Cephalopods—the
class of animals that comprises octopuses and squids—are ubiquitous throughout
the ocean, including in the deep sea. However, researchers still don't know
very much about the distribution, diversity and behaviors of cephalopods in
areas like the abyssal plains of the ocean floor. This is mostly due to the
inherent difficulty of studying the area, along with what is thought to be a
low abundance of cephalopods in the abyssal plains and their avoidance
behaviors.
Yet, in March of 2023, researchers
observed a rare and unique behavior in a deep-sea squid while taking visual
surveys in the Clarion-Clipperton Zone (CCZ) using a remotely operated vehicle
(ROV) with multiple cameras. The observation is documented in a recently published study in the journal Ecology.
Hiding in plain sight
As the ROV traversed the deep sea 4100 meters beneath the ocean's surface, its angled camera first captured what the research team thought were biogenic stalks—living organisms that appear as stalk-like structures, such as glass sponges or large tube worms that live in the depths of the sea. Four seconds later, the down-facing camera captured a squid quickly swimming across the camera's field of view.
During one of the transects, systematic video
recordings of the seafloor as the ROV moved forward, we captured a whiplash
squid passing directly beneath the ROV and entering the field of view of the
downward-facing camera. Credit: Ecology (2025). DOI:
10.1002/ecy.70257
The research team was baffled, as
the previous shots of the surroundings showed no evidence of a squid being
present. However, after reviewing the footage, they made an unexpected
discovery.
"On closer inspection, we
discovered that the squid had been buried under mud, between polymetallic
nodules, and only emerged moments before being recorded in the water column. In
the angled video, it can be seen motionless, positioned upside-down with the
siphon and both of its elongated tentacles extending rigidly toward the water
column.
"The squid only became obvious
after it abandoned this behavior and swam away, disturbed by the proximity of
the ROV. This was puzzling as mastigoteuthids, including the only other
specimen detected at the CCZ, typically occur near the bottom in a tuning fork
posture," the study authors explain.
The squid was observed to have
short arms and long white tentacles, with a mantle length of around 10
centimeters and a tentacle length of around 22 centimeters. The team says it is
likely a previously undescribed species of whiplash squid, from the family
Mastigoteuthidae.
Rare or just hidden?
The squid may have been exhibiting
this odd behavior, known as "masquerading", either to disguise itself from predators, like
the beaked whale, or from prey. Hiding and lying in wait for prey helps animals
conserve energy compared to chasing prey. The authors note that, to their
knowledge, this is the first time that masquerading has been observed for a
deep-sea cephalopod.
Across the Northeast Pacific abyss,
whiplash squids had only been encountered once before, and only four
cephalopods in total had been observed in the region since seabed surveying
began in the 1970s. Due to the rarity of observations, researchers have thought
that their abundance was quite low. However, it now seems that they may have
simply been good at hiding.
The study authors write, "As
with the number of genetic species, the occurrences and distributions we report
here are most certainly an underestimate, since (as this study shows)
cephalopods can self-disguise as well as sense and potentially avoid underwater
sampling vehicles, which are the main source of our ecological and taxonomic
knowledge for the abyssal Pacific."
The abyssal seabed's threatened future
The team says that these deep sea
regions are under threat from risks related to ocean acidification from climate change and seabed mining, which is
currently expected to increase in the near future. Better understanding the
ecosystems and abundance of creatures, like cephalopods, in the abyssal seabed
can help to inform conservation and management strategies, especially in areas
targeted for resource extraction.
The abyssal plains cover more than half of Earth's surface area, and this study underscores how much remains unknown about the habitats that exist there. More targeted studies with unobtrusive camera platforms are needed to better understand deep-sea cephalopod diversity and behavior, especially before these habitats become unrecognizable due to future threats.
Source: Deep-sea squid caught masquerading as sponge stalks in Pacific abyss
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