While digging in a stream bed to expose a spring on our farm in SW VA, I came across some very interesting salamanders that could easily be over-looked if you do not flip over rocks in spring seeps. These wonderful salamanders are all in a famiily (Plethodontidae) that are lungless, as strange and improbable as that may seem. Thus they can only respire through their skin and mouth and must stay damp at all times. So they are generally found in small cool streams or in damp terrestrial habitats near such streams. Why would these salamanders have lost their lungs which certainly would have been present in their ancestors? Could this be an example of the principle that structures that are unnecessary become vestigial and degenerate? But why would lungs be useless to these salamanders? Perhaps the high concentration of oxygen in the cold moist habitats they occupy made lungs unnecessary.
The variety of these predatory salamanders is remarkable as illustrated here by just these three examples. Two of the more extreme body forms are illustrated by a photo of the black-bellied and Blue Ridge two-lined salamanders together. The black-bellied is the pit bull or tiger of this Lilliputian world – it is quite robust and large headed with a big bite to both protect itself against predators and to eat insects, crustaceans and other salamanders. The bigger the mouth, the larger prey you can eat- a great illustration of “gape-limited” predation. Look at a close-up of the head and you will see the last view afforded to its victims! On the other hand the two-lined is slender with a small head and is limited to smaller prey. The third species, the red salamander, is intermediate in size. These three salamanders illustrate the principle by which competition among closely related species is limited by differences in body shape and size.
You will have noticed a considerable difference in color of these three salamanders. The black-bellied is dark, the two-lined golden, and the red salamander is bright red with dark spots. Why might this be the case? The red salamander is believed to be a mimic of the red eft stage of the newt. I have shown a photo of the eft as it begins to make a transition into the adult stage which is yellowish green; earlier the eft is bright orange red. Could the two-lined salamander possibly be a mimic of the later stages of the eft? The black-bellied may be dark as a means of camouflage against predation by reptiles, birds and mammals as it forages on land and in shallow water.
So throw caution to the winds and go wading in a shallow stream and turn over some rocks and you may be surprised by what you find. There is a hidden and wonderful world of salamanders and other creatures awaiting discovery.
Bill Dunson, Englewood, FL & Galax, VA