Failure to Launch: Understanding Reproductive Failure in Turtles and Tortoises
SHOW NOTES
Alessia’s love for turtles and tortoises can be traced back to her childhood in the Seychelles [5.12]. Growing up in the Island Nation, she established a connection to the ocean very early on in life. But, although she always held the ocean “close to her heart”, becoming a marine scientist wasn’t always her career of choice. “I couldn’t decide between the marine world and the land world. All I knew is that I had a deep passion for studying animals.” She explains. In a way, Alessia’s current focus on the Order Testudines is the best of both worlds, allowing her to keep one foot in the terrestrial environment (tortoises) and the other underwater (turtles).
Alessia’s research seeks to understand the drivers of reproductive failure in both tortoises and turtles [17.48]. This particular interest was sparked years ago, before Alessia had even thought about PhDs. Before university, Alessia took on her first job as a research and field assistant in the Seychelles, working with turtles and terrapins. For this position, she spent a lot of time visiting and revisiting nests, and noticed that there was always a proportion of eggs that didn’t hatch. Furthermore, there were also a small subset of those eggs that had no evidence of development (in other words, no obvious embryo inside, just a yolk). Alessia discovered that these undeveloped eggs were quite a mystery. It was difficult to ascertain just by eye whether an embryo had died early, or whether the eggs were simply unfertilised. This set Alessia on a path of discovery. While completing an integrated masters in Zoology, she came across a field of research that aimed to tackle the same question, but in birds. Alessia began to wonder if the same methods could be applied to Testudines – and there were the seeds of her future PhD. Alessia’s initial curiosity has now grown into a fully-formed PhD project, based at the University of Sheffield.
But why is it important to understand reproductive failure in the first place? Does it matter if a few eggs don’t make it? In the current climate, it is critical [34.36]. Over 60% of all turtles and tortoises are threatened with extinction – that means that if you looked at any two species of turtle or tortoise, there would be an over 50% chance that one of them is endangered in some shape or form. Some have argued that this makes them more threatened than all birds, or even sharks. There are multiple reasons for this, namely the illegal pet trade, habitat destruction, and marine pollution. This means that reproductive failure can have a larger impact. “It’s becoming more and more important [to understand], as we’re trying to navigate in this world of change.” Says Alessia. Additionally, the underlying causes for reproductive failure may also be linked to human activity. Climate change, for example, is a big worry when it comes to turtle and tortoise reproduction. In the great majority of species, temperature influences the sex of the hatchlings [30.47]. As a general rule, cooler temperatures result in more males, and warmer will cause more females to develop. Under normal conditions the ratio of male:female would be relatively equal, but at extreme temperatures a sex bias may occur. For example, in Florida, studies have shown that for the last four years, 99% of all hatchlings born were female. This could cause problems for the longevity of the population. And that’s just the impacts that we know of – some factors may cause the egg not to hatch at all, the embryo to die prematurely, or affect fertilisation rates. This is all what Alessia is trying to disentangle.
Studying turtle and tortoise eggs from around the world is no mean feat. First, Alessia has to ship the unhatched eggs from the nesting site to the lab, which involves a lot of paperwork and some very confused couriers [35.45]. The majority of wild specimens in Alessia’s research have come from the Seychelles, including D’Arros – with help from the Save Our Seas Foundation D’Arros Research Centre. After significant effort, the eggs make their way across hemispheres, eventually arriving at the University of Sheffield where Alessia conducts her labwork. In addition to the wild eggs, Alessia has also received captive specimens from a number of Zoos and Aquaria, who have partnered with Alessia on the project. Then, finally, once all the eggs have arrived, Alessia can begin in earnest [39.50]. She starts by carefully dissecting them, and carefully removing the tiny part where fertilisation occurs. Then, she applies a special dye that sticks to and stains DNA. This can help detect the presence of embryonic cells, which would indicate that the egg had been fertilised. In this case, the dye will turn the cells bright blue. Alessia describes it as “quite beautiful. They look like something out of the galaxy or night sky.”
This method, which Alessia has adapted from studies on birds, is the focus of her new paper, Understanding Early Reproductive Failure in Turtles and Tortoises, which was published this year (2024). Alessia was able to prove that this was a reliable method for analysing the type of reproductive failure, separating lack of fertilisation from embryonic death [46.21]. Her research also has important implications for the conservation of turtles and tortoises. She has found that not only do different species have different causes of reproductive failure – for example, hawksbill turtles were suffering embryonic mortality, but other species had higher rates of unfertilised eggs – but that there are differences between populations of the same species, like the Aldabra giant tortoise. This means that conservation strategies need to be made at both the species and population level, taking account of different biological and ecological factors between species, but also the different pressures faced by specific populations. So this is why I’m saying that it really needs to be looked at on the population level. “For instance, if we look at the sea turtles and the giant tortoises, the sea turtles, they have the entire sea to roam.” Says Alessia. “They can go to different islands. If they find other adults, they have the entire sea to work around with. They’re not confined to one specific spot. The giant Aldabra tortoises on the other hand, most of the time, they’re going to be on the same island they’ve always been on. It’s very rare that they’ll drift to another place…but this is why you have these different islands that potentially there’s different problems going on…even if you’re looking at one species it could be different in different places.”
In this sense, Alessia’s research is an unfinished story. She plans to head back to the Seychelles in the near future to collect more eggs, and dive deeper into some of these nuances in order to better inform conservation efforts [50.04]. “The methods we’ve developed, this is just the starting point. It is pointing you into the right direction. And that’s really useful for conservation because time and money is very limited. And if you can get your questions down, and you know from the get go, you save time and money…and you’re not just doing guessing games, which is what I feel is happening a lot because there is no other choice. I’d like to give people that choice.”
You can follow Alessia and find out more about her work on Instagram and TikTok (@turtle_eggsplorer) and check out her Save Our Seas Foundation project here.
ABOUT OUR GUEST
Alessia Lavigne
PhD Researcher, University of Sheffield
Alessia Lavigne is a Seychellois/Italian PhD researcher and Science Communicator, who aims to share the beauty of her experience in research and turtles via the incredible power of social media. Her first close contact with the world of turtles was as a Field Research Assistant in her home country: the Seychelles. During this time, she learnt many lessons and gaps in our knowledge when it came to understanding turtles – information she took with her when she pursued an MBiolSci Zoology in the UK at the University of Sheffield.
For her Masters’ research project, she was determined to know why undeveloped turtle eggs were failing to hatch; this was currently a mystery in science as methods so far struggled to tell if these eggs failed due to (microscopic level) embryo death or fertilisation failure. Therefore, the goal of her project was to re-adapt methods originally designed for bird eggs and use this in turtle eggs! Making this simple difference is incredibly important for global conservation management of threatened turtles and tortoises! It will be a necessary tool to monitor the impacts of factors such as climate change, pollution, global warming and more on the reproductive health and early embryo development of turtles.
In partnership with multiple conservation groups in the Seychelles and UK zoos, they have now successfully re-adapted these methods in five different species of turtles and tortoises. Following graduation with Honours, she was awarded two grants to assess the fertility and embryo survival rates for threatened turtles and tortoises in Seychelles using these methods by Save Our Seas Foundation and Seychelles Conservation and Climate Adaptation Trust.
She was later awarded a PhD scholarship to extend her research into the drivers of reproductive failure of threatened turtles and tortoises – an exciting journey she shares on Tiktok and Instagram to spark inspiration and care for science and conservation through her experiences inside and outside the lab.
