Alpine salamander
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The alpine salamander (Salamandra atra) is a black salamander that can be found in the Alps, and through the mountainous range in Europe.<ref name="Salamandre noire unique">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> It is a member of the genus Salamandra. Their species name, atra, may be derived from the Latin ater, meaning dull black.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> The salamanders' coloration has evolved over time, as some species are completely monochrome black and others have yellow spotting and marks.<ref name="Burgon-2020" /><ref name="Bonato-2005" /><ref name="Karch.Ch (Swiss information center for amphibians and reptiles)">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name="TREVISAN-1991" /> Their life expectancy is at least 10 years. There are four subspecies of the alpine salamander, with varied distribution and physical coloration.<ref name="DE MEESTER-2020">Template:Cite journal</ref> Unlike other salamanders, whose larvae are developed in water, the alpine salamander and its subspecies are a fully terrestrial species in life and gestation.<ref name="DE MEESTER-2020" /> They give birth to live young.<ref name="Guex-1986" />
Alpine salamanders produce toxic compounds from their skin.<ref name="DE MEESTER-2020" /> These compounds may protect them from both predator and microbial threats.<ref name="Lüddecke-2018" /><ref name="Vences-2014" /><ref name="Scalera-2004" /><ref name="Spitzen - van der Sluijs-2018" />
DescriptionEdit
Alpine salamanders are often small in size, and dark brown or black.<ref name="DE MEESTER-2020" /> Members of the subspecies are not wholly black or brown monochrome, but rather have mosaic or spotted patterns.<ref name="DE MEESTER-2020" /> Members of the subspecies Salamandra atra aurorae have bright splotches on its dorsal side and head. The color is often bright yellow, but can range to shades of white or even gray.<ref name="DE MEESTER-2020" /> Distribution of the pigment is dependent on the distribution of certain cells, so may be smooth and even or patchy.<ref name="DE MEESTER-2020" />
Female S. atra tend to be larger than the males, and can grow up to 151 millimeters, or around 5.9 inches.<ref name="DE MEESTER-2020" /> Males will grow to around 144 millimeters, or 5.6 inches: both measurements include the tail.<ref name="DE MEESTER-2020" /> Males have swollen, visible cloacae, and are more slender than females.<ref name="DE MEESTER-2020" /><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> The salamanders have parotid glands posterior and lateral to their eyes, giving them an elongated head shape.<ref name="DE MEESTER-2020" /> They tend to have between 11 and 13 costal grooves along the sides of their bodies, and a double row of dorsal glands runs down their backs on either side of their spines, down to the tips of their tails.<ref name="DE MEESTER-2020" />
ColorationEdit
Most alpine salamanders that are either completely black (melanistic) or predominantly black have the dark pigment as a baseline, but the evolution behind this dark coloring has a winding history.<ref name="Burgon-2020">Template:Cite journal</ref> Scientists have studied the hypothesis of if the salamanders start completely black, or if they evolved like that over time.<ref name="Bonato-2005">Template:Cite journal</ref> DNA-evidence traced through maternal lineages suggest the latter: that salamanders evolved their black coloration over time.<ref name="Bonato-2005" />
Biological pigmentation is determined by presentation of specific color-producing cells, called chromatophores, which absorb and/or reflect light in a particular way to then appear as a color.<ref name="TREVISAN-1991">Template:Cite journal</ref><ref>Template:Cite journal</ref> In S. atra, there are different cells present or activated, which yield different colors: melanophores contribute to the dark coloration by producing the dark pigment melanin,<ref name="TREVISAN-1991" /> while xanthophores produce a yellow pigment,<ref name="Burgon-2020" /> and iridophores are simply light-reflecting.<ref name="Burgon-2020" /> The fully-black phenotype seen in S. a. atra results from the salamanders' melanophores in the dermis and epidermis, producing melanin alone.<ref name="Bonato-2005" /><ref name="TREVISAN-1991" /> Xanthophore-iridophore complexes are responsible for production of yellow spotting, which appears bright.<ref name="Bonato-2005" /> In species without yellow patches, it appears that they do not ever develop these cells.<ref name="Bonato-2005" /> In S. a. aurorae or other salamanders with different coloration on different parts of their body, two distinct skin types are present: one that only contains melanophores (black), and one that has melanophores, xanthophores, and iridophores in combination.<ref name="TREVISAN-1991" />
