Question

Name two aquatic animals which have no gills.

Answer 1

Hint: Gills serve the same function as our lungs. Gills extract oxygen from water and send it into the animal’s bloodstream. For this reason, most of the aquatic animals that get oxygen from water are unable to survive on land very long.

Complete answer:
Gill is a type of respiratory organ found in many aquatic animals, including some insect larvae, a number of worms, nearly all crustaceans and mollusks, all fishes, and a few amphibians. The gill consists of feathery or branched tissue richly supplied with the blood vessels, especially near the gill surface, facilitating the exchange of carbon dioxide and oxygen with the surrounding water. The two aquatic animals without gills are whales and dolphins. These animals come to the water surface in order to breathe as they can’t breathe underwater without gills.
Whales and dolphins are mammals and they breathe air into their lungs. They breathe through the nostrils, called a blowhole, located right on the top of their heads. This allows them to take breaths by exposing the top of their heads to the air while they are resting or swimming under the water. After each breath, the blowhole gets sealed tightly by strong muscles which surround it, so that water cannot get into the dolphin or whale’s lungs.

Note: Deep-diving whales such as Cuvier’s beaked whales or sperm whales may go over an hour between breaths. They have high amounts of myoglobin and haemoglobin to store oxygen in their blood and muscles can reduce their heart rate and even may shut down some organs when they dive in the deep to help them survive.