The Shallow-Water Crinoid Fauna of Kwajalein Atoll, Marshall Islands: Ecological Observations, Interatoll Comparisons, and Zoogeographic Affinities

Zmarzly, D.L.
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University of Hawai'i Press
Twelve species of comatulid crinoids in three families were found to inhabit reefs at Kwajalein Atoll during surveys conducted both day and night by divers using scuba gear. Eleven of the species represent new records for the atoll, and five are new for the Marshall Islands. A systematic resume of each species is presented, including observations on diel activity patterns, degree of exposure when active, and current requirements deduced from local distributions. More than half of the species were strictly nocturnal. Densities of nocturnal populations were much higher than those typically observed during the day . Occurrence and distribution of crinoids about the atoll appeared to be influenced by prevailing currents. Some species, of predominantly cryptic and semicryptic habit by day, occurred at sites both with and without strong currents. While these species were able to survive in habitats where currents prevailed, they appeared not to require strong current flow. In contrast, the remaining species, predominantly large, fully exposed comasterids, were true rheophiles; these were found on seaward reefs and only on lagoon reefs in close proximity to tidal passes . Comparison of crinoid records between atolls in the Marshall Islands shows Kwajalein to have the highest diversity , although current disparities between atolls in the number of species recorded undoubtedly reflect to some extent differences in sampling effort and methods. Based on pooled records, a total of 14 shallow-water crinoid species is known for the Marshall Islands, compared with 21 for the Palau Archipelago and 55 for the Philippines. The Marshall Islands comatulid fauna is predominantly an attenuated western Pacific fauna, dominated by widely distributed members of the family Comasteridae. A field identification key for crinoids of the Marshall Islands is provided.
Zmarzly DL. 1985. The shallow-water crinoid fauna of Kwajalein Atoll, Marshall Islands: ecological observations, interatoll comparisons, and zoogeographic affinities. Pac Sci 39(4): 340-358.
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