The teenaged son of one of my school colleagues was exploring the woods near his house when he came upon a curious situation. The melting of the winter snow combined with the limited rains that we’ve had this spring worked to form pools on the forest floor. Some of these pools were nothing more than puddles that had formed in the ruts of an old logging road and in one of these pools, he discovered several egg masses that had been left there by an overly optimistic amphibian.
The problem, as he saw it, was the fact that this particular puddle was small and shrinking fast. He estimated that the eggs would not fully develop before the water disappeared, so he took the initiative to go back to his house, grab a 5-gallon bucket out of his garage, and save the eggs. Knowing that there are young people who understand the natural world and care about what happens to wild creatures is a wonderful thing that gives me hope for the future.
The boy returned home with a bucket full of eggs and presented them to his mother, who is a biology teacher at my school. She then brought the bucket to school and each of the biology teachers adopted one of the egg masses. Mine ended up in a 500-ml beaker that sits in a quiet spot by one of the windows in my classroom and we have had daily discussions about what creature might have laid the eggs. I have also tried to engage some of my students in the process of monitoring the eggs and a couple of them have shown some genuine interest. For them, watching the development of the embryos has become something of a passion.
Today’s photo, which I took last week, shows enough detail to allow a reasonable identification. These are not baby frogs. Instead, they look like baby salamanders. You can make this determination by the presence of external gills (red arrow) that emerge from just behind the heads of these creatures. Frogs also have gills with which to “breathe” underwater, but their gills are not visible. Instead, they are hidden under a thin layer of skin on the bulbous bodies of the little frogs. The creatures in our photo are longer and more linear, which suggests salamander. My current hypothesis is that these are the growing larvae of the Spotted Salamander (Ambystoma maculatum).
One of the great joys of writing this column is the fact that I always seem to learn something new along the way. The general size and shape of the eggs and the egg mass were familiar to me, but what I didn’t know is that Spotted Salamander eggs have a symbiotic relationship with a type of algae known as Oophila amblystomatis. The genus name “Oophila” is a combination of the Greek words “oion,” which means “egg”, and “philia,” which means “to love.” The species name is a misspelling of the salamander’s genus name, “Ambystoma.”
The algae live inside the eggs, which explains the faint green color that you can easily see in the photo. The algae take the carbon dioxide produced by the growing larvae and use it in the process of photosynthesis. In return, the larvae receive oxygen and sugars, which help them to grow. We just happen to be studying the concept of symbiosis in class this week, and my students have rightly identified this relationship as “mutualism” — a relationship between species in which both benefit. The algae get a place to live and a source of carbon dioxide, while the salamanders get some food and a plentiful source of oxygen. Perfect!
Once the larvae hatch out of their gelatinous eggs, they will need to be brought to a new home. Spotted Salamander larvae are aggressive little carnivores (another vocabulary word that my students have recently learned) and they need a large supply of tiny aquatic invertebrates to feed upon. In the bottom right-hand corner of the photo you can see the larvae of a fly (blue arrow). This little critter looks something like a shrimp and would most likely be devoured by the baby salamanders after they had a chance to grow a bit larger. So, the clock is ticking for this baby fly. Can it grow to adulthood before the developing salamanders grow large enough to eat it?
All of this shines a light on the astonishingly complex ecosystem that can be found in a simple puddle in a forest. Larger pools, known as vernal pools, will contain enough water to allow the full lifecycles of these little animals to play out before the water disappears. Smaller pools allow the story to start, but the water dries up before the story has time to finish. So, the plan is to hold onto the larvae until they hatch and then bring them back to the same forest where a couple of larger pools exist. Everyone involved has had a chance to watch a fascinating life cycle up close, while the salamanders themselves have been saved. Another form of mutualism that benefits salamanders and humans alike!
Bill Danielson has been a professional writer and nature photographer for 28 years. He has worked for the National Park Service, the US Forest Service, the Nature Conservancy and the Massachusetts State Parks and he currently teaches high school biology and physics. For more information visit www.speakingofnature.com, Speaking of Nature on Facebook, or the Speaking of Nature Podcast.