How many nuclei is present in the mature cyst of E. histolytica?
Correct Answer: 4
Description: Mature cyst of Entamoeba histolytica has 4 vesicular nuclei. Such cyst represents the infective form and pass out of the host in feces, after which the glycogen and chromatoidal substance are slowly metabolized and disappear. Initial cyst of E histolytica contains a single nucleus, a glycogen vacuole, and one or more large cigar shaped ribosomal cluster known as chromatoid bodies. Cysts of E.histolytica are highly resistant to desiccation and even to ceain chemicals. Cysts in water can survive for a month while those in feces on dry land can survive for more than 12 days. They tolerate temperatures up to a thermal death point of 50 C, chlorine concentrations normally found in municipal water supplies, and normal levels of gastric acid. Humans are the principal hosts and reservoirs of E histolytica. Transmission from person to person occurs when a parasite passed in the stool of one host is ingested by another. Ref: Ray C.G., Ryan K.J. (2010). Chapter 51. Rhizopods. In C.G. Ray, K.J. Ryan (Eds), Sherris Medical Microbiology, 5e
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