Phylum Platyhelminthes Flashcards
Nervous system
Cephalic ganglia (brain) and long nerve cords
Excretion
Protonephridia and osmo-regulation
Gas exchange
No lungs, diffusion through skin only
Symmetry
Bilateral, dorso-ventrally flattened
Tissue layers
Triploblastic
Coelom
Acoelomate, no body cavity
Gut
Blind gut, one opening
What are the 3 classes in Phylum Platyhelminthes?
Class Turbellaria - Free living flatworms
Class Trematoda - Flukes
Class Cestoda - Tapeworms
Class Turbellaria Characteristics
Free-living, mostly aquatic
- Predators or scavengers
- Ciliated epidermis (locomotion)
- Eversible proboscis/pharynx
- No circulatory system
- Hermaphroditic
What are 3 Orders in Class Turbellaria?
- Order Acoela
- Order Polycladida
- Order Tricladida
What kind of larvae do Turbellarians have?
Miller larvae
Turbellarian regeneration
Strange
- Can cut in certain places and will grow back with extra cephalic region (head)
What are the endoparasitic Classes of Platyhelminthes?
Class Trematoda - Flukes
Class Cestoda - Tapeworms
What are 3 main adaptations for endoparasitism?
- Modified body walls to protect from host enzymes
- Strategies to invade hosts with complex life-cycles of definitive and intermediate hosts
- High reproductive potential with lots of eggs and polyembryony (Asexual duplication of developmental stages )
What are the characteristics of endoparasite body walls?
- Protect from host enzymes and resist host defenses
- Loss of cilia and reduction of musculature
- Reduction of sensory structures
- Nutrient absorption through body wall, not digestion
3 Characteristics of Class Trematoda
- Single mouth
- Bi-lobed digestive tract
- Body unsegmented
4 Characteristics of Class Cestoda
- Anterior hooked scolex (anchor to host)
- Division of body into proglottids
- No digestive tract
- No mouth
Trematode life-cycle
- Miracidium from definitive host feces
- Infects snails, produces sporocyte
- Burst from intermediate host (snail)
- Enter water as Cercaria
- Infect fish and encyst in muscle
- Get eaten by definitive host and start cycle again
Cestode life-cycle
- Mature segment detaches (gravid proglottid) or releases eggs
- Definitive host feces infects envr
- Gets taken up by beef or cow (usually) as intermediate host
- Encysts in muscle
- Infected intermediate host is consumed by definitive host
- Cycle starts again
