October 23, 2014, 1:06 am

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  • Hawaiian cold-water coral tissue
Two wax histology blocks containing tissue from Hawaiian deep-water precious corals (© R.G. Waller, 2006).

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Slicing and dicing

So how do we study coral reproduction?  There are many ways to do this. One important technique is known as ‘Histology’. Histology is used in many fields of research and gives us a way to look at the internal structure of an animal – it is particularly useful in medical science. We take the coral and decalcify it, that is to get rid of the skeleton using an acid, so that we can just look at the soft tissues. We then dehydrate the tissue using various grades of alcohol and embed the tissue in wax, creating a hard wax cube (see image to the left). We then slice up this cube, creating thin sections just a few microns thick through the coral, which we mount on a slide and stain various colours depending on what we want to look at. Looking at these thin sections under the high power microscope can tell us what sex the coral is, how many eggs are in a coral and even what stage of development the eggs and sperm are at.

There are other ways to examine coral reproduction too. If the eggs or sperm are large enough you can dissect them out and look at them under the microscope. The Transmission Electron Microscope or the Scanning Electron Microscope can also be used to look at how eggs and sperm are produced, or what the surface of a larva looks like. You can also collect corals and keep them alive in aquaria and wait for them to reproduce, then look for the larvae to describe and study them.