Models for examining the growth of corals should look more closely at the polyps, says a new study published in The Journal of Theoretical Biology.
A team of computational biologists from the University of Amsterdam say that although biologists know that growth in colonial stony corals is down to the collective behaviour of individual polyps laying down calcium on the colony's exoskeleton, existing growth models for corals look at the polyps as a single continuous surface.
To prove their point, the team created a computational model which looked at each polyp on the colony. Each polyp could take up resources, deposit calcium, create new polyps and die, and the model was also capable of spontaneous branching, just like a real coral.
The computer simulation suggests that branching is caused by a "polyp fanning effect" where polyps on a convex surface have a competitive advantage over their counterparts on flat or concave bits of the coral colony.
The team says that the influence of specific polyps on a colony can alter the branching pattern and the shape of the entire colony as well as its growth. Branch thickness and growth-form compactness, for example, appears under the model to be due to the spacing of polyps.
If you have broadband you can view some of the team's stunning rotating Virtual Reality Markup Language (VRML) models in MPEG format on their website.
For more information see the full paper: Merks RM, Hoekstra AG, Kaandorp JA, Sloot PM. (2004) - Polyp oriented modelling of coral growth. J Theor Biol. 2004 Jun 21;228(4):559-76.