(vi) Nautilus

The nautilus is native to deep ocean waters. It has a multi-chambered shell. Each chamber is sealed and contains gas which provides the nautilus with buoyancy to float. Like the octopus, squid and cuttlefish, the nautilus uses jet propulsion to move forward. It sucks in water, then expels it in a fast, strong stream to propel itself forward.

The nautilus has as many as 90 small tentacles that it uses to catch food, such as shrimp, fish or small crustaceans. It then uses its powerful beak to crush the food. The nautilus is considered a living fossil because its form has remained unchanged for over 400 million years.

(vii) Echinoderms: Starfish, Sea Urchin and Family

Echinoderms are marine animals that live in the ocean. Common echinoderms include the sea star, sea urchin, sand dollar and sea cucumber. Most echinoderms have arms or spines that radiate from the center of their body. The central body contains their organs, and their mouth for feeding.

Sea stars, commonly known as the starfish, have 5 or more arms attached to their body.

On the bottom of the Starfish are small tube feet to help with movement and feeding. The starfish’s mouth is underneath and is capable of eating other sea life such as clams and mussels. Another type of echinoderm is the sea urchin. Sea urchins have many spines connected to their body. These spines help to protect them from predators.

(a) Starfish

The starfish or sea star is native to all of the world’s oceans. There are about 1,800 different species of starfish with the greatest variety living in the tropical Indo-Pacific region. Most starfish have five arms, although some have fewer or more arms. Like other echinoderms, starfish have small tube feet on their underneath body to help with movement and feeding. The starfish’s mouth is underneath, and it has two stomachs in the mouth. The stomach sack can come out through the mouth to engulf and digest food, such as clams and mussels.