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Coral Identification: Coral 5

This page is to document the Id of the coral of Cabrerad (David)
The acropora sp. chosen was provided as several small frags glued to a small rock in various orientations. I have bleached a frag containing two branches and what appears to be two distinct axial corallites and at least one incipient axial corallite.


Growth form: Caespitose-Corymbose (a bit of a guess given this is a frag)
Axial structure:

  • Outer diameter: Mean: 2.6mm (range 2-3 mm). I did notice the axials are not perfectly round and one diameter is longer than the one perpendicular to it.
  • Inner diameter: Mean: 0.9mm (range 0.8-1 mm)
Septa: 12 (6 primary and 6 secondary, 2 cycles?)
What I am calling primary septa are the longer ones and they extend about a third of the inner diameter. What I am calling secondary septa are about half the length of the primaries. The picture is blue corrected for contrast. It was the best I could do with a scope made to look at cells. I need to find a dissecting scope I can use to take picture

Radial structure:

  • Types of radials: Almost all the corallites appear tubular (but almost nariform at the very tip near the opening) There are a few appressed tubular and sub immersed radials.
  • Radials are appressed (some dimidate): roughly a 45 degree angle for most.
  • Opening shape: Oblique
Measurements:
  • Length: 3.5-5 mm ( the corallite I think is incipient is longer, 7 mm)
  • Outer Diameter: 1mm X 2mm
  • Inner diameter: the septa are oblique and run almost the entire length of the opening (0.8mm X 1.8mm). The measurements are consistent among corallites, with the shorter length radials having slightly smaller openings.
Septa: Many have no distinct septa that I can see and some appear to have 5-6 septa. Below is an example where I could not make anything out.

Coenosteum: some areas around the radials appear reticulate. Close to the radials and at the base of the coral, the coenosteum tends towards costate; the spinules are lined up, but do not form plates on the radials.
preliminary pics with a dissecting scope The micrometer on the slides is calibrated so that 100 units=50mm (so 1mm is 20 units).
Picture of axial and radials:

Side View of Radials:

Coenosteum and radials (10 units = 1 mm, entire micrometer is 10 mm):


Probable Group: I concluded my group was nasuta
Some of the species characteristics were identical for all the species in the group and some I could not ID in my acro with any degree of certainty (the synapticicular rings). Lucky for me these rings were identical in all the species except for one which I was able to eliminate due to other characters.
Using the options as seen on the Wallace chart:
1.branch formation: 0
2.branching orders: 1
3.colony outline: All species identical (mine is frag so can't tell)
4.Predominant outline: All species identical (mine is frag so can't tell)
5.Branch diameter: 1
6.Coenosteum: 0
7.Radial corallite coenosteum: 1
8.Between radials coenosteum: 1
9.Spinule shape: 5,6
10.Radial corallite sizes: 0
11.Radial corallite inner wall: 0
12.Radial corallite shape: 0, 4
13.Radial corallite openings: 0
14.Axial/radial ratio: 1
15.Axial corallite outer diameter: 2
16.Radial corallites: 2
17.Branch thickness: 1
18.Branch taper: 2
19.Max branch length: all identical (mine is frag)
20.Radial crowding: 1
21.Axial corallite syn rings: can't tell
22.Skeletal porosity: 1
23.Radial corallite syn rings: can't tell

So counts are (number of matching characters out of 18:

  • A. nasuta: 14
  • A. cerealis: 16
  • A. valida: 15
  • A. arabensis: eliminated due to geography
  • A. secale: 13
  • A. lutkeni: 12
  • A. kimbeensis: 13
So A.cerealis wins by score and a closer look at the two species. One major difference between A. valida and A. cerealis was that the latter has rather uniform reticulate structure adjacent to the radials and between the radials. In addition, the skeletal characteristics more closely match that in Corals of the World. My sample does not exhibit any of the tubular radials with unique bulge and round opening seen in A. valida. The description that the radials begin appressed and flare out more as they reach the axial corallite also matches my coral. One character that matches A. valida is branch thickness, but my thickness at 10 mm is near the intersection of the characters for the two species. As a result, I am fairly confident mine is A. cerealis.

This page updated last on December 12, 2006.

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