Great star coral colonies form massive boulders and domes over 5 feet (1.5 m) in diameter in waters of shallow and moderate depths. In deeper waters, this coral has been observed growing as a plate formation. It is found throughout most reef environments, and is the predominant coral at depths of 40–100 feet (12.2–30.5 m). This coral occasionally has a fluorescent red or orange color during daytime; it has recently been suggested that this hue is due to
phycoerythrin, a
cyanobacterial
protein. It appears that, in addition to
symbiotic zooxanthella, this coral harbors
endocellular symbiotic cyanobacteria, possibly to help it
fix nitrogen. However more recently, Oswold
et al. (2007) showed an absence of functional phycoerythrin in
M. cavernosa. The species is
gonochoric (colonies can be either male or female) and spawns one week after the full moon in late August. Skeletons show sex-related differences, with females having a less dense skeleton compared to males, which is presumably due to reallocating energy to egg production. ==Bleaching==