Studying sea star sperm in Sweden

boy-urchinsHow many people would travel to one of the most beautiful coastal tourist destinations in northern Europe, at the height of summer, and spend three weeks sitting in a 10 degree cold room with their eyes glued to a microscope? Not many, I’d guess, but it’s exactly what I’ve done by visiting the Kristineberg Marine Station in Sweden.

I’ve swopped my tent on the Arctic ocean for another wonderful place to come and work, but yet again am nose to a microscope all hours of the day. Most of the world’s top marine biology stations are set in truly beautiful surroundings, but are generally full of people far too busy working to get out and enjoy the surroundings properly.

The Kristineberg Marine Laboratories, part of Gothenburg University, is situated in a really pretty part of the Swedish fjords, and is a fantastic place to come and do marine research as it has wonderfully clean seawater and an amazing array of marine species live here. I’m here to continue my ocean acidification research, looking at how the change in seawater pH caused by increased carbon dioxide in our atmosphere might affect the reproduction of small marine invertebrates, or more specifically, how it might impact the performance of their sperm.

Marine invertebrates makes up over 80% of the oceans biodiversity, and many of these small creatures reproduce by simply shedding their eggs or sperm straight into the water, often in synchronised spawning clouds, so that fertilisation happens ‘by chance’ in the open sea. This is often referred to as a fertilisation ‘lottery’, as the chances of sperm and egg meeting seems so small, yet these small animals have adapted to maximise the chances of this happening in numerous clever ways.

One such adaption shared by many species is the ability of the sperm to sense the egg and then swim towards it. But, how might a change in pH affect this swimming ability? That’s the main question I’m asking with my research, and I’m looking at a whole range of animals to see how their sperm ‘performance’ might be affected by future ocean conditions. By measuring sperm swimming speeds, respiration, and viability of sperm under future ocean conditions, I’m giving the sperm a future health check. So I’m basically doing the kind of tests that an IVF clinic would do, except on mussels and sea stars under future ocean conditions!

So how do you get a mussel or sea star to spawn and provide the valuable sample to be analysed? Well actually it’s pretty easy; most marine invertebrates store their eggs and sperm for a while before spawning, so that they can all release them at the same time and increase their odds in the fertilisation lottery. They then use a number of environmental signals to tell them all when to spawn, so all you have to do is mimic these signals to get them to spawn in the lab. Normally a good shake to mimic the tide coming in and some warmer seawater is all they need, but we can also use a small hormone injection to start spawning for some species. Sperm have a pretty short life span so it’s a mad dash to get as many measurements made as possible. I’m finding different species are showing quite different responses to the ocean acidification conditions, and it’s now my aim to understand why this is.

This kind of information will add another important piece to the puzzle in terms of our understanding of climate change impacts in our oceans, and really help us understand which species are going to be most susceptible to ocean acidification and which ones might be less affected. I have a lot of sperm to count and analyse for now though, whilst gazing out the window at the beautiful fjords. Still at least it’s not -40⁰C this time, and I can go and jump in the sea at the end of the day.

Posted by Dr Ceri Lewis, NERC Research Fellow (College of Life and Environmental Science).

Follow Ceri’s updates from Sweden via her Twitter feed @CezzaLew

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