Curse of Medusa’s head: animating the corals

Corals are still seen by most people as still mineral-plants, not keystone animals. Changing our intuitive understandings of the value of natural things – which seems to have moved on little from the medieval Great Chain of Being- might help to stop biodiversity losses.

‘Perseus and Andromeda with a Dodo and Seashells’ (1627) is a somewhat misleading title for a painting by the Dutch artist Gillis d’Hondecoeter. The Ovidian drama of Perseus saving the chained maiden Andromeda from the ferocious sea monster using the literally petrifying head of the gorgon Medusa is but a mere background detail.

Foregrouding the painting is an array of pristine shells, two ostriches, various waterfowl and dodo going about its business, trying to look inconspicuous. These elements sit together in bizarre incongruity, just like objects in the collections and cabinets of wonders that were so popular at the time d’Hondecoeter was painting, the 17th century.

Perseus and Andromeda with a Dodo and Seashells (1627), Gillis d’Hondecoeter

What the backgroud cameo depicted was not only a deed of stonkingly cliched heroism, but aso the generation story of another group of popular cabinet wonders: the corals. Telling of Perseus’s victory, Ovid went on a little aside. He described how the lush seaweed bed Perseus makes to protect the sensitive serpents atop Medusa’s head from sand absorbed her potency, turning rigid and mineral. The ocean nymphs think this is rather neat and spread the seeds of these plants through the oceans, sowing seaweeds that are living beneath the waves and turn to stone on contact with the air.

Ovid’s account characterised the prevalent scientific view on corals until the eighteenth century. Corals were mineralised plants, pliant below the waves and hardened when brought up to air. Aristotle, another classical authority who shaped views of nature until relatively recently, also described ‘zoophytes’ that were animal-plant hybrids. Different views sparked fierce debate on what exactly corals were throughout the medieval, up to the nineteenth century. Nobody quite knew what to make of them.

Natural philosophers experimented on these strange objects that seemed to break all the categories of natural things. They were minutely depicted in the pages of printed natural histories, included alongside other inexplicable oddities such as fossils. Corals were also traded globally and were prized objects in the Wunderkammern or cabinets of curiosity owned by everyone who was anyone, and even some nobodies through this period.

Corals were polished, carved, gilded, arrayed in gorgeous tableaux. They were prized all the more because no-one could agree on what exactly they were, until their animal status was slowly bestowed in the 18th century amidst a cultural fascination with polyp-like creatures.

Cabinet of Curiosities (1690’s), Domenico Remps, Museo dell’Opificio delle Pietre Dure, Florence

These mythologies and byegone natural histories are not so distant as we might think. I worked at an event at ZSL London Zoo recently, giving short workshops on corals to the increasingly tipsy adults out for a good time. They were attracted by the fabulous specimens of Acropora, Platygyra, Heliopora, Montipora laid out on the table. But the inebriation, far from making them difficult to deal with, instead opened up a child-like sense of wonderment at what I had to tell them.

Save a few stray marine biologists, most people’s conceptions of these things differed very little from Ovidian or Aristotelian descriptions. They examined these familiar-exotic coral skeletons with the same fascination as sixteeth-century collectors, full in the belief that these things were either somehow not living, or were plants that became hard when they were dried in the air.

When I told them that corals were not plants but, in fact animals, very like tiny sea anemones that lived in large colonies of clones, all originating from one planktonic larvae that had buried itself in the seabed and begun secreting a calcium carbonate skeleton around itself to begin a new, sedentary, colonial life, they professed their world-views beginning to shake.

Polyps of Great Star Coral, Wikimedia commons

When I told them that a coral polyp can live or 100 years, that each clonal colony is essentially immortal, and that they have viscious turf wars with one another, the audience were awed and expletives were uttered. Especially after I told them that these corals reproduce sexually once a year, releasing clouds of gametes into the water in a coolly synchronised night orgiastic frenzy, resulting in more wandering larvae.

