Jewel anemones come in a variety of colours

SOME PEOPLE TRAVEL THOUSANDS OF MILES to see a bit of brightly coloured sea-snot.
They do!
Nudibranchs are big business, and not just for photographers, as youll find when sat around the hotel bar or liveaboard saloon after a days diving.
Someone will mention the nudibranchs they saw. I swear that these tiny critters get more love than most of the sharks divers encounter, but then, it doesnt take much to tell the six or seven most-common elasmobranch species apart.
Nudibranchs, on the other hand, come in all manner of shapes, colours and sizes.
Add in their various external furniture and its a mardi gras of species that have divers nose-to-page in as many books as possible.
Yet few of us associate Blightys shores with these colourful sea slugs. Few divers even realise that we have them around the UK. Tell a newspaper reporter, and hell call it a sign of global warming that such tropical marvels should wash up in northern seas.
But nudibranchs have always been here; we just didnt bother to look for them. Take the diminutive Limacia clavigera, a fairly widespread species across the UK from the Scilly Isles up to the Shetlands. It doesnt even have a common name.
This small creature is often passed over by divers hunting for big lumps of metal or larger marine life, but its coloration does make it stand out.
I found several on a Porthkerris shore dive in Cornwall, hunting for their favourite food - encrusting bryozoans.
These mats (one species is called the sea mat) are food for many of the UKs prolific sea slugs.
They grow on kelp and rocks and look almost like a skeleton, but are in fact a colony of individual animals that filter nutrients from the sea.
Clavigera is easily distinguished because, although there are several white-bodied nudibranchs, none of them have its distinctive egg-yolk-yellow-tipped protuberances.

LESS FLAMBOYANT BUT AS UNLUCKY in the naming stakes is Acanthodoris pilosa. This nudibranch can grow to around 5cm and is covered in small bumps, giving the body a puffy appearance. Coloration ranges from pure white to dark brown.
At the head end are two club-shaped tentacles and at the back a fairly impressive crown of feathery gills. These slugs are often confused with the very similar Goniodoris nodosa.
Both are generally found within the mossy mat of life that covers rocky reefs around western coasts as they feed on sea chervil. This bryozoan makes up a large proportion of the toupee of life covering the rocks.

ONE BRITISH SEA SLUG that does have a common name is also found on rocky reefs. Aplysia punctata is smooth-bodied, and its slender face is uncannily like that of a hare - that and its long tentacles are a giveaway that this is a sea hare. Rusty brown in colour, it also lacks external gills.
Sea hares feed primarily on seaweeds and are distributed across the UK, but because they blend so well with their surroundings, they are hard to see. I found the one pictured only because it was traversing some dark stones.
Pick up Paul Naylors book Great British Marine Animals and youll see just how many nudibranch species we have. Some are exquisitely coloured, others brutish in appearance, but all are small, delicate and fascinating to find. All you need is a small section of shallowish reef and keen eyes.
If you cant find a nudibranch, youll still find something of interest. Anemones, for example, are exceptionally widespread.
The larger species such as the plumose are obvious, well-known and often ignored. Many wreck divers know the jewel anemones that live on hulls, but few stop to study them.
A rock covered in jewel anemones is awash with colour not seen outside those Isle of Wight sand-tube tourist trinkets. Thats because of one of the primary means of reproduction for jewels is budding, where one individual produces an identical anemone by branching it off.
Over time, the exposed rocks become covered with wedges of colour because, like many anemones, jewels are all coloured differently. As the colonies bud off, the colour grows outwards

NEAR JEWEL ANEMONES, divers often find clumps of Sagartia elegans, a larger anemone that prefers horizontal to vertical substrate. It is easily distinguished by the classic ring-like pattern that leads out to its fringe of stinging tentacles, quite unlike its neighbour the daisy anemone, which is otherwise similar in size and physical appearance.
The daisy anemones markings are more like wheel spoke lines radiating from the mouth.
One species never mixed up with others is the snakelocks anemone. Its distinctive thin, purple-tipped green tentacles are a common sight from rock pools down to below the kelp-line, although the 8-10m mark within the kelp-zone is the best place to find them.
My interest is less in the anemone but in what shelters within its protective cape of tentacles - Leachs spider crabs.
Scientists dont know the precise relationship between the two species, but its the only place Ive ever found these diminutive crabs.
They cover themselves in weed or sponge for further camouflage, and you need to look carefully within the tentacle mass (particularly on larger anemones) or around the stem.
The crabs are fairly territorial, and
I have seldom seen more than one in an anemone, except when two are fighting over the space. Next time you pass a snakelocks, see if you can find one.

Limacia clavigera hunts through the bryozoan mats that carpet the seafloor.
A pure white Cadlina laevis tucked in to the bryozoan carpet.
juvenile anemone on seagrass frond
gravel sea cucumber
Sagartiogeton undatus anemone in a seagrass field
another jewel anemone colour scheme.
Leachs spider crab inside a snakelocks anemone
Cadlina laevis nudibranch, with gills retracted
another little gem of a jewel anemone
hermit crabs often use parasitic anemones for protection.
a sea hare is much easier to see on dark rocks
Gavin Parsons