Category: Life Collections

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Crayfish of the world united

by Sammy De Grave, head of research

How many species of crayfish can you name? Not many, or perhaps none? Well today, for the first time, a list of all the species of crayfish in the world has been published, thanks to a collaborative effort between Professor Keith Crandall at George Washington University and Dr Sammy De Grave, head of research here at the Museum.

The new list draws together much recent work and gives biologists access to a single, comprehensive summary of all the recognised species of crayfish for the first time. The new classifications group crayfish into 669 species, 38 genera, and five families, with two superfamilies corresponding to the Northern and Southern hemispheres.

Fallicambarus devastator. Image: Chris Lukhaup

On the occasion of this taxonomic triumph it seems like a good opportunity to take a look at some interesting crayfish from around the world.

Outside biological taxonomy, crayfish are much better known as a source of food. They are eaten worldwide, but especially in the southern US, Australia, and Europe, where the Red Swamp Crayfish (Procambarus clarkii) is most commonly on the menu. As a result, the Red Swamp Crayfish has been introduced into several countries and has out-competed the local species.

Several other species are also known as invaders. The Signal Crayfish (Pacifastacus leniusculus), native to North America, is now very abundant in Europe, and is out-competing the native Noble Crayfish (Astacus astacus).

The Noble Crayfish (Astacus astacus), above, is native to Europe, but is being out-competed by the introduced Signal Crayfish (Pacifastacus leniusculus). Image: Chris Lukhaup

Another remarkable crayfish is the Marmorkrebs, a species which still has no official taxonomic name. It was first noticed in the aquarium trade in Germany in the 1990s, but no natural populations are known. But the really interesting thing about this species is that all known individuals are female: it is parthenogenetic, which means the females reproduce from eggs without fertilisation – no males involved!

The Marmorkrebs crayfish has no official taxonomic name and is parthenogenetic – all individuals are female, genetically identical and reproduce without males. Image: Chris Lukhaup

Unfortunately, Marmorkrebs has escaped from aquaria in several countries, and is outcompeting local species due to its fast reproduction. Of most concern is its occurrence in Madagascar, where it competes for food and space with the endemic Astacoides crayfish, a much larger but slower-growing species.

Astacopsis madagascariensi, above, is being out-competed in Madagascar by the Marmorkrebs, which has escaped from several aquaria. Image: Chris Lukhaup

The Tasmanian Giant Crayfish (Astacopsis gouldi) is considered to be the largest freshwater invertebrate on the globe. Although its size has declined in recent years due to over fishing, historical specimens weighed up to 6kg and could reach 80-90 cm in length.

The completion of the new world crayfish list allows for further refinements to the conservation status of the animals too. Current Red List assessments show that 32 per cent of crayfish are already thought to be threatened with extinction, a similar number to freshwater shrimps and crabs.

It is really exciting to finally have a single source for the world’s freshwater crayfish taxonomy. Such a resource will impact a wide variety of fields that rely on crayfishes as study organisms. We hope it will also advance conservation efforts of these keystone species of highly endangered freshwater ecosystems.
– Professor Keith Crandall, George Washington University

The paper, An updated classification of the freshwater crayfishes (Decapoda: Astacidea) of the world, with a complete species list, is published today in the Journal of Crustacean Biology.

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The beautiful spiral

By Mark Carnall

At this year’s Oxford Festival of Nature I ran a spotlight session on cephalopods, the group of molluscs that includes squids, octopuses, cuttlefish, nautiluses and ammonites. While many visitors recognised the distinctive shells of nautiluses, they often weren’t too sure about the animals that made them.

Top: Chambered nautilus (Image: Manuae) Middle: Glassy nautilus (Image: Johan Jacob Tesch) Bottom: Paper nautilus, or argonaut (Image: Comingio Merculiano)

This is not surprising because, confusingly, there are three different animals often referred to as ‘nautiluses’ and which all create strikingly similar shells or shell-like structures. This is deeply mysterious because there is no direct biological relationship between either the animals or the structures they make…

To helpful clarify just what’s going, here’s a quick guide to glassy nautiluses, chambered nautiluses and paper nautiluses, and the beautiful spiral structures they create.

