Unusual to photograph Trapania rudmani on this kind of background. It might have been moving between food sources. This was taken at the Poor Knights Islands (Cream Gardens).
It's a right royal pain when a nudibranch doesn't have a scientific name. New Zealand has a good selection of undescribed Trinchesia sp. nudibranchs and without a name how is one supposed to tell one from another in conversation? So I now call this nudibranch the 'rasta' nudibranch, because it has really awesome dreadlocks.
I've had plenty of recent sightings of this small species. Active during the daytime. Consistently in the 8-14 metre range. Egg coils common.
19-Nov-2016 Barren Arch (Splendid Arch), Poor Knights Islands
Despite good sightings I do believe that this nudibranch is rarely seen. It is small and blends in remarkably well with its food source. I attribute my success at spotting this nudi to having developed an eye for recognising its habitat and a patience for sitting there until I locate it.
Discovering a new species is not as easy as you might think. There’s that moment in the water when you’re looking at a creature and it looks kind of familiar but different. You don’t quite know if you’re seeing something ordinary or extraordinary. There's pressure to get photos - no photos, no identification. Once you have photos you start on the research and connect with a scientist. It takes time; there's a lot of uncertainty.
15th October - I was scuba diving at night in French Cove at the Poor Knights Islands. It was one of those sloppy weekends when there’s enough of a swell running so that shooting macro is like trying to hammer a nail in a washing machine... a bit painful.
Mooching around at about ten metres I spotted some small white egg coils. The flash of white in my torchlight grabbed my attention; I saw a small nudibranch moving on a red hydroid. Closer examination revealed three animals and I fired off some shots as best I could in the conditions. I had a feeling this might be a night-active nudibranch. I pictured it hiding within the bushy hydroid during the day. That theory was shot to pieces the next day when I spotted a similar active animal on a reef wall outside of Matt’s Crack. Neat white egg coils were there too.
There was something vaguely familiar about this nudibranch. I searched for a match. The Auckland University Underwater Club's Molluscs gallery is extensive and has a lot of my personal images in it. It didn’t reveal anything. A quick scan of Skip’s (Ian Skipworth's) nudibranch gallery did. There was a single photograph from Dusky Sound in Fiordland from 2006 and a tentative identification of Eubranchus rubeolus.
Fiordland in the deep south of New Zealand is a long way from the Poor Knights Islands. We do have nudibranchs that live across this range though. Jason mirabilis and Aphelodoris luctuosa are two examples, commonly found from Fiordland to the Knights.
I turned to google to try to find out more. The Sea Slug Forum popped up. In 1964 Burn described Eubranchus rubeolus from a single specimen found in Victoria in Australia. In 1971 Miller identified 4 specimens from Dunedin. Then everything went quiet, until Ian Skipworth photographed some animals in Fiordland in 2006. I ran into Skip at a BBQ recently and I asked him about Eubranchus rubeolus. He said he encountered the species just that one time in Fiordland, no encounter since.
Now a nudibranch that looks like Eubranchus rubeolus shows up at the Poor Knights Islands. 1964, 1971, 2006 and 2016 - that’s a long time between records. Clearly an expert opinion was needed so I emailed Dr Richard Willan, Curator of Molluscs at the Museum and Art Gallery of the Northern Territory in Australia. Dr Willan studied side-gilled sea slugs and sea hares at the University of Auckland. He knows a staggering amount about New Zealand's nudibranchs. I’m lucky to be able to call on his help in identifying kiwi underwater molluscs.
Dr Willan reviewed one of my images and took a look at Skip’s photo from Fiordland. While the nudibranchs look similar to my eye, he concluded "differences would certainly exceed variation within a single species". What does that mean? It looks likely that this is a new species of nudibranch.
I'm not laying claim to discovering a new species. We don't have a cohesive group of nudibranch enthusiasts in New Zealand. I can't say how many photos of this species might be floating around. So I'm putting my images and information out there in the hope that it can become an online resource to connect others who might be interested in learning more or sharing more.
Thanks to the power of social media my story doesn’t end here. On the weekend Shane Housham from Northland Dive photographed a similar nudibranch. I wasn’t surprised to learn that his discovery came from Danger Rock, a known nudibranch hot spot just south of the Bay of Islands. He observed a single animal. I note that his images do not show the nudibranch on the red hydroid that appears to be its food source in my images from the Poor Knights Islands.
Here's what I know about Eubranchus sp.
The nudibranch appears to be from the family Eubranchidae - Eubranchus sp. It has been found in a depth of 10 to 12 metres. The animal is small with a length around 10 millimetres. It has a white stripe on its oral tentacles, red speckles on its head, a red/orange cap and inflated cerata with a golden apex. Active specimens have been spotted at both day time and night time. The red hydroid may be its food source.
I need your help to learn more! Have you seen this species? Now is the time to look and look hard. Nudibranchs have a tendency to be short-lived which can make them fleeting in time. I have observations from three different northern dive sites. Can you add to this? Please contact me if you think you’ve seen this species.
Photographic confessions of a nudiholic!