British Sea Creatures

By Tooni Mahto (Marine Biologist and Britain's Secret Seas presenter)

Plankton

Some of the most wonderful in their weirdness are also the smallest - if just a single member of the planktonic community was blown up to human sized, it would be the best-known eccentric creature on our planet. As it is, a microscope is generally required to fully appreciate the ugly majesty of some of these little bugs. Most of the species that attach to the bottom of the sea have larvae that drift in the water column, and there appears to be no physiological relationship between a larva and what it will eventually turn into - the caterpillar/butterfly equivalent.

Barnacles

From head-on, barnacle larvae look like disembodied horned and hairy cat-heads, but when they eventually weld themselves to the rock, they morph into recognisable barnacles that (to scale) have the largest penises in the animal kingdom. How else are you going to pro-create if you're stuck to the floor and your nearest hope to project your genes into the future is similarly adhered?

Copepods

Some members of the plankton are lifers. Copepods cruise the shallows for their entire existence; these transparent, elongated bed bugs with frills are world-class, predatory speed machines, shooting around at about 500 body lengths per second. Admittedly, most are less than 1mm long, but there are few other creatures on the planet that can achieve those kinds of speeds.

Coccolithophores

Coccolithophores are tiny calcareous members of the plankton, but so beautifully tessellated they look like an Escher design. Collectively, a coccolithophore swarm can be seen from space as a creamy psychedelic swirl in a blue sea, which is a timely reminder of the massive importance this biomass of microscopic beings has to our planet - they're food for bigger beasts, but also a sink for our excess atmospheric carbon and the algal component produces about half of the oxygen in our atmosphere. Never under-estimate the power of plankton.

Sea Squirts

One of the strangest groups of creatures of all is the sea squirts. Their comical title belies the fact that although they are still invertebrates, they actually belong in the same phylum as we do - the chordata. Take, for example, the baked bean sea squirt. Looking like, well, a baked bean with two tubes sticking out of it, its larval phase has a notochord, the primitive back bone that makes these filter feeding invertebrates one of our closest marine relatives. After getting into the 'nearly a vertebrate club' during it's juvenile stage, it performs a volte face into true backbone-less existence attached to the sea floor, and then spends its existence inhaling seawater, exhaling seawater, inhaling, exhaling... you get the picture.

Molluscs

If pressed to choose a favourite phylum, and it has to be said that hasn't happened up to this point, I would have to go with the molluscs. Who can resist the strange charms of an iridescent cuttlefish, a bulbous octopus or a bug-eyed squid? They all glisten with certain intent, as though they know what you're thinking. Mind readers they may not be, but intelligent they are - although animal 'intelligence' is a hotly debated topic, octopuses that can use tools, figure their way out of mazes and are master escapologists and rate higher on the intellectual scale than many Homo sapiens I have come across. In fact those in the cephalopod class are given 'honorary vertebrate' status in the UK, meaning they're afforded the same legal protection as a vertebrate animal. Most species are the ultimate masters of disguise, spotting them whilst diving always proves tricky, but a flicker of movement gives them away and you can watch a cuttlefish manoeuvring like a stealth bomber, the tiniest ripple of its mantle turning it to any angle, until it shoots off, powered by water fired jet propulsion. I've often envied their millisecond swift ability to change colour and texture. Just imagine shifting from zebra stripes to glitter ball and the effect that would have, hence the mating ripples of most cephalopods tend to be rather dramatic. Who can ever tire of beings that have blue blood and four hearts?

Limpets

Even limpets are pretty marvellous. I have always been touched by the idea of a limpet returning to its home-scar at the end of a long forage session, to its own comfortable rock depression, nestling down like an old man into a well loved armchair. Although a limpet's carved rock face is the line between desiccation and living to graze another day. Once upon a time, Victorian scientists marched along beaches and expostulated theory as fact, deciding that limpets navigated according to the angle of the sun and moon, the polarization of light and recognition of the undulations of the rock. Impressive for something that on first glance appears so conically basic. As it turns out, they follow chemical clues left in their slippery trails, but they are specific enough to be able to pick out their own slime from all the other limpets that are busily going about their business, like using your sense of smell to navigate through London.

Curious creatures

It would be a very long read indeed to go into all the peculiar species around our shore, so I shall end with the most curiously named critters I could find. There's the sea hare that's more of a tortoise at cruise speed; with an internal shell wrapped in soft undulations of tissue, they're bizarre horned molluscs that take on the colour of the algae they eat. There's the sea mouse that is actually a hirsute worm, and whose genus name, Aphrodita, is inspired by the Greek Goddess of Love, Aphrodite, although looking at them the question 'Why?' does seem valid. The bloody Henry starfish is a deep, sanguine red starfish that everts its stomach to digest its food outside of its body. Then there's the sea potato that is an urchin and the sea gherkin that's a sea cucumber that can shift its skin structure from gloopy flaccidness to the sausage-firm at a moments notice. The elaborately entitled By-the-wind-sailors are colonial organisms, with polyps making up a hard disc that sits above the water and catches the wind, whilst propelling stinging tentacles to wreck predatory havoc on unsuspecting plankton. Their cousin, the Portuguese man o'war, employs the same eating tactics, but it floats on a large bubble topped with a purple mohican and has 20-metre long tentacles dangling ominously below. Both species are warmer water inhabitants, but an inhospitable wind results in mass standing's on the west coast.

British seas are the most magical of locations, whether you're by the sea, on it or in it. The diversity of differences never fails to astound me, and every time I go on the hunt for another peculiar beast I never am left wanting. We have an astonishing array of marine wildlife of all sizes, shapes, curious foibles and incomprehensible forms, and it's up to us to ensure there are safe havens for them all, from basking shark to barnacle larva.