Bigfin squid

Anatomy

The specimens in the videos looked very distinct from all previously known squids. Uniquely among cephalopods, the arms and tentacles were of the same length and looked identical (similar to extinct belemnites). The appendages were also held perpendicular to the body, creating the appearance of strange "elbows". Most remarkable was the length of the elastic tentacles, which has been estimated at up to 15–20 times the mantle length. This trait is caused by filament coiling of the tentacles, a trait that is rare among similar species.^[4] Estimates based on video evidence put the total length of the largest specimens at 8 m (25 ft) or more, with some estimates up to 12 m (40 ft).^[21] Viewing close-ups of the body and head, it is apparent that the fins are extremely large, being proportionately nearly as big as those of bigfin squid larvae. While they do appear similar to the larvae, no specimens or samples of the adults have been taken. While their exact identity is unknown, all of the discovered specimens can be observed to have a beige color body, translucent fins, near-white tentacles, and dark eyes.^[4] These species of squids are mainly identifiable by their long thin arms and specific colors. The squid also have a unique brachial crown that sets them aside from other known families.^[10]

Feeding behaviour

Little is known about the feeding-behaviour of these squids. Scientists have speculated that the bigfin squid feeds by dragging their arms and tentacles along the seafloor and grabbing edible organisms from the floor.^[22] Alternatively, they may simply use a trapping technique, waiting passively for prey such as zooplankton^[12] to bump into their arms^[22] (see Cephalopod intelligence). The diet of the bigfin squid is unknown. However, cephalopods are known to feed on crustaceans, jellyfish, and even other cephalopods.^[23]

Observation timeline

The first visual record of an adult bigfin squid was in September 1988. The crew of the submersible Nautile encountered a bigfin squid off the coast of northern Brazil, 10°42.91′N 40°53.43′W, at a depth of 4,735 metres (15,535 ft). In July 1992, the Nautile again encountered these creatures, observing two individuals during a dive off the coast of Ghana at 3°40′N 2°30′W, first at 3,010 metres (9,880 ft) depth, and then again at 2,950 metres (9,680 ft). Both were filmed and photographed.^[20] In November 1998, the Japanese crewed submersible Shinkai 6500 filmed another bigfin squid in the Indian Ocean south of Mauritius, at 32°45′S 57°13′E and 2,340 metres (7,680 ft).^[24]

Eric Leveton's video, which was later shared with Vecchione, was taken from the remotely operated underwater vehicle (ROV) of the oil-drilling ship Millennium Explorer in January 2000, at Mississippi Canyon in the Gulf of Mexico (28°37′N 88°00′W) at 2,195 metres (7,201 ft), and allowed for a size estimate. By comparison with the visible parts of the ROV, the squid was estimated to measure 7 metres (23 ft) with arms fully extended.^[20] The Nautile filmed another Indian Ocean specimen at 19°32′S 65°52′E and 2,576 metres (8,451 ft), in the area of Rodrigues Island, in May 2000.^[20] In October 2000, the crewed submersible Alvin found another bigfin squid at 1,940 metres (6,360 ft) in Atwater Valley ^[wd], Gulf of Mexico (27°34.714′N 88°30.59′W).

These videos did not receive any media attention; most were brief and fairly blurry. In May 2001, approximately ten minutes of crisp footage of a bigfin squid were acquired by ROV Tiburon, causing a flurry of attention when released.^[25] These were taken in the Pacific Ocean north of Oʻahu, Hawaii (21°54′N 158°12′W), at 3,380 metres (11,090 ft). This video and the pre-2001 videos (which had not previously received much scientific attention) were documented by Vecchione et al in a paper that year, and some of the earlier footage was further analyzed by Guerra et al (2002).^[18][20]

On 11 November 2007, a bigfin squid was filmed off Perdido, a drilling-site owned by Shell Oil Company, located 200 statute miles or 320 km off Houston, Texas in the Gulf of Mexico. The ROV that filmed the squid had originally been sent to retrieve drilling equipment from the seabed, and encountered the squid floating near a well. After being circulated within the oil industry, the footage was shared with National Geographic News to have its identity determined, and was released to the public in 2008. This video received significant online attention in the years since its filming.^[22][26][27]

Observations of bigfin squid were made in the Great Australian Bight during towed camera and remote operated vehicle surveys in 2015 and 2017 respectively.^[4] In 2018, the first observations of a bigfin squid were made from the Southern Caribbean, off the coast of Colombia.^[28]

In March 2021, during the expedition to document the wreck of the USS Johnston, the submersible DSV Limiting Factor recorded footage of a juvenile bigfin squid from the Philippine Trench at a depth of 6,212 metres (20,381 ft). This is the deepest observation of any squid, and rivalled only by some unidentified cirrate octopods from the same habitat as the deepest observation of any cephalopod. This makes Magnapinna the first squid known to inhabit the hadal zone.^[5][6]

On 9 November 2021, a video of a bigfin squid was captured at a ridge feature off the West Florida Escarpment by an ROV from the NOAAS Okeanos Explorer as part of the Windows to the Deep 2021 expedition.^[29][30] The squid was found at a depth of 2,385 m (7,825 ft).^[31]

ROV SuBastian of Schmidt Ocean Institute observed a bigfin squid in close proximity to a black smoker-type hydrothermal vent on 4 April 2023, during the "In Search of Hydrothermal Lost Cities" expedition. The squid was seen at a depth of 1,931 m (6,335 ft).^[32]

List

Date - Dates are given to the level of precision available from the source material - telemetry displayed is used for observations where an ROV video is the primary source

Observer - Corresponds either to the person who collected the specimen; the vessel the specimen was collected on, or the vessel that observed the specimen for video-only observations.

Location - Given in Latitude/Longitude when available, otherwise the general region is given. For ROV dives with navigation data available, a link to the corresponding dive track is given, unless a more precise location is specified by a secondary source. Some coordinates from commercial ROVs are specified via UTM rather than Latitude/Longitude.

Depth - Supplied based on precision available from collection method for physical specimens; otherwise telemetry from ROV observations is used.