- Arms with two regions: short, proximal-arms with large suckers and long, very slender distal-arms covered with minute suckers.
- Arms suckers with bi- to quadra-serial suckers on proximal-arms, multiple irregular series on distal arms.
- Tentacles with two regions: short, proximal-tentacles that may or may not bear numerous suckers and long, very slender distal-tentacles covered with numerous minute suckers.
- Tentacles without keels, terminal pads or locking apparatuses.
- Buccal crown
- Buccal connectives attach to ventral margins of arms IV.
- Eyes large.
- Head short without distinct neck or brachial pillar.
- Funnel with oval locking-apparatus without tragus or antitragus.
- Fins terminal.
- Fins large, ca. 70-90% of ML.
- Muscular mantle restricted to the anterior 10-15% of the sessile region (ie, attached region of fins that doesn't include the free anterior fin lobes) of the fins.
- Short tail usually present. May represent drawn-out tip of fins that have been damaged.
- Photophores absent.
Figure. Ventral and dorsal views of the brachial crowns of M. pacifica, 51 mm ML . Drawing from Vecchione and Young (1998).
Figure. Ventral view of Magnapinna pacifica, holotype. Note that the muscular mantle terminates in the anterior region of the fins. Photograph from Vecchione and Young (1998), modified.
Most described specimens are based on paralarvae or juveniles. The adult/subadult squid, observed from submersibles or ROVs, have the following features: The arms and tentacles typically are held in an unusual position: They extend at sharp angles to the body axis then abruptly (sometimes at a 90° angle) turn anteriorly. The "elbow" is, roughly, two thirds of the length of the mantle away from the body axis. This arm posture recalls the way in which the tentacles of Mastigoteuthis spp. are held apart although with the aid of the ventral arms. Rough estimates from videos indicate total lengths up to 7 m (Vecchione, et al, 2001). Arms and tentacles are approximately equal in thickness and length. The tentacles are usually not easily recognizable in videos; the arms and tentacles, therefore, appear as 10 equal appendages. Length of the arms/tentacles of the squid pictured below are about 10 times the ML although they are highly contractile. Guerra et al (2002) estimated that an individual they observed had arms/tentacles about 15-20 times the ML. The relative length of the arms/tentacles is far greater than in any other squid. The head appears to be small. Fin Length of the specimen pictured below is about 80% of the ML. Guerra et al (2002) estimated the fin length of their specimen at about two thirds of the ML. The fin position is terminal.
Figure. In-situ images of Magnapinna sp., Gulf of Mexico. Left - Side view showing long appendages. Right - Dorsal view showing common posture with proximal-arms/tentacles at nearly right angles to the body axis. Video frames of taken by DSV Alvin, Woods Hole Oceanographic Institution. Dives co-sponsored by NOAA Undersea Research Program, Minerals Management Service and National Energy Technology Lab.
|Tentacle base much wider than arm IV base||Proximal-tentacle with numerous suckers||Proximal-tentacle with glandular structures.||Chromatophores abundant ||Habitat|
|M. pacifica||Yes||Yes||No||Yes||North Pacific, North Atlantic |
|M. atlantica||No||No||Yes||Yes||North Atlantic|
|Magnapinna sp. B||No||?||?||No||North Atlantic|
|Magnapinna sp. C||No||No||?||Yes||South Atlantic|
|M. talismani||No||No||?||Yes||North Atlantic|
Due to the poor condition of the single specimens of Magnapinna spp. B and C and M. talismani, our present understanding of the species in the family may be flawed. M. atlantica, M. talismani and Magnapinna sp. C could belong to the same species. The feature that most clearly separates M. atlantica is the presence of glandular structures on the proximal-tentacles. The recent discovery that these structures become relatively smaller with size and are easily lost due to damage indicates that these structures may have been lost in M. talismani and Magnapinna spp. B and Magnapinnasp. B, however, appears to differ from the others in the longer free-of-the-fin mantle and the broader orifices of the proximal-arm suckers.
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