Making a skeleton out of iron: the ‘scaly-foot gastropod’

The three known forms of Chrysomallon squamiferum, from Kairei, Longqi, Solitaire vent fields (left to right)

Gastropod researcher Chong Chen writes:

Meet Chrysomallon squamiferum, or the ‘scaly-foot gastropod’ – the only metazoan (multi-cellular) animal capable of making a skeleton out of iron! Uniquely among gastropod molluscs it carries hundreds to thousands of scales on the foot like a suit of scale armour; these scales as well as the shell usually has a layer of iron sulfides. The function of these scales has been speculated to be protective or detoxification (by accumulation of sulfide waste), but their true function is yet unknown. As part of the iron armour is made of greigite (Fe₃S₄), a magnetic form of iron sulfide, this amazing animal actually sticks to strong magnets. And it also rusts. That’s right – upon contact with oxygen and water, the whole exterior slowly turns to a layer of reddish rust from metallic black.

Why doesn’t it rust in its natural environment, you may ask. Well, its environment is not exactly ordinary, either. The scaly-foot only occurs in deep-sea hydrothermal vents of Indian Ocean, more than 2500 m deep and often on ‘black smoker’ chimneys spewing out hot vent fluid exceeding 350°C. Hydrothermal vents are typically oxygen-poor environments and this might prevent the animal from rusting. The wonder doesn’t stop here – it houses endosymbiont bacteria in its enlarged oesophagus which is capable of turning chemicals in the vent fluid (poisonous to most animals) to energy, and rely on these for nutrition. So it basically keeps a food farm inside the body and does not need to feed!

Hydra, an active ‘black smoker’ vent chimney in Longqi field, Southwest Indian Ridge

With shell length that averages at around 35 mm and exceeds 45 mm in large individuals, it is a very large peltospirid snail compared to most others in the family which are below 15 mm in shell length. Originally discovered in 2001 from deep-sea hydrothermal vents of Indian Ocean, despite being a charismatic species there, it was not formally described and named until 2015. Furthermore, recent find of a white population without iron on the sclerites deepens the mystery about its sclerite formation – much more exciting secrets are waiting to be unveiled from this remarkable species!

A specimen of Chrysomallon squamiferum photographed live (Photo: David Shale)

You can watch a video of Longqi hydrothermal field featuring Chrysomallon squamiferum in their natural habitat here:

http://www.youtube.com/watch?v=y6iK19xaYJg

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The longest lived animal in the world?

Dr Richard Preece, Curator of Molluscs at the Museum of Zoology, writes:

There have been a number of potential contenders for this crown including Giant tortoises, large whales, Asian elephants and some reptiles and fish but none of these animals has been shown to live for more than 200 years. This is not the case with the Ocean quagog (Arctica islandica), a bivalve that frequently lives for several centuries. The oldest known specimen from Iceland was shown to have lived for 507 years. How can we be so precise about its age? The answer is that bivalves, like trees, deposit annual growth increments that can be counted and crossmatched enabling the construction of long chronologies extending back hundreds or even thousands of years. The fact that the same pattern of growth increments is recognisable within populations, and even between species, demonstrates conclusively that the bivalves are responding to identical environmental signals. Such signals include water temperature and nutrient availability, as well as other factors. Knowledge of these controlling factors enables the reconstruction of past oceanic conditions at annually-resolved resolutions, so providing critical archives for the study of climate change and variations in the position and strength of ocean currents and in water chemistry. The fact that these bivalves live so long has also attracted attention from gerontologists interested in understanding why these particular animals do not die in the usual way.

Image courtesy of Professor James Scourse, University of Wales, Bangor

Dragonflies and Damselflies

Examples of the beautiful damselfly Neurobasis daviesi, named after Allen
Davies, the donor of the collection. It is a native of Palawan in the
Philippines.
© University Museum of Zoology, Cambridge 2013

Russell Stebbings, Senior Museum Technician, writes:

The Museum’s holdings of Dragonflies and Damselflies (Odonata) are of international importance. Whilst we currently hold a small British collection, mostly dating from the 19^th and early 20^th Century, our greatest strength is amongst the non-European or ‘Exotic’ groups.

We have material collected from a number of important overseas island habitats, such as Hawaii, New Britain and the islands of the Indian Ocean, particularly the Seychelles. We have collections from Borneo and the Skeat Expedition to Peninsular Malaysia. Additionally, we have an outstanding named collection, that of Professor Allen Davies (1923-2003) which occupies some 11 cabinets. He collected and exchanged insects in order to assemble the finest genus-level collection then (2003) in private ownership. His collections represent localities across the Americas, Africa, Australasia, and Asia including China, Taiwan, Indochina and Burma. He was responsible for discovering and naming several species himself and remained an active collector and researcher until the final year of his life.

One particularly interesting feature of the Davies collection is the larval exuviae. These are the delicate ‘skins’ of the freshwater dwelling larvae, shed as they emerge as winged adults. Some of these ‘skins’ are very large, and the powerful jaws, used in seizing prey as large as tadpoles, frogs and fish, can clearly be seen.