Glassy nautilus

Shell of a ‘glassy nautilus’ Carinaria lamarckii.

The glassy nautilus is the outsider of the ‘nautiluses’. It is actually a free-swimming gastropod – the group of molluscs that includes snails, slugs and limpets. The glassy nautilus creates extremely fragile transparent, glass-like shells, but unlike many other shelled gastropods, it can’t retract into its shell, which only covers a small portion of the body.

These fragile shells are understandably quite rare and are said to be worth their weight in gold; unfortunately that wouldn’t be very much as they are extremely light.

Chambered nautilus

Bisected young Nautilus shell showing the internal chambers. The small tubes along the middle of the chamber walls is where the siphuncle runs, a structure that moves fluid and gas in the chambers.
Bisected young Nautilus shell showing the internal chambers. The small tubes along the middle of the chamber walls are where a structure called the siphuncle runs; this moves fluid and gas in the chambers.

Perhaps the most familiar of the three creatures here are the chambered nautilus,  cephalopods belonging to a very old group that first appeared nearly 500 million years ago. Despite being known and collected for a long time – examples of polished Nautilus shells mounted in gold and silver from the 16th century can be seen at the Ashmolean Museum – the living animals weren’t actually scientifically described until the 19th century.

‘Chambered’ refers to the internal walls of the shell which form chambers as the animals grow. The living nautilus occupies the most recently grown and largest chamber. A structure called a siphuncle runs throughout the chambers, adjusting the gas and fluid in each to aid in buoyancy.

A nautilus shell cut in half, or sectioned, is often used as a symbol to demonstrate the mathematical beauty of nature, and you’ll see it in logos worldwide. Unfortunately, as with most biology, these chambers aren’t formed with mathematical regularity; growth rates are affected by environment and diet.

It was thought that measuring the chambers in fossil nautiloids, if they were laid down regularly, could tell us how far the moon has been from Earth in the past. Disappointingly, this is not the case.

Argonauta, or paper nautilus

The fragile ‘paper nautilus’ the egg case and brooding chamber of an argonaut, Argonauta.
The fragile ‘paper nautilus’: the egg case and brooding chamber of an argonaut, Argonauta.

The last of our ‘nautiluses’ is the argonaut, or paper nautilus, which is a type of octopus. The structure it creates looks superficially similar to the shells of the chambered nautilus and glassy nautilus, and not surprisingly it was thought to be a paper thin shell with some affinity to the chambered nautiluses. In fact, paper nautiluses ‘shells’ are not true shells at all, but are structures secreted by female argonauts as a brood chamber for eggs.

Preparation showing series of argonaut egg cases of varying sizes.
Preparation showing series of argonaut egg cases of varying sizes.

Argonaut shells are arguably better known than the animals that make them. But unlike other kinds of mollusc shells, which can be reliably used to delineate different species, argonaut shells take a diverse array of forms across individuals thought to be of the same species. Female argonauts can also repair and replace these cases, adding to variation in their forms.

A strange similarity
What’s striking about chambered nautilus and argonaut shells is their superficial similarity, despite the animals being in two distantly-related cephalopod groups. Both argonauts and nautiloids use their shells to remain buoyant in the water column but there are a myriad of different biological solutions to solving this problem, so why so similar?

The three different kinds of ‘nautilus shells’ from left to right chambered nautilus Nautilus, glassy nautilus Carinaria and paper nautilus Argonauta.
The three different kinds of ‘nautilus shells’ from left to right chambered nautilus Nautilus, glassy nautilus Carinaria and paper nautilus Argonauta.

