Genetics closer to understanding the elusive giant squid

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 that 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.

“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,” said 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.

“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.”

“Using genetics at this level, to study such a charismatic but poorly understood beast, has never been tried before,” said 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,” said Dr Strugnell.

The research paper has been published in the 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 Genetics Department 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 the museum.