Which of the following show regressive metamorphosis?
Hydatid cyst
Cysticercoid
Cysticercus bovis
Cysticercus cellulosae
Ans. is 'a' i.e., Hydatid cyst(Ref: D.R. Arora, 3rd/e, p. 141)* Regressive metamorphosis: Sometimes, hydatid cyst (containing protoscolices) may rupture in intermediate host to release its content in the tissue. If such a patient survives, the released protoscolices may revert to hydatid cyst instead of developing into an adult worm (Normally protoscolex give rise to adult worm).
Parasitology