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Curator of Micropalaeontology's blog

5 Posts tagged with the ostracod tag
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Postdoctoral research visitor Ceran Sekeryapan from Turkey has been studying lacustrine ostracods from our collections over the past week with the intention of adding records to the database of Non-Marine Ostracod Distribution in Europe (NODE). This database, combined with details of modern climate records and Geographical Information System (GIS) software is increasingly being used to reconstruct past air temperatures.

 

 

Cypris pubera, a freshwater ostracod (courtesy of Dr David Horne).

 

  • Ostracods and temperature

 

It has long been known that some non-marine ostracod species prefer colder while others prefer warmer climates. The Mutual Ostracod Temperature Range (MOTR) method, developed by Dr David Horne at Queen Mary University of London, calibrates each species by calculating the range of air temperatures that they can tolerate. This is done by plotting the present geographical distribution of each species and using detailed modern records of climate in these locations to calculate a seasonal air temperature range.

 

Other factors affect the distribution of ostracods, for example the chemisty, depth and hydrology of different water bodies harbouring ostracods.

 

  • Reconstructing past climates

 

Many species present in the modern day are also present in the Quaternary fossil record covering the last 2.5 million years. The MOTR method plots air temperature ranges of each species present in a fossil assemblage so that a mutual temperature range can be derived.

 

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Temperature ranges of non marine ostracod species identified by Horton et al. (1992) from a Hoxnian site about 400,000 years old at Woodston, Peterborough. The mutual temperature range for the month of January is calculated and shows slightly lower mean temperatures than the present day (courtesy of Dr David Horne).

 

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The same species are plotted for July and show temperatures similar or slightly warmer than the present, a seasonal conclusion in general agreement with studies on plant macrofossils, pollen and molluscs (courtesy of Dr David Horne).

 

  • Developing our collections

 

Ceran has been identifying species part of a large microfossil collection donated in 1991 by Prof. John Neale of the University of Hull. As well as providing new identifications and ratifying previous interpretations, she will provide new latitude and longitude references for the sites that our material has come from using a method called georeferencing. Modern maps and available resources like Google Earth are used to provide up to date latitude and longitude readings that were not present in the original data.

 

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Coverage of Recent non marine ostracod records in the OMEGA database (courtesy of Dr David Horne).

 

  • The global picture

 

Key data from the NODE database and other large datasets from Canada, USA, southern Africa and Japan are being assembled in OMEGA (Ostracod Metadatabase of Environmental and Geographical Attributes). This will facilitate improved calibrations as well as biogeographical and biodiversity research. Details from large museum collections like ours are continually being used in this work.

 

  • The future

 

Testing and refinement of the MOTR method can only make this climate interpretation tool more accurate in the future. Ceran will be applying this method and gathering more data from sites in Turkey. Contributions to the OMEGA database are also invited as part of a citizen science project. Museum collections are also set to play a vital role in this study.

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In 2011 we accepted a donation of 2,500 microscope slides containing over 90,000 ostracods from the personal collection of Prof. Richard Dingle. Richard has been visiting the Museum for almost 10 years now and has organised, documented and subsequently donated this major collection.

 

The material in the collection represents a lifetime of work on ostracods and underpins research that has helped illuminate some major questions in evolution, detailed the movements of ancient continents and shown patterns of migration of ostracods across oceans. Some important type specimens are also included in the collection.

 

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One of the slides that Richard has prepared before donation to the Museum. The total length is 7cm. Each of these specimens has been positioned on the slides during visits to the Museum by Richard; a very time consuming and painstaking process.

 

 

  • The opening of the Atlantic Ocean


From the late Jurassic (very roughly 150 million years ago) the ancient continental mass of Gondwana began to split, creating the Atlantic and Indian oceans. This left the Agulhus Bank off the tip of southern Africa in a central "cross roads" location between warm and cold waters, a situation that persists to the modern day.

 

 

Richard was able to show that mid Cretaceous South African ostracod faunas were similar to those of the Falklands, indicating the presence of an Agulhus Bank/Falkland Plateau prior to the plates separating and creating the present day Atlantic Ocean.

 

 

  • How and when do ostracod species migrate across oceans?

 


Studying the benthic (bottom dwelling) ostracods from the Agulhus Bank enabled Richard to document the influx of Madagascan type faunas from the emerging Indian Ocean and their onward passage to South America.

 

 

Various oceanic barriers to migration existed and were subsequently bridged. The ostracod faunas were able to show the timing of the influx of south/central Atlantic faunas into the SW Indian Ocean.

