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Magnapinna squid. Credit: Osterhage et al. (PLOS ONE, 2020) CC BY
One of the most notable groups of deep-sea squid is the Magnapinnidae, known for their large fins and extraordinarily long arm and tentacle filaments. Little is known of their biology and ecology as most of the specimens are damaged and juvenile and sightings in situ are scarce, counting around a dozen globally.
As part of a recent large-scale research program in the Great Australian Bight, remotely operated vehicles and a towed camera system were deployed at depths of 946-3258m resulting in five Magnapinna sp. sightings.
These represent the first Bigfin Squid records in Australian waters and more than double the known records from the Southern Hemisphere, reinforcing a hypothesis of cosmopolitan distribution. Since most of the previous observations were of single Magnapinna squid these multiple sightings were quite revealing, having been found in close spatial and temporal proximity to each other. The morphological differences indicate that each sighting is from an individual rather than multiple sightings of the same squid.
In terms of morphology, previous in situ measurements were roughly based on nearby objects of known size, but this study used coupled lasers visible on the body of a Magnapinna squid, providing more precise scaling of size.
Juvenile-sized squids have also been recorded and it is confirmed that they possess the long distal filaments that have so far been mostly missing from the specimens due to damage.
The authors described fine-scale habitats, in situ staining and behavioral components, including a horizontal example of “elbow” position and wrapping of distal filaments – a behavior not previously seen in squid. These sightings increase our knowledge of this elusive and intriguing genre and reinforce the value of the imagery as a tool in deep-sea squid research.
Reference: “Multiple Observations of Bigfin Squid (Magnapinna sp.) in the Great Australian Bight reveal rarely seen distribution patterns, morphological features and behaviors “by Deborah Osterhage, Hugh MacIntosh, Franziska Althaus and Andrew Ross, 11 November 2020, PLOS ONE.
DOI: 10.1371 / journal.pone.0241066
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