造礁サンゴ幼生の分散過程 : 分散範囲を規定する幼生の定着可能期間とエネルギー源 Larval dispersal processes of reef-building corals : Larval settlement competency and energy source as factors controlling dispersal ranges
Larval dispersal in marine invertebrates plays a significant role in the maintenance and conservation of adult populations. Reef-building corals spawn eggs and sperm, or brood larvae (planulae) and shed them directly into the water. Larval dispersal is physically determined by ocean currents and biologically by egg and larval behaviour, buoyancy in the water column, and the period during which larvae can settle after spawning or release (settlement-competency periods). In addition, the settlement-competency periods may be affected by the available energy source during the planktonic phase. However, little is known about how these factors determine larval dispersal ranges. Here, I review larval dispersal processes of corals based on our researches of the two different dispersal types. The planula larvae which have mainly narrow dispersal ranges (fine scale, shorter than 1 km) occurred throughout the water column and have shorter settlement-competency periods. This is due to a lower lipid content and the influence by weaker tidal currents. In contrast, the planula larvae which have mainly wider dispersal ranges (40 km or more) are characterized by positive buoyancy and longer settlement-competency periods. This is due to the energy from a higher lipid content; especially wax esters. In addition, the symbiotic dinoflagellates in some larvae provide additional energetic resources which may allow longer larval dispersal.
- Sessile organisms
Sessile organisms 25(1), 1-10, 2008-02-29