Our recent caving expedition produced numerous photos of starfish. This then prompted a wiki investigation.
Nom, Nom, Nom – Sun Star (Stichaster Australis) vomits its way through some mussels at the Bay with the Dragon Boat Rock.
This particular starfish (Stichaster australis), commonly known as a Sun Star, or patangaroa is native to New Zealand, found mainly on the South Island and West Coast.
It is known for being a fierce predator. Who knew we were in so much danger?
Fortunately it’s easily recognized by its distinctive 11 arms.
Sun Star’s primary prey is green-lipped mussels and apparently it can lick entire rock faces clean. (According to DOC it performs an important ecological function, as its voracious appetite allows other less common mussels to survive).
And now some general starfish trivia:
- Starfish are an echinoderm.
- Unlike almost every other animalian life-from, starfish exhibit radial symmetry instead of bilateral symmetry. They typically have an odd number of arms, the most common is five. The number of arm varies from species to species.
- Their mouth is underneath and anus is on top.
- They have a microscopic eye at the end of each arm, which allows them to detect light and dark.
- They move via an elaborate hydraulic vascular water-pumping system.
- Yes, they can move. They can even hunt, but only tend to catch very slow moving things.
- The funny eye looking thing on top of the starfish is a water filter (madreporite), and supplies it with water to its vascular system.
- They have two stomachs. One is an internal stomach used for digestion. The second is an external stomach which the starfish can vomit out and use to engulf its prey. After it has digested the nutritious bits it swallows the stomach back into its body.
- They have no brain, but do have a central nervous system.
- If you chop off an arm it grows back.
- If you chop off an arm, and include a bit of the central starfish, an entire starfish grows back. I think this means you can create 11 new Cave Bay starfish if you happen to have an 11-sided cookie cutter. Must investigate…