# 2.4 Morphology

## Macromorpholoy

Macromorphology is here defined as the shape of the entire colony which can express inter- or intraspecific (polymorphic) variation. 

#### Colony Shapes

![](/files/pZ24WYLzLeZpgEFgdbRC)

![](/files/vl4eariEun1URBfvIree)

## Micromorphology 

#### Anatomy of a Calice 

![](/files/qjDwtAYUk4X039fPCDSb)

* corallite - the entire structure of the coral skeleton 
* calice - cup in coral skeleton 
* Septa - wall-like structures that radiate from the sides of each corallite 
* Columella - extends upward from the floor of the calice
* Basal plate - partition that provides new elevated bottom in the corallite when coral polyps grow by withdrawing itself upward and secreting a new basal plate

## Variation with depth 

#### Macromorphology 

* massive → tabular (<mark style="color:purple;">Graus</mark>)
* Spherical/massive → tabular/platelike (<mark style="color:purple;">Gleason 1992</mark>)
* More → less branching (<mark style="color:purple;">Muko 2000, Oliver 1983</mark>)
* Higher rugosity → lower (<mark style="color:purple;">Todd 2002/2004</mark>)
* hemispherical → flat branching morphology (<mark style="color:purple;">Jauber 1977</mark>)
* massive → flat OANN (<mark style="color:purple;">Dustan 1975</mark>)
* vertical → horizontal plates in Turbinaria (<mark style="color:purple;">Anthony et al. 2005</mark>)
* growth in any direction → vertical growth only
* slower growth -> faster (<mark style="color:purple;">Bosscher & Meesters 1992</mark>)
* Massive -> platelike (<mark style="color:purple;">Bosscher & Meesters 1992</mark>)
* low -> high skeleton density (<mark style="color:purple;">Bosscher & Meesters 1992</mark>)
* high -> low calcification rate (<mark style="color:purple;">Goreau 1959</mark>)
* fast -> slow growth of branch tips (<mark style="color:purple;">Goreau 1959</mark>)
* large -> small branch diameter (<mark style="color:purple;">Einbinder 2009</mark>)
* hemispherical -> platelike branching structure (<mark style="color:purple;">Einbinder 2009</mark>)
* 3D -> 2D architecture (<mark style="color:purple;">Dustan 1975; Falkowski and Dubinsky 1981;</mark>

  <mark style="color:purple;">Fricke and Schuhmacher 1983; Vermeij and Bak 2002;</mark>

  <mark style="color:purple;">Anthony and Hoegh-Guldberg 2003</mark>)
* low -> high branch spacing and long -> short branches  (<mark style="color:purple;">Kaniewska et al. 2008</mark>)&#x20;
* high -> low intra-colony shading (<mark style="color:purple;">Dustan 1975; Falkowski and Dubinsky 1981;</mark>

  <mark style="color:purple;">Fricke and Schuhmacher 1983; Vermeij and Bak 2002;</mark>

  <mark style="color:purple;">Anthony and Hoegh-Guldberg 2003</mark>)
* thicker -> thinner branches (<mark style="color:purple;">Bak and Meesters 1998; Muko et al. 2000; Mass et al. 2007, Nir et al. 2011</mark>)
* hemispherical -> horizontal/flattened/encrusting (<mark style="color:purple;">Bak and Meesters 1998; Muko et al. 2000; Mass et al. 2007</mark>)

#### Micromorphology&#x20;

* large -> small  calice size in MCAV (<mark style="color:purple;">Studivan et al. 2019</mark>)\*&#x20;
* small → large polyps (<mark style="color:purple;">Nir et al. 2011</mark>)\*
* corallite expansion/ larger → smaller corallites (<mark style="color:purple;">Todd 2004b, 2004c</mark>)
* larger → smaller corallites in MCAV (<mark style="color:purple;">Beltran-Torres & Carricart-Gavinet, 1993</mark>),
* Deeper → shallower calice relief in OANN may be shading strategy (<mark style="color:purple;">Klaus et al. 2007</mark>)
* large -> small calices (<mark style="color:purple;">Einbinder 2009</mark>)
* A whole bunch of changes (<mark style="color:purple;">Soto et al. 2018</mark>)

\*cryptic lineage or morphotype?&#x20;

#### Summary from <mark style="color:purple;">Todd 2008</mark>

* Summary: in shallow, more complex colony morphology, corallite extension, branch or tuberculae formation, higher surface area to capture more sun or provide self shading, reduce drag resistance and increase sedimentation shedding ability
* Summary: in deep, simple flat morphology and decrease in corallite size will maximize light collection and minimize the amount of tissue needing support

### Light Interactions

* Skeletal structure is critical to light scattering to either maximize or minimize the number of photons that get to the symbionts for photosynthesis.&#x20;
* Micro-structure appears to be more important than colony structure for light scattering, and scattering happens most within the recently deposited, surface CaCO3 (<mark style="color:purple;">Swain et al. 2018</mark>)&#x20;

## References

#### <mark style="color:purple;">Bosscher & Meesters 1992</mark>&#x20;

Shallow corals grow more slowly. Colonies go from massive - platylike along a depth gradient. Denser skeleton at depth.&#x20;

#### <mark style="color:purple;">Brakel 1977</mark>

No change in calice morphology along a light gradient in Porites sp.&#x20;

#### <mark style="color:purple;">Goreau 1959</mark>

Calcification rate was significantly higher in light environments. Top/end of branches & colonies grow faster. Detailed description of calcium carbonate reactions&#x20;

#### <mark style="color:purple;">Studivan, Milstein & Voss 2019</mark>

This study assessed morphological calice variation MCAV across a depth gradient.  Mean corallite diameters were smaller and spacing was greater in deeper areas. The authors also identified two morphotypes (shallow depth specialist w/ large calices + generalist), which were associated with genetic structure in some sites. The generalist species was associated with higher chl and symbiont concentrations.&#x20;

#### <mark style="color:purple;">Einbinder 2009</mark>&#x20;

Calices got smaller with depth. Branch diameter got smaller with depth. macromorphology changed from branching structure being hemispherical to more platelike.&#x20;

#### <mark style="color:purple;">Todd 2008</mark>

This is a review of morphological plasticity in corals. Many of the findings they synthesized are listed above. Todd summarizes best practices for measuring plasticity in coral (must be on genotype clones).&#x20;

#### <mark style="color:purple;">Nir et al. 2011</mark>

The authors quantified morphology, chl, PAM and ITS2 along a depth gradient. They did not find expected decreasing patterns in chl but offered other explanations for this trend. They found thinner branches and larger polyps at depth. They also suggest that this species has multiple ecomorphotypes (so maybe a cryptic lineage situation).&#x20;


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