A new international study involving La Trobe University geneticist Dr Jan Strugnell has come up with a surprise finding: there may well be just one species of giant squid, rather than the 21 previously described species.
‘What we found was totally unexpected – the data suggests that the Giant Squid is likely to be one single global species that is capable of long distance travel,’ says Dr Strugnell.
The work, just published by Britain’s Proceedings of the Royal Society B (Biological Sciences), has added fuel to the giant squid debate. These creatures – spanning up to 18 metres – have puzzled and captured the imagination of biologists and lay people alike.
The new genetics research is an important step in understanding the elusive giant squid that was filmed in its natural habitat for the first time this year.
Dr Strugnell is an internationally recognised expert on the origin and distribution of marine life, especially squids and octopuses.
She says 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 suspect that the population went through a “bottle-neck 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 and 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, it has been very hard to understand their behaviour and biology as they live deep in the ocean.
DNA from 43 squids
The research team into the giant squid was led by Dr Tom Gilbert from the Centre for Geogenetics, Natural History Museum of Denmark and University of Copenhagen.
He says ‘using genetics at this level, to study such a charismatic but poorly understood beast, has never been tried before.’
‘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 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.
Dr Strugnell says the next step 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’.
The research paper is titled ‘Mitochondrial genome diversity and population structure of the giant squid Architeuthis: genetics sheds new light on one of the most enigmatic marine species’.
Other scientists involved in the study include Inger Winklelmann, 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 squids used in the study came from Museum Victoria. – Dian Lipiarski
Images of squids by research team members Angel Guerra and Tsenemi Kubodera