Species of the month: Eight-armed Sea Star
The Eight-armed Sea Star (Meridiastra calcar) is a common sea star found on reefs and under rocks throughout much of Australia, from southern Queensland to south-west Western Australia.. It is brightly coloured, and as you can see from the photos below, ranges from bright oranges, reds, and browns, to greens and blues on the upper surface. This colour variation is genetically controlled and can vary greatly between individuals in the same rockpool. They are omnivorous, feeding on both algae, mussels and other animals swept into rockpools.
Sea stars have been commonly known as starfish in the past, but biologists are trying to phase this out as they are not fish! Sea stars belong to a group called echinoderms (meaning spiny skin), which includes sea urchins and sand dollars. Echinoderms have radial symmetry, often having five or multiples of five arms.
Recently Rose explored a reef at Cape Douglas and found these excellent examples of colour variations. If you’ve seen any, Jess would love to see photos.
Eight-arm Sea Star (Meridiastra calcar), Cape Douglas (Photo: Rose Thompson)
Eight-arm Sea Star (Meridiastra calcar), Cape Douglas (Photo: Rose Thompson)
Eight-arm Sea Star (Meridiastra calcar), Cape Douglas (Photo: Rose Thompson)
Eight-arm Sea Star (Meridiastra calcar), Cape Douglas (Photo: Rose Thompson)
Eight-arm Sea Star (Meridiastra calcar), Cape Douglas (Photo: Rose Thompson)
