Invertebrates

Sea Stars

Scientific Name

Asteroidea spp.

Other Common Name(s)

Starfish

Body Weight

Depending on species, some might reach 5 kg

Body Length

The largest species, sunflower star (Pycnopodia helianthoides), can be around 1 m in diameter. The tiniest species is only less than 5 mm.

Finger pointing, sea anemone, and diver silhouettes

A five-armed starfish with orange spots on a sandy seabed next to rocks.

Habitat

Ocean

Diet

Clams, oysters and sea snails

Fun Facts

A majority of sea star species have 5 arms, but some grow more – as many as 50. Each arm is covered with tiny tube feet on the underside. Working like mini suction pipes, they allow the sea star to attach to rocks or move slowly on the seafloor.

Sea stars can open the shells of their prey with their tube feet. They extend their stomachs out of their mouths at the bottom, and secrete digestive juice. They then suck in the food before retracting their stomachs.

Close-up of an octopus arm with pink suckers.

Light pink starfish with visible tube feet against a dark blue background.

Red starfish with intricate white patterns on a dark, rocky seabed.

Distribution

Found globally in all oceans from tropical to polar waters

Threats & Conservation

Threats

Urbanisation & Infrastructure
Overexploitation of Biological Resources
Human Disturbance & Ecosystem Disruption
Invasive Species & Diseases
Pollution
Climate Change

Over 20 species of sea stars have declined in numbers due to a lethal epidemic in the past decades. Some scientists have suggested that climate change, which alters sea temperature, may be a trigger. On the other hand, excess carbon dioxide in the atmosphere may acidify seawater and eventually dissolve the shells of marine life. Some sea stars are keystone species and their decline will bring about serious disruption in their ecosystems. Additionally, in certain regions, urban development has directly destroyed sea star habitats and led to sewage runoff into the ocean. Invasive species, such as oysters and crabs, also compete with sea stars for food and space.