Nature Notes
By Bob Thomas

One of our most interesting animals that makes its appearance each October is the marbled salamander, Ambystoma opacum. These cute amphibians, festooned with broad black and white bands, round heads, and large eyes are active year round in burrows just beneath the surface in mixed-deciduous forests throughout most of the state.

Each fall, the males move to low areas that typically flood during winter rains. They place spermatophores, small sperm packets that sit atop a jelly-like stalk, on leaves and soil on the floor of the incipient pond. There are times when the population is so large that the ground becomes quite slippery with spermatophores. As the females arrive, they squat over the spermatophores and pick them up with their cloacal lips. The sperm are stored in little cloacal pockets in the female called spermathecae, and the eggs are fertilized as they pass by the spermathecal openings during laying. Females normally find a hiding place beneath a log where they lay their eggs. The females coil around the eggs to keep them moist with mucus secreted by glands in their skin.

The eggs begin embryonic development, but delay hatching until their nests become submerged as the winter rains arrive and water flows into the forest potholes. The eggs absorb water, and they rupture due to increasing turgor pressure, thus releasing the larvae into the puddles. Although this normally happens in deciduous forest habitats, I have seen larval marbled salamanders in isolated roadside ditches containing no logs, suggesting that egg laying may take place in crawfish holes.

One of the benefits of the ephemeral nature of their aquatic habitat is that there are few predators that consume the salamander larvae. In fact, the marbled salamander larvae are usually the top aquatic predators, along with diving beetles and fishing spiders.

After weeks in the winter pools, the larvae lose their external gills and dorsal fins and grow four legs. They move to land, acquire their adult pattern, and their metamorphosis is complete.

Marbled salamanders may remain on the surface, protected under logs, leaves, and other debris throughout the winter. By mid-spring, they are back in their burrows moving just a few inches below the surface.

This segment of their life cycle gives them and the other members of their genus the common name mole salamanders, with reference to the much larger, but subterranean, mammalian moles.

Also published in Delta Journal, The Times Picayune, December 21, 2008.
 

Marbled salamanders, Ambystoma opacum,                                This female marbled salamander is seen
are scientifically very interesting,                                               but also laying eggs in a moist rotten log.
among our most adorable little critters.                                      Photo by Brad Moon.
Photo by Bob Thomas.
 

After the eggs are layed, the female typically                             Larval marbled salamanders hover in the
rests near them and keeps them moist by                                  water column of temporary pools and feed
using her secretions.                                                                on any living thing they can get in their mouths.
Photo by Bob Thomas.                                                            Photo by Bob Thomas.

A younger Patrick Thomas and his find,                                   Matt Taylor and Patrick Thomas turn a log
a marbled salamander.                                                           in a mixed-deciduous forest north of Lake
Photo by Bob Thomas.                                                         Pontchartrain and find marbled salamanders
                                                                                           in the tunnel beneath the log.
                                                                                           Photo by Bob Thomas.