Assemblages of Two Gall Crabs within Coral Species Northern Red Sea, Egypt

The crab size, abundance, distribution and density of two gall crabs species (Hapalocarcinus marsupialis Stimpson, 1859 and Opecarcinus aurantius Kropp, 1989) associated with the most abundant and common coral species have been studied in 5 sites along the Egyptian Red Sea coast. Three hundred and forty five coral galls were collected; 276 coral galls were found in Stylophora pistillata and 59 galls in Pocillopora verrucosa. The mean size of coral galls is ranged between 1.42±0.37 cm and 2.17±0.62 cm for S. pistillata (at Qula'an and Hurghada, respectively), while the size of galls in P. verrucosa is ranged between 1.35±0.19 cm and 1.48±0.17 cm (at Hamata and Hurghada, respectively). S. pistillata showed the highest gall crab numbers per colony (10.43 galls colony-1) at Hurghada, while P. verrucosa recorded the highest number (3.83 galls colony-1) at Qula'an site. S. pistillata recorded the highest coral galls density (63 with a mean of 9±3.32) and crab density (20.59% with mean 3±2.6) at Hurghada site. P. verrucosa recorded the optimum galls number (23 with mean of 3.8±1.5) and crab density (6.86% and mean of 1.3±1.7) at Qula'an.