The yellow coloring on some alpine salamanders is thought to be an aposematic strategy to fend off predation.<ref name="Vences-2014">Template:Cite journal</ref> The pure black coloring is also hypothesized to be a form of thermoregulation,<ref name="Vences-2014" /> though it may also be considered a warning to some predators.<ref name="Vences-2014" />
Taxonomy and subspeciesEdit
- S. a. atra is a fully melanistic (black) subspecies from central, eastern and Dinaric Alps.<ref name="Karch.Ch (Swiss information center for amphibians and reptiles)" /> This subspecies is the most widespread.<ref name="Romano-2018" />
- S. a. aurorae, the golden alpine salamander, has golden or yellow spots on its back and primarily lives in a small area in the Venetian Prealps near Asiago, and in the Italian Alps.<ref name="Bonato">Bonato, Fracasso. Movements, distribution pattern and density in a population of Salamandra atra aurorae (Caudata: Salamandridae). Amphibia-Reptilia 2003, 24, 251-260.</ref>
- S. a. pasubiensis, with fewer yellow spots than S. a. aurorae, lives in a different part of the Venetian Prealps.
- S. a. prenjensis lives on Prenj Mountain, part of the Dinaric Alps in Bosnia and Herzegovina. The validity of this subspecies is yet to be confirmed, and some scientists in the field debate if this salamander should be considered its own independent species.<ref name="DE MEESTER-2020" /><ref name="bonato2001">Bonato & Steinfartz. Evolution of the melanistic color in the Alpine salamander Salamandra atra as revealed by a new subspecies from the Venetian prealps. Italian Journal of Zoology 2001, 72, 253-260.</ref>
Genetic analysis suggests that the Corsican fire salamander (Salamandra corsica) is the closest related species, and the black-yellow coloration is an ancestral feature of alpine salamanders. Proposed colonization from south (Prealps) to Alps was carried out by the fully melanistic (derived feature) S. a. atra after the last retreat of the ice sheets.<ref name="bonato2001" />
Habitat and distributionEdit
HabitatEdit
As terrestrial organisms, these salamanders live on land.<ref name="DE MEESTER-2020" /><ref>Template:Cite journal</ref> S. atra tend to live underneath stones or logs, or in rocky crevices in their mountainous habitat.<ref name="DE MEESTER-2020" /> They also are diurnal, and most active in the day with periods of inactivity, rest, or sleep at night.<ref name="Romano-2018" /> They will engage in nocturnal activity on a weather-dependent basis.<ref name="Helfer-2012">Template:Cite journal</ref> Ideal weather for alpine salamanders is rainy or post-rain, at temperatures between Template:Convert.<ref name="Romano-2018" />
Geographic distributionEdit
The alpine salamander is found from the France–Switzerland border at the western end of its range, all the way through Austria to the Dinaric Alps at the eastern edge of its territory. This salamander typically lives at altitudes above Template:Convert above sea level, even reaching Template:Convert of elevation.<ref name="DE MEESTER-2020" /> The western Alps (in France and Italy) are inhabited by a similar species, Lanza's alpine salamander (Salamandra lanzai), in only one small areaTemplate:Citation needed. S. atra generally live in forested biomes, particularly deciduous-coniferous mixes.<ref name="DE MEESTER-2020" /> They also can inhabit meadows or grasslands in the mountains,<ref name="DE MEESTER-2020" /> and tend to do well with a mix of tree types.<ref name="Gautier-2003">Template:Cite journal</ref><ref name="Romano-2018">Template:Cite journal</ref>
Their range spans several nations, including: Slovenia, Croatia, Bosnia, Hersegovina, Montenegro, Kosovo, France, Italy, Austria, Algeria.Template:Citation needed
Home range and territorialityEdit
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They thrive in forest environments that have silver fir and beech trees.<ref name="Gautier-2003" /><ref>Template:Cite journal</ref> Coniferous forests that have high proportions of Norway spruce and European larch trees also provide adequate habitats, even though the salamanders live on the ground floor.<ref name="Gautier-2003" /> Because alpine salamanders are completely terrestrial, they have on-land territories that they tend to return to throughout the day and for refuge. They often return to the same sites for much of their lives.<ref name="Gautier-2003" /> Any time that they leave their sites, they expose themselves to predation and also to the chance of losing their site.<ref name="Gautier-2003" /> Alpine salamanders are ectothermic, so losing a refuge or shelter could leave them exposed to the elements and be extremely costly, if not fatal,<ref name="Gautier-2003" /> due their lack of an internal thermoregulation mechanism.