Current research in the Department of Zoology is monitoring the species and distribution of Dragonflies in the streams of Sabah (Borneo) in order to assess river ‘health’ whilst riparian habitats (between land and rivers or streams) are undergoing severe change.

Barnacles aren’t acorns

Barnacles and Kakapo

Dr Beverley Glover, Director of the Cambridge University Botanic Garden, writes:

You might not expect a botanist to have strong feelings about the collections in the Zoology Museum, but I’ve always believed that a good biologist doesn’t let a little matter of kingdom stand in the way of studying interesting organisms. I have 2 particular favourites that I like to visit from time to time. On the stairs, the kakapo (Strigops habroptila, or owl parrot) is something of an old friend. This New Zealand flightless parrot is critically endangered in the wild, prey to invasive predatory mammals such as cats and rats. As an undergraduate student at the University of St. Andrews I used to eat my sandwiches at lunchtime in the Bell Pettigrew Museum (their equivalent of our Zoology Museum), and I had a favourite spot next to the kakapo. When I moved to Cambridge I was really glad to find another specimen of my old friend here!

My other favourite is the display of barnacles. People don’t often think about barnacles – certainly I never had until I saw my first real live ones under a microscope on a field trip, for our first year Evolution and Behaviour class, that I was leading along with John Flowerdew from the Zoology Department. Barnacles look at first glance like just another gastropod mollusc, sitting on a rock under a shell. But in reality they are arthropods, members of the same class (the crustaceans) as crabs and lobsters. They have adopted a very specialist lifestyle, glueing their bodies to the rock at the head end, secreting calcareous plates around their body for defence, and waving their legs through the hole in the top of the shell to catch small particles of food in the water. The barnacle display in the museum showcases all this perfectly, with some closed up specimens of the very common acorn barnacle on a rock, a drawing showing how the animal looks magnified, and an especially clever display of the goose barnacle with the shell removed to display the animal inside. Barnacles always remind me that by thinking about the plants and animals around us from a fresh perspective we can develop some fantastic insights into the natural world.

Large Blue and Large Copper Butterflies

Large Blue butterflies © University Museum of Zoology, Cambridge 2013

Professor Paul Brakefield, Director of the Museum of Zoology, writes:

The Insect Room of the Museum smells wonderful – at least to any entomologist – and its beautiful mahogany cabinets team with important specimens.I am especially taken with two drawers about which our Curator of Insects, Dr William Foster, had told me. Opening one reveals numerous flashing bright blue butterflies – they are all small but each one is larger than the blue butterflies still flying in Britain today. They are all important specimens of the Large Blue Butterfly which sadly became extinct here in the last century in spite of efforts to save it. I opened this drawer recently to show a special visitor, Jeremy Thomas – an exciting moment! It was especially apt since Jeremy is the key conservationist who, having made fascinating discoveries about the intricate life cycle of the Large Blue and its interplay with ants, dedicated tremendous effort to returning this species to some of its old haunts in England. Jeremy set up an ultimately highly successful re-introduction program that was launched using live butterflies collected in Sweden. Our old specimens of the original British population can now be compared with these new large blues on our islands to reveal more about how evolution works. A neighbouring drawer also produced a wonderful series of Large Copper Butterflies, flashing a fiery copper red in the light. This species is alas also now extinct in the UK, and is similarly larger and more spectacular than the Small Copper Butterfly that remains quite common here. The Large Copper is very much of local interest having flown in many Fenland habitats. I have seen them myself flying in good numbers within the city limits of Kracow in Poland but never of course in Britain. The drawer of our local specimens brings home to us the sadness of any loss of species from our islands but perhaps a species as beautiful as the Large Copper has a special impact. However, the story of the Large Blue demonstrates how dedicated knowledge and conservation can provide the springboard for a successful return. Our Museum collections can also play an important role here, both with respect to research and to raising awareness.

Large Copper butterflies © University Museum of Zoology, Cambridge 2013

Pea Clams, genus Pisidium

Drawer of Pea Clams © University Museum of Zoology, Cambridge 2013

Individual Pea Clam © University Museum of Zoology, Cambridge 2013

Hilary Ketchum, Newton Trust Fund Project Assistant at the Museum, writes:

From 2011 to 2012 I worked at the Museum on a short term contract as a catalogue data assistant. My job was to catalogue the museum’s collection of bivalve molluscs, making an online database that could be accessed by researchers worldwide.

To finish the project in one year we worked out that I would need to catalogue one drawer of shells per day, and for eight months I met this target without much difficulty. I really enjoyed my work. I got to handle some of the museum’s most beautiful and important specimens, and found out some fascinating stories about the people who had collected them.

Then one day I came across a drawer containing hundreds of glass tubes. Inside each were tens of minute browny-green shells. This was in stark contrast to the colourful sea-shells I had been cataloguing before. The shells in the tubes belonged to a kind of freshwater bivalve of the genus Pisidium (also known as pea clams). They had been collected by a former curator at the museum who was interested in their distribution in rivers and streams. He had published numerous papers on the subject and had collected them for many years. This single drawer of specimens took me not one day, but a whole month to catalogue.

