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Animal Kingdom

Multiple Choice Questions

181.

'Water vascular' system is found in

sea-anemone
sea-pen
sea-cucumber
sea-horse

182.
Retrogressive metamorphosis occurs in

Hemichordata

Cephalochordata

Urochordata

Vertebrata

Urochordata

Metamorphosis is a change from the juvenile to adult stage in which larval stage is quite different from the adult stage.

In retrogressive metamorphosis, the larva possesses advanced characters which are lost during the development and the adult is either sedentary or degenerated with primitive characters.

Urochordate adults, being sedentary show degenerative characters, while the free swimming tadpole larva shows advanced chordate characters which are lost during metamorphosis. Parasitic crustaceans, like Sacculina and copepod parasites and stylopids and scale insects (Insecta) also show retrogressive metamorphosis.