The grasping coral Xenia has large and long polyps extending from a smaller spherical base. When active, the polyps are continually opening and closing ("grasping") presumably to feed on plankton. I remember this as quite common in the 1970s, particularly on lagoon and large pinnacle reefs in the mid portion of Kwajalein Atoll, and was also common at Enewetak Atoll in the 1980s. After returning to Kwajalein in 1988, however, I had a hard time finding it again, rarely seeing small clusters of colonies on some midlagoon pinnacle and seaward reefs. Finally a large patch of colonies was discovered on the first large reef south of Meck Island. One Marshall Islands nudibranch is known to prey upon this coral, and a species of Caphyra crab lives commensally on Xenia colonies.
When disturbed, the polyps cease grasping and close into little "fists."
Created 16 October 2020