Deep pelagic biology

The deep pelagic habitat is a vast volume of cold, dark water where food is scarce and bioluminescence is the principal source of light and communication. Understanding the adaptations that allow animals to successfully inhabit this daunting realm has been a difficult challenge because investigators have had to conduct their work remotely. Research in the deep water column is going through an essential transformation from indirect to direct methods as undersea vehicles provide unprecedented access, new capabilities, and new perspectives. Traditional methods have accurately documented the meso- and macro-scale zoogeographic patterns of micronekton and zooplankton, as well as their distribution and migration patterns in the vertical plane. The new in situ technologies have enabled advances in studies of behavior, physiology, and in particular, the role of gelatinous animals in deep pelagic ecology. These discoveries reveal a deep-water fauna that is complex and diverse and still very poorly known.     

Pheromone deactivation catalyzed by receptor molecules: a quantitative kinetic model

A quantitative model of pheromone-receptor interaction and pheromone deactivation, the supposed rate-limiting processes underlying the receptor potential kinetics, is worked out for the moth Antheraea polyphemus. In this model, the pheromone interacts with the receptor molecule while bound to the reduced form of the pheromone binding protein. The receptor molecules--besides their receptor function-- catalyze the observed shift of the pheromone-binding protein from the reduced to the oxidized form (Ziegelberger, G., Eur. J. Biochem., 232, 706-711, 1995), which deactivates the pheromone bound to pheromone binding protein. With the following parameters, the model fits morphological, radiometric, electrophysiological and biochemical data: a maximum estimate of 1.7 x 10(7) receptor molecules/cell (with 40,000 units/micron 2 of receptor cell membrane), rate constants k1 = 0.2/(s.microM) for the association, k2 = 10/s for the dissociation of the ternary complex of binding protein, pheromone and receptor, and k3 = 10/s for the deactivation via the redox shift. With these parameters, the duration of elementary receptor potentials elicited by single pheromone molecules (approximately 50 ms) reflects the lifetime of the ternary complex, tau = 1/(k2 + k3). The receptor occupancy produced by the model for threshold stimuli fits the sensitivity of the receptor cell to single pheromone molecules.