Which of the following show regressive metamorphosis?: (A) Hydatid cyst, (B) Cysticercoid, (C) Cysticercus bovis, (D) Cysticercus cellulosae
Answer is A. 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).