It’s tempting, though not scientific, to suppose that argonauts are somehow tapping into their deep evolutionary history of chambered shelled relatives; however, superficial resemblance aside, the shells of argonauts are chemically, mechanically, structurally and physiologically completely different to those of the chambered nautilus.

So how and when did argonauts evolve this egg case-making behaviour? Fossil examples provide little evidence of how it happened and don’t reveal whether case-making is the ancestral state that has subsequently been lost in related free-swimming cephalopods that brood their young differently.

So the strange similarity between these three structures – the shell of the chambered nautilus, that of the glassy nautilus (not a nautilus really, but a gastropod), and the egg case of the argonaut – remains a beautiful and intriguing mystery.

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A rare beetles turns 21

by Darren Mann, Head of Life Collections

Many years ago, when re-identifying dung beetles in the collections of the British Entomological and Natural History Society, I found a specimen that I didn’t immediately recognise. So I borrowed it, and after a few hours of checking the European literature back in Oxford, I realised that I’d found a beetle that had not been recorded anywhere in Britain before.

The small black circles show the locations of known records for Melinopterus punctatosulcatus.

The dung beetle in question was Melinopterus punctatosulcatus, a species widely distributed across Europe but until this discovery unknown in Britain, despite its presence in the BENHS collection. This is because it had been misidentified as a different species: the beetle superficially looks like two closely-related species, and so had been overlooked by beetle collectors for over a hundred years.

Since that initial specimen, I have scoured numerous UK museum collections and to date have found a total of just 20 specimens, distributed across the World Museum in Liverpool, the National Museum Wales in Cardiff, and here in the Museum of Natural History in Oxford. All these specimens are from Deal, Kent and were caught between 1891 and 1910.

The last known record is of a single specimen from Ryarsh, Kent collected in 1938, which just happens to be the first specimen I found some 20 years ago in the BENHS collection.

The male genitalia of Melinopterus punctatosulcatus. The appearance of the genitalia is one of the best ways of identifying one species of beetle from another.

But this week, the 21st known specimen was discovered in our collections by Mary-Emma, a placement student who is with us from the University of Reading. She uncovered the beetle during the re-curation and identification of a collection made by A. J. Chitty. Thankfully the specimen was a male, so we were able to confirm the identification using the genitalia – one of the best ways of determining a species.

It seems that Mr Chitty had a knack for finding this particular species of dung beetle, since 14 of all the known specimens were caught by him at Deal. It’s just a shame that he didn’t realise his amazing discovery at the time.

Mary-Emma identifies Melinopterus punctatosulcatus by examining the dissected genitalia, visible on the right hand side of the monitor screen.

In the recent Conservation Status Review of dung beetles, Melinopterus punctatosulcatus was designated as Regionally Extinct in the UK because there have been no known sightings since that one in 1938. So this species possibly went extinct in Britain before we even realised that it was here. And were it not for museum collections we may never have known it once lived in Britain at all.

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Is it real? – Skeletons and bones

One of the most common questions asked about our specimens, from visitors of all ages, is ‘Is it real?’. This seemingly simple question is actually many questions in one and hides a complexity of answers. 

In this FAQ mini-series we’ll unpack the ‘Is it real?’ conundrum by looking at different types of natural history specimens in turn. We’ll ask ‘Is it a real animal?’, ‘Is it real biological remains?’, ‘Is it a model?’ and many more reality-check questions.

This time: Skeletons and bones, by Mark Carnall

Them bones, them bones… They are all over the place in most museums of natural history: suspended above you, parading around you, or towering menacingly over you in the case of the attention-grabbing Tyrannosaurus rex. When it comes to skeletons you might think the ‘Is it real?’ question is pretty easy to answer; the bones are there, tangibly real, right?