This high dependency on a quality nest site supports the theory that many terrestrial salamanders, including S. atra, engage in territorial behaviors.<ref name="Gautier-2003" /> Capture-recapture methods suggest that the species is very stationary;<ref name="Basile-2017">Template:Cite journal</ref> Template:Convert was the maximum observed distance traveled by one individual during the summer season. About 120 individuals per hectare were counted in most suitable areas with over 2000 individuals per hectare also observed, suggesting that this rather cryptic species is quite abundant.<ref name="Bonato" />
Territorial behaviorEdit
They employ scent-marking techniques for territorial behaviors, and to mark their territories using fecal pellets so they can identify their own shelters.<ref name="Gautier-2003" /> Scent-marking is an intra-species communication, where chemical signals convey specific messages to other S. atra individuals.<ref name="Gautier-2003" /><ref>Template:Cite journal</ref> Alpine salamanders can determine if a found fecal pellet has been left by a member of their same sex and/or species.<ref name="Gautier-2003" /> Thus, this technique serves a double purpose to warn other salamanders that that particular location has already been claimed.<ref name="Gautier-2003" />
Females are more likely to return to their home site, while males are more emboldened to enter another male's territory.<ref name="Gautier-2003" /> Their fecal pellets allow them to both participate in homing behavior, or returning to their own site, and territoriality, and determine intruders on their territory or invade the spaces of others.<ref name="Gautier-2003" />
ConservationEdit
Alpine salamanders are not resilient to habitat changes— few terrestrial salamanders are— so risks of climate change altering their living spaces is severe.<ref name="Basile-2017" /> Although alpine salamanders are listed as Least Concern on IUCN Red List, their numbers are decreasing.<ref name="iucn"/> Additionally, some subspecies of S. atra are in greater danger.<ref name="Romano-2018-2">Template:Cite journal</ref> Population numbers are declining in S. a. aurorae, for example.
One of the greatest dangers to alpine salamanders overall is commercial deforestation in their habitats.<ref name="Romano-2018-2" /> Machinery like tractors or other forestry tools can compress the soil, eliminating some of the small insects that S. atra eat or eliminating potential nooks and burrows for them to use as shelters.<ref name="Romano-2018-2" /> Many scientists propose changes in the lumber industry as an attempt to heal these habitats.<ref name="Romano-2018-2" /> These salamanders may also change their morphology as global temperatures rise.<ref name="Ficetola-2016">Template:Cite journal</ref> Amphibians and other organisms that do not internally regulate their body temperature may need adaption mechanisms to remain at ideal physiological temperatures in the face of changing climates.<ref name="Ficetola-2016" /> Other issues like acid rain or precipitation changes could prompt many animals, including alpine salamanders, to be forced into new habitats.<ref name="Ficetola-2016" /> Alpine salamanders play a crucial role in their ecosystems.<ref>Template:Cite journal</ref> There are already animal and ecosystem conservation laws in Europe, but many scholars recommend additional ones to protect the flora and fauna.<ref name="Scalera-2004">Template:Cite journal</ref>
PredatorsEdit
Due to their toxicity,<ref name="Lüddecke-2018">Template:Cite journal</ref><ref name="Vences-2014" /> as well as decreased concentration of animals at high altitudes,<ref name="Luiselli-1994">Template:Cite journal</ref> researchers are unsure of consistent predators for alpine salamanders with limited observation.<ref name="DE MEESTER-2020" /> These salamanders do move slowly, which could increase their risk of being caught.<ref name="Luiselli-1994" /> Generally, predators of the broad category of toxic Salamandra species can include birds, rats and snakes, as well as other, larger carnivorous mammals like raccoons, minks, wild boars and foxes.<ref name="Lüddecke-2018" />