Fortunately after that, again it was plain-sailing, and I finished cataloguing all 10,000 bivalve specimens as well as another 2000 other molluscs, including the cephalopods and chitons. The catalogue is now available through the museum’s website, and visitors to the museum can see a new display all about bivalves in the Upper Gallery.

Passalid Beetles

© University Museum of Zoology, Cambridge 2013

Dr William Foster, Curator of Insects here at the museum, writes:

The Passalids, or Bess Beetles, are one of my favourite insects. They live deep inside rotting logs in tropical rainforests, and the main reason I like them is because they are so smooth, chunky and handsome. They live in small family groups, and only rarely emerge into the daylight. They are quite hard to find, but it is a huge thrill to open up a log and suddenly find a family of about 20 large clean red and black beetles, together with their young larvae, bumbling around in the damp wood and sawdust. They are highly social animals. The larvae and adults sing to each other, and some people claim that they have the widest song repertoire of any animal. The adults sing by rubbing their abdomen against their wing cases. The larvae have only 4 walking legs; the two hind legs are modified as small paws that are scraped against the thorax to produce a range of sounds.  The Bess Beetles are probably the most social of all the beetles. They always live in family groups, and probably help to feed each other. The larvae are not able to make their pupal cases on their own, and they rely on help from other adults in the colony to pack sawdust around themselves to make a solid case: without this protective case the pupae will die.

We studied several colonies in mountain forests near Chiang Mai in Thailand. We were trying to see whether the colonies had a single reproducing female and male, with all the other adults being sterile “workers” as in termites, but this seems not to be the case. All the adults stay with the family until fully grown, but they all appear to be able to reproduce and none of them were sterile.

The photograph shows part of a draw of Passalids from the Insect Room of the University of Zoology. The different species all look very similar, with sold tank-like bodies and complex comb-like antennae. They do differ in size and this is quite a good way of trying to tell the different species apart. I think that one day we will find a species that lives in really large family groups and is fully social, like termites and ants, with a single reproducing queen and king.

Squid, Dibranchiata

© University Museum of Zoology, Cambridge 2013

Julian Jacobs, Departmental Administrator for the Department of Zoology writes:

The specimen I would like to nominate is the little squid “dibranchiata”. I find this pale, ghostly creature quite fascinating for a number of reasons. Like all cephalopods it has an other-wordly quality. It can adapt its colouration, it has a highly developed nervous system and advanced eyes. It apparently behaves cooperatively and suggests intelligence. An alien life-form from another planet could hardly look more astonishing! And small as it may be, this creature cannot fail to make you think of its terrifying big cousins. Scaled-up, this small and delicate creature becomes a terror of the deep, a deadly hunter possessed of fearsome suckers ad beak, a match for Sperm Whales 1000m below the surface of the sea. Fictionalized portrayals in Moby Dick and Twenty Thousand Leagues Under the Sea may be exaggerated, but oddly enough their deep-water habitat has protected them from being properly filmed. So even in the age of Attenborough-style natural history filming, the squid whether large or small, retains a kind of mystery that prompts fear and wonder.

Pycnogonids, Sea Spiders

Sea Spiders

Dr Chloe Cyrus-Kent, a past PhD student of the museum, writes:

Among the museum’s wonderful arthropods, to me the pycnogonids stand out as being both beautiful and completely bizarre too. They are stunning specimens and look like aliens from outer space come to baffle zoologists and amaze all who see them!

Eurypterus remipes – a Sea Scorpion

© University Museum of Zoology, Cambridge 2013

Prof Michael Akam, Head of the Department of Zoology at the University of Cambridge, and former Director of the Museum of Zoology, writes:

The Eurypterids, or Sea Scorpions, were the most terrifying group of arthropods that ever lived, roaming the Paleozoic seas from about 460-255 million years ago.    The fossil specimens that we have in the Museum are quite small, 15-20cm,  but the largest specimens were truly fearsome predators – up to 2.5m long, with single claws of more than 80cm.  Our specimens come from New York State, an area famed for them.  Indeed, sea scorpions are the State Fossil of New York.

I visited one of the fossil quarries myself.  We contacted the owner, who invited us to visit his workshop.  It looks like any other small farmstead in upstate New York, nestled in the hills.  His barn, though, is full not of hay and horses, but rock saws and air drills, for preparing these most wonderful fossils, which he displays all over his house (and on the internet too, at http://langsfossils.com/eurypterids.htm)

I’m no palaeontologist, but even so, he took us up to the quarry behind the house, handed us a hammer and chisel, and invited us to split some of the blocks of shale he had excavated the previous year, and left for the frost to weaken.   The eurypterids are so abundant in this rock, that almost every split yielded a fossil or two.

Eurypterids belong to the large group of arthropods called chelicerates – a group characterised by having pincers rather than antennae as their front limbs.  Spiders and scorpions are the most familiar living chelicerates, but these land animals are only distantly related to the sea scorpions.  The closest living relatives of the sea scorpions are probably the horseshoe crabs – another ancient group of wonderful arthropods, and the only marine chelicerates to survive to the present day.