 

 

 

Richard's work has also contributed to various theories about the migration and sometimes isolation of ostracods lineages across oceans by island hopping. The collection also shows the migration of the important genus Magungaella from pre-glacial to younger glacial high latitude sites.

 

 

 

  • Can evolution work in reverse?

 

In a nutshell, Dollo's Law suggests that once an evolutionary trait has evolved, it can't be un-evolved. Richard's collection of ostracods from Marion Island in the Southern Ocean, shows the re-appearance of eyes in deep water ostracod genera that were previousy considered blind.

 

Richard proposed a gene-reactivation hypothesis to account for this. The possession of eyes is key to classifying ostracods and evaluating their evolutionary history, a matter of continuing controversy amongst ostracod workers.

 

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An example of Poseidonamicus, one of the deep sea genera of blind ostracods used by Richard Dingle to show that sightedness returned later in geological time in shallow water forms. This example is from the Aberystwyth Collection and photographed by Gene Hunt now at the Smithsonian Institution, Washington.

 


 

  • What do ostracods tell us about ancient environments and oceans?


It has been suggested that 40 million years ago there was a major global deep sea event that caused a disruption in deep sea populations. Richard's findings derived from Ocean Drilling Programme/ Deep Sea Drilling Programme collection sites, have contributed to discussions and conclusions about this ancient event.

 

The collection now at the Museum also provides the source data for Richard's triangulation method of palaeo-environment prediction, based on late Cretaceous (roughly 70-85 million year old) ostracods.

 

Similarly, Richard proposed that ostracod provinces existed around the margins of the ancient continental mass of Gondwana. Examples of these assemblages are also present in the collections he donated to the Museum.

 

 

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The collection that Richard donated is vast in terms of numbers of specimens and represents a lifetime of work on ostracods. Hopefully it will be remembered not only for the large number of items present but also for the excellent science it backs up. More about Richard Dingle's Collection and his work can be found in a paper published this month in the Journal of Micropalaeontology.

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Every quarter we are required to provide numbers of visitors, enquiries and loans to show how the collections are being used. These are passed to the Museum Trustees and subsequently the Department of Culture, Media and Sport (DCMS) as a performance indicator to help justify the expense of maintaining such an amazing collection.

 

At the Museum a new loan type - Surrogate Loan - has just appeared on the horizon to record when we send images of our specimens rather than loaning the specimens themselves. Usually I would sigh and say something under my breath about having too much administration. However, as someone who deals with a lot of images of my collection I'm really glad. Recording surrogate loans gives us and the managers who allocate Museum collections management resources a really useful indication of how much the microfossil collection is being used.

 

Below are a few images I have sent out recently as surrogate loans along with a few comments about them and how they are being used.

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This is the ostracod Lophocythere caesa britannica from the Jurassic (about 160 million years ago) of the UK. The scanning electron microscope picture was taken by me for Prof. Robin Whatley, now retired from University College Aberystwyth, University of Wales. Prof. Whatley has donated a large number of specimens to the Museum during his career and is putting together an extensive publication describing some of them. Robin can't travel easily so his wife Caroline Maybury has been amazingly helpful in preparing the material in our collections for imaging and putting the specimens away afterwards. We would certainly not have sent that many specimens out on loan because they are too fragile and important reference specimens.

 

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This is an image of the conodont Distomodus staurognathoides from the Silurian (about 425 million years ago) of Iran. It is part of donation by Dr Vachik Hairapetian who has provided us with some very interesting material in recent years. Some of it has been published or like this specimen, is in the process of being published. Conodonts from this area of the world are largely undescribed so it is important that this material is recorded as their occurrences can help with future geological interpretations of the region.

 

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This an extreme close up of a piece of chalk from the Sevens Sisters in Kent taken by my former colleague Jeremy Young. It shows tiny rings of calcareous nannoplankton called coccoliths and was sent to artists Francisco Queimadela and Mariana Calo who visited in February. This followed an open day of the micropalaeontology collections associated with an exhibition at the Gasworks Gallery at the Oval, London. They are also doing an exhibition at the Gasworks Gallery.

 

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This is another ostracod, this time from the Coralline Crag of Norfolk donated in 2011 by Dr Adrian Wood of Coventry University. I took scanning electron microscope images of all the specimens in his donation to help with his publications on ostracods from East Anglia. Adrian has been very helpful in preparing the specimens for accession to our collections by labelling slides and providing electronic data that can be easily incorporated into our database.

 

Throughout my career as a curator I have sent a lot of specimen images to enquirers so I'm very glad that this practise in now being recorded as a performance indicator. Hurrah for surrogate loans!

