July 31, 2013
Stalking The Illusive Snot Otter
Snot otter is the apt nickname for the hellbender salamander, the largest salamander in North America. It can grow up to two feet long and live for 30 years. Despite their size, they are notoriously difficult to find, because they spend most of their time under large rocks. I had never heard of it and, apparently, neither have most of the people in the Appalachian region where it is found. Just about the only way to find one, until now, was to pry up a large river boulder in a stream and snorkel underneath. This necessity made it very difficult to determine the numbers and health of the species. The amphibian may be on the decline and could end up on the Endangered Species list, so knowing where it is and where it is breeding is important for its protection. Fortunately, science has come to the rescue of the snot otter.
For the last five years, researchers have been looking for aquatic animals in a new way – by testing the water for their DNA. “In the water samples we found DNA from animals as different as an otter and a dragonfly,” says Philip Francis Thomsen, a Danish researcher.
“We have shown that the DNA detection method works on a wide range of different rare species living in fresh water – they all leave DNA traces in their environment which can be detected in even very small water samples from their habitat.”
With the amount of water in a shot glass, scientists can detect the existence, and even the number, of animals that are in that body of water. The Danish study shows, by comparing the DNA method to a traditional physical count, that there is a clear correlation between the amount of DNA in the environment and the density of individual organisms, meaning that the DNA detection method may be useful in estimating population sizes as well.
In the case of the hellbender, researchers can even tell if the water they are testing is a breeding ground, because the salamanders shed a lot more DNA when they are breeding. The amphibian is being studied by conservation scientist Stephen Spear.
Imagine how useful it will be to be able to know, using just a few ounces of water; exactly what fauna lives in a body of water and how plentiful they are. The ability to measure the biodiversity of an area will be a huge help in prioritizing conservation efforts, particularly in sensitive biomes such as coral reefs.
The method is already proving useful. It is being used to monitor for the presence of invasive species, such as American bullfrogs in France and Asian carp in the Great Lakes.
It can also be use in the oceans, where it is being used to track species that seem to be moving into more northern waters, possibly as a result of climate change. These include the sardine and the long-finned pilot whale, both surprisingly located off the coast of Denmark.
This technology even has applications for studying land animals. Their saliva contains DNA, so their presence at a particular watering hole can be detected.
This DNA analysis is so easy and inexpensive that its ability to help us understand and protect the aquatic animals in our world is immense. It is easy to see a host of practical applications that will help us to sustain the biodiversity of our planet.
Image Credit: Logan Gerber, University of Florida