Bigfin squid

Bigfin squids are a group of rarely seen cephalopods with a distinctive morphology. They are placed in the genus Magnapinna and family Magnapinnidae. Although the family was described only from larval, paralarval, and juvenile specimens, numerous video observations of much larger squid with similar morphology are assumed to be adult specimens of the same family.
The arms and tentacles of the squid are both extremely long, estimated at. These appendages are held perpendicular to the body, creating "elbows". How the squid feeds is yet to be discovered.
Magnapinna is thought to be the deepest-occurring squid genus, with sightings as deep as below the surface, making it the only squid known to inhabit the hadal zone.

Taxonomy

Magnapinna is the sister group to Joubiniteuthis, another little-known deep-sea squid with an unusual body plan and long arms. Both Magnapinna and Joubiniteuthis are monotypic genera within their own families, Magnapinnidae and Joubiniteuthidae respectively. They are also closely related to the "whip-lash squid" in the families Chiroteuthidae and Mastigoteuthidae.''''

Physical specimens

The first record of this family comes from a specimen caught off the Azores on 10 August 1883. Due to the damaged nature of the find, little information could be discerned, and it was classified as a mastigoteuthid, first as Chiroteuthopsis talismani and later as Mastigoteuthis talismani. In 1956, a similar squid was caught in the South Atlantic, but little was thought of it at the time. The specimen was illustrated in Alister Hardy's The Open Sea, where it was identified as Octopodoteuthis sicula.
During the 1980s, two additional immature specimens were found in the Atlantic, and three more were found in the Pacific. Researchers Michael Vecchione and Richard Young were the chief investigators of the finds, and eventually linked them to the two previous specimens, erecting the family Magnapinnidae in 1998, with Magnapinna pacifica as the type species. Of particular interest was the very large fin size, up to 90% of the mantle length, that was responsible for the animals' common name.
A single specimen of a fifth species, Magnapinna sp. B, was collected in 2006. Magnapinna sp. A was described as Magnapinna atlantica in 2006.
The genus was described from two juveniles and paralarva, none of which had developed the characteristic long arm tips. However, they did all have large fins, and were therefore named "magna pinna", meaning "big fin".

Sightings

The presumed adult stage of Magnapinna is known only from video observations from submersibles, deep sea oil rig cameras, and remotely-operated vehicles ; no physical specimens have yet been collected, leaving their exact identity unknown. These individuals and the collected juvenile specimens share the large fins and the vermiform arm tips with no suckers, but the iconic elongated arm tips are known only from the presumed adult individuals. Although it has not been directly confirmed whether these squid are the same as the Magnapinna known from specimens, it is largely accepted that they are members of Magnapinnidae.
Although observations had been made over a decade earlier, adult bigfin squid only became known to science in 2001, when marine biology student Heather Holston sent footage of what she described as a "21-foot-long squid" to teuthologist Michael Vecchione. The footage had been recorded from an ROV in the Gulf of Mexico in January 2000 at the request of Holston's boyfriend Eric Leveton, who planned on showing it to her. Leveton was a structural engineer aboard the oil-drilling ship Millennium Explorer, who had happened to look into the ROV operation shack when the squid was observed by operators. Although Vecchione initially surmised from Holston's description that the footage might be the first video of a live giant squid, he realized that the video itself portrayed a completely different squid that had no known identity.
Further discussions with other cephalopod researchers found no leads on the identity of the squid, and it was thus dubbed the "mystery squid" for a portion of time. Analysis by Vecchione et al of previous footage from submersibles found other video records of bigfin squid, the earliest from 1988. Around the same time, new high-quality footage of a bigfin squid was also recorded off Hawaii by the ROV Tiburon. In December 2001, Vecchione et al published a paper collating these observations; this was also the first paper to identify them as potential members of the Magnapinnidae, which had been named by Vecchione from the juvenile specimens a few years earlier. Independent of Vecchione's publication, Guerra et al published a paper the following year analyzing some of the early bigfin squid footage, and also identified them as potential adult magnapinnids.

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. 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. Estimates based on video evidence put the total length of the largest specimens at or more, with some estimates up to. 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. 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.

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. Alternatively, they may simply use a trapping technique, waiting passively for prey such as zooplankton to bump into their arms. The diet of the bigfin squid is unknown. However, cephalopods are known to feed on crustaceans, jellyfish, and even other cephalopods.

