Platyhelminthes

Front 1

platyhelminthes nervous system?

Back 1

CNS
nerve ladder:
-Bilobed head ganglion (“brain”)
-Pair of ventrally located nerve cords, and
-Cross-strands connecting the two nerve cords.

Cephalization

Front 2

platyhelminthes excretory system?

Back 2

-Protonephridia (tubules)
-Blind end of each tubule is a flame cell.
-Flagella provide the force to pump water through the system.
-Functions primarily in water balance
-Nitrogenous wastes (ammonia) removed by diffusion.

Front 3

platyhelminthes reproductive system?

Back 3

-May be asexual and/or sexual
-Asexual via transverse binary fission or budding
-Have a highly complicated reproductive system for sexual reproduction.
-Most are hermaphrodites; these individuals are monoecious.

Front 4

platyhelminthes classes

Back 4

Turbellaria (planarians/Dugesia)
Trematoda (parasitic flukes)
Cestoda (parasitic tape worms)

Front 5

how does the class turbellaria eat?

Back 5

-Mostly carnivorous
-Use chemoreception to detect prey
-Entangle prey in mucous secretions
-After wrapping body around prey, extends pharynx for feeding.

Front 6

characteristics of class Trematoda

Back 6

-Parasitic flukes
-Have one or more suckers for attaching to host
-Many have complex life cycles involving one or more host.

Front 7

Life Cycle of Clonorchis sinensis (class Trematoda)

Back 7

-Infects humans and other fish-eating mammals
-Eggs enter water with feces but don’t hatch until ingested by snail (secondary host)
-leave snail as free-swimming CERCARIA
-burrows under fish (temporary transport host) scales and sheds tail, become METACERCARIA cysts in fish muscle
-ingested by humans (primary host)

Front 8

characteristics of cestoda

Back 8

Long flat bodies composed of:
-Scolex (for attachment to host)
-Chain of proglottids (reproductive units) aka STROBILA
no head!

Usually require at least two hosts
-Adults are parasitic in digestive tract of vertebrates.
-Secondary hosts can be vertebrates or invertebrates

No digestive system
Body surface covered with microvilli (MICROTRICHES)

Nearly all are monoecious

Front 9

Describe the body plan for Platyhelminthes

Back 9

Tissue-organ grade of organization, triploblastic, bilateral symmetry (dorsoventrally flattened), acoelomate, incomplete gut (GVC), cephalization present

Front 10

major features that distinguish Platyhelminthes from the other phyla we’ve studied so far (i.e., Porifera, Cnidaria)

Back 10

**no single unique characteristic (SYNAPOMORPHY) for phylum as a whole

Bilateral symmetry (dorsoventrally flattened), triploblastic, CNS and cephalization present, tissue-organ grade of organization

Front 11

Describe the life cycle of Clonorchis sinensis.

Back 11

Eggs produced in liver of adult worm—exit host in feces—egg eaten by snail (second host)—becomes tadpole-like cercaria and swims away—burrows in body of fish and becomes metacercaria—fish eaten by human

Front 12

digestion in Class Cestoda

Back 12

cestodes (tapeworms) do not have a digestive tract. they depend on host digestion and absorb all nutrients across its tegument. the entire surface of cestodes is covered with microvilli (MICROTRICHES) which greatly enlarge the surface area of the tegument.

Front 13

What is the difference between a primary and intermediate (secondary) host?

Back 13

the primary (definitive) host is where a parasite reaches maturity /sexually reproduces. A secondary (intermediate) host harbors a parasite only for a short transition period.

Front 14

What is the function of the cercaria (sa-care-ee-a) larva of the Class Trematoda

Back 14

cercaria are free-swimming larva. their function is to leave the secondary host (snail) and find a new host (fish) to encyst the muscles of (as metacercaria).

Front 15

Describe the life cycle of Taenia pisiformis

Back 15

-Ripe proglottids detach in the human intestine, leave body in feces, crawl onto grass, and are ingested by cattle
-eggs hatch in the cow's intestine, freeing oncospheres (on-cos-spheres=shelled larvae), which penetrate into muscles, encyst, and become "bladder worms"
-human eats infected rare beef, and bladder worms are freed into the intestine where it attaches to the intestinal wall, forms strobila (stro-bye-la), and matures.