Big surprise in giant squid research

La Trobe University geneticist Dr Jan Strugnell is part of an international group of biologists that have added fuel to the giant squid debate. Their research suggests there is just one single species of giant squid, capable of long distance travel, rather than the 21 previously described species that were thought to exist. 

Squid tentacle‘What we found was unexpected – the data suggested that the Giant Squid is likely to be one single global species that is capable of long distance travel,’ says Dr Strugnell.

‘Additionally, giant squids have very low genetic diversity which is uncommon for a highly dispersed large population. We can't be sure of the reason for this– we hypothesise that the population went through a ‘bottleneck event’ due to predators or competitors decreasing the size and gene pool of the population.

‘Perhaps this was followed by climatic changes associated with the last ice age, negatively impacting predators or competitors and allowing the giant squid to increase in population size. We expect the population expansion to have occurred between 32 000-115 000 years ago resulting in a larger population with a restricted gene pool,’ says Dr Strugnell.  

‘Even though these squids are found all around the world and are enormous, spanning 18 metres, it has been very hard to understand their behaviour and biology as they live deep in the ocean and were only first filmed in their natural habitat this year, says Dr Strugnell.

‘Using genetics at this level, to study such a charismatic but poorly understood beast, has never been tried before,’ says Dr Tom Gilbert, team leader, Centre for Geogenetics, Natural History Museum of Denmark and University of Copenhagen.

‘Through our global team of collaborators we managed to obtain extremely high quality samples from across the giant squid's known range, and, by applying state-of-the-art DNA sequencing tools, obtained a large scale dataset with which we will try to explain some of the things that have puzzled us about the species.’

The research team sequenced a segment of mitochondrial DNA from 43 squids from around the world, including some from Australian waters, to determine the number of Giant squid species that exist. Mitochondrial DNA is only passed on from mother to offspring.  

‘The next step of our research is to validate these findings and determine whether our theories about the evolution of this species are correct by analysing nuclear DNA, which is found in most cells, and to establish if this low diversity exists across the entire genome,’ says Dr Strugnell.

The research paper – titled ‘Mitochondrial genome diversity and population structure of the giant squid Architeuthis: genetics sheds new light on one of the most enigmatic marine species’ – has been published on Royal Society Journal Proceedings of the Royal Society B (Biological Sciences).

Other scientists involved in the study include Inger Winkelmann, a PhD candidate at Denmark’s Centre for Geogenetics who also worked with La Trobe’s Department of Genetics and sequenced and analysed the majority of DNA; and Dr Mark Norman, Head of Sciences at Museum Victoria.  Some of the individuals used in the study came from Museum Victoria.

Read more about Dr Strugnell's marine life research.


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Dr Jan Strugnell
Genetics Department
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Dian Lipiarski
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