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,, at a depth of. In July 1992, the Nautile again encountered these creatures, observing two individuals during a dive off the coast of Ghana at, first at depth, and then again at. Both were filmed and photographed. In November 1998, the Japanese crewed submersible Shinkai 6500 filmed another bigfin squid in the Indian Ocean south of Mauritius, at and.
Eric Leveton's video, which was later shared with Vecchione, was taken from the remotely operated underwater vehicle of the oil-drilling ship Millennium Explorer in January 2000, at Mississippi Canyon in the Gulf of Mexico at, and allowed for a size estimate. By comparison with the visible parts of the ROV, the squid was estimated to measure with arms fully extended. The Nautile filmed another Indian Ocean specimen at and, in the area of Rodrigues Island, in May 2000. In October 2000, the crewed submersible Alvin found another bigfin squid at in, Gulf of Mexico.
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. These were taken in the Pacific Ocean north of Oʻahu, Hawaii, at. This video and the pre-2001 videos were documented by Vecchione et al in a paper that year, and some of the earlier footage was further analyzed by Guerra et al.
On 11 November 2007, a bigfin squid was filmed off Perdido, a drilling-site owned by Shell Oil Company, located 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.
Observations of bigfin squid were made in the Great Australian Bight during towed camera and remote operated vehicle surveys in 2015 and 2017 respectively. In 2018, the first observations of a bigfin squid were made from the Southern Caribbean, off the coast of Colombia.
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. 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.
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|NOAAS Okeanos Explorer] as part of the Windows to the Deep 2021 expedition. The squid was found at a depth of.
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.

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.

