Phylum:
.
Platyhelminthes
,
Parasite Monster Inside Me Part 2
Platyhelminthes
Origin of the word platyhelminthes: Latin for flat
Animals in this phylum include: tapeworms, planarians,
saltwater flatworms
Level of organization:
-organs and organ systems
-Acoelomate (no body cavity)
Symmetry: Bilateral (found in most higher organisms)
Basic Platyhelminthes body plan
Three Germ Layers: First phylum to have all
three
1) Ectoderm (outer)
2) Endoderm (inner)
3)Mesoderm (middle)
Organ Systems
Digestive system:
- Three branch system.
- Gastrovascular cavity (same as cnidarians)
- Gastro = digests food
- Vascular = distributes food and gases like the
circulatory system
Reproductive System:
Organ Systems
Digestive system:
-
Three branch system.
Gastrovascular cavity (same as cnidarians)
Gastro = digests food
Vascular = distributes food and gases like the
circulatory system
Reproductive System:
- Hermaphrodite (carry both male and female
reproductive organs)
Organ Systems
Nervous System:
- A ladder-like nerve network extending down from an anterior
brain.
Head
- Anterior Eyespots detect light
- Chemosensitive organs at auricles
Note: Sensory functions collecting at the anterior end of an
organism = Cephalization
Organ Systems
Excretory System:
Parts
- A web of interconnected tubes that end in flame cells
- Flame Cell: Contain beating cilia that create a continuous flow
of water out the excretory pore
Function
- Waste moves out of the cells by diffusion and are pushed into
the current created by the flame cells which leads it out of the
body through the excretory pore
Platyhelminthes and Parasitism
Half of the flatworm species are parasitic
Two main groups of parasitic flatworms
1)Tape worms:
- Endoparasite
- Adult stage survives in the intestine of a vertebrate host
Parts:
Scolex: Anterior end equipped with rings of hooks (B) and suckers (A)
that hold onto host intestine.
Proglottids: Reproductive segments (Carry eggs) released in feces
Platyhelminthes and Parasitism
Characteristics that make tapeworms successful
parasites
1) Strong outer skin that resists breakdown by
hosts digestive enzymes and acids
2) Produces millions of eggs per day (only a few
will make it to a proper host)
Platyhelminthes and Parasitism
Fish tapeworm (Diphyllobothrium):
- Found off the West coast of Canada and
Alaska (AKA here )
- Reaches up to 30ft in length
- Found in raw muscle meat of predatory fish
(eg. Salmon, trout)
Tapeworm Lifecycle
• Tapeworm lifecycle movie youtube
Tapeworms
Prevention:
Freezing meat at -10 C for several days kills the cysts
OR
Cooking the meat thoroughly will kill cysts
Symptoms:
- Usually asymptomatic (4/5 cases)
- Weight loss
- Abdominal pain
- Diarrhea
- Vomiting
- Fatigue
Platyhelminthes and Parasitism
Two main groups of parasitic flatworms
2) Flukes:
- Endoparasite
- Adult stage survives in the intestine of a vertebrate host
Parts:
- Oval shaped body similar to free living planaria with a
reduced digestive and nervous system
Types:
Named after the organ
they infect
- Liver fluke
- Lung fluke
- Blood fluke
Assignment
• Crossword
• Vocab 628-629