The day of the PhD defence: Le Qin Choo

March 23rd, 2022
Le Qin Choo

Thursday March 24th at 13:00, Le Qin Choo will enter the Agnietenkapel in Amsterdam to defend her thesis entitled “Genomic variability and population structure in shelled pteropods”. For her PhD research at Naturalis and the University of Amsterdam, she studied the population structure and the amount of variation pteropods have across their entire range.

Follow the ceremony

Le Qin’s defence will take place Thursday March 24th at 13:00 at the Agnietenkapel in Amsterdam and can be followed online


During an expedition of 25 days at sea, Le Qin woke up at 2 AM almost every morning to put down plankton nets. She collected pteropod samples in the dark, because pteropods come up to the surface to feed during the night. She analysed the collected samples in a lab in Norway, where they worked on a new technique to look at different parts of the genome. “I’m very proud of applying this technique where we looked at their genome-wide variation, because it hadn’t been done in pteropods before. Now we have a lot of information on them”, Le Qin adds. She gained these experiences during her PhD at the Plankton Diversity and Evolution department at Naturalis, studying the genomic variation of pteropods.

Le Qin studying pteropods on board the Pelagia research vessel, together with her fellow PhD student Lisette Mekkes
Le Qin on the Netherlands Initiatives Changing Oceans expedition (left) and studying pteropods on board the Pelagia research vessel, together with her fellow PhD student Lisette Mekkes (right).


for snails

Growing up in Singapore, Le Qin often went to the beach with her sister, where they plucked snails off rocks and played with small crabs. This is where her interest in snails started, and it became even bigger when she started working at the lab on intertidal snails when she was in high school. “I think snails are really adorable organisms,” Le Qin says, “because of their little shells, and their little eyes. They’re such graceful creatures.” 

After her Master internship, which was also about snails, she worked at the marine lab in Singapore, waiting for the perfect PhD opportunity to come by. “One day my master supervisor sent me an email about a PhD opening. I thought: “It’s about snails, it's about global climate change, I’m in!” So I applied for it and here I am”, Le Qin says enthusiastically.

Did you know you don't pronounce the first p in pteropods?

Here’s how to remember it:

“Why can't you hear pteropods urinate?” 

“Because the p is silent.”



Pteropods are also called sea butterflies, because of the way they fly and flap in the water. They are important planktonic organisms, because they’re at the base of the marine food chain. Apart from that, shelled pteropods have very thin shells that are susceptible to ocean acidification. Therefore, we use them as “canaries in the coalmine” to detect early signs of changes in the ocean ecosystem. 

During her PhD, Le Qin studied the genetic variation of pteropods and their variation in shell shape. She analysed the samples she collected herself on the expedition, as well as other samples collected up to ten years ago. Her aim was to see if there are one big or several smaller populations of pteropods.


Le Qin unravelled some interesting findings about the structure of the Atlantic Ocean. The Atlantic Ocean is one basin of water where she encountered three different pteropod populations. From the genome analyses, she found that these populations don’t appear to interbreed with each other. “Maybe these populations can even be considered different species. For now we only know what their differences are on a genomic level. We need to study many more specimens and find out more about their morphological or ecological differences to be certain they are different species”, she explains. 

Together with a masters student, Le Qin is conducting ongoing research to look into genetic differences across more specimens in the Atlantic Ocean, including young pteropods. They want to find out if these populations are indeed separated despite their life stage and years of sampling.

more secrets

Next, research can focus on finding differences among these pteropod populations, including their shell shape, behaviour and ecology. In the future, we will hopefully know more about how pteropod diversity is organised in the open ocean and whether there are some barriers that these plankton can see but we cannot. Le Qin explains why this is relevant: “This could tell us more about how plankton can diverge in the open ocean, and that’s important for speciation: the study on how species arise and how they’re maintained.” This is crucial information if we are using pteropods as bioindicators of ocean ecosystem changes. We want to be able to compare their ability to respond to ocean changes across different species.


Starting in April, Le Qin starts a new postdoc position at a lab in Sheffield. “I will be working on intertidal snails and study how they speciate in their habitat through changes in their genome. These changes are chromosomal inversions, which means that some parts of the genome are switched around.” She is looking forward to working on this new project in the coming two years.


Le Qin Choo did her PhD at the Plankton Diversity and Evolution department at Naturalis, under supervision of Katja Peijnenburg.

Read Le Qin’s thesis here