Masashi Yamaguchi’s scientific contributions

Most coral-reef asteroids of Guam, at least 24 species in total, represent those which are widely distributed in the Indo-West Pacific. The diversity of asteroid fauna in Micronesia and its surrounding region follows a general trend of a faunal center in the rich Indo-Malayan Archipelago area with the number of species diminishing eastward in the scattered and remote oceanic islands. Larval development in many common reef asteroids is oriented toward dispersion by producing planktotrophic and surface-floating larvae which stay in the pelagic environment for three weeks or longer. The major oceanic surface currents flow westward, driven by steady trade winds in the area surrounding Guam and most of the Micronesian Islands. It is argued that local recruitment of asteroid populations might be hazardous under such circumstances where coastal water masses would hardly conserve larval populations inshore. Juvenile populations of reef asteroids have been rarely located in the field, in spite of conspicuous adult populations. Feeding habits, life histories, and other aspects of natural histories of reef asteroids are discussed.