Yesterday I saw this very charming sea hare, Dolabrifera brazieri, moseying across a shallow pond and grazing on algae, again at Flat Rock, near Ballina, northern New South Wales. It’s about 9 cm when stretched out.
Sea hares are molluscs and have internal shells. They are generally regarded as toxic, and are reported to have killed dogs that have eaten them. They exude a purple dye if they are upset. Some species form head-to-tail chains to reproduce in the warm waters of late summer. They live only a year or so – fast growers.
I first thought the minute orange nudibranch below was Berthellina citrina, which is a side-gilled sea slug and does not have the ‘naked gills’ you can see at the rear of the creature in the second photo below. The top photo shows the size out of water, so scrunched up. The black dots are rhinophores, which are scent or taste receptors (not eye spots). Rhinophores come in all sorts of amazing shapes, sizes and colours.
The photo below shows the nudi in water, and the gills are visible at the back. It looks yellow in the photo, but actually is orange/red as above. Nudibranch expert Gary Cobb says it’s Rostanga arbutus.
Another side-gilled sea slug, seen on an earlier visit, is Pleurobranchus peroni (thanks to Gary again for the correction to my ID). You can see the shell through the semitransparent skin on the back. The ‘side gill’ is under the mantle.
A further live shell of interest seen on a previous visit is the umbrella shell, Umbraculum umbraculum (thanks to Gary for the correction). The white thing in the middle of its back is its shell. It cannot contract into it, hence the term ‘umbrella’ – but maybe ‘parasol shell’ would have been a better name.
I once read a piece about a diver who decided to test the theory that brightly coloured nudibranchs advertise the fact that they taste awful by putting one in his mouth. He confirmed it – a braver man than me.