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So how do you get a fossil named after you? The easiest way is to make friends with a Palaeontologist who is good at discovering things and is looking for names to call their new finds. A slightly harder way is to find a new fossil species and give it to a Palaeontologist who names it after you.  (In case you were wondering, it is against the rules to call new discoveries after yourself ). Just before ChristmasI had a visit from my old friend Stuart Sutherland from Canada who named a fossil after me back in 1994. I have four fossils named after me and have named some after others too. Here are the stories behind each of them.

 

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On graduation day in 1993; Professor David Siveter, Andrew Swift, Stuart Sutherland and a young looking Giles Miller.

 

Stuart and I were studying for our PhDs at the University of Leicester in the late 1980s and early 1990s. We both had similar field areas in the Welsh Borderland around Ludlow and often scheduled fieldwork for the same time, occasionally helping each other to collect study samples. One summer evening I was helping Stuart to collect samples deep in the Mortimer Forest outside Ludlow. Foolishly I managed to hammer my thumb drawing blood and we had to return to our accomodation early.

 

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Angochitina milleri Sutherland, 1994. This chitinozoan is less than half a millimetre in length.

 

I didn’t realise but Stuart made a note of the sample number and once he dissolved it back in the lab, he found a new species of chitinozoan that he named Angochitina milleri Sutherland, 1994 in my honor. Chitinozoans are tiny organic jug shaped organisms. To this day is it still unclear what they are but they are very useful age diagnostic constituents of marine rocks in the middle Palaeozoic era (very roughly 360-480 Million years ago). Some think that they are some sort of egg case as they sometimes appear linked in chains.

 

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The ostracod Progonocythere milleri Wakefield, 1994 from the Jurassic of Scotland. It is just less than a millimetre long.

 

While Stuart and I were living in Leicester we shared a house with our good friend Matthew Wakefield who was studying ostracods from the Jurassic of the Inner Hebrides, Scotland. He had discovered several new species that he kindly named after his housemates. New species number 2 is therefore Progonocythere milleri Wakefield, 1994. You will notice that after each milleri is the name of the author and the date of publication. I am honoured to have both of these two species named after me and published in Monographs of the Palaeontological Society, a very prestigious journal that has also published Darwin’s work. The holotype of P. milleri also resides in the collections currently in my care.

 

The third milleri is more tenuous as the author, Jonathan Adrain (now University of Iowa) discovered lots of new species of trilobite from the Canadian Arctic while he was working at the Museum. He discovered so many that he decided to use the phone list of the Department of Palaeontology at the time to name his various new species. Hence Gerastos milleri Adrain, 1997. In fact there were not enough names on the list to completely cover all his new discoveries so he decided to name some of them after his favourite pop group, The Beatles. His publications therefore include a macartneyi a harrisoni and a petebesti!

 

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Kannathalepis milleri Marss & Gagnier, 2001, scales from an ancient fish from the Canadian Arctic.


At the time I asked Jonathan if he could provide some spare rock from his trilobite studies so that I could attempt to extract microfossils. Some of these samples contained some fish scales that I passed on to my good friend Dr Tiiu Märss of Tallinn Technical University, Estonia with whom I was working at the time. One of these samples contained some fragments of a new fish hence the fourth new species named after me Kanathalepis milleri Märss and Gagnier, 2001.

 

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Pictures taken on fieldwork with Tiiu in 1995; with Peter Tarrant at Man Brook and taking a sample from under a tree half way up Caer Caradoc, Shropshire.


Tiiu also passed me some samples from the Canadian Arctic from which I discovered some new species of ostracod that I named Beyrichia marssae Miller, Siveter and Williams, 2010 and Platybolbina adraini Miller, Siveter and Williams, 2010 in honour of Tiiu and Jonathan. However, you will notice from the date after these names that it took me a much longer time to publish my new species!

 

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Beyrichia marssae and Platybolbina adraini.


As you can see from the stories above, the naming of species new to science sometimes provides historical information about the lives of scientists, their collections and collaborations. Working at the Museum and being involved in science has meant that I have met a lot of people from all around the world, some of whom have decided to honour me by naming new species after me for various reasons.

 

Sometimes names become superceded when later research shows that they were not really new. Someone may have already described them or they could be a smaller part of something already described. As far as I know all the milleris are still as valid as the friendships gained through working in science. It was lovely to speak to my Estonian colleague Tiiu while working on this post. I see Matt Wakefield regularly at scientific meetings about ostracods. It has also been great to see my old friend Stuart again.

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Some of the Museum's most important ostracod specimens were re-examined recently using synchrotron technology. The results published in the journal Science showed that these very delicate but exquisitely preserved fossils gave evidence for reproduction using giant sperm back in the Cretaceous period about 100 million years ago.

