Sea Anemones – Natural histories of extraordinary species that changed our world
Visit almost any rocky shore around the British Isles at low tide and you’ll see what look like well-sucked wine-gums glued to the stones. Touch them and they are soft and yielding, almost too vulnerable, you might think, to survive a twice-daily battering from the waves. But with the return of the tide, they blossom like hothouse flowers, extending sticky tentacles to trap small sea creatures. They are sea anemones, creatures that subvert our view of animal life and which, as we’ll find out, may hold the elixir of life itself.
Sea anemones are related to the corals and jellyfish. They have a simple structure, a ring of tentacles that feed small invertebrates or tiny fish into the soft hollow column that acts as a stomach. Food goes in and waste products come out of the same oral disc. Anemones can produce eggs that hatch into free-swimming larvae which, depending on the species, soon settle down on rocks or in mud. They can also reproduce asexually by budding, producing small identical replicas of themselves much as plant bulbs do.
The most conspicuous British species is the beadlet anemone. It anchors itself to rocks, but is also surprisingly mobile and can float or crawl slowly to a better location. They even fight each other in extreme slow motion, using their electric-blue beadlets (acrorhagi) which are just below the rings of their tentacles. These beadlets harbour stinging cells. Each anemone lashes at the other with mini-harpoons which adhere to its opponent’s surface, creating damaging weals. Not to be messed with, these ‘flowers’. They are tough too and can survive exposure to summer heat, drying winds and winter cold as well as varying levels of salinity in their rock pools.
Anemone means ‘wind-flower’ and to our ancestors these strange creatures with their tentacles waving in the ocean currents must have resembled something botanical rather than zoological. For a long time the sea anemone was thought to be a missing link between the world of plants and animals. We’ve endowed some of our common species with two flower names. The dahlia anemone is a thick-tentacled sunburst of a creature which could easily win Best in Show at a country fête, while the daisy anemone is a burrower in mud and sand.
But not all look floral. One of the most spectacular species is the snakelocks anemone which sports long green tresses of violet-tipped tentacles which it is unable to retract fully and so remains open, hence its alternative name, ‘opelet’. Its Medusa-like appearance is very striking as it sways among kelp fronds in rocky gullies. As wide as 20 centimetres across, its bright green colour is the result of algae living symbiotically within its body tissues. Their chlorophyll fixes sunlight filtering through the water and distributes the organic compounds produced by photosynthesis to the anemone. Its tentacles are sticky to touch and loaded with stinging cells with which it catches a variety of small swimming creatures, though one species of crab, Leach’s spider crab, is happy to live alongside or even inside the deadly snakelocks.
Plumose anemones are creatures of the sea-bed and often decorate wrecks and reefs in hundreds or thousands. Their long columns are crowned with a feathery mass of delicate tentacles which both capture plankton and secrete the enzymes needed to dissolve their tiny shells.
Other sea anemones live in mud, or on rocks. One, Calliactis parasitica, rides on top of the shells chosen as homes by hermit crabs. It deters predators that might attack the crab, and happily sweeps up morsels of food that the crab leaves behind: hermit crabs can be messy eaters.
The lives of sea anemones are fascinating enough, but it was their bright colours and ornate appearance that enchanted early naturalists. In the early nineteenth century they became very desirable aquarium animals. The challenge was that it was impossible to keep them alive in glass tanks. Without aeration and the correct amounts of salt and other minerals, the water soon became fetid and the anemones and other marine creatures died.
It was the desire to observe and understand strange underwater life that drove the popularity of aquaria. The idea of keeping plants and aquatic life in glass cases was pioneered by surgeon Dr Nathaniel Bagshaw Ward in the 1830s. He noticed that ferns and other plants thrived in the humidity created by a glass container and that the addition of plants to water allowed its inhabitants to survive for longer. Before this, zoologists such as Anna Thynne had observed that adding weed to water and movement of the water prolonged the life of creatures there, but without realising why. Until Ward’s revolution in understanding how plants could oxygenate aquaria, anyone who wanted to keep fish or marine creatures in still water was forced to change the water daily to prevent it becoming stagnant. This was a tedious and time-consuming process unless, like the marine biologist Sir John Dalyell, you had servants to bring a fresh supply of seawater daily to your house. This combination of wealth and willing servitude, according to one account, allowed him to keep a beadlet sea anemone (affectionately known as ‘Granny’) alive for twenty-eight years: the animal outlived him by decades and was at least sixty-six years old when it finally perished in 1887.
Dr Ward’s invention, known widely as the Wardian case, transformed the study of natural history and sparked a mid-Victorian obsession with collecting aquatic creatures and especially ferns which thrived well in the limited light of gloomy Victorian parlours. Pteridomania, the craze for collecting ferns, swept through the country and fern-sellers could be found at London street-corners, hawking roots ripped from far-flung rural spots. So extensive were their depredations that many fern populations have since failed to recover and some counties lost particularly sought-after species such as the Royal Fern.
