Two species (M. hjorti, M. magna) have been observed from submersibles drifting just above the ocean floor with tentacles dangling within a few mm of the bottom, presumably, to capture copepods and other small plankters of the epibenthic zooplankton (Roper and Vecchione, 1997). The tentacles extend from the tips of the ventral arms (arms IV) from where they reside in the tentacular sheaths (i. e., between the arms and their lateral membranes). The tentacles are typically held apart by the ventral arms (the "tuning fork" posture) so they "fish" independently of each other (Roper and Vecchione, 1997). AVI and MPEG formated video clips of this behavior is available at Cephalopods in Action.
Figure. Left top - Side view of the head and brachial crown of M. agassizii. Arrow points to the tentacle base neatly enveloped by the lateral membrane of arm IV. Photograph by David Shale. Right top - Ventral view of Mastigoteuthis sp. hanging in the water just above the ocean floor, submersible photograph, Hawaiian waters. The arrow points to the place where the tentacle emerges from the tentacular sheath of the left arm IV. Photograph modified from Young, et al. (1999), courtesy of the Hawaii Undersea Research Laboratory. Bottom - Dorsal view of a portion of a ventral arm (arm IV) of M. agassizii with the tentacle (white) mostly hidden within the tentacular sheath. The entire length of the tentacle apparently can be held within the tentacular sheath. Photograph by David Shale. Views of M. agassizii were photographed in a shipboard aquarium by David Shale on an NSF cruise with Marsh Youngbluth, Harbor Branch Oceanographic Institution, N.E. Atlantic waters. The brilliant red color in both images has been reduced in Photoshop to accentuate detail. © David Shale
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