|AMPHIBIANS OF THE METRO AREA
Red-spotted Newt (Notophthalmus viridescens
The Red-spotted Newt is a common aquatic salamander. These salamanders have an unusual
and complex life history. Adult newts are completely aquatic and can be found swimming in small
ponds, slow moving streams, and lakes. The green adult newt has a row of red spots on each
side, and external gills to absorb oxygen from the water.
In the spring, the adult female newt lays eggs attached to aquatic vegetation. The eggs hatch in
three or four weeks (length of incubation depends on the temperature of the water) into a small
gilled aquatic larvae. The aquatic larvae is followed by an unusual stage of development - a
terrestrial "sub-adult" called the Red Eft. The red eft is a bright red salamander stage that
sometimes, but not always, occurs after the larval stage, before the salamander returns to the
water to live as a green aquatic adult. Red Efts can be found under damp logs or occasionally
walking on the forest floor in the rain. I have never found a red eft in the Piedmont of the
Baltimore-Washington area and I expect the red eft stage is usually bypassed here, with the
salamander remaining aquatic throughout its life. I have found red efts to the west of our area,
in the Appalachian Mountains.
The red-spotted newt is known to accumulate toxins in its skin to protect it from predators. The
bright red color of the terrestrial red eft stage is thought to be a warning coloration to warn
predators that the newt is poisonous. The toxins that have been found in these newts are
tetrodotoxin and toxic analogs of tetrodotoxin, including 11-oxotetrodotoxin and
6-epitetrodotoxin. The origin of these toxins is a mystery. It has been suggested that the newts
may be accumulating the toxins from the environment, possibly from bacteria growing on the
newts skin, rather than producing it themselves. Tetrodotoxin has been found in a variety of
animals including Pufferfish (of the family Tetraodontidae, from which the name of the toxin was
derived), some snails, a poison arrow frog, the blue-ringed octopus, and others.
A red-spotted newt in a slow moving stream at Gunpowder State Park.