Kim R. Reisenbichler

Light Production by the Arm Tips of the Deep-Sea Cephalopod Vampyroteuthis infernalis

The archaic, deep-sea cephalopod Vampyroteuthis infernalis occurs in dark, oxygen-poor waters below 600 m off Monterey Bay, California. Living specimens, collected gently with a remotely operated vehicle (ROV) and quickly transported to a laboratory ashore, have revealed two hitherto undescribed means of bioluminescent expression for the species. In the first, light is produced by a new type of organ located at the tips of all eight arms. In the second, a viscous fluid containing microscopic luminous particles is released from the arm tips to form a glowing cloud around the animal. Both modes of light production are apparently linked to anti-predation strategies. Use of the tip-lights is readily educed by contact stimuli, while fluid expulsion has a much higher triggering threshold. Coelenterazine and luciferase are the chemical precursors of light production. This paper presents observations on the structure and operation of the arm-tip light organs, the character of the luminous cloud, and how the light they produce is incorporated into behavioral patterns.

Effects of seasonal pack ice on the distribution of macrozooplankton and micronekton in the northwestern Weddell Sea

The presence of mesopelagic organisms in the guts of surface-foraging seabirds feeding in open areas within seasonal pack ice in the Antarctic has given rise to questions regarding the effects of pack ice on the underlying mesopelagic community. Bottom-moored free-vehicle acoustic instruments were used in concert with midwater trawls and baited traps to examine the abundance, size distribution and vertical distribution of pelagic organisms in the uppermost 100 m of the water column during the austral spring of 1992 in two areas of the northwestern Weddell Sea, one covered by seasonal pack icc and the other free of ice cover. Acoustic largets were more abundant and significantly larger at the open-water station than beneath pack ice. However, targets at the ice-covered site exhibited a pronounced diel pattern, with the largest targets detected only at night. Samples from night trawls at the icecovered site contained several species of large, vertically-migrating mesopelagic fishes, whereas these species were absent from trawls taken during the day. In addition, baited traps deployed in pack ice just beneath the ice-water interface collected large numbers of scavenging lysianassoid amphipods, while deeper traps beneath the ice and traps at the open-water station were empty, indicating the presence of a scavenging community associated with the undersurface of the ice. These results sapport the idea that mesopelagic organisms migrate closer to the surface beneath pack ice than in open water, exposing them to possible predation by surface-foraging seabirds.

Microextraction of total lipid from mesopelagic animals

Abstract A modification of the Bligh and Dyer lipid extraction method ( Canadian Journal of Biochemistry and Physiology , 37 , 911–917, 1959) is described. The technique utilizes commercially available Teflon membrane microfiltration units that permit filtration and solvent separation to occur simultaneously. Thus, rapid and efficient microextraction of total lipid (20–200 μg) can be accomplished from tissue homogenates at reduced solvent volumes. The primary advantages of this modification include increased accuracy for small samples, increased productivity and reduced exposure to solvent fumes. Extraction efficiencies ranged from 95 to 100% for standards and naturally occurring lipid extracts of two midwater fish species. Precision of the method, measured as per cent standard deviation between replicate extracts of whole fish homogenates, range from 0.7 to 2.7%.

Macropinna microstoma and the Paradox of Its Tubular Eyes

Abstract The opisthoproctid fish Macropinna microstoma occupies lower mesopelagic depths in Monterey Bay and elsewhere in the subarctic and temperate North Pacific. Like several other species in the family, Macropinna has upward-directed tubular eyes and a tiny, terminal mouth. This arrangement is such that in their upright position, the visual field of these highly specialized eyes does not include the mouth, which makes it difficult to understand how feeding takes place. In situ observations and laboratory studies reveal that the eyes of Macropinna can change position from dorsally-directed to rostrally-directed, which resolves the apparent paradox. The eyes are contained within a transparent shield that covers the top of the head and may provide protection for the eyes from the tentacles of cnidarians, one of the apparent sources of the food of Macropinna.

Automating MBARI's midwater time-series video surveys: The transition from ROV to AUV

MBARI has been conducting remotely operated vehicle (ROV)-based video surveys of the upper 1000 meters of the water column in Monterey Bay, California for over 23 years. These surveys have produced a unique midwater time-series data set that has enabled MBARI scientists to observe changes in mesopelagic animal distribution and community structure in Monterey Bay over that time period. These changes can generally be associated with both short and long term changes in water mass structure, including some now being associated with climate change. This historical data set is becoming even more important as we begin to observe the effects of climate change on community structure and ecology in the midwater environment and try to predict the impact of future change. However, this data set comes at a high cost in ROV and support ship time required to conduct the surveys. In order to sustain these surveys into the future, a more cost effective approach is required. In an effort to reduce cost, improve methodology and develop a system that has the potential to be exported to other institutions, MBARI has developed a high definition video module to be deployed on its Dorado class autonomous underwater vehicle (AUV). This paper explores the challenges of this development, the chosen solutions, and presents early data derived from our initial inter-comparisons of video collected concurrently with MBARIs ROV and midwater imaging AUV.

MBARI's Midwater Ecology Low-Light Imaging System Development

This paper focuses on the technology for an imaging system that allows MBARIs midwater ecologists to detect both illuminated, nearly transparent organisms and stimulated bioluminescence. The system utilizes high intensity red LEDs and an ICCD camera with the ability to gate the detected light. This system uses less power than traditional underwater video systems and provides a higher contrast image for use in future automated counting systems