About the Cover
Cover
Amphipods, a diverse group of crustaceans found in marine, terrestrial, and freshwater environments, are common members of benthic communities in the coastal waters of Antarctica. The cover image shows a circumpolarly distributed amphipod, Abyssorchomene plebs, collected from McMurdo Sound, Antarctica. A. plebs is a benthic scavenger up to 2 cm in length. Each side of its head bears a pear-shaped compound eye that can see both to the side and overhead. Animal eyes are often adapted structurally and physiologically to the environment in which they must function. A. plebs lives over a depth range that extends from approximately 10 to 800 m, and thus may experience light regimes from bright and polychromatic to dark and monochromatic, in an environment where ice cover and other seasonal changes produce dramatic fluctuations in the daily cycle of light and dark. These conditions, combined with a low temperature that remains constant at near -1.86 °C, make visual adaptation an interesting question.
On pages 140–148 in this issue, Jonathan H. Cohen and Tamara M. Frank used electroretinography to study the visual physiology of A. plebs. They determined spectral and irradiance sensitivity, as well as temporal resolution, of the A. plebs eye, and relate these aspects of visual function to the ecology of this benthic scavenger. Their findings suggest that the A. plebs eye is well-adapted for a slow lifestyle in a low-light marine environment, where maximizing photon capture occurs at the expense of detecting fast events. For example, as a species that finds food by scavenging, A. plebs has more need to detect lurking predators than to spot fast-moving prey. These results shed light onto visual function at cold Antarctic temperatures, provide a useful complement to similar studies on deep-sea crustaceans in somewhat less extreme environments, and raise questions as to the neural mechanisms that underlie slow visual systems like that of A. plebs.
Credits: Photo, Roberta Hannibal (University of California, Berkeley); cover layout, Beth Liles (Marine Biological Laboratory).
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Copyright © 2007 by the Marine Biological Laboratory.
