Salamanders are some of the most diverse creatures on the planet. Being densely populated in North America's Appalachian Mountains, they are also foun
Salamanders are some of the most diverse creatures on the planet. Being densely populated in North America’s Appalachian Mountains, they are also found all the way to the rolling upland hills and low plateaus of Europe. These lizard-like creatures are hyper-adapted to the some times brutal conditions they call home. From cave salamanders who are rendered partially or completely blind to harmonize their species with the total darkness they inhabit in subterranean environments; to various giant river salamanders that can reach several feet in length to blend in with the rocky substrate of the river basin. Salamanders are secretive, sundry, and unlike any other order of caudates on Earth. This list is a breakdown of just four of the most unbelievable adaptations the order Urodela contains.
What is an adaptation?
To put it broadly “Evolutionary adaptation, or simply adaptation, is the adjustment of organisms to their environment to improve their chances at survival in that environment” (NGS 2023). There are a handful of ways living things can modify themselves to fit into the ecosystem they occupy, falling into two main categories, behavioral and structural. Behavioral adaptations are ones used to service the animal in survival, typically in response to an outside force (NPS 2020). For example, bears go into hibernation in response to colder temperatures. Structural adaptations are “physical features of an organism that enable it to survive in its environment” (Teaching 2023). The thick fur that bears have to cope with freezing temperatures and protect themselves from would-be predators is structural. Due to the solitary nature of these covert cold-blooded vertebrates, the most obvious of their adaptations will be structural and thus the primary subject of today’s investigation.
Spring salamander. Photo by Chance Feimster
There are 10 families in the order Caudata (salamanders and newts) and approximately 800 extant species of salamander (AmphibiaWeb 2024). This number is ever-changing as new species are constantly being discovered, old species are reclassified based on modern genetic testing, and some species are lost to extinction. Most of these are found in North and Central America, but caudates are found on every continent except Antarctica and Australia. Given that each of these continents is highly variable in landscape and climate, there are scores of adaptations to uncover.
The Furious Fire Salamander
Sprawling across the hills of central Europe, the fire salamander (Salamandra salamandra) calls deciduous and beech forests home. A figure of ancient superstition, this salamander was once thought to have been born from the heart of fire. The mythology likely comes from early European settlers collecting logs to build fires (said logs being ideal protection from predators and arid afternoons for the fire salamander) and subsequently watching as these black and yellow amphibians writhed out to avoid being burned by the flames (SD wildlife explorers 2024).
Fire salamander. Photo by Eric Isselee
Aside from their fascinating lore, fire salamanders also possess a unique ability to defend themselves and strike prey. It lies right behind their eyes. If they feel threatened, they will release a poisonous liquid from glands within their head. This alkaloid excretion is highly toxic and causes respiratory paralysis and sometimes death within vertebrates (Mann 1895). While not typically a danger to humans who encounter the toxin, save for ingestion of the chemical, certain reptiles, birds of prey, and small mammals who do not have immunity to their poison may face an unfortunate fate (Weterynarjyns 2017). It may be that this functional and efficient toxin has led to this being such a long-lived species; one salamander kept captive in the German Natural History Museum of Koenig was recorded to be more than 50 years old. To put it in perspective, the average lifespan of most salamanders is 10-20 years (NWF 2024).
Blackberry salamander. Photo by Chance Feimster
The Shape-Shifting Newt
Only a handful of organisms on Earth exhibit forms of metamorphosis. Metamorphosis is the transition of a juvenile to an adult in multiple distinct stages; think caterpillar to butterfly (Oxford Dictionary 2024). The Eastern newt (Notophthalmus viridescens) is one of those few select creatures that express this shape-shifting adaptation.
Eastern newt. Photo by Chance Feimster
Hailing from North American rivers, swamps, and streams, this slow-moving salamander can be identified in its first stage of life as a moss-green larva. This life stage is characterized by being fully aquatic, using gills to breathe, and are sometimes referred to as ‘newt tadpoles’ (Arc Trust 2023). The second stage can be recognized by a red body and black-ringed orange spots called the eft stage or terrestrial stage. The larva has now lost its gills in favor of lungs as it emerges from the ponds from which they hatched. That bright red coloration, also known as aposematic coloration, reminds potential predators to stay away, signaling that they, like many in the family Salamandridae, secrete a poisonous toxin through their skin. In fact, “during the eft stage…they are 20 times more toxic than at any other stage” (Beardsley Zoo 2024). And if that isn’t enough to ward off predation, the newt may flee after dropping one of its limbs, as they are one of many species in the order Caudata known to regrow lost limbs (Yu et al., 2022).
Red eft. Photo by Chance Feimster
Similarly to their larval stage, the red eft will consume various insects on forest floors where they traverse the leaf litter. They use the cover of fallen leaves and the ability to produce a mucus layer along their skin to absorb oxygen in the air around them (Burke Museum 2024). The newts must keep moist skin to respire, if they remain dry for too long a period, subsequently, they will not be able to breathe and will die.
The eft will remain terrestrial for several years before completing the last transition in its journey (CT DEEP 2015). The final stage involves a coloration shift trading in that vibrant warning shade for a camouflaging green brown to blend in with the streambed. Alongside that pigment change our efts tail will return to its larval-keeled shape, acting as a rudder as this creature will return to aquatic life. The fully-fledged newt will ideally remain subaquatic for the duration of its life but will occasionally surface and live earthbound if their inhabited pool dries up (Great Parks 2024). A fascinating, dynamic adaptation to the ever-changing global climate.
