Some ecological factors in a living area of solitary coral Heterocyathus Aequicostatus, Milne-Edwards and Haime with emphasis on its symbiotic relationship with a sipunculid Aspidosiphon corallicola, Suiter
Abstract:
Studies on the distribution of the solitary coral, Heterocyathus aequicostatus and the sipunculid, Aspidosiphon corallicola in the northern part of Sichang Island, Sriracha district, Chonburi province were carried out. Some ecological factors in this area were also determined. Moreover the relationship between the solitary coral and the sipunculid was observed. The result showed that the coral, H. aequicostatus and sipunculid, A. corallicola were mostly distributed on the medium sand substrate (0.25-0.50 mm. grain size) on which the thin layer of silts covered the surface. They were mostly found at the depth of 5-7 metres about 80-180 metres in distance from the coral reef edge. The solitary corals density found in the area ranged from 35-133 individuals per square metre while the density for the young sipunculid were 72-384 individuals per square metre. The nature of sipunculid were 72-384 individuals per square metre. The nature of substrate in particular to the grain size and texture was found to be the most important ecological factors in determining the distribution of these two faunas. The symbiotic relationship between the solitary coral, H. aequicostatus and the sipunculid, A. corallicola was observed. They were found together since juvenile larvae and thus lived with one another onward. The solitary coral provided the sipunculid protection from predators and support preventing the latter from sinking into substrate while moving. The sipunculid on the other hand, would provided support and help the coral to stand in upward position on the substrate. Larvae of H. aequicostatus and A. corallicola were found to settle on different substrates namely gastropod shells, dead corals and lime fragments in the same proportions