| Biology: |
Oceanic (Refs. 1983, 97142). Mesopelagic (Ref. 77090). Paralarvae and juveniles are epipelagic to upper mesopelagic, then undergo ontogenetic descent into the lower mesopelagic, bathypelagic and bathyal zones. Adults undergo diel vertical migration and ascend into the epipelagic zone at night. Juveniles have been captured at night within 175 m from the surface, while the remains of a large specimen (50 kg) were taken from the stomach of the bottom-living shark, Centroscymnus coelolepis, caught on a bottom-set longline at 1,246 m. A mature female of 1.4 m mantle length had 250,000 ovarian eggs. Observations on bioluminescence from living animals verified a rapid flash response from the arm tip photophores, as a startling or warning function, and a steady glow from the visceral photophores as is common for protective counter illumination. In situ video footage reveals it to be a strong swimmer, both forward and backward, propelled by its huge fins, and changes directions quickly by bending its body. Observed attack on a bait rig showed speeds of 7.2 to 9 km/h and emission of short, bright flashes from its 2 arm-tip photophores before it attacked. It also emits long and short intermittent glows when swimming around the lighted bait rig. Preyed upon by many species of pelagic fishes, including lancetfish (Aleposauris ferox), tunas, swordfish (Xiphias gladius), hammerhead, tiger and blue sharks, as well as odontocete cetaceans: short-finned pilot whale and most especially, sperm whales in all oceans (Ref. 97142). |