L11:Cestodes Flashcards
How does the male system of cestodes develop
=>developes in proglottid
=>formation starts in the immature proglottid and completes in the mature proglottid
=> the organs disappear in gravid proglottid
Describe the morphology of adult cestodes
elongated, billatery symetrrical, dosroventrally flat and segemented
scolex: anterior, attachment structures
cyclophilidea has 4 suckers and maybe hooks
other pseudophyllidea has slits called bothria
neck: only unsegmented region posterior to scolex, origin of proglottid
strobila: chain of proglottid each are independant functioning units, move down as more are formed
so there are the immature newly formed, mature proglo with male and femal reprodutive organs and gravif with embryonated eggs
What are cestodes, general characteristics
=>monoecious, hermaphroditic
=>self and cross-fertilisation
=> genital pore where eggs exit
=> gravid proglottid detach from parent and disintegrate or exit the host
=> Male and female organs absent from gravid proglottid
What is the male reproductive system made of in cestodes
- one or many testes depending on species
- Vas efferents which is tubular structure that transports spermatozoa from testes
- A tightly coiled cas derefense for transporting sperm
- seminal vesicle to store the sperm
- cirrus sac cirrus - male copulatory system
- male genital pore that opens to common genital atrium
Where does the female reproductive system develop from
Form only in the mature proglottids and are functional from there
*only the egg-filled uterus remains in the gravid proglottid
What are the structures of the cestode female reproductive system
- single ovary where ova is produced
- oviduct
- vagina that carries the sperm to the ootype
- ootype which is a region in oviduct where fertilisation and egg assembly happen
- Vitellaria yolk gland where yolk and eggshells form
- Mehli gland that secretes essential eggshell material
- Tubular uterus that contains egg in branches
What are the general characteristics of cestodes reproductive system eggs
- eggs are passed from the host are mostly embryonated
- eggs contain hexacanth larvae called ONCOSPHORES
*oncosphere has 3 pair of hooks and encased in inner envelope surrounded by a second membrane called an embryophore
*the embryophore is also encased in outer membrane
*shell or capsule encapsulates the egg
whats an oncophores
eggs that contain hexacanth larva
What are the types of eggs in cestodes1
- operculated with immature embryo passed into the environment
- non-operculated with embryonated embryo when passed into the environment
Discuss how eggs pass into the environment generally with cestodes
Eggs remain viable in the external environment for weeks to months
released as operculated or non-operculated
What is the tegument, what is it composed of and key roles of each
skin that covers the entire external surface
=> microthrices microvilli for:
movement
surface area to absorb nutrients
sensory + secretory
glycocalyx carbohydrate layer covering tegument for:
protection from digestive enzymes, nutrient absorption, maintain surface membrane
Why is absorption so important
Flatworms don’t have a digestive tract so all nutrients are derived from host molecules, meaning they must cross tegument
What is the purpose of the osmoregulation/excretory system, what are the two key cells
maintains optimal hydrostatic pressure in the worm for extensory movements of the strobila and scolex with two components
The flame cells and the Collecting canals
flame cells: ciliated cells forming the basic unit of the excretory system
Collecting Canals: carry water to and away from scolex, running the length of strobila
What is the excretory system, cells, caviat in some species. What is the connection between osmo and exec system
some species the osmo/excre system is only excre because they cannot regulate osmotic pressure and change movement to environment
the excre system ensure survival as host can conserve water and eliminate salts, allowing them to maintain osmo pressure
What are the characteristics of the nervous system in cestodes?
brain is scolex and main nerve center of cestode
the nervous system is like ladder and the nerves run anteriorly and posteriorly in the body
many sensory organs arranged species-specifically
