An extensive survey of deep waters off the coast of Australia has resulted in a trove of bigfin squid sightings. And by trove, we mean the detection of five individuals — these deep-sea creatures are exceptionally rare, so any new observations are quite valuable to scientists.
“Deep-sea cephalopods are highly diverse and widespread yet often shrouded in mystery,” opens a new study published today in PLOS ONE.
The deep-sea cephalopod in this case is a strange and poorly understood marine animal known as the bigfin squid. The new paper, co-authored by marine biologist Deborah Osterhage from CSIRO Oceans and Atmosphere in Tasmania, Australia, describes a recent deepwater survey in which five of these animals were captured on camera. The resulting data is filling in some important gaps about bigfin squid, such as their distribution, physical characteristics, and behaviour.
Sightings of this odd squid, a member of the Magnapinnidae family, are scant, and little is known about them. To date, there have been only three confirmed sightings in the Southern Hemisphere, all in the eastern Pacific. Dead specimens, mostly juveniles, sometimes make an appearance, but they’re often badly damaged by trawling. What we do know, however, is that these squid have large fins and extraordinarily long “vermiform” arm and tentacle filaments that dangle behind them like impossibly long strands of spaghettini.
Osterhage and her colleagues recorded the bigfin squid during expeditions of the Great Australian Bight Deepwater Marine Program. From 2015 to 2017, the team scoured this region to learn more about the geology and ecology of the Great Australian Bight (GAB), a large open bay off the continent’s southern coast. They did so with a remotely operated vehicle (ROV) called Investigator, which was equipped with a high-definition video camera, lights, and paired lasers. A camera towed behind the boat took still photos every five seconds.
The researchers managed to cover 281 square kilometres during the survey, collecting 75 hours of video and over 10,000 still images. The towed camera scanned depths between 946 to 3,258 metres. This all resulted in five sightings of bigfin squid, which more than doubles the number of sightings in the Southern Hemisphere. What’s more, it’s the first time that bigfin squid have ever been seen in Australian waters.
Interestingly, these animals were observed close together. In one case, two squid were seen within 12 hours of each other, and in another case just 6 km apart. In all, the five bigfin squid were seen in only two areas, two in one, and three in the other. The clustering of these individuals is likely due to “specific environmental needs” and/or “increased reproductive opportunities,” according to the paper.
As for their preferred habitat, the squid seemed to like areas containing soft sediment, the lower slopes of erosion channels, and the upper sections of submarine canyons. The animals were spotted at depths between 2,000 to 3,000 metres. As to whether the relatively high number of individuals seen in this part of the GAB equates to a bigfin squid hotspot “remains to be seen,” write the authors.
The authors ruled out the possibility that some sightings were of the same individual, noting physical differences among the specimens. Because the squid were often filmed or photographed without a frame of reference, the researchers turned to a technique in which paired lasers were pointed at their bodies, thus providing a sense of scale. They were able to measure, for example, the length of their unique filaments, the longest of which was 183 cm long.
The researchers also got a sense of their behaviours. During one of the sightings, a squid swam away from the camera and settled into a vertical position just slightly above the seafloor. Three of its filaments then became coiled, in what is a previously unknown behaviour among squid, say the authors. The squid moved their bodies through the water by flapping their fins and making oscillating, back-and-forth movements (i.e. sinusoidal undulations).
Another behaviour reported by the researchers is known as the “elbow pose.” Here, the squid assume a vertical posture, with their appendages are spread outwards while the end-most points of the filaments dangle downward at a sharp angle, in some cases close to 90 degrees, toward the seafloor. A previously unknown variation on this pose, in which the squid’s body is horizontal relative to the seafloor, was documented during the expedition. The authors aren’t entirely sure about the point of all of this, but they think it might be a fishing posture used to catch prey.
The squid were usually pale, featuring hues of pink, orange, and dark reddish-brown. In some cases the mantle (the main part of the squid body) and fins appeared slightly translucent. And in fact, the orangey colour may actually correspond to an internal organ (possibly a digestive gland), say the authors.
“These sightings add to our knowledge of this elusive and intriguing genus, and reinforce the value of imagery as a tool in deep-sea squid research,” conclude the scientists.
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Australian wildlife continues to astound. Late last month, for example, researchers described the discovery of an unusually tall coral reef measuring 500 metres tall hosting a unique ecosystem. More strange creatures are sure to be discovered and described in the coming months and years, so stay tuned for more exciting findings from this part of the world.