Tadpoles Developing

The last few weeks have been rather busy and a little bit stressful.  Several days elapsed until additional spawn was laid, and whilst I was waiting I was starting to panic that I wouldn't be able to complete my experiment. Since then, I have had over a dozen clumps of spawn. It has been a little difficult to catch this quickly once it has been laid, as the frogs tend to lay new spawn on top of existing spawn so that it forms a mat. I actually now have four replicates of the experiment running: all of the first batch (Replicate A) seems to have spoiled so I took a further batch (Replicate D) to ensure I had three sets of results to compare.

Another stressful moment was when my pH meter failed: I discovered that water had got into the battery compartment and fried the electrics. I ordered another on overnight delivery, and although it was much more expensive it seems a lot slower and only produces readings to 0.1 decimal place. I have taken to checking it against the calibration fluid before I start checking my water treatments as I am not overly confident in the new meter so am erring on the side of caution.

Now that I am over a week into the experiment and have three replicates running I am starting to get some good results. It was impossible to identify the early stages of development without a microscope, but once the embryo started to develop a tail bud I could allocate it to the appropriate Gosner stage.  Development seems to be progressing very quickly, with just a day or two between the tail bud first developing and the gills forming. The embryos are now moving, mostly curling and uncurling, within the central egg sack. The next stage to look for is a heart beat behind the gills, but I am not sure I would be able to see this without a microscope.

Although none of the embryos have hatched yet, there are some obvious developments. The least acidic treatment, at 5.5 pH, seems unaffected and is developing in line with my control group which is in neutral pond water.  The tadpoles in moderately acidic water of 4.5 pH seem to be about a day behind in development terms, and there are slightly more deformities/undeveloped eggs.

The most acidic treatment, at 3.5 pH, is much different - none of the eggs are developing. The inner sack has turned opaque and the eggs generally are cloudier and more condensed. In some of them, the nucleus seems to have broken apart. I am continuing to monitor them, but doubt any will hatch.

I have taken lots of photos and notes to remind me of each development stage, and this should make it easier when I come to write the discussion section of my dissertation.