The articulated skeleton of a Barn Owl

Bones are only found in fish, amphibians, reptiles, birds, and mammals. Other animals possess hard parts which can confusingly be named using similar language, such as the cuttlebone of cuttlefish, or the ‘skeletons’ of corals. These hard parts may resemble bone but are formed in different ways to true bone like the ones we possess.

Unlike taxidermy, discussed in the previous instalment, on the face of it bones are less easy to manipulate and so less likely to be subjectively represented. But individual bones did not exist individually in life, and articulated skeletons, where bones have been attached together, have been manually reassembled to illustrate the shape of the whole animal. The accuracy of an articulated skeleton can depend on a number of things, including the skill and knowledge of the person doing the assembly, the completeness of the bone material, and even the preparation of the bones themselves.

The skeleton of an Atlantic Bluefin Tuna, on display in the Museum

In life, the skeletons of the bony animals are also supported by hard but spongy cartilage and tendons which are not so easily preserved after death. Yet it is the support of the cartilage and tendons, and the form of the surrounding muscle tissue, which gives an animal its natural appearance.

Some articulated skeletons do not account for this non-bony connective tissue. For example, all of the vertebrae in an articulated backbone may be touching each other, whereas in life there would actually be a disc in between each vertebra. Articulated skeletons are often positioned so that parts of the skeleton can be easily seen and accessed, even if the positioning is not realistic or even physiologically possible.

The Museum’s parade of articulated mammal skeletons – no cartilage or tendons in sight…

There are also lots of smaller bones which often aren’t preserved as they are too fragile or don’t attach to other bones in life. Examples include clavicles, or collar bones, penis bones, and the hyoid, a bony structure in the neck that supports the tongue. Some skeletons are composite specimens, so they may be made up of bones from multiple individuals to replace missing or damaged parts. Other parts of skeletons on display in museums may have been reconstructed with plaster or filler.

The way that a specimen is ‘skeletonised’ – the processes used to prepare a skeleton from a carcass – can also have a huge effect on the size and shape of bones, altering the size by up to 10 per cent, which can introduce errors in bone measurement, especially for small-boned bats, rodents, lizards, frogs, and fish.

So while there’s a tendency to assume that skeletons are more ‘real’ than other kinds of preserved specimens, they too have their biases. The next time you look at a skeleton try to imagine what is natural and unnatural about its construction, and ask yourself – is it real?

Next time… Fossils
Last time… Taxidermy

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What big teeth you have…

Not many summer placements involve being face to face with a grey wolf. The latest intern getting her hands dirty in the Life Collections Conservation Lab is Kathryn Schronk, from the BSc Conservation of Objects in Museums at Cardiff University. Here she tells us a little bit about herself and what she’s been working on during her time at the Museum…

Desiring a bit of a respite from broken pottery and rusty metal, I came to the Museum of Natural History to gain some experience with different objects and materials: namely taxidermy. I mean, why not? The possibility of getting up close and personal with wild animals was tempting, and I wouldn’t get a limb gnawed off or an eye poked out either, as might be the case with live creatures. A win-win situation!

Kathryn airbrushing synthetic hair in the Conservation Lab

Natural history specimens were always off in some strange yet fascinating realm I knew nothing about until a few weeks ago. Curiosity got the better of me, and here I am, surrounded by dead things and not the least bit freaked out. Except for the spiders; they’re still creepy, dead or alive.

The wolf who cried for help, before treatment.

My first project was a taxidermy grey wolf (Canis lupis). After many years on display, the skin has dried out and become brittle, causing it to crack and tear. These tears were visible around each hind legs, the neck, and at the tail, actually separating it from the body.

Some of the filthy cotton pads

I first cleaned it to remove dust and dirt; using a museum vacuum followed by 50:50 alcohol and water on large cotton pads for the more stubborn, ingrained dirt.

My attention was then turned to the tears at the legs. While quite long in length, there was not much of a gap between the two pieces of skin, which would make a repair easier to undertake. These were repaired with adhesive film and polyester cloth as a support material, which I slid underneath the skin and behind both sides. This was done to reduce the stress upon the brittle, dry skin and prevent the tears from increasing.

