About NZ's Nudibranchs
The meaning of Nudibranch, is ‘Naked Gill' as this refers to the feathery growths that are located near the rear end of the animal. These function as a breathing apparatus. There are over 80 known species of Nudibranchs from New Zealand waters. One of the best places to see the spectacular blue and brown gem Nudibranch, (Dendrodoris denisoni), and Verco's Nudibranch (Tambja verconis), resplendent in gold and blue is in the warm waters around the Poor Knights Islands.
In contrast to this, New Zealand's largest and ugliest species, is called the Wellington Nudibranch. It is capable of reaching a maximum length of 20 centimetres, has an orange body and is covered in large wart-like growths.
Strategic Defences
As Nudibranchs are carnivores they feed specifically on sponges & sea firs (Hydroids) as well as sea squirts. Lacking the protection of a hard shell it might be thought that their soft bodies would make easy prey for fish and starfish alike. This is not the case, as most predators avoid them due to their defence mechanism that contains unpleasant chemicals in their bodies. However, the Roboastra luteolineata preys on fellow nudibranchs.
The pink and white Jason's nudibranch (Jason mirabilis) has a remarkable defensive system. They feed on polyps and by some unknown method, they incorporate the hydroids stinging cells into growths (cerata) on their backs.
Any predator biting into these growths will trigger the stinging cells receiving a dose of poison. Scientists think the bright colours of Nudibranchs are adaptive strategies that warn predators of poisons or nasty-tasting chemicals.
Sea Hares of NZ
There are eight species of Sea Hare in New Zealand. The fleshy slugs have prominent tentacles that with some stretch of the imagination could resemble the ears of a Hare. With some species a small internal shell protects their gills. They are all herbivores, feasting on succulent seaweeds that provide adequate camouflage. In the case of predators getting too close they have the ability to shoot out a poisonous purple dye.
Interestingly enough, Sea Hares are hermaphrodites, meaning each animal has both male and female sex organs. Mating often occurs in mass groups as they line up to fertilize the eggs of the next animal in front. They release their eggs in a colourful tangle, with the resemblance of knitting wool or spaghetti.
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This stunning shot was taken by Andrew Simpsom
Jasons Mirabilis taken by Andrew Simpson
Tambja Nudibranch. Photo by Peter Morris
Tambja Verconis. Unknown Photographer
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