One notable predator of S. atra is young snakes.<ref name="Luiselli-1994" /> In particular, juvenile European adders (Vipera berus) pose a risk because they live at similarly high altitudes to alpine salamanders.<ref name="Luiselli-1994" /> S. atra have been suggested to make up just under half of these snakes' diets in some locations.<ref name="Luiselli-1994" /> They may hunt for alpine salamanders during early morning hours, when S. atra is most active.<ref name="Luiselli-1994" /> There also has been recorded evidence of these snakes swallowing alpine salamanders.<ref name="Luiselli-1994" /> V. berus, alongside the grass snake (Natrix natrix), are noted predators of alpine salamanders in the Italian Alps.<ref name="DE MEESTER-2020" />
FeedingEdit
Male and female alpine salamanders have relatively similar diets.<ref name="Roner-2020">Template:Cite journal</ref> Some specific organisms they prey on include species such as beetles, snails, millipedes, and spiders,<ref>Template:Cite journal</ref> but alpine salamanders display preferences among prey.<ref name="Roner-2020" /> S. atra typically consume organisms from the Coleoptera and mollusca taxa.<ref name="Roner-2020" /> These taxa are the most crucial component of their diet. They also tend to eat larger prey since they themselves are larger salamanders.<ref name="Roner-2020" /> Such preference indicates a dimensional selectivity, in which the energy intake of prey consumption is maximized.<ref name="Roner-2020" /> Though alpine salamanders have definite dietary preferences, they have a substantial amount of variation in their diet<ref name="Roner-2020" /> that corresponds to their own optimized physical needs and prey-catching abilities.Template:Citation needed
Mating and interactionsEdit
Mating patternEdit
The alpine salamander engages in a promiscuous mating pattern,<ref name="Helfer-2012" /> meaning that they engage in multiple partner pairings. Males travel farther than females do, potentially to follow a scent emitted by females, and typically while still in their juvenile stage.<ref name="Helfer-2012" /> Female S. atra find and defend their shelters, which is a potential reason that they may stay more local than males.<ref name="Helfer-2012" />
Male-male behaviorEdit
Males are more likely to engage in chasing other males, as well as actually fighting with each other.<ref name="Di Nicola-2022">Template:Cite journal</ref> Oftentimes, one male will mount the other, loosely grasp it with his forearms, and start rubbing his head on the other male.<ref name="Di Nicola-2022" /> The two males will switch roles, and in one studied interaction, continued like this for seven minutes before parting ways.<ref name="Di Nicola-2022" /> In a second documented fight, the behavior was more intense. When one member tried to leave, the other male chased it to re-engage.<ref name="Di Nicola-2022" /> This encounter lasted eight minutes. There is both photographic and video evidence of these behaviors.<ref name="Di Nicola-2022" /> Researchers are unsure if it is caused by territoriality, confusion on sexual identification and mistaken mating, or true combat.<ref name="Di Nicola-2022" />
Gestation and reproductionEdit
Alpine salamanders live in a sex ratio of 1:1.<ref>Template:Cite book</ref> Mating occurs on land. The male clasps the female at the forelegs, and fertilization is internal. S. atra are categorized as viviparous, meaning that their young are born alive and unlike many other amphibians, do not go through metamorphosis<ref name="DE MEESTER-2020" /><ref name="Guex-1986" /> They give birth to 2 young, sometimes 3 or 4. New young alpine salamanders may measure as long as Template:Convert at birth, with the mother measuring only Template:Convert.Template:Citation needed
Female alpine salamanders have uteruses that are composed of a single luminal epithelial cell layer, connective tissue, and smooth muscle.<ref name="Guex-1986">Template:Cite journal</ref> The uterine eggs are large and numerous, but, as a rule, only one fully develops in each uterus. The embryo is nourished on the yolk of the other eggs, which more or less dissolve to form a large mass of nutrient matter. The egg mass can be as long as between 25 mm and 40 mm long.<ref name="Guex-1986" /> The embryo passes through three stages:<ref name="Cambridge University Press-1911">Template:Cite EB1911</ref>