 

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A scanning electron microscope of an exceptionally preserved ostracod from Brazil showing details of unusually preserved soft body parts.

 

From images obtained by scanning electron microscope we have known since the 1970s that the Cretaceous ostracod Harbinia micropapillosa was almost identical in body form to modern day examples. Usually ostracods, microscopic crustaceans that inhabit aquatic environments, leave only their calcareous shells in the fossil record. However, these exceptional fossils from Brazil include details of their organic soft body parts not normally fossilised.

 

These specimens were first found by legendary evolutionary biologist Dr Colin Patterson while he was studying the fossil fish from the same rock formation. He passed them to Dr Ray Bate who published them under the name Pattersoncypris. However, some ostracod workers now believe that they should be classified under the name Harbinia which was first described by a Chinese worker in 1959 and therefore takes naming priority.

 

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The European Synchrotron Research Facility (ESRF) at Grenoble in France.

 

In 2007 we had a request by Dr Renate Matzke-Karasz (University of Munich) and a group of co-workers to take our specimens to Grenoble in France to have them analysed in the synchrotron beam ID19. A synchrotron is a giant ring where electrons are accelerated to great speeds and then bent into a circular path by magnets. Strong magents are used which cause the electron beam to deviate and at this point a very bright, intense synchrotron x-ray is emitted. Sometimes synchrotrons are referred to as diamond light sources as a result. These very intense synchrotron x-rays are then focussed into a beam which can be used for analysis at a sub micrometer scale ideal for our microfossils.

 

Some types of modern day ostracods are well known for their use of giant sperm in reproduction. Dr Matzke-Karasz and her co-workers were interested to see if our fossil specimens (Robin Smith thesis collection) contained any evidence for giant sperm or the organs responsible for its production and storage. As the curator of the specimens it was my job to transport them safely to Grenoble and to handle them while they were being analysed. I also took part in the analysis which went on all day and all night for two days. Fortunately we did get some sleep as there were four of us. We took it in turns with two of us analysing the fossils and two analysing the comparative modern specimens in 6 hour shifts.

 

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Positioning the specimen so that it is aligned with the beam. (Don't worry about the scary red lines. The beam was only switched on when we were all safely out of the room!).

 

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Dr Radka Symonova (then at Charles University, Czech Republic), Renate, Dr Paul Tafforeau (ESRF) and Dr Robin Smith (Lake Biwa Museum, Japan) examining some early scans in our experimental cabin home for the two days.

 

The specimens were placed in the beam and then rotated 180 degrees while 1500 x-ray cross sections were taken at regular intervals. These x-ray images were then combined together using specially designed software to produce 3-dimensional images (Holotomographic reconstructions). Although we could immediately see evidence for important internal structures while we were analysing the specimens, a lot of work was still required to produce the final results. The slices that make these 3-dimensional images were analysed for internal structures by Renate and her team back in Germany. Artificial colours were painstakingly added to each slice by hand to show these structures more clearly.

 

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One of the x-ray cross sections of a fossil specimen before it was combined into a 3-dimensional image.

 

The results clearly showed differences between males and females. The males had distinctive tubes in the position where modern day ostracods have  a sperm pump called a Zenker's Organ. The females had inflated sacks in the position where modern day ostracods have sperm receptacles. These are only inflated once they have been impregnated with giant sperm. Our results had shown that this reproductive strategy had been in place more than 100 million years ago.

 

 

Video of a female specimen of Harbinia micropapillosa. The orange sacks are the sperm receptacles.

 

So why is this important? As I showed in the dinosaur exhibition blog item, it is vital to know how organisms reproduce so that you can correctly interpret their fossil record and distribution in modern day environments. Ostracods are often restricted to particular environments and can be useful indicators of changes in climate. This particular ostracod species is common in Cretaceous non-marine sediments offshore Brazil and is therefore of interest to oil exploration companies as a marker for key rock formations.

 

Reproduction with giant sperm is not just restricted to the ostracods as other organisms including fruit flies and some types of frog also use this strategy. The evolutionary significance and history of this type of reproductive strategy is still unclear. What is certain is that specimens in the Museum collections show that this was also happening over 100 million years ago!

 

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Some acrylic palm of the hand sized scale models produced from the 3-D synchrotron scans and used at the "Science Uncovered" event.

 

 



Giles Miller

Giles Miller

Member since: Apr 21, 2010

This is Giles Miller's Curator of Micropalaeontology blog. I make the Museum micropalaeontology collections available to visitors from all over the world, publish articles on the collections, give public talks and occasionally make collections myself.

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