nudibranchs

Long time no post! Due to a combination of not-so-good weather and work I have not been in the water much the last few months. I attempted some seaweed photography but most times the viz was bad; the one time the conditions were great, somehow all my photos turned out to be a bit meh and I could not be bothered to post them. (For some older shots on seaweed diversity see here, and many older posts as well.) Anyhow, my exciting news is that I finally bought a new strobe (an INON D-200 for those who are interested) because my old Sea&Sea strobes just proved to be too temperamental. Something I should have done a long time ago, but the thrifty Dutchman in me just never pulled the trigger. I have now taken it out twice this weekend and it works like a charm! Now I just need to practice, as it is actually still very hard to go from an OK photo to a truly good pic. Above a shot of a baby urchin Psammechinus miliaris. The true stars of the weekend however were nudibranchs.

A very special find (shown to me by fellow rockpool photography enthusiasts Martin and Greg) were two Goby egg-eating seaslugs Calma gobioophaga. This tiny species can only be found on the goby eggs it eats. With such a ‘niche niche’ and with very good camouflage it is no wonder that reports of this species are rare. A fun fact: its protein-rich diet means it does not have to poo and it therefore does not have an anus…The rock with the eggs and nudis was very shallow and so it was a challenge to get the port of the camera housing under water. Luckily Greg assisted with pointing out the nudi and holding my strobe in place. Freshly hatched goby fry could be seen hovering above the eggs (the fact that a predator was munching through their brothers and sisters might have triggered some of the hatching). The cerata (the fleshy lobes on the nudi’s back) seem to have two goby eyes in them to make them better blend in!

Finally, two other nudibranch species, neither very colourful. Both are predators of anemones: first the largish Grey sea slug Aeolidia papillosa and second the smaller species Aeolidiella alderi. Both adequate shots but I need to practice to make them truly good. I will probably buy a second INON strobe so I can practice wide angle shots as well when diving. I hope to go out a lot more during summer and will make sure to post here about my finds and progress!

This Saturday I was at the marina in Newlyn, where local natural history expert David Fenwick was kindly showing me how he obtains the samples he finds so many creatures in (worms, copepods, tunicates, forams and many other things). Todays focus was on nudibranchs, arguably the most beautiful group of little critters. David has recorded an amazing 46 nudibranch species from these pontoons alone! As this is the most Southwesterly pontoon in the country, it is a bit of a ‘sentinel site’ for southern species with northward-shifting ranges. Indeed David has found a species new to the UK that has also been discovered in the south of Spain and possibly off the coast of Morocco. He often sends samples away to (inter)national labs for sequencing and further investigation and frequently shares his finds on facebook (see the links page for relevant facebook groups). For all things marine in Cornwall see his website: Aphotomarine, an edicational resource dedicated mainly to the photography and diversity of marine life that is found in the coastal waters and rockpools of south-west England. Also check out his Aphotofungi, Aphotoflora, Aphotofauna and Stauromedusae.uk. Luckily for me, I can show off some of David’s images in this post too.

The drill: scrape off seaweeds (mainly kelps) covered in tunicates, hydroids, other seaweeds and silt (very mucky business, especially when collected lying on a pontoon covered in seagull-excrement). Next, vigorously wash the seaweeds in a bucket. Sieve the resulting silty water, pick out larger objects (sea squirts etc) from the sieve and gently wash the silt away in a fresh bucket. Then transfer the material to a white tray for preliminary inspection. Some nudibranchs can be observed this way, but the bulk of the animals only show themselves after the sample has been brough home. In warm weather, samples can get deoxygenated, so a battery-powered airpump is a good thing to have. To avoid sloshing, plastic vessels are filled to the brim by opening the lid slightly when held underwater.Back home, samples are placed in the fridge and subsamples are periodically checked under the stereomicroscope. Most animals are a bit more active in the cooled water but some are not. Some come out in the dark, others in the light, so changing the conditions is necessary to see everything that is hidden in the debris. David processed the samples that same afternoon and indeed a lot more came crawling out! From top to bottom: Cuthona amoena, C. foliata, Doto sp., Eubranchus farrani, Facelina annulicornis, F. auriculata, Polycera faeroensis, Elysia viridis (juvenile), Palio nothus, Aegirus punctilucens (juvenile) and Polycera quadrilineata (same species at the top of the post). For more beautiful nudibranch photos see the relevant Aphotomarine section. A very cool activity indeed, although at this point in my life I have not enough time at my disposal to do it justice…However, there definitely will be some smaller olloclip-iPhone sessions at Mylor marina soon!