Ambystoma opacum

Author: Brad Shankwiler

Common Names

• Marbled Salamander

Higher Taxa

• Class: Amphibia
• Order: Caudata
• Family: Ambystomatidae
• Tribe: Ambystome
• Genus: Ambystoma
• Species: opacum

Identification

Geography

Table I: North American Distribution of A. opacum

Natural History

• Offspring:
  The female A. opacum breeds in the fall, unlike most Ambystomatids, and deposits her eggs on land, usually near water and in a depression. This nest is then flooded by rain and the larvae begin to develop (Pough, et al. 1998). The eggs are laid in a group but stay unattached to one another and will not hatch until surrounded by water. Up until this point, the brood is carefuly guarded by the mother (Conant, et al. 1998).
• Habitat:
  Wide range of living from "moist sandy areas to dry hillsides." (Conant, et al. 1998).
• Density:
  Alternation in the weather will affect density of population. A. opacum lay thier eggs in the fall, then their larvae spend the winter in stagnant water, such as ponds. The early breeding, unusual for Ambystomatidae, allows for the Marbled Salamander to have a head start in development. This makes them the dominant predator on other larval amphibians, and thus more surviving A. opacum than other larval species of Ambystoma in the deme. However, "during severe winters, Marbled Salamander larvae die" (Pough, et al. 1998).
• Diet:
  Although the A. opacum can be trined to eat small portions of meat, they tend to eat live earthworms and other invertebrates (Conant, et al. 1998). Some Marbled Salamanders are cannibalistic. Most species will choose an unrelated individual to eat before a sibling, because eating a "conspecific would be selectively disadvantageous." (Pough, et al. 1998) However, Susan C. Walls and Andrew R. Blaustein proved this to be the opposite in the case of A. opacum. Kin being the preferred prey, they suggested cannibalism of smaller kin can greatly increase the direct fitness of an individual while at the same time causing no change in the indirect fitness. This may be due to smaller realatives not being able to survive and metamorphose before the water dries out (Walls, et al. 1995).

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