Amphibians
Small-Mouthed Salamander
Ambystoma texanum · also called small-mouthed salamanders
The small-mouthed salamander’s narrow mouth looks like a minor detail, but it is a genuine specialisation, shaped specifically for pulling earthworms out of soil more efficiently than a wider-mouthed relative could manage. That same species has also, almost incidentally, become one of the genetic donors behind an ancient lineage of all-female salamanders that has persisted for millions of years by borrowing exactly what it needs and discarding the rest.
Overview
The small-mouthed salamander, Ambystoma texanum, is a slender mole salamander native to bottomland forest and floodplain habitat across the central and midwestern United States. Its narrow mouth is specialised for extracting earthworms from soil.
A quiet contributor to a strange lineage
Beyond its own straightforward life history, the small-mouthed salamander plays a supporting role in one of vertebrate biology’s odder stories, its genome periodically drawn on by an ancient, all-female hybrid salamander complex that reproduces by kleptogenesis rather than conventional sexual reproduction.
Status
Least Concern — widespread and stable across suitable bottomland forest and wetland habitat throughout the central and midwestern United States.
Small-Mouthed Salamander: common questions
Why is it called a small-mouthed salamander?
The small-mouthed salamander gets its common name from its notably narrow, restrictive mouth, a feature well suited to gripping and pulling earthworms out of soil and leaf litter, reflecting a somewhat more specialised diet compared with several related mole salamander species that have broader mouths and more varied feeding habits.
How is the small-mouthed salamander connected to all-female salamander lineages?
The small-mouthed salamander is one of several mole salamander species whose genome has historically contributed to an ancient, all-female hybrid salamander lineage that reproduces through kleptogenesis, a process in which the unisexual females mate with males of related species like the small-mouthed salamander to trigger egg development without necessarily incorporating that male's genetic material.
Where does the small-mouthed salamander breed?
Like many of its mole salamander relatives, the small-mouthed salamander breeds in temporary, fishless woodland pools created by seasonal rain and snowmelt, timing its breeding migration to take advantage of pools without fish, which would otherwise prey heavily on its eggs and larvae.
Where in the United States is the small-mouthed salamander found?
The small-mouthed salamander is native to bottomland forest, floodplain, and adjacent wetland habitat across a broad area of the central and midwestern United States, generally favouring woodland areas with suitable temporary breeding pools available nearby during the appropriate season.