The Subterranean Salamander
Considered a vulnerable species on the IUCN Red List due to its heavily restricted range of approximately 2,000 km², the Tennessee cave salamander lives its life in the encompassing darkness of southern United States cave systems (Norman 2024). This blush-pink cave dweller displays several traits that reveal its affinity for underground life. External gills, a long tail fin, small eyes sans eyelid, and a thick snout reveal the retention of larval stage attributes, reminiscent of the first stage of life displayed in many salamanders and newts undergoing metamorphosis, referred to as paedomorphic. Paedomorphism is when an animal “retain[s] juvenile features as an adult” (Oxford 2024).
Cave salamander. Photo by Chance Feimster
This is an intriguing adaptation as cave salamanders have been found, albeit rarely, naturally metamorphosed when the conditions favor it (Yeatman and Miller 1985). In the laboratory, metamorphosis may also be induced (Dent and Kirby-Smith 1963).
In many ways the Tennessee cave salamander, Gyrinophilus palleucus, and the Eastern newt are alike, beginning life as aquatic larvae equipped with many kindred features such as the keeled tail and gills (Niemiller 2023). Until, of course, the Eastern newt abandons the subaqueous initial life stage for a terrestrial chapter whilst the cave salamander may remain totally aquatic (Norman 2023).
Much about this salamander remains a mystery. Partly due to their endemic nature which can be defined as a “species that [is] found in a particular geographical region and nowhere else in the world” (BYJUS 2020). As a species restricted to limestone caves in the southwestern Appalachian Mountain range, there are rare opportunities for viewing and research (Godwin 2024). In fact, of the 20 sightings in the state of Alabama, there are questions about true Tennessee cave salamander identifications versus larval stage spring salamander (Gyrinophilus porphyriticus) misidentification, as they share many overlapping morphological characteristics.
Regardless, there is high concern for this secretive species’ survival. This creature is dependent on water quality and pollution is a major threat to their livelihoods (IUCN Red List). The International Union of Conservation of Nature (IUCN) points out the importance of advocating for the protection of various watersheds that flow through the cave salamander’s range.
A Mesozoic Monster
The Mesozoic era spans from approximately 251.9 to 66 million years ago (NPS 2024). This era has since been nicknamed “The Age of Reptiles” by modern archeologists to signify the domination of “Dinosaurs, crocodiles, and pterosaurs [ruling] the land and air” (NPS 2024). The Mesozoic era was a bustling time in earthly history as Pangea broke apart, sea levels rose and expanded, and herps thrived globally. This era is often divided into three distinct “Periods: the Triassic, the Jurassic, and the Cretaceous” (NPS 2024). Honing our focus on the latter, the Late Cretaceous period, roughly 65 million years ago is where the story of the Eastern hellbender (Cryptobranchus alleganiensis) begins. This 2-foot-long salamander, the largest in North America and third largest on earth (following the Chinese and Japanese giant salamanders) inhabits a sweeping distance “from New York near Lake Ontario to northern Georgia, even reaching as far west as southern Illinois” (Sea-Grant 2016).
Eastern hellbender. Photo by Chance Feimster
The origin of the name ‘hellbender’ is unclear, but there are several theories. Namely that American settlers saw this grey slimy beast crawling along rocky streams and thought “It was a creature from hell where it’s bent on returning” (Johnson and Briggler 2004). This salamander may have a foreboding name, but in reality, is not only harmless but a sign of good water quality (Keitzer et al 2013). Akin to a canary in a coal mine, the hellbender tells scientists whether local streams meet adequate requirements to support the sensitive giant salamander often nicknamed “snot otter” or “Allegheny alligator” (Allen 2017). Designated vulnerable in 2021 by the IUCN Red List, the North Carolina Wildlife Commission corroborates this designation by emphasizing their necessity for safe water, “if there is a healthy hellbender population in a stream, there is clean water” (NCWRC 2023). In such pristine waterways, hellbenders can live to be 30 years of age, commonly seen eating crayfish, insects, and small fish (Pike 2015).
These wrinkly salamanders are adapted to swiftly moving streams by way of their flattened anatomy. And those wrinkles, quite surprisingly serve a very specific function, increased surface area means increased respirational capabilities (Nature Conservancy 2024). All of those folds, called “frills,” work to aid this aquatic animal in breathing underwater, drawing out dissolved oxygen from the flow of waters they inhabit (Bates 2015). They do maintain practically vestigial (retention of a biological structure that has lost some or all of its ancestral function) lungs (Christensen et al. 2009). These lungs are primarily used for buoyancy in the waterways rather than breathing on land. On top of that, hellbenders can navigate stony brooks with more than just their small, substandard eyes that sit at the top of their heads detecting light. But rather than complex eyesight forming total pictures of their surroundings, they have light-sensing cells all around their body (Mattison 2005).
Eastern hellbender
These ancient cryptobranchids have had millions of years to improve upon their multiplex of adaptations. And their intuitive anatomy is evidence of adaptive ingenuity.
A Lasting Legacy
Entering the Anthropocene (geologic epoch in which homo sapiens dominate the earth) is no small feat for any ancient order. Urban sprawl, dispersed zoonotic diseases, and climate change are all threats to the endurance of caudates (Virginia DWR 2024). Volunteering with local organizations and spreading awareness about the fragility of local ecosystems and their importance for the biosphere as a whole are just a couple of steps anyone can take to protect salamanders.
Salamanders, like many amphibians, are known as an indicator species (Defenders of Wildlife 2024). As sensitive individuals who can provide scientists with invaluable information about how the ecology of a region is changing, they act as the mouthpiece for the outdoors. And all they need is for mankind to listen. Amphibians are nature’s scale, acting as predators to some and prey to many, they maintain equilibrium in the environments they populate. In the hope of allowing these creatures to bolster balance in habitats worldwide, it is the job of every conservationist to continue to support and advocate for their protection.
Wesley Shaver is a naturalist with Coastal Expeditions in Charleston, South Carolina, advocating for wildlife conservation through environmental education.
Citations
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