA ("planarians")
-Most planarians are free-living, or non-parasitic.
-A ciliated epidermis is present on both adults and larvae.
-Planarians feed by extending a muscular, tubular pharynx through their ventrally-located mouth.
-All planarians (freshwater and marine) have a simple life cycle.
Examples:
**"Common brown planaria" (Dugesia tigrinum)
*"Marine planaria" (Bdelloura)
CLASS: TREMATODA ("flukes")
-Almost all flukes are internal parasites (endoparasites) that live within the body of a vertebrate host. A few species are ectoparasitic.
-The body covering (tegument) of adult flukes is not ciliated.
-The flattened, leaf-like fluke body bears "suckers" for host attachment.
-Most flukes feature a complex life cycle that includes 2 or more hosts.
Examples:
**"Human/Oriental liver fluke" (Clonorchis sinensis)
*Other common flukes including:
"Sheep liver fluke" (Fasciola)
"Blood fluke" (Schistosoma)
"Intestinal fluke (of man) (Fasciolopsis)
CLASS: CESTODA ("tapeworms")
-All tapeworms are endoparasites that live within a vertebrate host.
-No cilia are present at any time.
-The ribbon-like tapeworm body features an anterior scolex (head) followed by numerous body "segments" known as proglottids. Proglottid types include immature, mature, and gravid.
-In tapeworms, the digestive system is entirely absent!
-All tapeworms feature a complex life cycle with 2 or more hosts.
Examples:
**"Dog tapeworm" (Taenia pisiformis)
*Other common tapeworms including"
"Human/beef tapeworm" (Taeniarhynchus)
"Sheep tapeworm" (Monezia)
"Small dog tapeworm" (Dipylidium)
"Hydatid tapeworm" (Echinococcus)
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NOTE: ** = Study this organism from slides provided in regular slide boxes.
* = See demonstration microscope or materials.
BY READING IN YOUR LABORATORY MANUAL OR TEXTBOOK, YOU SHOULD BE ABLE TO ANSWER THE FOLLOWING QUESTIONS CONCERNING THE ORGANISMS LISTED BELOW:
1. "Common Freshwater/Brown Planaria" (Dugesia)
Phylum?
Class?
Where in their freshwater habitat would you look to find living specimens and during what time of day are they most likely to be active?
Are planarians parasitic?
STUDY SLIDES of preserved/stained specimens:
(1) Whole mount (w.m.).
(2) Transverse section (c.s. or x.s.) through the pharynx region.
KNOW the structures/terms found in heavy print on pages 136-140 of your laboratory manual.
OBSERVE DEMONSTRATION MATERIALS (preserved or living)
2. "Human/Oriental Liver Fluke" (Clonorchis)
Phylum
Class?
Is this organism parasitic? Where do adults of this fluke live? Where can the immature (larval) forms of this fluke be found? In what part of the world is this fluke a "problem"? How do humans become infected with this fluke?
STUDY SLIDE of a prepared/stained whole mount (w.m.) and KNOW the structures/terms found in heavy print on page 144 of your laboratory manual.
OBSERVE DEMONSTRATION MATERIALS of other flukes, fluke life-cycle stages, etc. and note their distinctive features.
3. "Dog Tapeworm" (Taenia)
Phylum?
Class?
Where do adults of this parasitic worm live? Do tapeworm adults possess a digestive tract? What, and how, do tapeworms eat? How do dogs become infected?
STUDY SLIDE of a prepared/stained whole mount (w.m.) and KNOW the structures/terms found in heavy print on pages 149-152 of your laboratory manual.
OBSERVE DEMONSTRATION MATERIALS of other tapeworms and note their distinctive features.
PRINCIPLES OF ZOOLOGY
LAB # 3-B (Supplement)
(Written and provided by Dr. Olson, Professor Emeritus)
The PSEUDOCOELOMATE PHYLA ("pseudocoels")
LAB. MAN.: EXERCISE #10-A/B: Pages 157-166
TEXT: CHAPTER #15: Pages 304-323
The "pseudocoels" are a group of highly-variable phyla whose members have little in common except the possession of a fluid-filled body cavity called a pseudocoel. Zoologists beleieve that all of the phyla that possess a pseudocoel most-likely evolved from a flatworm-like ancestor (possibly the planarians). PLEASE NOTE: The term PSEUDOCOELOMATE IS NOT A PHYLUM NAME!!!!!
GENERAL CHARACTERISTICS of the PSEUDOCOEL PHYLA:
1. As in the flatworms (Platyhelminthes), members of all the pseudocoelomate phyla feature the organ-system level of development, exhibit bilateral symmetry, and are triploblastic.
