Life History & Behaviour

This species of coral follows the basic life history plan that most corals have evolved.  There is a broadcast spawning event in which all adult individuals release their eggs or sperm into the water.  These come together as gametes do, and form larvae (see figure 2). This larva is a free swimming organism. Once it finds an appropriate substrate it begins to metamorphose (Mayorova et al, 2012).  Cues the animal uses to find a suitable habitat are chemical, biological and environmental and aren’t totally understood by scientists (Stanely et al, 2012).  Coral can also reproduce asexually is this is generally to add polyps to an existing colony,rather than the creation of a new colony (see figure 3) (Pinzon et al, 2012). The coral polyps produced asexually are genetically identical to their parent colony (Pinzon et al, 2012). 

P. densa is a filter feeder, which means it filters the water and extracts plankton for energy (Ruppert et al, 2004). This is an efficient way to feed on a coral reef as they are the most productive areas in the ocean.  To supplement this mode of feeding; however, they also have a symbiotic relationship with zooxanthellae (Ruppert et al, 2004).  These bacteria photosynthesize and it is understood that coral gains energy from hosting these cells, while the bacteria gains waste products from the coral that are invaluable to the survival of the bacteria. 

Each individual polyp is so small that they can breathe by diffusion, the oxygen enters their body via the tentacles near the mouth and is carried around the body in the cells.  


Figure 2: sexual reproduction in Scleratinian coral. Adapted from Ruppert et al, 2004. 



Figure 3: clonal reproduction in polyp zooids for Scleratinian coral.  Adapted from Ruppert et al, 2004.