Zoology Test 2a Flashcards
What are Platyhelminthes?
- flatworms
- acoelomates
acelomates
without a body cavity (coelom)
What is in between the epidermis and gastrodermis?
parenchyma
How does embryo of Platyhelminthes differ form that of Cnidarians?
- triploblastic rather than diploblastic
- ectoderm, mesoderm and endoderm
- mesoderm gives rise to true muscle tissue, bones, circulatory system and other internal organs
symmetry of platyhelminthes
bilaterally symmetrical
- must actively search for food and mates
- body flattened dorso-ventrally
- cephalization
anterior
front
posterior
back
dorsal
back
ventral
front
cephalization
- possess head where central nervous system and sensory organs are located
digestive system in platyhelminthes
incomplete digestive system
- mouth but no anus
- some of these worms don’t have a mouth and absorb nutrients through their specialized skin
- tegument with microtrix to enlarge surface area for absorption
excretion and respiration in platyhelminthes
- simple diffusion
- flattened body aides in process, easier for diffusion to occur
Platyhelminthes
- Turbellaria
- Monogenea
- Trematoda
- Cestoda
types of turbellaria
- free living flatworms
- dugesia (planaria)
types of monogenea
- small ectoparasites
types of trematoda
- larger ‘flukes’
- endoparasites
types of cestoda
- tapeworms
Dugesia
- type of turbellaria
- also called planarian
- freshwater, tremendous powers in regeneration
digestive system of dugesia
- y-shaped with reversible pharynx for feeding
turbellaria reproduction (dugesia)
- asexually by fission (fragmentation)
- sexually via complex organ system (syngamy)
- monoecious
characteristics of Monogenea
- ectoparasite
- don’t harm host
- attach via a haptor to host
- only sexual reproduction (only produce one adult at a time)
characteristics of Trematoda
- parasitic flukes with two or three hosts per life cycle
- snail is always found in life cycle (intermediate host)
- vertebrate is almost always definitive host
- Clonorchis (human liver fluke)
- both asexual and sexual reproduction
parasites
- loss of sensory structures
- loss of organ systems
- increased reproductive ability
definitive host
where parasite has sexual reproduction
intermediate host
parasite has asexual reproduction
characteristics of cestoda
- includes tapeworms
- are endoparasites of vertebrate digestive system with highly specialized anatomy
- anatomy consists of series of proglottids and a ‘head’ bearing a scolex
- monoecious
types of cestoda
- Taenia (beef tapeworm)
-
scolex
hooks or suckers
What is found inside a proglottid?
- reproductive organs (both male and female)
- nerve cords
- flame cells for excretion, excretory ducts, muscles and parenchyma
characteristics of platyhelminthes nervous system
- have up to five pairs of nerve cords
- freshwater flatworms, there is a ladder-type = one pair of lateral nerve cords connected to cerebral ganglia
osmoregulation in platyhelminthes
- flame cells lined with cilia drive fluids through a series of tubules which open to outside through series of pores
life cycle of clonorchis
- ingested and burrows into the bile duct of the liver
- egg containing miracidium (larvae) travels through intestines and defecated
- snail ingests the egg
- the egg hatches and the miracidium feed on the snail tissue and becomes germ tissue (redia) via asexual reproduction
- this germ tissue is called a sporocyst, they release redia
- redia release cercaria via asexual reproduction which travel through water and imbed themselves in fish
- they become the metacercarial cyst in the fish muscle and wait to be ingested by final host
- cyst develops into adult and sexually reproduces to begin life cycle again
Clonorchiasis
- caused by Clonorchis sinensis
- life cycle is broken by sanitary disposal of human feces and cooking fish throughly
Schistosomiasis
- infects 300 million worldwide
- caused by human blood fluke, Schistosoma sp.
- female lives an external canal of male
- dioecious
differences in life cycle of schistosoma
- cercariae burrow directly into skin of humans wading in water
- cercariae enter human blood stream and give rise directly to adults
causes of eggs in schistosoma
- pass from circulatory system to digestive system and are voided in feces
- considerable damage occurs; eggs cause ulceration of linings of intestines and urinary bladder
- can cause cirrhosis of liver
Swimmer’s Itch
- caused by cercaria of trematode fluke
- temporary dermatitis in human skin
- humans are the wrong definitive host for fluke, so cercariae penetrate human skin, but don’t survive
life cycle of beef tapeworm
- gravid proglottid is released through fecal matter of humans
- shelled larvae is released
- contaminated grass is eaten by the cow and ingested
- cysts form in the muscle of the cow
- develop into a invaginated scolex/cysticercus
- the meat is then cooked and if not cooked throughly it will continue to live and then be ingested into human and repeat life cycle
tapeworm facts
- only about 1% of cattle are infected with this in america
- throughly cook meet to avoid it
- can live in dogs, cats, humans
- can be found in meat, poultry or fish
- some encyst in organs
- some cause more serious pain
