Spotted Salamander, Ambystoma maculatum

Wednesday, February 24, 2010

Nature Notes
by Bob Thomas

Spotted salamanders, Ambystoma maculatum, are beautiful and intriguing forest critters. They reach about six inches long, and have paired yellow spots down the back that shine against a rich black background. Two of the spots at the back of the head are usually pale orange.

Like other species of the same genus, they spend most of their year ambling about in tunnels just beneath the surface of the leaf litter on mixed-deciduous forest floors. They range from New England to the Gulf Coast, and may be locally abundant, but scattered in distribution.

As winter approaches, cool rains begin to fall and pools begin to form in the forests. Spotted salamanders are stimulated to move to the surface and enter the newly formed puddles, always in the evenings. Males walk around on the submerged leaves and deposit tiny spermatophores. Each spermatophore consists of a ball of sperm sitting atop a stalk – somewhat resembling a golf ball on a tee.

As females enter the pools, the males approach them with a courtship dance that results in the females picking up the sperm caps with their cloacal lips (a cloaca is a common opening of the reproductive, excretory, and alimentary systems). Sperm are stored in small pockets inside the females' cloaca called spermathecae and are released to fertilize eggs as they move through the cloaca.

As eggs are extruded, they are enveloped in a thin liquid that immediately swells and solidifies like gelatin encasing the eggs. Their eggs and larvae have an interesting symbiotic relationship with a particular alga, Oophila amblystomatis. As stated, the eggs are encased in a jelly coating, and thus are protected from desiccation and predation. The down side of the jelly is that the larvae do not have access to oxygen. The algae photosynthesize and provide oxygen to the developing salamanders and, in exchange, the carbon dioxide produced by the larvae feed the photosynthetic activity of the algae. Perfect mutualism. In addition, I suspect the algal growth on and in the gelatinous masses add to their camouflage.

Within a couple of weeks, the larvae hatch and swim into the pools. Their goal is to grow by consuming small organisms, metamorphose into adults, leave the wetlands and burrow back into their earthen tunnels by the onset of spring, and continue their circle of life.

Of course, there are obstacles. Puddles may dry or predators such as larger marbled salamander larvae may be present and gobble them up.

If you travel farther north, these events are shifted to later in the year. For instance, the breeding events happen as the snows melt and pools form. At Audubon Greenwich Center in Greenwich, CT, spotted salamanders become active in April; in south Louisiana they become active in December or thereabouts.

Spotted salamanders are more fun in the south since they are active for months and provide exciting moments in natural history discovery.

Also published in Delta Journal, The Times Picayune, December 28, 2008.

Adult spotted salamander, Ambystoma maculatum.  Adults are about 5-6 inches in total length.  Photo by Bob Thomas.                                      

Adult spotted salamander, Ambystoma                                       Adult female spotted salamander
maculatum. Adults are about 5-6 inches                                     with a normal sized egg mass after
in total length.                                                                          it has gelled.
Photo by Bob Thomas.                                                            Photo by Bob Thomas.

                                    

Close up of a spotted salamander egg mass.                               A number of spotted salamander egg masses.
Note that two larvae have exited their egg                                  The puddle is drying and the tops of the egg
envelope and are moving through the jelly.                                 masses are exposed to the air.
Also, note the green algae, Oophila                                             Photo by Bob Thomas.
amblystomatis, around the developing
larvae.
Photo by Bob Thomas.