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Welsh Ospreys, DNA and Genetics - Part I

Posted: Saturday 23rd September 2017 by Emyr MWT

By guest writer and DOP volunteer, Dr. Helen Ougham


Emyr, undoubtedly the most persuasive person I've ever met, succeeded in convincing me that I should write a blog or two ("or three, or four" as he ominously added recently...) - I'm a volunteer at DOP, so many of you will have met me with my red top on, but I'm also a geneticist by background, and of course in the last few years I've become very interested in osprey genetics. So here's the first of my two (or more?) blogs.


What's this genetics thing anyway?

Some dictionaries define it as the study of genes, which is true but not necessarily very helpful. It's more useful to think of it as the study of heredity, or how individuals inherit characteristics from their parents. In our case that could mean whether we have straight, wavy or curly hair, say, or whether we love or loathe broccoli (genetics means that to some people it tastes unpleasantly bitter whereas to others it's delicious). It also governs why one girl can look very like her mother whereas her sister looks quite different, even though they both have the same parents. More than that, though, it's what ensures that we are all human, while Monty and Glesni's chicks are always ospreys and not eagles or cuckoos.

Merin, Celyn and Brenig in 2015 - definitely ospreys


In ospreys and other birds, genetics is also responsible for a lot of the behaviour we see. A striking example is migration.

When this year's chicks Aeron, Menai and Eitha set off for Africa in August, they'll be flying around 6000 kilometres over land and sea to reach a destination they've never seen, and without any help from their parents. How do they know where to go? It's coded into their genes, as instructions that they inherited from Monty and Glesni. In the same way, the majority of osprey fledglings will probably never have fished before this great journey (althought we know Eitha did, twice), but now they'll need to feed themselves - their genes will tell them how to spot and catch a fish and grasp it firmly in those wonderful talons.


Eitha with her catch, but most young ospreys catch their first fish actually on migration


How does genetics work?

The short answer is "DNA". It wasn't until the 1940s that scientists proved that DNA (short for DeoxyriboNucleic Acid) is the substance that carries the genetic information in the genes of almost every living thing on this planet, including plants, fungi and animals. You and I, Monty and Glesni all have DNA, and we have it in almost every cell in our bodies.


DNA uses a form of code - indeed, it's known as the genetic code - to carry the information. You can think of it as a sequence of letters, each of which can only be A, C, T or G (the letters are short for the chemical compounds that make up the DNA molecule). But those letters can be combined in an enormous number of different ways, and a sequence that goes, say, CTAGGCAGT gives a very different instruction from one that runs TACCGTTAG.

Each gene is made up of several thousand of these letters, or DNA bases as they're known in the trade; but there's also a lot of DNA that isn't in the form of genes. In total, each cell in our bodies has around 3,000,000,000 - three billion - of these bases. Most birds have about one billion DNA bases in every cell, less than we do because they don't have so much of the "non-gene" DNA.

If you were to look for the DNA in one of our cells, or one of Monty's, you'd find most of it in the nucleus, a structure within the cell that's enclosed by its own membrane. The DNA, together with protein, is in the form of chromosomes.

A human usually has 46 chromosomes - 23 each from his or her mother and father. Birds have more than this; a typical number is 80, but ospreys have 74. This means that each chick will have inherited 37 chromosomes from Glesni and 37 from Monty. Here's a picture of what osprey chromosomes look like at one particular stage in the life of the cell (the people who wrote the paper took a picture, then rearranged it so that the chromosomes are arranged neatly in pairs):

From The karyotype of the osprey, Pandion haliaetus (Aves: Falconiformes) published in 1987 by H. Ryttman, H. Tegelström, K. Fredga & J. Sondell, in the journal Genetica, vol 74 pages 143-147. 

Why are we interested in studying osprey genetics?

First and foremost, we want to know how related all the Welsh ospreys are to one another, and to other ospreys in the UK.

Only one of the breeding adults at the four Welsh nests we know about is ringed, Glesni, who was hatched and ringed at a nest near Rutland Water in Leicestershire, as was Blue 24 and also Monty's first partner Nora. Where did the other Welsh breeding birds come from?

The Glaslyn male, Aran, with a garfish. Is he related to Monty?

By studying their DNA we may be able to answer this question. The work is being done by Dr. Matt Hegarty's group in Aberystwyth University, in collaboration with the team at Sheffield University headed by Dr. Deborah Dawson, an expert in bird genetics who has kindly provided some material ("primers") that Matt and his colleagues are using. I'll explain more about these primers and what's being done with them and our osprey DNA in the next blog.

Our other top priority is to check the sex of each of our chicks - we know that the weight of each chick is a good guide to whether it's female (heavier) or male (lighter), but sometimes it's difficult to tell if the weight is somewhere in the middle, as happened with Merin in 2015. The DNA will tell us for certain. Again, I'll say more about this in the next blog.

Merin being weighed in 2015. She is a female despite being almost 10% lighter than her younger (by two days) sister, Celyn. Or is she?

Longer term, though, there are so many things that genetics and DNA might be able to answer.

Why are ospreys' feet different from those of most birds of prey? How do they manage to digest entire fish, scales, bones, fins and all (apart from the opercula that cover the gills)? What genes tell our ospreys to fly to Africa, while other European ospreys may only go as far as southern Spain? These aren't questions that can be answered in the near future, but the more we know about osprey genetics the better chance we'll have. Who knows, we might even be able to discover why Monty's eyes are deep amber instead of yellow!

Monty (left) and Nora in 2011


How do you get a sample of osprey DNA?

One of the best ways is with exactly the same method as is often used in humans - buccal swabs.

This is a technique that can be applied in paternity testing, where the DNA of a potential father can be compared with that of the baby whose parentage is in doubt; or in criminal investigations, when the police need to discover who left evidence at crime scenes in the form of blood, saliva or other body material. "Buccal" means "to do with the cheek", especially the inside, and this is a place where it's easy to collect body cells, mixed with saliva, because the insides of our cheeks shed cells all the time, replacing them with new ones. The same is true of ospreys (and other birds and animals). So by wiping gently with a swab like this, which has a soft foam end, some of our osprey chicks' cells can be collected without harming the birds. :


 

In the UK, as in many countries, this can only be done under licence and by someone with the right qualifications and experience. I'm always impressed by the courage of anyone willing to go in past those formidable beaks to gather cheek cells, but this is where the thanatosis response is so helpful: Monty and Glesni's alarm calls will have told the chicks to play dead, and they'll lie flat and (fairly!) still while they're weighed, measured and fitted with their Darvic and metal rings. Taking the buccal swab samples at this time makes it safe for both the young ospreys and the person getting the samples.


What happens next?

The swab is placed in a plastic tube which contains a preservative liquid, and then it's stored in the cool until it's needed. DNA is actually quite tough - this is why it's possible for forensic scientists working on cold cases to get it out of old blood samples, and for biologists sometimes to study the DNA of extinct animals by extracting it from bones. It's also why the broken shell of one of Blue 24's eggs laid in 2016 has yielded enough DNA to work with, despite not being retrieved until over a year later.

Kim retrieves Blue 24's egg shell this summer, 13 months after being laid

 

Right now the swabs from Aeron, Menai and Eitha (along with those from two of the three other Welsh nests) are waiting in a fridge in Aberystwyth University until geneticist Matt Hegarty and his colleagues can analyse them, as they've already done for the 2016 samples. In the next blog I'll tell you about what they'll be doing and how we hope to use the results.

Will we be able to work out one day where Monty is from?

 

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