2. All "pseudocoelomates" possess a space or cavity (pseudocoel)between their outermost body wall and their digestive tract wall. This fluid-filled cavity is called a "false cavity" because:
(1) It lacks a thin mesoderm lining called the peritoneum.
(2) It is the persistent (left-over) blastocoel of the embryo.
The "advantages" of having a pseudocoel (as opposed to being acoelomate) are:
(1) Space for development or housing of body systems.
(2) Space for storing and/or circulating substances.
(3) Improved freedom of movement.
(4) Fluid in cavity acts as a hydrostatic "liquid" skeleton.
3. Distinctive Systems:
Digestive System
Pseudocoelomates are the first (simplest) animals to possess a complete digestive tract (mouth, intestine, and anus all are present)!! However, the intestine wall lacks muscle tissue (mesoderm) so there is no peristalsis activity.
Reproductive System
Most pseudocoelomates are dioecious (feature separate sexes) and clearly exhibit sexual dimorphism (males and females look distinctively different).
Locomotion is pseudocoelomates is limited to an inefficient, somewhat primitive thrashing action because (1) the body is covered by a flexible non-elastic cuticle (bends but won’t stretch) and (2) possession of only longitudinal muscle fibers.
GENERAL TAXONOMY of the PSEUDOCOEL PHYLA: (condensed for this lab)
KINGDOM: ANIMALIA
PHYLUM: NEMATODA ("nematodes")
-The most-numerous and widespread of all the pseudocoelomates!
-Body (whether microscopic or much larger) typically elongated, cylindrical, non-segmented, and pointed at each end.
-Obvious sexual dimorphism with males distinctively smaller than females and with a "coiled" posterior end.
-Many nematode species are important parasites of man and domestic animals!
Examples:
**Human Intestinal Roundworm.....(Ascaris)
*Hookworm..................................(Necator)
*Trichina worm.............................(Trichinella)
*Dog Heartworm...........................(Dirofilaria)
*Pinworm......................................(Enterobius)
PHYLUM: ROTIFERA ("rotifers")
-All are freshwater, microscopic, and non-parasitic pseudocoelomates.
-Feature a distinctive, ciliated corona (for food capture) and a jaw-like mastax for chewing captured food items.
Example:
*CommonFreshwater Rotifer.......... (Philodina)
PHYLUM: NEMATOMORPHA ("horsehair worms")
-Have an long, thin body that resembles of horse’s hair in size, shape, and color.
-The non-parasitic adult worms live in freshwater ponds, pools, and rain puddles. The larval worms are internal parasites of insects.
Example:
*Common Horsehair Worm.............(Gordius)
PHYLUM: ACANTHOCEPHALA ("spiny-headed worms")
-Feature an anterior, spiny proboscis (snout) used for attachment to the intestinal wall of a vertebrate host (like a pig).
-The worm’s larval stage parasitizes the "grubs" (immatures) of insects called "June bugs" or "May beetles". Pigs become infected by eating the soil-inhabiting "grubs". The parasitic adult worms occur in the pig’s intestine.
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: ** = Study organism in detail from your dissection of the adult worm and from the transverse-section slide provided in the regular slide box.NOTE
* = See demonstration 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. "Human Intestinal Roundworm" (Ascaris)
Phylum?
Where does the adult stage of this parasite normally occur?
How does man become infected with this parasite?
COMPLETE A DISSECTION of Ascaris FOLLOWING INSTRUCTIONS GIVEN by your instructor and by your laboratory manual and KNOW the structures/terms found in heavy print on pages 157-160 of your laboratory manual.
STUDY SLIDE of a transverse-section (c.s. or x.s.) of a female Ascaris worm and locate as many parts as you can using Fig. 10-2 on page 161 as your guide
OBSERVE DEMONSTRATION SLIDES/SPECIMENS of other parasitic nematodes. How do each of these parasites get into their host? (See pages 162-164)
2. "Common Freshwater Rotifer" (Philodina)
Phylum?
OBSERVE DEMONSTRATION SLIDE and KNOW structures/terms in heavy print on page 165 of your laboratory manual.
If living specimens are available, make a "wet-mount" slide and observe these creatures in action.
3. "Freshwater Horsehair Worm" (Gordius)
Phylum?
Where do adult and larval horsehair worms normally live? Are they both parasitic?
OBSERVE DEMONSTRATION SPECIMENS and see page 166 of your laboratory manual.
4. "Spiny-headed Worm of Pigs" (Macracanthorhynchus)
Phylum?
Where do the parasitic adults of this worm normally live? How do pigs become infected?
How do these worms attach to their host?
OBSERVE DEMONSTRATION SPECIMENS and see page 166 of your laboratory manual.