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BIOLOGY OF ANIMALS LABORATORY
LAB # 4-A (Supplement Spring09) (Written by Dr. Olson, Professor Emeritus; modified by Dr. Alan D. Christian and J.D. Wilhide)
PHYLUM: PLATYHELMINTHES ("flatworms")
LAB. MAN: EXERCISE #9-A/B/C: Pages 139-
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:
- 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.
- The asymmetry of the poriferans (sponges) and the radial symmetry of the cnidarians are 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).
- 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.
- Because flatworms lack a coelom (have no fluid-filled spaces 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.
- 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
BY READING IN YOUR LABORATORY MANUAL OR TEXTBOOK, YOU SHOULD
BE ABLE TO ANSWER THE FOLLOWING QUESTIONS CONCERNING THE
ORGANISMS LISTED BELOW:
- "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.
For the study slides KNOW the following structures/terms found on pages 140-143 and Figure(s) 9-01 – 9-02 of your laboratory manual. STRUCTURES/TERMS: anterior, posterior, dorsal, ventral, head, auricles, eyes, pharynx, mouth, thigmotaxis, chemotaxis, phototaxis, gastrovascular cavity, extracellular digestion, intracellular digestion, excretory canal, protonephridia (flagellated flame cells), nerve ladder, cerebral ganglia, lateral nerve cords, transverse nerves, eyespots (ocelli), epidermis, rhabdites, circulular muscles, longitudinal muscles, dorsoventral muscles, acoelomate, parenchyma,
OBSERVE DEMONSTRATION MATERIALS (preserved or living)
- "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.)
For the study slide KNOW the following structures/terms found on pages 147-148 and Figure(s) 9-03 of your laboratory manual. STRUCTURES/TERMS: oral sucker, ventral sucker, tegument, parenchyma, mouth, pharynx, esophagus, excretory pore, bladder, testes, vas efferens, vas deferens, seminal vesicle, seminal receptacle, ovary, yolk ducts, uterus, cercariae
OBSERVE DEMONSTRATION MATERIALS of other flukes, fluke life-cycle stages, etc. and note their distinctive features.
- "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.)
For the study slide KNOW the following structures/terms found on pages 151-155 and Figure(s) 9-06 – 9-08 of your laboratory manual. STRUCTURES/TERMS: strobila, proglottids, suckers, hooks, tegument, scolex, genital pore, gravid proglottids, rostellum, excretory canal, immature proglottids, sperm duct, testes, vagina, ovaries, oviducts, uterus, vitelline gland, shell gland, vas deferens, nerve cord OBSERVE DEMONSTRATION MATERIALS of other tapeworms and note their distinctive features.
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)
(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: *Common Freshwater 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.
NOTE: ** = Study organism in detail from your dissection of the adult worm and from the transverse-section slide provided in the regular slide box.
- = See demonstration materials.
BY READING IN YOUR LABORATORY MANUAL OR TEXTBOOK, YOU SHOULD BE ABLE TO ANSWER THE FOLLOWING QUESTIONS CONCERNING THE ORGANISMS LISTED BELOW:
- "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 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 163 as your guide For the dissection and study slides KNOW the following structures/terms found on pages 160-167 and Figure(s) 10-01 – 10-02 of your laboratory manual. STRUCTURES/TERMS: DISSECTION - spicules, mouth, vulva, cuticle, collagen, pseudocoel, longitudinal muscle cells, excretory canals, excretory por, pharynx, intestine, anus, vagina, oviducts, ovaries, testis, vas deferens, seminal vesicle, cloaca, spicules; SLIDES - cuticle, epidermis, longitudingal muscles, pseudocoel, excretory canals, dorsal nerve cord, ventral nerve cord, oviducts, ovaries, intestine, testes, vas deferens, seminal vesicle
OBSERVE DEMONSTRATION SLIDES/SPECIMENS of other parasitic nematodes. How do each of these parasites get into their host? (See pages 164-165)
- "Common Freshwater Rotifer" ( Philodina ) Phylum?
