Trematodes (Flukes)

Small, flat, leaf-like worms, flattened dorso-ventrally with @@no body cavity@@
Body mass consists of: @@mesodermal parenchyma@@, where internal organs are embedded
@@Oral and ventral suckers@@ that help attach to the host
Infest various organs of the human host
* e.g. intestinal veins, urinary bladder, liver, lung
Use @@freshwater snails@@ as an @@intermediate host@@

Liver Fluke

Domain: Eukaryote

Kingdom: Animalia

Phylum: Platyhelminthes (flatworms)

Class: Trematodes (flukes)

$Hermaphrodite$ : organism that has both kinds of reproductive organs and can produce both gametes associated with male and female sexes

Life cycle beginning: hermaphroditic adult fluke produces %%eggs in the human%% (definitive host)

eggs are %%excreted%% into the environment
first larval stage (miracidium) develops inside the eggs
the larvae seek out and infect suitable %%snail species%% (first intermediate host)
%%asexual reproduction%% occurs in the snail
* several intermediate development forms can be distinguished (sporocyst, redia) and the final larval stage (cercaria)
leave the snail and seek out %%second intermediate host%%
* a fish or crustacean
in the second intermediate host, the cercaria form cysts called $metacercaria excysts$
if the infected %%raw or under-cooked fish%% or crustacean is eaten by a human, the metacercaria excysts, and the fluke %%invades tissues%% (such as the lung or liver) and begins %%producing eggs%%

called “blood flukes”
have separate distinct sexes
similar life cycle to hermaphroditic flukes
==only one intermediate host (snail)==
acquired by: schistosome cercaria %%directly penetrating%% the skin in %%contaminated rivers and lakes%%
adult schistosomes take up residence in various abdominal veins
in fresh water, the organisms infect snails (in which they multiply)
* cercaria are released into the fresh water