The tear around the left leg, before (left) and after (right) repair

There were massive cracks inside the mouth, where the old fill material had failed. After some testing, I chose a fill material that was flexible and able to withstand a fluctuating museum environment. This was an EVA adhesive, coloured with pigments to match the surrounding gum.

The muzzle needed substantial retouching, due to fur loss around the nose and eyes. Using conservation grade acrylic paints, I layered the colours, matching the various shades of the wolf’s coat. A very fine bristled brush was used to create the natural texture, painting on each hair practically one by one.

Lastly, I created a synthetic patch of fur made out of polyester teddy bear stuffing to combat the bald patches in front of the legs. The fibres were airbrushed with acrylic paints to match the coat and then felted onto a backing material which was adhered to the wolf using EVA adhesive. These repairs made the tears less noticeable and the wolf more aesthetically pleasing and realistic.

The wolf after conservation treatment

The wolf has now returned to the museum display, looking much livelier. Let’s hope he attracts a wolf whistle or two.

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Going, going… not gone?

by Darren Mann, head of Life Collections

Extinct or not extinct; that is a question raised by a report into the status of the beetles of Great Britain, published last year by Natural England. It may sound easy to determine whether a species is extinct or not, but tiny insects can be very hard to spot, despite the best efforts of many people.

The results of the report were alarming: using the International Union for Conservation of Nature criteria, just over half of our dung beetles are in decline, five have gone regionally extinct, and a further four were classified as Critically Endangered (Possibly Extinct) in Great Britain.

Prompted by this assessment, targeted surveys were made at known historic sites for some of our rarest and possibly extinct species. Over the past two years we have already made some exceptional discoveries, including new sites and new county records for several rare dung beetles.

 

My favourite finds from recent field exploits are the discovery of two new populations in Gloucestershire for the Critically Endangered Aphodius quadrimaculatus, and the rediscovery of Heptaulacus testudinarius in the New Forest, Hampshire after 35 years with no records. But sadly we have failed to find four of our target species at their last known sites.

Finally, after ten years of repeated site visits, we did finally find one of our rarest species, the Ainsdale dung beetle Amoecius brevis. This small beetle, just 3.5-4.5 mm long, was first found in Britain in 1859. It’s restricted to the Ainsdale and Birkdale sand dunes of Lancashire, where there were several records from the early 20th century, one record in 1962, and four records from the 1990s.

A specimen of Amoecius brevis from the Museum, collected in 1903

The last known record was of a single specimen caught in 1996. The lack of recordings for the past 20 years, despite a large number of surveys, led us to proclaim it Critically Endangered and ‘Possibly Extinct’ in the Natural England report.

Unlike many of our other dung beetles, which prefer fresh dung, Amoecius brevis breeds in older dung of large herbivores, such as cattle and horses, and rather unusually, in the UK it is also found breeding in rabbit latrines.

So it was in pursuit of rabbit latrines that we spent five days walking up and down sand dunes, covering an area of about 5km2. We then used a fine mesh sieve and tray to search through the dung and sand beneath. When our first beetle appeared it took a few minutes for the euphoria to fade, and then to our delight a further three were found in the next handful of sand and rabbit dung, along with a few more a little way down the coast.

In one sense, proclaiming a small, inconspicuous and evidently hard to find beetle as ‘Possibly Extinct’ is premature, but without that designation who would bother to go and look? Would wildlife conservationists give it any attention?

Since the Natural England Status Review was published, surveys have been commissioned for four rare dung beetles; in the case of the Ainsdale dung beetle at least, this has proven very successful.

I hope that the rediscovery of this very rare beetle will highlight the importance of invertebrate conservation as a whole. In the meantime, our data will feed in to conservation management plans for the Ainsdale site, safegaurding this little beetle’s future.