Using the expanding steam railway network, Victorian naturalists ventured further afield and were to be seen in favoured places such as Tenby and Torquay swarming over coastal rocks to harvest their bounty. Seaweeds, anemones, starfish and shrimps, all were fair game and it was considered a seemly pastime for women who waded in while their husbands looked on. Some of the collecting was on a commercial scale. Aquaria had become so popular – thanks to the removal in 1845 of excise duties on plate glass which brought its price within the range of the middle classes – that a huge aquarium warehouse was set up near Regent’s Park for the sale of what Rebecca Stott, Professor of English Literature at the University of East Anglia, calls ‘theatres of glass’. One journalist wrote in 1856: ‘In London itself the collecting seems to be at fever point. In West End squares, in trim suburban villas, in crowded city thoroughfares, in the demure houses of little frequented backstreets and in the wretched streets of Spitalfields and Bethnal Green, everywhere you see the aquarium in one form or another.’
As this craze gathered momentum, natural history writers were producing guides to collecting and identification. Sea anemones were championed by Philip Henry Gosse, a reluctant schoolteacher who willingly forsook a career in the classroom for that of an author and illustrator. He was a devoutly religious man, a member of the Plymouth Brethren, and firmly believed that Christ would return to earth in his lifetime. Gosse had been inspired by the nature he’d seen living in North America. When he returned to London in 1839, he hankered for the coast and quickly moved to Devon where he spent most of his time collecting specimens, painting and writing. We can gauge some measure of his absorption in natural history by his diary entry on the birth of his only child: ‘Received green swallow from Jamaica. E. delivered of a son.’
This child, Edmund, grew up to be a poet and critic who chronicled his charged relationship with his father in a vivid memoir, Father and Son (now the only one of the two Gosses’ many books remaining in print), describing ‘the hush’ around stern father and lonely son ‘in which you could hear a sea anemone sigh’. But at the time it was Philip’s books that had the most impact. He was responsible for the widespread use of the word ‘aquarium’. His 1854 book The Aquarium, the last word on the subject, became so popular that it was sold at railway stations and, along with five other works, earned him over £4,000, a sum that equates to around £250,000 in today’s money. He experimented with different minerals to provide the right conditions for his tanks of creatures and spent many hours observing the inhabitants. This fascination raised many questions in his mind. For instance, observing the anemone Calliactis, he wondered who was influencing who. Was it the hermit crab transporting the anemone around, or the anemone that controlled the crab in some way? He even drew human analogies between warring anemones and crabs, likening the activities of the ‘male’ crab and ‘female’ anemone to a married relationship.
His greatest achievement was Actinologia Britannica, a study of the British sea anemones and corals, published between 1858 and 1860. Gosse’s precise and accurate depictions of these creatures in this highly coloured work are some of the finest ever produced. Bizarre tentacled ‘flowers’ surmount stubby gelatinous columns in the limpid waters of secluded pools or cling to romantic rocky shorelines, awaiting the return of the tides. Outstanding in their use of colour and design, the illustrations are supported by a sweeping breadth of knowledge. These dazzling images combined with lucid descriptions and enthusiastic science brought sea anemones to a wider audience.
The height of the aquarium boom was between 1850 and 1865. These aquaria were not just decorative items, rock pools in the parlour, but also opened a window on a previously inaccessible world. The journalist George Henry Lewes was asked to write about the aquarium craze and went with his lover Mary Ann Evans (who wrote under the pseudonym George Eliot) to study marine life over two summers in Devon and South Wales. The pair brought their daily trophies back to local guesthouses where they improvised aquaria from pie-dishes. According to Rebecca Stott, George Eliot was transfixed by the marine melodramas played out in these makeshift rock pools and, maybe inspired by them, shortly afterwards wrote her first novel, Scenes of Clerical Life: ‘I think it’s extraordinary that Mary-Ann Evans had not published a novel and woke up one morning with stories spilling out of her head full of comedy and witty observations of village life.’
For George Henry Lewes, observing marine life at close quarters provoked all kinds of philosophical questions:
We must always remember the great drama which is incessantly acted out in every drop of water in every inch of Earth. Then and only then do we realise the mighty complexity, the infinite splendour of nature. Then and only then do we feel how full of life, varied, intricate, marvellous, world within world, yet nowhere without space to move is this single planet on the crust of which we stand and look out onto shoreless space peopled by myriads of other planets larger if not more wonderful than ours.
There was a larger fascination behind the aquarium craze. It coincided at its peak with the publication of Charles Darwin’s On the Origin of Species in 1859. Many Victorians were questioning the use of different creatures to humanity, and the purpose of other life on earth. Faced with the variety of bizarre species that could be brought into the sitting room, it became clear that these animals existed completely independently of us. Rebecca Stott sees this as another stage in a growing perception of a challenge to the human place at the centre of the world, what H.G. Wells would later call the ‘dethronement of man’.
It’s ironic that they should have been championed by a man who had been largely rejected by the scientific establishment for quite the reverse, his valiant attempt to explain the latest scientific discoveries as part and parcel of God’s plan. Calling his theory Omphalos, Greek for ‘navel’, Philip Gosse took as his starting point that while Adam, because he had been made not born, wouldn’t have needed a navel, nevertheless he must have had one; and following the same logic he proposed that fossils were instantly formed by God at the moment of creation. The book came out two years before Darwin but the reaction was still very negative. Even Gosse’s close friend, the novelist Charles Kingsley, wrote that he had read ‘no other book which so staggered and puzzled’ him, that he could not believe that God had ‘written on the rocks one enormous and superfluous lie for all mankind’.
