Phylum Nematoda - PowerPoint PPT Presentation

1 / 20
About This Presentation
Title:

Phylum Nematoda

Description:

They lack circular muscles so they cannot crawl as we saw the leech do on dry surfaces. ... Aquatic species have ventral glands (called renettes) posterior to ... – PowerPoint PPT presentation

Number of Views:910
Avg rating:3.0/5.0
Slides: 21
Provided by: smi99
Category:
Tags: nematoda | phylum

less

Transcript and Presenter's Notes

Title: Phylum Nematoda


1
Phylum Nematoda
  • AKA Unsegmented roundworms.

2
Nematodes
  • Advancements over flatworms
  • Has a two-hole digestive tract.
  • Not as advanced as higher worms, such as
    earthworms because
  • They lack body segmentation.

3
Nematodes, contd
  • Unsegmented roundworms are classified into about
    16,000 species, but the actual number of nematode
    species could be as high as 500,000.
  • Nematode facts
  • Colorless
  • Range in length from microscopic to several
    meters long.
  • May be free-living or parasitic.

4
Nematode Habitat
  • Nematodes live in
  • Parasitic nematodes live within a host
  • Free-living nematodes live in marine, freshwater,
    or damp soil environments.

5
The Nematode lifestyles
  • Nematodes generally live one of two types of
    lifestyles free-living or parastic.

6
Free-living Lifestyle
  • Eating habits
  • Herbivores eat plants
  • Carnivores eat animals
  • Omnivores eat both plants animals
  • Saprophagous -Eat dead organic matter (from
    animals only), Yummy
  • Free-living and have the eating habits mentioned
    on the previous slide.
  • The free-living nematodes are important because
    they add organic matter to the soil and putting
    holes in the soil to better allow water movement
    through the soil.

7
Parasitic Lifestyle
  • Parasitic feed off of a host.
  • These worms feed of the blood or tissue fluids of
    their hosts.
  • We will learn about four types of parastic
    nematodes filarial worms, hookworms, trichina
    worms, and ascaris worms.
  • Interesting tidbits
  • The filarial worms cause the disease
    elephantitis, pictured to the left.
  • Trichina worms cause trichinosis the horrid
    disease contracted from eating undercooked pig
    products.

8
Nematode Body Plan
  • Nematodes have three cell layers
  • Ectoderm outer tissue layer (epidermis)
  • Mesoderm middle tissue layer (muscle)
  • Endoderm innermost tissue layer (body cavity)
  • They are known as psuedocoelomates because they
    have an internal cavity that is not lined with
    peritoneum therefore it is not a true coelom.
  • They are bilaterally symmetrical as is every
    organism we study from here on out.

9
Nematode Epidermis
  • The outside of the nematode is made up of a
    tough, flexible, noncellular layer known as the
    cuticle.
  • The cuticle is secreted by epidermal cells.
  • It functions to
  • Resist penetration in free-living.
  • Resist enzymatic digestion in parasitic.
  • Maintains internal hydrostatic pressure.
  • The cuticle usually molts 4 times during
    maturation.

10
Nematode Digestive System
  • One way digestive system remember this means
    that food goes in one way and out another. Just
    like us.
  • The digestive tract is a linear progression, as
    shown below
  • mouth ? pharynx ? intestines ? rectum ? anus
  • Food is pushed through this system by hydrostatic
    pressure.

11
Nematode Musculature
  • The nematode body wall has only longitudinal
    muscles.
  • Remember longitudinal means lengthwise, so they
    only run from the anterior to the posterior end
    of the worm.
  • These muscles are used for movement.
  • When these muscles contract it causes the
    thrashing movements from head to tail.
  • They lack circular muscles so they cannot crawl
    as we saw the leech do on dry surfaces.

12
Excretory System
  • Aquatic species have ventral glands (called
    renettes) posterior to the pharynx that absorb
    waste from the pseudocoelom and empties the waste
    through the excretory pore.
  • Parasitic nematodes have a more advanced
    excretory system.

13
Parasitic Excretory System
  • Their system is known as a tubular system that
    develops from the renette system of the
    free-living worms.
  • The renettes unite to form two large canals,
    known as the excretory canals that open to the
    outside by an excretory pore which is located by
    the head.
  • A little odd to excrete wastes near your head,
    eh?

14
Excretory System Diagram
15
Reproductive System
  • Most nematodes are
  • Dioecious two different types of reproductive
    cells ex. sperm egg.
  • Dimorphic two different sexes ex. male and
    female.
  • As you might guess, they reproduce sexually.
  • The males are slightly smaller than the females.
    Why?

16
Female Reproductive System
  • Consists of a pair of ovaries attached to an
    oviduct that has a swollen proximal end that
    forms a seminal receptacle.
  • Each oviduct becomes a tubular uterus, and the
    two uteri come together to form a vagina that
    opens to the outside through a genital pore.

17
Male Reproductive System
  • Most male nematodes have only a single testis
    attached to the vas deferens which expands into a
    seminal vesicle which connects to the cloaca.
  • What are all these things?
  • Vas deferens aka sperm duct, releases sperm
  • Seminal vesicle stores sperm cells
  • Cloaca hole that sperm is ejected from
  • They also have a flap of tissue called the bursa
    that aids in the transfer of sperm to the female
    genital pore.

18
Reproductive System Diagram
19
Brief Parasitic Nematode Info.
  • Pinworms
  • Most common roundworm in the U.S.
  • Adults reside in the large intestine.
  • Enter humans by being eaten.
  • Hookworms
  • Found in the southern U.S.
  • Adults live in the small intestine of humans.
  • Enter host through the skin, usually between the
    toes. That makes you want to walk around
    barefoot, doesnt it?
  • Trichina
  • Live in humans other omnivores (like piggys)
  • Adults live in the small intestine of its host
    larvae encyst in the stomach and skeletal tissue
    (ouch!)
  • Enter host by being eaten.

20
Nematode Nervous System
  • Nematodes have two nerve cords in their bodies.
  • Ventral nerve cord runs along the belly.
  • Dorsal nerve cord runs along the back.
  • They have a central nervous system consisting of
    a circular brain.
  • The nervous system allows the nematode to detect
    its environment and react to it.
  • Aquatic nematodes have a pair of ocelli (eyes).
Write a Comment
User Comments (0)
About PowerShow.com