Starfish

The fossil in question: Cantabrigiaster fezouataensis from the Lower Ordovician (Tremadocian) Fezouata Shale, Zagora Morocco
The fossil in question: Cantabrigiaster fezouataensis from the Lower Ordovician (Tremadocian) Fezouata Shale, Zagora Morocco

Starfish-like fossil holds clues to evolutionary past

A well-preserved fossil dating back 480 million years is being used by researchers at the University of Cambridge to decipher the origins of the modern-day starfish.

Named Cantabrigiaster fezouataensis, the fossil was discovered in Morroco's Anti-Atlas mountain range. Frozen in time for 480 million years, the fossil yields features that are similar to both sea lilies and modern-day starfish.

The crown-of-thorns starfish can sometimes be hard to spot using traditional survey methods.

New test to detect crown-of-thorns starfish

Outbreaks of crown-of-thorns starfish (CoTS) are bad news for coral reefs, so it is essential that they are detected and dealt with as soon as possible.

But detecting an outbreak in its early stages is not easy. What’s more, they sometimes hide under coral plates, while the younger ones can be as small as just a few millimetres.

To counter this, the researchers at the Australian Institute of Marine Science (AIMS) developed a new test to detect the presence of the starfish on coral reefs.

Ochre Starfish wait out the low tide on a rocky shore off Vancouver Island
Ochre Starfish wait out the low tide on a rocky shore off Vancouver Island

Ochre starfish have a cooling system

The Ochre starfish Pisaster ochraceous is most commonly found in the Northeastern Pacific, where, at low tide, it can often be seen in tidal pools and sitting tucked away in rock crevices.

During low tide, it is exposed to the air and cannot move until it is submerged again at high tide. If it is also exposed to the sun, it can suffer heat stress.

Pisaster ochraceous can be found on wave-washed rocky shores, from above the low-tide zone to 90 m in depth. Because they can live in shallow water they need to survive in these living conditions, including strong surges, big temperature changes, dilution by rainfall, and dessication. Pisaster ochraceous is very resistant to dessication and it can tolerate a loss of thirty-percent of its body weight in body fluids.