#	Date	Observer	Location	Depth	Comment	Sources	Video	Collected	Catalog #
1	Aug 10, 1883	Talisman Expedition	34°46'N, 36°11'W	3175m	Juvenile or sub-adult, damaged during trawl and missing arms. Retrieved near the Azores. Designated "Chiroteuthopsis Talismani"		N/A	Yes
2	September 9th, 1924	S. S. Pickle	Cape Town	240fms	Magnapinna sp. C. Collected during surveys by John Gilchrist off South Africa in 1924. Designated "Octopodoteuthopsis sp. A" by G. C. Robson		N/A	Yes
3	March 18th, 1954	J. E. Fitch	30°22'N, 129°45'W	N/A	From Alepisaurus ferox stomach caught by observer		N/A	Yes	USNM 885787
4	May 2-3, 1961	R/V "Chain"	11°13'N, 29°54'W to 11°21'N,30°06'W	0-125fms	Cruise 17 R.H. Backus		N/A	Yes	MCZ Malacology 370373
5	Jan 16, 1966	R/V Anton Bruun	-34.016666°, -84.966666°	0-2900m	Magnapinna pacifica		N/A	Yes	MCZ Malacology 392887
6	1985-1987	N/A	Off Oahu	0-300m	Unknown larva, described as "big-fin"		N/A	Yes
7	Sept 11th, 1988	Nautile	10°42.9'N, 40°53.4'W	4735m	, RV Nadir supporting			No	N/A
8	July 1992	Nautile	3°40'N, 2°30'W	3010m	, RV Nadir supporting		N/A	No	N/A
9	July 1992	Nautile	3°40'N, 2°30'W	2950m	, RV Nadir supporting, possibly same individual from 9		N/A	No	N/A
10	April 23, 1995	David Starr Jordan	33°49'N, 121°51'W	0-200m	Cruise 9505, Station 24		N/A	Yes
11	September 16th, 1995	N/A	27°09'N, 86°07'W	N/A	M. atlantica holotype		N/A	Yes
12	June 21st, 1997	Discovery (1962)\|Discovery]	37°14'N, 32°18'W	N/A	Captured at Discovery station 13198 #7		N/A	Yes
13	November 1, 1998	DSV Shinkai 6500	32°45'S,57°1'E	2340m	Shinkai 6500 Dive 460 Cruise YK98-08 MODE'98 Leg4 - Atlantis II Fracture Zone -			No	N/A
14	January 2000	Commercial ROV	28°37'N,88°00'W	2195m	ROV operating from Millenium Explorer			No	N/A
15	May 2000	Nautile	19°32'S, 65°52'E	2576m	, RV Atalante supporting		N/A	No	N/A
16	October 2000	DSV Alvin	27°34.7'N,88°30.6'W	1940m	RV Atlantis supporting DSV Alvin, WHOI cruise			No	N/A
17	May 16th, 2001	Tiburon	21.9°N, 158.2° W	3380m	RV Western Flyer supporting ROV Tiburon			No	N/A
18	September 4th, 2001	Kaikō ROV	19.13000, -155.09720	2586m	KAIKO Dive 208 Cruise KR01-12_leg2			No	N/A
19	September 13th, 2001	Kaikō ROV	19.83670, -154.54330	3890m	KAIKO Dive 215 Cruise KR01-12_leg2			No	N/A
20	November 26th, 2003	Hercules 8	26°10'48"N, 94°37'23"W	2750m	Discoverer Deep Seas supporting ROV Hercules 8			No	N/A
21	December 29th, 2003	Hercules 8	26°15'N, 94°40'W	3050m	Discoverer Deep Seas supporting ROV Hercules 8		N/A	No	N/A
22	July 11th, 2004	R/V G.O. Sars	42°8'N, 29°3'W	N/A	Bergen Museum MAR-ECO cruise super station 46, local station 374		N/A	Yes	ZMBN 77634
23	May, 2006	R/V R.S Carney	2928-2489m	26°05'00"N, 94°36'30"W	Badly damaged adult male		N/A	Yes
24	May 30th, 2006	DSV Alvin	2739m	26°10'51"N, 94°37'22"W	RV Atlantis Dive 4195, subadult male		N/A	Yes
25	November 2007	RV Polarstern	3°13'N,15°00'W	1000-2000m	Cruise		N/A	Yes	N/A
26	November 11th, 2007	Commercial ROV	N9485524.76, E1017934.76 converted from UTM	2500m	Shell Perdido, Alaminos Canyon Block 857			No	N/A
27	January 16th, 2009	Triton XLS-22	Alaminos Canyon Block 258	2453m	TXLS-22 from support vessel DMT Emerald	Unpublished SERPENT Project		No	N/A
28	June 8th, 2009	Commercial ROV	N1026271.0, E9486831.5	2593m	"Eastern Array Installation"	Unpublished SERPENT Project		No	N/A
29	Feb 25th, 2011	M/V Meg Skansi	ONSAP Station B246N	200-600m	Collected by MOC10 net sampling during M/V Meg Skansi cruise MS6 as part of DEEPEND-RESTORE		N/A	Yes	N/A
30	Sep 15th, 2011	M/V Meg Skansi	ONSAP Station SE5D	200-600m	Collected by MOC10 net sampling during M/V Meg Skansi cruise MS8 as part of DEEPEND-RESTORE		N/A	Yes	N/A
31	April 27th, 2012	Little Hercules	See	1961m	NOAA Okeanos Explorer EX2012 Leg3 Dive 13			No	N/A
32	July 10th, 2013	Commercial ROV	Walker Ridge 95	1578.4m		Unpublished Serpent Project		No	N/A
33	July 29th, 2013	Commercial ROV	Mississippi Canyon block 525	1784m		Unpublished Serpent Project		No	N/A
34	November 14th, 2013	Oceaneering Millenium #57	26.13 N 94.88 W	2388m	OCS Study BOEM 2020-022		N/A	No	N/A
35	June 12th, 2014	Oceaneering Millenium #115	28.15 N 87.60 W	2278m	OCS Study BOEM 2020-022		N/A	No	N/A
36	April 23rd, 2014	Abyssal Lander	-37.2200 S -179.7740 W	4708m	RV Thomas G. Thompson TN309, HADES		N/A	No	N/A
37	June 27th, 2014	ROV Hercules	28:43.2808 N 088:06.5962 W	1687m	Nautilus Expedition NA043			No	N/A
38	November 2nd, 2014	Oceaneering Millenium #115	28.59 N 87.84 W	2317m	OCS Study BOEM 2020-022		N/A	No	N/A
39	November 15th, 2015	Towed Camera	-34.432, 129.987	2178m	RV Investigator			No	N/A
40	November 16th, 2015	Towed Camera	-34.377, 129.985	2110m	RV Investigator			No	N/A
41	January 19, 2016	ROV Victor		3664m	Pourquoi Pas?			No	N/A
42	February 14th, 2017	Commercial ROV	9°12'25.732"N, 76°49'55.091"W	1884m	Old Purple Angel Well			No	N/A
43	March 24th, 2017	FCV 3000 work-class ROV	-35.049, 130.905	3060m	REM Etive			No	N/A
44	March 25th, 2017	FCV 3000 work-class ROV	-35.049, 130.902	3002m	REM Etive			No	N/A
45	March 25th, 2017	FCV 3000 work-class ROV	-35.050, 130.904	3056m	REM Etive			No	N/A
46	April 14th, 2017	Commercial ROV	9°25'59.282"N, 76°44'54.110"W	2294.20m	Gorgon 1 Well		N/A	No	N/A
47	June 3rd, 2018	N/A	30.0255, -19.758333	100-200m	Pelagic trawl		N/A	Yes	ICMC000146
48	September 3rd, 2019	ROV SuBastian		1092m	ROV SuBastian Dive 295,			No	N/A
49	January 28th, 2020	ROV SuBastian		3000m	ROV SuBastian Dive 312,			No	N/A
50	March 2021	DSV Limiting Factor	Philippine Trench	6212m				No	N/A
51	December 2021	ROPOS	Central Indian Ocean	3000m	INDEX 2021, supporting RV Pelagia			No	N/A
52	November 9th, 2021	Deep Discoverer	See		2:56:25			No	N/A
53	April 4th, 2023	ROV SuBastian	Puy Des Folles Seamount	1931m	ROV SuBastian Dive 501,			No	N/A
54	September 2024	DSV Bakunawa	Tonga Trench - Pacific Ocean	3300m				No	N/A
55	October 2025	ROV Hercules	-17.5260, -159.6761	5180m	Nautilus Expedition NA176, Dive L1011			No	N/A