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Solution


Q.

A jawless fish, which lays eggs in fresh water and whose ammocoetes larvae after metamorphosis return to the ocean is             [2015]
1 Neomyxine  
2 Petromyzon  
3 Eptatretus  
4 Myxine  

Ans.

(2)

Petromyzon (Lamprey) belongs to the Class Cyclostomata of Phylum Chordata. It is a jawless fish which lays eggs in fresh water. The eggs hatch in about 3 weeks into minute transparent larvae called ammocoetes. After metamorphosis, the young lampreys swim down to the sea where they remain for 3 or 4 years before reaching maturity, when they once again migrate to streams or rivers to spawn and die. Gonads become mature at that time when adults return to rivers for spawning.