Most salamanders start life as aquatic larvae and metamorphose to become terrestrial adults, returning to the water only to lay eggs. But mudpuppy salamanders (Necturus maculosus) remain aquatic throughout life. By retaining their juvenile features, along with other adaptations, they are able to inhabit rivers, perennial streams, ponds and lakes throughout eastern North America, from southern Canada to Georgia. They can even be found in the Midwest.
Muddy Rock Lookalikes
Mudpuppies, also called waterdogs, have gray-brown to black, spotted skin, which helps them merge with the muddy river bottoms where they live. Their long, flattened bodies -- 8 to 20 inches in length -- make it easy for these aquatic salamanders to hide during the day under rocks and logs. They come out at night to feed on fish, other amphibians and invertebrates.
Lungs and Gills
Larval salamanders usually absorb their gills during metamorphosis, but mudpuppies retain large, feathery reddish brown gills positioned on both sides of their heads. External gills more efficiently extract oxygen from water than internal lungs. In habitats in which the water is well-oxygenated, mudpuppies have shorter gills than those inhabiting poorly oxygenated waters. As they can absorb oxygen through their skin and rise to the water's surface to breathe using their internal lungs, mudpuppies can survive when oxygen levels are low. They also use their lungs for buoyancy in the water, just as fish use their swim bladders.
Walk and Swim
Mudpuppies walk about the bottoms of ponds and rivers. Their short, flattened limbs make this easy. They can swim well, too. Their short, laterally compressed tails -- high and narrow, rather than round or flattened -- along with their juvenile fleshy tail fins, aid in their swimming efficiency.
Mudpuppies have sensory cells on their bodies that detect pressure and movement in the water. They help the mudpuppies escape from predators such as fish, larger aquatic salamanders, water snakes, otters and herons. By holding their legs against their flanks and lashing their tails, they can swim off rapidly. Mudpuppies also have skin glands that produce a slippery coating over their bodies, which makes it hard for predators to get hold of them.
Mudpuppies retain the useful larval ability to regenerate lost limbs and tails and to repair damage to their bodies. They can even regenerate parts of their brain. Sometimes a new limb grows as a damaged one repairs itself -- giving a mudpuppy an extra leg.
Mothers on Guard
Mudpuppies mate in the fall, but females store the sperm to fertilize their eggs in the spring. They dig nest chambers, usually sheltered by rocks or logs, and attach 18 to 180 eggs to the ceilings of their nests.The females stay with the eggs, probably to defend them, for a month, sometimes two, until the larvae hatch.
- Thomas Northcut/Stockbyte/Getty Images