When I went on to say that, in fact, corals were coloured because of the photosynthetic symbionts, various species of algae called zooxanthellae that live in the corals’ cells, giving the corals colour from bright photosynthetic pigments, the revellers’ strawberry and lime Kopparburg-soaked minds were blown.

Coral outcrop on Flynn Reef
Outcrop on Flynn Reef, Toby Hudson, (Wikimedia commons)

In fact, corals that make skeletons and have these symbionts are only some coral species- there are soft corals and corals that don’t have any symbionts. But the zooanthellate ‘hard corals’ are the best known, because they produce the reefs close to land. These are the most biodiverse habitats in the sea, containing 25% of all marine fish species in only 2% of the ocean’s floorspace.

The zooxanthellae and seletons are the strength and weakness of these species. The symbionts provide extra sugars and fat from photosynthesis, which allow corals to grow more quickly than those without these residents. The corals, in turn, give the zooxanthellae protection and materials from their filter feeding. However, this also means that require these corals must remain in light shallow waters with the right temperature conditions. Zooxanthellae are pretty diva as symbionts go.

Coral bleaching, which is happening ever-more frequently as human-wrought changes are alter the global ecosystem, happens when these zooanthellae decide things arent to their liking in the corals’ tissues, such as if the temperature changes. They flee into the water, taking their photosynthetic abilities with them. The coral is left colourless and hungry. If they are left hungry for too long, they die, and all that is left are their exquisite mineral skeletons.

In living corals, these skeletons are the communal homes of millions of tiny fleshy coral polyps. They are highly adapted to local wave and sedimentation conditions with a variety of branching, plate-like, or encrusted structures. But they mean that corals cannot adapt very quickly to rapid large-scale environmental changes. Corals can only grow slowly to stay within the photic zone, where the light is. Sea-level changes, pollution and physical reef destruction are ever-shifting goal-posts with which the corals simply cannot keep up. Add to that the difficulties of building calcium carbonate structures in an acidifying environment, and things look undeniably bleak.

There is a curious irony that, in far less than the time it has taken for us to decide what corals are biologically, we might have changed the world so much as to make their continued existence impossible. Bleachings are becoming worse and more frequent, coral reefs are dying rapidly. In 50 or 100 years there may be no more coral. The ‘rainforests of the seas’ might have turned to galleries of crumbling stone effigies like Medusa’s lair.

Maybe corals will overcome temperature changes by switching which symbiont species they contain, to ones that can tolerant different temperatures, maybe coral planting projects will slow the loss. But how can we prevent it?


When I got to this point in my talk, I took a pause for breath and noticed violently dismayed faces. People who had, but ten minutes ago, had no idea these things were animals, were now outraged on their behalf. Animating corals, moving them closer to the human, gave them greater value in people’s instinctual natural histories. From mineral-plants, to plant-animals they were now animals as we were, that warred, fed, farmed and could be riotously sexual.

Perhaps changing our intuitive understandings of the value of natural things – which seems to have moved on little from the medieval Great Chain of Being- might help to stop these losses. It’s been effectively replaced by a ‘Great Chain of Consciousness’, which values other living things on a scale of empathetic compatibility.

This won’t be ecologically valuable in the long term. Emotion and consciousness are traits evolved in only a tiny proportion of species, the rest have no use for them, but they all rely on each other. We need more of a shift from such anthropocentric perceptions to a networked view of the natural world.

The perspective of d’Hondecoeter’s painting, is suggestive: a human drama is played out as a background to the variety of creatures without consciousness or humanity. But they feed the sea monster which Perseus fights, make the sand and weeds on which he stores Medusa’s head, their bodies even went to make the stone cliffs to which Andromeda is chained. The drama collapses without them.


Pieces of Platygyra, Fungia and an unidentified species skeletons from my cabinet



Brechth rose

2 thoughts on “Curse of Medusa’s head: animating the corals

Add yours

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

Blog at

Up ↑

%d bloggers like this: