The weather is slowly taking a turn for the worse now, so if there is a window to get in the water I am ready for it (I am absolutely dreading the coming half year of wind, rain, darkness and no snorkelling or diving!). Last weekend I took a look underwater in my local seagrass patch in Flushing. The viz was not great at all (as anticipated), so I was looking to do some macrophotography. I clocked plenty of egg masses and indeed some Polycera quadrilineata, which is one of the more common species here in Cornwall but up there with the prettiest! Individuals of this species are often white with yellow stripes and dots, but they can have black lines as well. After taking ages reviewing shots full of backscatter and re-positioning my strobe, the photos started to work out. I noticed one blade of seagrass with two individuals side by side. I suspected they were mating but as they are quite small and my eyesight is getting worse, the anatomical action that was going one only became apparent reviewing the photos back on land. Nudibranchs are simultaneous hermaphrodites and when they mate act both in the female and male role. In the pics below you can see the sexual organs protruding from their right flank. Interesting!
I was on a roll and I pretty much stayed the entire dive on the same square meter, taking photo after photo of the slugs around me. I follow the ‘spray and pray’ routine of photography to make sure at least some of the pics are in perfect focus and without overblown highlights, although the downside of this method is that you have to wade through 200+ pics afterwards. Using the nauticam cmc-1 wetlens I managed to get ‘supermacro’ and was rewarded with some really nice head shots, showing oral flaps, foraging on bryozoans on the seagrass and the slugs generally being very pretty! I am getting more and more into nudibranchs now and hope to find some other species before the sea turns too choppy!
P.S. The previous post was all about low depth of field images; for the photos in this post I took the opposite approach and used the smallest aperture available.
I am frequently amazed by the ability of animals to be perfectly camouflaged. Here are three examples of local crab species that do an impressive job of blending in. Above, the Furrowed (or Pebble) Crab (Xantho hydrophilus). An abundant species – multiple individuals will hide under every rock you lift up on the shore. Below a Broad-clawed Porcelain Crab (Porcellana platycheles) which also lives under rocks, flat and covered in tiny hairs. (This is actually not a true crab but the product of ‘carcination’ where non-crabs have evolved into a crab-like form. This has happened independently in at least five Crustacean lineages.) Finally a Green Shore Crab (Carcinus maenas) which is abundant in many locations although not so much locally. There are even better examples of crab camouflage around, but I either do not have good photo of them (Spider Crabs decorating themselves with sponges and seaweeds), or have never seen them myself as they live in water deeper than I normally dive (the Sponge Crab).
A nudibranch, a snail and a seaslug crawl into a bar…no seriously, what actually is the difference between these three types of molluscs? According to Kerney and Cameron (1979), those animals that cannot fit into their shell are called slugs, and those that can are called snails (definition brought under my attention by Ian Smith, see his amazing species accounts of British molluscs on flickr: Morddyn). Seaslugs either have an outer shell in which they cannot retract, an internal shell or no shell at all. The Solar-powered seaslug (Elysia viridis) pictured above is a species without a shell that is an example of a seaslug. Nudibranchs are a type of seaslug with ‘naked’ (nudi) gills (branchs) on their back. Nudibranchs never have a shell (although many have one when they are a larva). Books on nudibranchs often include seaslugs and sometimes they even feature snails! This happens when these species are related to seaslugs (the ‘lathe acteon’ or ‘beer barrel’ Acteon tornatilis is an example of that – a goal of this year is to take a good photo of that species). I have posted a range of photos on here as an illustrations of seaslugs (or not!); read the captions for species info.
I realised I had not posted (much) about this year’s rockpool snorkels so I am taking the opportunity to post a ‘picdump’ with a whole array of tiny species. These photos were taken with a macrolens, and for most a wetlens was used for even greater magnification. Above the White Tortoiseshell Limpet Tectura virginea, a tiny species living on calcified red seaweed. I have added species names to the photos below.
