In the last blog post, we discussed how egg and tadpole development can be broken down into various stages, called Gosner stages. The stages start with the fertilization of the egg (Gosner stage 1) and extend to Gosner stage 46, which is when the baby toad (also called an emergent) absorbs all of its tadpole tail.
Late last week, one of our tadpole tanks reached the developmental stage that we have been carefully monitoring for – Gosner 42! Gosner 42 is a really important time point in metamorphosis in which the tadpole starts to develop lungs. This means that the tadpole will soon give up its aquatic lifestyle for a new life on land.
We know that tadpoles are reaching this critical time point because they start to grow their front limbs. Did you know that both limbs don’t “sprout” at the same time? While we are monitoring for Gosner 42 stage tadpoles, it is not uncommon for us to see tadpoles swimming around with three legs!
Once one front leg is observable on a tadpole, we carefully collect it from the tank with a net and transfer it to a tank with shallow water and moss. This setup allows the tadpole access to both water and land as it finishes transitioning from gills to lungs.
As of today, we have 19 emergents from our first round of breeding several weeks ago. Several of these little guys still have some of their tail remaining, while others look just like tiny toads! Each emergent weighs less than a gram. It is hard to imagine that in a year they will weigh from 20 to 50 grams!
We are currently also caring for 47 tiny little toads that were head-started by our collaborators at Texas State University. These little toads are from egg strands collected around the Bastrop area and are the first wild toads to be brought into the facility since 2010. These toads will hopefully add “new genetics” to our captive colony, which is important so that we can maintain high genetic diversity in the eggs, larva, and toads that we release back into the wild in the coming years.
Stay tuned as we post more updates our newest additions!