The aquarium craze offered owners a new vision of themselves as one animal among millions of others. The big question was what man’s place in nature should be. The number of recognised species was multiplying so rapidly as a result of empire and sea exploration that it was fundamentally changing perceptions of functions such as reproduction. Slowly it became apparent that how humanity reproduced was not the dominant way that organisms on the planet did. Anemones that could either lay eggs or produce buds came as a revelation.
For all this fascination, aquaria were a short-lived fad and by the mid-1860s the craze began to wane. The tanks and their inhabitants were never easy to manage, even with an army of servants, and so they were thrown out or turned into display cases.
The real creatures proved rather less permanent, losing their shimmering colours when preserved as specimens in formaldehyde and alcohol. One way to catch the transient beauty of anemones and jellyfish was suggested by a curator of Dresden Museum in the 1860s. He commissioned father and son glassmakers, Leopold and Rudolf Blaschka, to create models of anemones and jellyfish to display their elegant features and subtle colours. Both men were skilled in lampwork, the drawing out of molten glass over a hot flame, a technique that was perfect for creating fine tentacles: any particularly tricky appendages were attached using fine copper wire. A fine speckling of paint on the glass gave the impression of translucent hues and a work of art was born. How they coloured and assembled the models is still being investigated by the Natural History Museum. Originally it was thought that they might have made each model individually to order, but it seems they made the parts separately in batches and assembled the components as orders came in.
The superb Blaschka sea creatures and flowers were originally intended as instructional models, but were soon in demand by museums and teaching colleges around the world. Miranda Lowe is curator of the Invertebrate Collection at the Natural History Museum, which commissioned over sixty-eight sea anemones in 1866 to show to the public. She is particularly fond of a specimen of Bunodes ballii, mounted on a plaster base painted with flecks of green and yellow to interpret the sandy or rocky shore on which the anemone lived. The anemone’s body has touches of pale yellow and red and its central part comprises an array of glass tentacles made from glass-coated copper wire. The Blaschkas were inspired to create anemones in glass by Philip Gosse’s illustrations and his scientific descriptions. Less reliably perhaps, they also received live specimens from a ‘Mr Smith’ in Weymouth, though it took three days for them to reach Dresden by post. Although Leopold and Rudolf supplied organisations around the world, they were driven more by a desire to teach and create than to make money. Towards the end of their career, they were commissioned by Harvard University to make 4,500 glass flowers for their botanical collection. But because they didn’t pass on their techniques, the secret of their extraordinary art died with them.
There are 185 Blaschka models in the London Natural History Museum’s collection including jellyfish, a Portuguese man-o’-war and several complex radiolarians, minute single-celled aquatic creatures with a complex shell or testa, made of silica, the same material that forms the basic ingredient of glass. These complex, bristling orbs, barbed and interwoven with copper wire and held together with resins, are astonishingly fragile and are now on display as one of the museum’s ‘Treasures’. Computerised tomography (CT) scanning of jellyfish in the museum’s collection, which provides screen images built up from several X-rays of the sculptures, is revealing their complex internal structure and, importantly, how they were made.
Although we understand sea anemones better now, they continue to spring surprises. Daniel Rokhsar at University College, Berkeley has studied the genome sequence of the starlet anemone Nematostella vectensis and discovered that these strange sea creatures are more closely allied to vertebrates, including fish and amphibians, than to insects or worms. For animals without brains, they also have genes that can create specialised nerve cells, though Rokhsar is not yet sure what these do.
As Sir John Dalyell’s sexagenarian anemone proved, these animals can live for a very long time. Their power of regeneration allows them to grow new tentacles. Rokhsar’s particularly tantalising discovery is that, even in old age, they don’t seem to develop cell aberrations or cancers, something that is very unusual. It could be that they slough off their skin cells so fast that they are continually replenishing themselves, but they may also contain some inhibitor to tumour growth. An even more exciting discovery is that Turritopsis dohrnii, a species of small jellyfish found in temperate to tropical regions, are biologically immortal. This means that when sick, old or in a state of stress they promptly revert to the polyp stage. They do this by altering the state of their cells, thereby transforming into new types. Since the species is immortal, its numbers could be rising fast. ‘We are looking at a worldwide silent invasion,’ said Dr Maria Miglietta, scientist at the Smithsonian Tropical Marine Institute. So, if jellyfish and anemones really are more closely related to us than we think, could studying them help us understand how we grow old? Far from being mere gumdrops on a rocky shore, anemones could offer the key to living longer.
The voice of these birds is very harsh and grating. It is heard occasionally when they are flying, and also when they are alarmed. When, however, a bird is wounded or captured alive, the horrible noise it makes is perhaps not surpassed in the animal world. It is something between a bray and the shriek of a locomotive, and is kept up continuously, so as to be absolutely unbearable.
Alfred Russel Wallace, The Malay Archipelago, 1869