A comparison between coral colonies of the genusMadracisand simulated forms

Abstract

In addition to experimental studies, computational models provide valuable information about colony development in scleractinian corals. Using our simulation model, we show how environmental factors such as nutrient distribution and light availability affect growth patterns of coral colonies. To compare the simulated coral growth forms with those of real coral colonies, we quantitatively compared our modelling results with coral colonies of the morphologically variable Caribbean coral genus Madracis. Madracis species encompass a relatively large morphological variation in colony morphology and hence represent a suitable genus to compare, for the first time, simulated and real coral growth forms in three dimensions using a quantitative approach. This quantitative analysis of three-dimensional growth forms is based on a number of morphometric parameters (such as branch thickness, branch spacing, etc.). Our results show that simulated coral morphologies share several morphological features with real coral colonies (M. mirabilis, M. decactis, M. formosa and M. carmabi ). A significant correlation was found between branch thickness and branch spacing for both real and simulated growth forms. Our present model is able to partly capture the morphological variation in closely related and morphologically variable coral species of the genus Madracis.Keywords: corals; morphogenesis; morphology; simulation; CT scan; Madracis INTRODUCTIONScleractinian corals exhibit great inter-and intraspecific variation in coral colony morphology (e.g. Veron 1995;Bruno & Edmunds 1997). Intra-specific variation often arises from plasticity in a colony's growth process in response to variable environmental conditions, such as flow speed, availability of light and availability of dissolved inorganic carbon (Muko et al. 2000;Todd et al. 2004;Todd 2008). Because genetic and environmental factors determine a colony's three-dimensional structure, the relative importance of either factor is often difficult to determine. Experimental studies whereby corals are grown under different environmental conditions are often limited by the slow growth rates of corals and difficulties with controlling environmental parameters of the system. Therefore, plastic responses to environmental changes are studied in relatively few (about 17) coral species (Todd 2008).To determine the degree of phenotypic plasticity among colonies of the same species under variable environmental conditions, various morphometric traits are measured to quantitatively assess whether changes in coral colony growth and form correlate with varying environmental factors (e.g. Bruno & Edmunds 1997). Morphological variation in corals exists on different scales, from differences in corallite structure within a single colony (Foster 1979) to variation among colonies in a single species. The present study aims to describe variability at the colony morphology level in species of the Caribbean coral genus Madracis. The Madracis species are characterized by the encrusting (M. pharensis), nodular (M...

Morphological variation and different branch modularity across contrasting flow conditions in dominant Pocillopora reef-building corals

“…For example, colonies had a low Bd and a more open branch structure at low-flow sites and a high Bd and low separation of branches at high-flow sites. Similar patterns of variation in the compactness of colonial morphologies have been described in other branching corals (Acropora, Madracis, Seriatopora, Stylophora, and Pocillopora) (Kaniewska et al 2008;Kaandorp 1999;Filatov et al 2010). Differences in Bd and AdB in Pocillopora corals could be a result of adjustments to physiological and mechanical requirements.…”

“…Colonial morphologies of branching corals respond to the intensity of water flow (Kaandorp 1999;Nakamura and Yamasaki 2006;Kaniewska et al 2008;Filatov et al 2010). In our study, differences in flow conditions were associated with morphological patterns in Pocillopora corals and differences in branch modularity (Figs.…”

“…3, 5). Morphological similarity at high flow has been reported for other marine organisms, including macroalgae (Stewart and Carpenter 2003;Roberson and Coyer 2004), corals (Kaandorp 1999;Filatov et al 2010), and fish (Langerhans et al 2003). This high morphological similarity does not seem to stem from a lack of genetic differentiation between individuals at the high-flow site, as evidenced an analysis of microsatellite loci by Pinzón et al (2012) who noted that the high-flow site (Punta Galeras) is composed of many genetically different colonies while the low-flow site (Isla Gaviotas) is dominated by extensive clones.…”

“…One possible explanation of these different trait morphologies is that the modifications may be morphological responses of the coral to decrease drag and prevent breakage at high-flow velocities. Under low-flow conditions, thin but wide branches induce turbulence, thereby enhancing the mass transport of nutrients (Chamberlain and Graus 1975;Kaandorp 1999;Einbinder et al 2009;Filatov et al 2010). Water flow is not only a critical factor in determining the mechanical aspects of colonial morphology, but it also influences the ability of polyps to capture particles (Sebens et al 1998) and exchange gas (Sebens et al 2003;Finelli et al 2007), and it affects uptake rates (Falter et al 2004), which in turn affect respiration, photosynthesis, and growth (Finelli et al 2007;Mass et al 2010;Schutter et al 2011) and might also determine susceptibility to bleaching (Nakamura and Yamasaki 2005).…”

Stationary Solutions of a Mathematical Model for Formation of Coral Patterns

“…Various modeling approaches on coral morphogenesis processes have been reported in [1] [3]- [9]. Morphogenesis of branching corals has been described by Diffusion-Limited Aggregation (DLA) type models in [1] [6] [10].…”