#2: The Clibanarius conundrum

It is often said that St. Piran’s hermit crabs (Clibanarius erythropus) are the bashful beauties of our local rocky shores. While this may be true during the day, in my experience, when the water temperature is 15C or below, these crustaceans are anything but shy. As soon as the sun goes down, especially in the summer when the intertidal waters range from 17 to 21C under the cover of night, these crabs come out in force, foraging and exploring for the snail shells they use to protect their squishy abdomen.

There is no doubt that these are charismatic crabs. With the speckled black and white eyes, rust-coloured antennules and antennae, and blue and red-striped legs, these hermits are stunning. However, despite being named for the patron saint of Cornwall, the St. Piran’s crab is not indigenous to the Cornish coast. Current research shows that this is a warm-adapted species, with a Mediterranean origin. It is found along the North coast of Africa, around the Greek Isles, up and down the coast of Italy and throughout the Côte d’Azur into Spanish and Portuguese waters.

Clibanarius erythropus

Mediterranean hermit crab

While beautiful, this is a nonnative species that may be causing local populations of native hermit crabs a bit of chaos.

Since the crab is a Mediterranean species, why is it called the St. Piran’s hermit crab? Well, it didn’t used to be called that. In 2016, BBC Springwatch held a competition to name this little invader, which won out. It seems to have the unfortunate effect of making the crab seem more local than it is. This would not be a problem if the crab had no ill effects. However, ongoing research by Ari Drummond and other members of The Crab Lab reveals that this crab is taking valuable shell resources from native species, especially the common hermit crab, Pagurus bernhardus.

If all that wasn’t bad enough, recently, the crab was nominated by The Guardian as Invertebrate of the Year. It goes to show that there is a politics to naming with winners and loosers, impacting in how the wider public perceive our natural world. It clearly pays to be a pretty species and have a name that makes you seem like you belong.

The Guardian article (linked above) and other anecdotal sources frequently state that this hermit crab died out because of an environmental disaster and subsequent clean-up efforts. I have been unable to find any scientific, research-based evidence that supports this claim. While the Torrey Canyon spill was an ecological catastrophe, this is not likely why C. erythropus disappeared from the local shores. Instead, after arriving on unusually warm currents in the late 1950s, this hermit spread along the coast until a decrease that returned water current temperatures to normal slowed the spread down. Now, record-breaking increases in water temperatures are coinciding with break-neck expansions. In some areas, this species has all but displaced the native common hermit crab [ongoing research]. Work comparing metabolic rates between the two species [in progress] shows early evidence in support that as warm water stresses the native hermits, the Mediterranean species thrives.

Clibanarius erythropus foraging

In the summertime, when the seas are warm this Mediterranean hermit crab comes out in force to find shells and forage.

The story of this Mediterranean crab shows how we need to be cautious when reporting and interpreting evidence about the spread or disappearance of a species. It is far too easy to find correlations rather than causations and report on these as fact rather than hypotheses. Additionally, before celebrating the arrival of a new species, we should assess its impact on native wildlife. As the climate warms and ranges of southern species expand northwards, we may see other new arrivals to the rock pools of Devon and Cornwall. It is essential that we recognise this as part of a global climate change, something that should concern us, and cause us to reflect on what these habitats will look like if the new arrivals drive the native inhabitants of these rockpools to local extinction.

Referenced material:

Barkham, P. (2024). St Piran’s hermit crab – an opportunist with stunning eyes. The Guardian. [online] 7 Apr. Available at: https://www.theguardian.com/environment/2024/apr/07/st-pirans-hermit-crab-an-opportunist-with-stunning-eyes [Accessed 19 Apr. 2024].

Bates, A.E., Pecl, G.T., Frusher, S., Hobday, A.J., Wernberg, T., Smale, D.A., Sunday, J.M., Hill, N.A., Dulvy, N.K., Colwell, R.K., Holbrook, N.J., Fulton, E.A., Slawinski, D., Feng, M., Edgar, G.J., Radford, B.T., Thompson, P.A. and Watson, R.A. (2014). Defining and observing stages of climate-mediated range shifts in marine systems. Global Environmental Change, [online] 26, pp.27–38. doi:https://doi.org/10.1016/j.gloenvcha.2014.03.009.

