By Jenny Edwards
The rocky shore invertebrate that is your nearest relative is probably the Cunjevoi or sea squirt. You wouldn’t think that this rough, leathery, motionless blob could be in any way similar to a human. Then again, some would say they know people just like that.
The larvae of Cunjevoi (Pyura stolonifera) and other sea squirts look a bit like tiny tadpoles and have a spinal chord but no backbone. They also have a rudimentary brain and eye spots. After a brief life of a few hours in the plankton the little “tadpole” attaches itself by the head to something solid near low water mark. It then transforms itself.
The tail is absorbed and the body rotates so that the mouth is away from the attached part. The creature then grows into a roughly cylindrical column with a tough, irregular outer coat or tunic that has two openings. The mouth opening leads into a sack which is perforated with thousands of gill slits. Sea water is drawn in at the mouth and food particles as tiny as bacteria are filtered out at the slits before the water current leaves through the “squirt” opening. The gills also extract oxygen from the sea water.
Naturalists were puzzled for thousands of years by this strange family of creatures. It wasn’t until 1866 when a very patient and brilliant Russian scientist, Kowalevsky, reared them through all the stages of their life that their true relationships were discovered.
Cunjevoi grow massed together where the waves are roughest near the low water mark and can also be found growing on wharf piles where there are strong currents of sea water, such as in Batemans Bay. The crevices between them provide a relatively sheltered home for hundreds of other animals so they are a very important part of the intertidal ecosystem.
The name Cunjevoi comes from the Aboriginal word used by the people of Brisbane Water. These sea squirts were used as food by Australia’s original inhabitants and are valued as bait by today’s fishers. The cut bodies of Cunjevoi can be seen on rock platforms everywhere but NSW Fisheries has now set a bag limit of 20 to help reduce the destruction. Cunjevoi are fully protected in Sanctuary and Habitat Protection Zones of the Marine Park.