About the Cover
Cover
Christmas Island, a territory of Australia in the Indian Ocean south of Java, is the summit of a submarine mountain that rises 361 m above sea level to a central plateau. Twenty-three species of air breathing crabs are endemic to Christmas Island, but the red crab Gecarcoidea natalis, with an adult population estimated at about 50 million, is the most numerous. For most of the year, the red crabs inhabit burrows in the floor of the rainforests that grow on the island's plateau. Thus, this species is fully terrestrial, except for a three-week marine larval stage--a feature of the reproductive biology that necessitates the spectacular annual mass migration, from the forest down to the coast. The red crab migration is initiated by the start of the monsoonal rains, but spawning is synchronized with the lunar cycle, and all of the female crabs release their eggs into the sea on just one or two nights of the year. As the front cover shows, the morning after the females spawn, the rocks and cliffs lining the entire shoreline of Christmas Island are packed shoulder to shoulder with red crabs.
Although the mass migration of G. natalis is a well-documented phenomenon--indeed a tourist attraction--the descriptions are primarily anecdotal, and quantitative data are very limited. In this issue (pp. 305-320), A. M. Adamczewska and S. Morris establish, for the first time, such fundamental ethological details as the routes taken by the migrating red crabs, their direction and speed of walking, and their destinations.
The red crab breeding season, which can last from 3 to 6 weeks, is the most active period of the year for these animals; their activities include the unusually long migration, intense courtship behaviors, mating, and spawning. Moreover, these activities follow an extended period of relative inactivity during the dry season. Such varied activity levels impose quite different physiological demands on the red crabs. In a companion paper (pp. 321-335), Adamczewska and Morris have assessed the physiological demands of migratory locomotion and of activities related to breeding. They measured key metabolites, metabolic fuel stores, metabolic status, and thus the capacity of the red crabs to maintain their varied activities.
(The photograph on the cover was taken by Agnieszka Adamczewska.)
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Copyright © 2003 by the Marine Biological Laboratory.
