Sea slug is one of ours
An unusual-looking sea creature that washed up on Ta¯hunanui Beach, prompting an online debate about what it was, has been identified as a sea slug common to Tasman Bay.
The Department of Conservation (DOC) said the sea slug, known as dorid nudibranch, was likely to be a variety named aphelodoris lactuca.
An exact identification was difficult because the slug was out of the water and its key features had retracted.
DOC marine technical adviser Clinton Duffy said New Zealand had a diverse range of sea slug fauna, ‘‘including nudibranchs like the one shown in the photographs.’’ The slug ‘‘appears to be the South Island colour form of the species.’’
Duffy said nudibranchs were common around the world but the species in the image was endemic to New Zealand.
The slug was found out of the water which meant it was likely to be dead or dying as they dry out quickly.
Duffy said nudibranchs were shortlived and some species exhibited boomand-bust population cycles; ‘‘the population increasing rapidly when
conditions are good and then crashing after they have spawned’’.
Not much is known about the New Zealand species.
Duffy said dorid nudibranchs feed on sponges and individual species of nudibranch appeared to prefer particular species of sponge. ‘‘This diet makes them unpalatable to predators and some species are toxic if eaten.’’
Pictures of the sea slug were posted on the Facebook page Nelson Snippets and attracted wide debate about what it was.