As part of my series of interviews with female animal behaviour researchers, in this post I'll be talking to Dr Tanya Latty. Dr Tanya Latty is a scientist at the University of Sydney in Australia. While her background is in entomology, having worked with ants, bees and beetles, recently she has been working with a more unusual creature, the slime mould.

There are two types of slime mould: cellular and acellular. In the past, Dr Latty has demonstrated that acellular slime moulds make decisions similar to the way we do as humans, trading-off speed and accuracy, exploring options before coming to a decision, but also making economically ‘irrational’ decisions.

In a recent paper, Tanya Latty with her colleague Chris Reid make the case that slime moulds are also useful organisms in which to study collective behaviour: how the choices of many individuals can lead to a particular pattern at a group level.  In the past, animals like insects, fish and birds have been studied to understand how individuals’ behaviour can lead to group-level phenomena, like the towering structures of termites and the anti-predator formations of starlings. In most cases, group-level phenomena arise without having any kind of ‘group leader’, instead individuals make decisions based only on what they can detect in their immediate environment. Here I ask Tanya Latty about why cellular and acellular slime moulds might help us understand collective behaviour.  

 

How did you first start working with slime moulds?

I was part of a larger project that was investigating problem solving in bees, ants and slime moulds- I was hired to work with bees and ants. Out of curiosity, I decided it would be fun to have a ‘pet’ slime mould, and was delighted to find out I could buy one online for $20. That first slime mould lived in a dish in my desk drawer for a few weeks. I started to notice that the slime mould in my drawer was behaving in similar ways to the ants I was studying at the time.  So I decided to re-jig some of my ant protocols to study behaviour in slime moulds.

Credit: Scot Nelson Flickr (CC BY-SA 2.0)

What finding has surprised you the most so far in terms of what slime moulds are capable of?

I was shocked when we discovered that slime moulds were susceptible to the same ‘irrational’ behaviour we see in humans. I started that experiment with the opposite expectation, and I was looking forward to making ‘slime moulds are more rational than humans’ jokesI had always assumed that irrationality was linked to the way brains processed information; the idea that a unicellular organism might be subject to the same cognitive oddities was really eye opening. Nowadays, almost nothing I learn about slime mould behaviour surprises me – it’s incredible how much they accomplish without a brain!

What advantages do you think slime moulds have over animals when asking questions about how individual decisions lead to collective behaviour?

Slime moulds are relatively easy to work with in the lab, which allows us to run many replicates simultaneously. In the acellular slime moulds (ex. Physarum polycephalum) It’s also possible to run experiments with fragments of the same parent amoeba, so you can control for genetic background (all fragments should be genetically identical).  On the other hand, one of the downsides of working with acellular slime moulds is the concept of an ‘individual’.  Fragments cut from a main amoeba can become independent individuals within minutes. Those ‘individuals’ don’t always behave in the same way, even when given an identical decision task. Yet, if you put the fragments together again, they happily fuse back into a single entity. Each fragment consists of many oscillating regions that seem to control slime mould movement. We know that the slime mould will pulse faster when it’s in contact with something it likes (ex. food) and slower in contact with something it dislikes (ex. light). Each oscillating region is capable of entraining nearby oscillating regions and we think that it is the interaction between these regions that governs slime mould information processing.  So are oscillating regions each ‘individuals’? Are fragments individuals? Or are we better off thinking of all the slime mould fragments that share a common origin as individuals, irrespective of whether or not they are currently attached to one another (after all, they can fuse together again).  The whole concept of individuality is incredibly fluid in the acellular slime moulds, and this can make it hard to think about how collective behaviour actually arises.

In contrast, cellular slime moulds (like Dictyostelium sp), live most of their lives as individual amoebas. If conditions deteriorate (food runs out), the individual cells will aggregate to form a multi-cellular ‘slug’ that crawls away. The slug than transforms into a spore head atop a long stalk – the cells in the spore part get to disperse away in search of better conditions, while those in the stalk are left behind. It’s an amazing example of co operation, and gives us insight into how multi-cellularity can arise.  Thanks to some great work by Dictyostelium researchers, we know a fair amount about the molecular signalling that coordinates slug formation. However, we know very little about how (or even if) the slug makes decisions. 

 Credit: Bernard Spragg Flickr

Do you think if we can gain a greater understanding of how complex decisions are made using slime moulds, this might help inform areas of artificial intelligence?

Slime moulds are an excellent model for how to build an information processing system without needing the complexity of a brain.  Slime moulds illustrate an alternative model for behaviour and information processing and I think they cold one day serve as inspiration for computer algorithm.

What advice would you have for women who are thinking of pursuing a career in science?

Do what you love! The road from student to Principle Investigator is long and fraught with obstacles, detours and disappointments. But if you are passionate about your research, it makes the journey, however bumpy, much more enjoyable. And don’t be afraid to fail. Everyone fails. A lot. Sometimes spectacularly. Don’t let imposter syndrome stop you from taking risks and from pushing the boundaries of your discipline. 

 

Reference

Reid, C. R., & Latty, T. (2016). Collective behaviour and swarm intelligence in slime moulds. FEMS Microbiology Reviews, fuw033. doi: 10.1093/femsre/fuw033