BIO 439: Complex Life Cycles: Vocabulary

Miracidium

ciliated larvae of digenetic trematodes; free-swimming forms penetrate foot of snail  

Sporocyst

life stage of digenetic trematodes; produces one redia or mother sporocyst   

Redia

life stage of digenetic trematodes; produces many cercariae  

Cercariae

life stage of digenetic trematodes; free-living body with tail and two suckers; penetrates second intermediate host, loses tail, and then encysts to metacercaria  

Scolex

holdfast or “head” of tapeworms

Strobila

“body” of tapeworm, which is generated from the scolex and consists of proglottids

Proglottids

segments of tapeworms—each consists of a complete of sex organs—immature, mature, and gravid   

Gravid

proglottids containing eggs

Apolysis

terminal proglottids are shed so as to pass eggs  

Metacestode

larval stage of tapeworm that develops within an intermediate host, appearing as a fluid-filled vesicle of cyst  

Cysticercus

metacestode of Taenia spp.  

Cysticercosis

infection with cysticerci of T. solium  

Neurocysticercosis

cysticerci of T. solium present in the brain  

Auto-infection

person infects themselves; one source of T. solium  

Internal auto-infection

if infected with adults passing eggs, then reserve peristalsis could move gravid proglottid/eggs from small intestine to the stomach, prompting infection; one source of T. solium