Bigfin squids are a group of rarely seen cephalopods with a distinctive morphology. They are placed in the genusMagnapinna and familyMagnapinnidae. Although the family is known only from larval, paralarval, and juvenile specimens, some authorities believe adult specimens have also been seen. Several videos have been taken of animals nicknamed the "long-arm squid", which appear to have a similar morphology. Since none of the seemingly adult specimens has ever been captured or sampled, it remains uncertain if they are of the same genus or only distant relatives. The arms and tentacles of the squid are both extremely long, and believed to be between long. These appendages are held perpendicular to the body, creating "elbows". How the squid feeds is unknown.
Physical specimens
The first record of this family comes from a specimen caught off the Azores in 1907. 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 Octopodoteuthopsis. 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 first visual record of the long-arm squid was in September 1988. The crew of the submersibleNautile encountered a long-armed squid off the coast of northern Brazil,, at a depth of. In July 1992, the Nautile again encountered these creatures, first observing one individual two times during a dive off the coast of Ghana at and depth, and then another one off Senegal at. Both were filmed and photographed. In November 1998, the Japanese manned submersibleShinkai 6500 filmed another long-armed squid in the Indian Ocean south of Mauritius, at and. A third video 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 allowed a size estimate. By comparison with the visible parts of the ROV, the squid was estimated to measure with arms fully extended. The ROV Atalante filmed another Indian Ocean specimen at and, in the area of Rodrigues Island, in May 2000. In October 2000, the manned submersible Alvin found another long-armed squid at in Atwater Valley, 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 long-armed 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. On 11 November 2007, a new video of a long-arm squid was filmed off Perdido, a drilling site owned by Shell Oil Company, located 200 statute miles off Houston, Texas in the Gulf of Mexico.
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. Estimates based on video evidence put the total length of the largest specimens at or more. 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, leaving their exact identity unknown.
Feeding behavior
Little is known about the feeding behavior of these squid. Scientists have speculated that bigfin squid feed 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.
