Marine Biology Research Division

Five species of Halobates are specially adapted to a pelagic life. They all occur in the Pacific Ocean, each with a well-defined zoogeographical range. Only two species were caught in a series of samples collected between Hawai'i and Tahiti: H. sericeus Eschscholtz, with an amphitropical distribution, and H. micans Eschscholtz, occupying the equatorial zone separating the northern and southern populations of the former. This disjunct distribution pattern may be maintained by zonal equatorial current systems. Although mixing of the two species may occur during seasonal weakenings of the currents, the two populations of H. sericeus appear to be quite separate, with little or no possibilities of genetic exchange.