Marine Institute

Marine Invertebrate Questions & Answers

Marine Invertebrates are animals that don't have a backbone.  See the following questions and answers for more information about crabs, lobsters, jellyfish and more.

Can crabs swim?

Most crabs crawl or walk along the ocean bottom.  However the velvet swimming crab can swim through the water column. They have a pair of paddle shaped legs at the very back of their body that help them propel through the water.

How do crabs/lobsters grow?

Crabs and Lobsters shed their shell and grow a new one. A crab’s hard shell limits the growth of the crab so when they want to grow bigger they must crack out of their old shell and find a hiding place as they are very soft and vulnerable to predators at this time. They then absorb water into their body and expand, allowing a larger shell to be hardened around their body.

Are sea anemones plants or animals?

Although sea anemones resemble plants they are in fact animals. Their long tentacles act like arms to grasp their prey and pull it into their mouth which lies in the centre of their body. They also have stinging cells on the tips of each tentacle which stun any fish to come in contact with them and thus help the anemone catch their prey. 

Can you eat jellyfish?

Yes, you can eat some jellyfish. For example, Rhopilema hispidum, R. esculentum and Nemopilema nomurai are all edible jellyfish.  Before being sold they are processed in a manner that deactivates the stinging cells of the tentacle making them safe to eat. In some countries they are considered a delicacy and are considered to be a healthy and nutritious food.

Do starfish have eyes?

Yes, starfish do have eyes, but not like human eyes. They have a small “eye spot” on the end of each arm that is able to sense light. These eye spots are not sophisticated enough to make out images but the starfish also uses their sensitive tube feet to navigate along the sea floor.