6 sea stars to see in South Australia

6 sea stars to see in South Australia

Is it a sea star or a starfish? Find out and learn about the six most pop­u­lar species you’ll find in SA waters.

To quick­ly clear things up, it’s a sea star. Back in the day they were known as starfish, but marine sci­en­tists have replaced it with sea star because, well, the starfish is not a fish.

The sea star is actu­al­ly an echin­o­derm, which is close­ly relat­ed to a sea urchin. 

Inter­est­ing­ly, sea stars have a mouth under­neath, a butt on top and a stom­ach inside. Their stom­ach can be pushed out of their mouth and onto their prey to feed. The arms of a sea star also con­tain diges­tive glands to help process food.

South Aus­tralia is home to one of the small­est species of sea stars, which grows up to one cm, as well as some large species which span about 50 cm across. 

Here are six pop­u­lar species you’ll find in SA waters:

1. Bis­cuit star 

The pret­ty, five-point­ed bis­cuit star is one of the most com­mon sea stars in SA.

Bis­cuit stars grow to about 10 cm across and have a large vari­ety of colours and pat­terns, and some­times a cen­tral star-burst pat­tern of a con­trast­ing colour. 

They are found on reefs and oth­er hard sur­faces, from the inter­tidal zone down to about 40 m deep. Look for them on the sur­face of jet­ty piles too, espe­cial­ly near sponges and sea squirts, which are their pre­ferred food.

Bis­cuit star. Sci­en­tif­ic name: Tosia aus­tralis (image cour­tesy of R. Agarwal) 

2. Vel­vet sea star 

Also known by divers as Patrick’ from Sponge­Bob Squarepants, vel­vet sea stars are found across south­ern and south-east­ern Aus­tralia, and around islands off east­ern Australia. 

This five-armed species is com­mon­ly seen on shal­low reefs and down to about 60 m deep. 

The vel­vet sea star is quite large, mea­sur­ing up to 16 cm across. They have smooth skin, usu­al­ly red, orange or cream with red mot­tling. Rings of lit­tle sacs called papil­lae pro­trude from the skin sur­face, which allow gas exchange, like breathing. 

Vel­vet sea star. Sci­en­tif­ic name: Petri­cia ver­nic­i­na (image cour­tesy of J. Baker) 

3. Car­pet sea star 

The very colour­ful, eight-armed car­pet sea star is com­mon­ly seen in rock pools in some parts of south­ern and south-east­ern Australia. 

It prefers wave-exposed loca­tions rather than shel­tered waters, and eats a wide vari­ety of small marine ani­mals and plants that live between and below the tideline. 

Car­pet sea stars can be a sin­gle colour or mix­ture of shades and pat­terns. Their colour­ing is usu­al­ly pur­ple, mauve, blue and green, orange, red, maroon, brown and grey.

Car­pet sea star. Sci­en­tif­ic name: Meridi­as­tra cal­car (image cour­tesy of sea-kangaroo)

4. Eleven-arm sea star

This large sea star grows to about 50 cm across and is the biggest sea star in south­ern Australia. 

As the name sug­gests, this species usu­al­ly has 11 arms, but arm num­bers can vary between sev­en and 14. The eleven-arm sea star can drop some arms when stressed – and regrow them. 

Two new sea stars can grow from a sin­gle eleven-arm sea star split­ting in half (bina­ry fis­sion) and – incred­i­bly – a whole new sea star can grow from one bro­ken arm! 

The star can be found at a broad range of depths in reefs and oth­er hard sur­faces, rub­ble and sandy sea floors. 

Eleven-arm sea star. Sci­en­tif­ic name: Cosci­nas­te­rias muri­ca­ta (image cour­tesy of Peter – fiftygrit) 

5. Six-armed cush­ion star 

This sea star is usu­al­ly less than 10 cm across and can be found across south­ern Aus­tralia in shal­low reefs, sea­grass beds and under inter­tidal rocks. 

Its six arms are short and have web­bing between them. Arms are usu­al­ly coloured dark pur­ple or maroon, and have bright orange tube feet underneath. 

Their diet includes red algae, lit­tle sea­weeds that grow on sea­grass­es and many kinds of inver­te­brates, such as sponges, sea squirts and worms. 

Six-armed cush­ion star. Sci­en­tif­ic name: Meridi­as­tra gun­nii (image cour­tesy of keggy_buoy)

6. Gran­u­lar sea star 

This five-armed, reef-dwelling sea star grows to about 20 cm across. They have wart-like lumps called tuber­cles on their arms. 

Like the eleven-armed sea star, the gran­u­lar sea star can drop arms when stressed, and regrow them, as well as grow that arm into a new sea star. 

Gran­u­lar sea stars feed on sea squirts and bivalve molluscs. 

Gran­u­lar sea star. Sci­en­tif­ic name: Unio­pho­ra gran­i­fera (image cour­tesy of D. Muirhead) 

This sto­ry and images were pre­pared with the help of Marine Ecol­o­gist and Edu­ca­tor Janine L. Baker. 

Read about some oth­er marine species you can find in SA marine parks, like blue dev­il fish,cut­tle­fish, and oth­er baby marine ani­mals. Or you might like to learn about a recent sur­vey­ing expe­di­tion to the Fleurieu’s rocky reefs and what makes them so special.

Main image: Vel­vet sea star – Petri­cia ver­nic­i­na (image cour­tesy of John Turnbull)

This con­tent was pro­duced in part­ner­ship with  Good Living