Doney, S.C., Ruckelshaus, M., Emmett Duffy, J., Barry, J.P., Chan, F., English, C.A., Galindo, H.M., Grebmeier, J.M., Hollowed, A.B., Knowlton, N., Polovina, J., Rabalais, N.N., Sydeman, W.J. and Talley, L.D. (2012). Climate Change Impacts on Marine Ecosystems. Annual Review of Marine Science, 4(1), pp.11–37. doi:https://doi.org/10.1146/annurev-marine-041911-111611.

Hawkins, S.J., Evans, A.J., Moore, J., Whittington, M., Pack, K., Firth, L.B., Adams, L.C., Moore, P.J., Masterson-Algar, P., Mieszkowska, N. and Southward, E.C. (2017). From the Torrey Canyon to today: A 50 year retrospective of recovery from the oil spill and interaction with climate-driven fluctuations on Cornish rocky shores. International Oil Spill Conference Proceedings, 2017(1), pp.74–103. doi:https://doi.org/10.7901/2169-3358-2017.1.74.

Ramos, J.E., Pecl, G.T., Moltschaniwskyj, N.A., Semmens, J.M., Souza, C.A. and Strugnell, J.M. (2018). Population genetic signatures of a climate change driven marine range extension. Scientific Reports, [online] 8(1). doi:https://doi.org/10.1038/s41598-018-27351-y.

Southward, A.J. and Southward, E.C. (1977). Distribution and ecology of the hermit crab Clibanarius erythropus in the western Channel. Journal of the Marine Biological Association of the United Kingdom, 57(2), pp.441–452. doi:https://doi.org/10.1017/s0025315400021858.

Southward, A.J. and Southward, E.C. (1988). Disappearance of the warm-water hermit crab Clibanarius erythropus from south-west Britain. Journal of the Marine Biological Association of the United Kingdom, 68(3), pp.409–412. doi:https://doi.org/10.1017/s0025315400043307.

#1: If you build it

What do you do when researching a fascinating topic, 8-12 hours daily alone in a lab? You start to question your own sanity! Don't misunderstand me; I LOVE my work and research. But, standing for hours upon hours in a refrigerated box (no, seriously, I mainly work in a room that is 15C or 59F with no windows and a very loud fan) without speaking a single word to a soul, quickly becomes soul-sucking, especially if you like people, sharing ideas and collaborating on a project. I have no problem working alone. But I find it difficult to justify my efforts if I’m not doing anything for anybody but myself. For me, science isn't about me and what I'm doing. It's about the world and all the cool things we can learn by observing and asking questions!

So after being told, "Too bad, that's what a PhD is", I said, "Yeah, OK, but it doesn't have to be that way". And honestly, it shouldn't be that way. Science is supposed to be collaborative. Innovation and inspiration flourish when we work together with different people. It's that whole "two minds are better than one" mentality. It's not that my brain can't solve problems and come up with ideas. The fact is, my brain is a product of the many different lived experiences and ideas I've been lucky enough to learn about. Other people have different views, experiences and educational histories. There is incredible value in such diversity of opinion and imagination. Not seeking that out is a waste.

I'm not one to stand for the status quo if and when it's not good enough. Realising my research would benefit from more collaboration, I decided enough of the isolation in a lab. Time to get other people involved. But how?

My mum is a huge American baseball fan, so I've seen the movie Field of Dreams a fair few times. If you've not heard of this film, you probably weren’t born in the USA in the 1980s. Basically, the protagonist converts a cornfield into a baseball field after hearing a ghostly voice tell him, "If you build it, they will come". He turns an American cornfield into a "field of dreams", inspiring people and uniting a community. He transforms his world by believing in what things could be rather than what they are right now.

This is what I'm working towards with The Crab Lab. Rather than accepting my PhD for what it was "supposed to be"--an individual research project on a narrow topic with limited reach and influence--I built a lab. Rather than accepting that things were "good enough", I am trying to improve them. It seems to be working. It's hard work, but the things that are worth it aren't supposed to be easy. And science is not and should never be about a single researcher alone in a lab working in isolation on a subject. That's how things get missed and messed up. It's far better to have people working together to discover what makes this world work.

Enter The Crab Lab. It's my PhD, but way better. It's a community of students, scientists and local interest groups working together. My research focuses on the biology, ecology and behaviour of intertidal hermit crabs. Our Crab Lab shows that taking a narrow topic and inspiring people to get involved benefits science and society. We do more work and do it better. Because we are doing it together. I built a lab and inspired a lot of different people to join in and make it better.

A huge thanks goes out to all of you who have gotten involved. I’m glad you’re here. We’re going to discover amazing things together. Each of you is going to make all the research and work more worthwhile.