- The first stage is when they are still enclosed within the egg and living on its own yolk.<ref name="Cambridge University Press-1911" />
- The second stage is when they are free, within the vitelline mass, eating it directly with their mouths.<ref name="Guex-1986" /><ref name="Cambridge University Press-1911" />
- The final stage occurs when there is no more vitelline mass. The embryo is possessed of long external gills, which serve as an exchange of nutritive fluid through the maternal uterus, these gills functioning in the same way as the chorionic villi of the mammalian egg.<ref name="Guex-1986" /><ref name="Cambridge University Press-1911" />
Generally, at altitudes of Template:Convert above sea level, a pregnancy lasts two years, and at altitudes of 1,400-1,700 m above sea level, the pregnancy lasts around three years, though anything within a 2-4 year range is considered standard.<ref name="Guex-1986" /> Alpine salamander embryos are unique in how they are able to take in these nutrients through a long gestation.<ref name="Guex-1986" /> A portion of the mother's uterine wall becomes nourishment after the salamanders have already eaten the unfertilized eggs,<ref name="Guex-1986" /> (called oophagy or stage 1 and 2).<ref name="Guex-1986" /> They then partake in epitheliophagy, or stage 3, where they ingest these zona trophica cells until birth, and have special tooth-like developments that allow it to do so without detriment to the mother.<ref name="Guex-1986" />
PhysiologyEdit
Glands and toxinsEdit
As mentioned above, alpine salamanders have poison glands.<ref name="DE MEESTER-2020" /> They are known to produce some alkaloid molecules and peptide products, and thus have a mustard-like scent associated with them.<ref name="Lüddecke-2018" /> Salamandra bioproduction is still a developing research area. Salamandarines are a chemical secretion produced by the skin of alpine salamanders, as well as some fire salamanders.<ref name="DE MEESTER-2020" /><ref>Template:Cite journal</ref> They are neurotoxins, and are synthesized via a biochemical pathway, completely independent of dietary intake.<ref name="DE MEESTER-2020" /> This means that they make these chemicals within their bodies, not as a result of ingesting poisonous substances.The starting material for this nerve-block is most likely cholesterol, and it is about twice as potent as cyanide.<ref name="DE MEESTER-2020" /> This pales in comparison to other toxins produced by salamanders, but S. atra do not only use this powerful substance to paralyze prey: they may have antimicrobial properties that protect them against bacterial and fungal infections.<ref name="DE MEESTER-2020" /><ref name="R-2012">Template:Cite book</ref> Salamandorone is another biochemical compound produced by S. atra, and though it is less potent against prey it is the strongest antimicrobial weapon these salamanders have.<ref name="DE MEESTER-2020" /><ref name="Spitzen - van der Sluijs-2018">Template:Cite journal</ref><ref name="R-2012" />
There are two main categories of toxin studied, samandarine and samandarone.<ref name="DE MEESTER-2020" /><ref name="Vences-2014" /> There also exist many other compounds, as well as miscellaneous alkaloid secretions.<ref name="DE MEESTER-2020" /> Both samandarine and samandarone are produced by S. atra species.<ref name="Vences-2014" /> It is hypothesized that salamandarine is more commonly produced in alpine salamanders as a predator defense mechanism, and salamandorones are produced where there is greater infection risk.<ref name="DE MEESTER-2020" /> There is also noted geographic variation in toxin production by alpine salamanders.<ref name="DE MEESTER-2020" />
Immunobiology and protectionEdit
Samandarone, a toxin they produce via skin secretion, has noted antimicrobial activity.<ref name="DE MEESTER-2020" /> In one study, this toxin was present where there was infection risk, but at low concentration.<ref name="DE MEESTER-2020" /> There is a wide arsenal of toxins produced by S. atra , many of which are antimicrobial or could be precursors to other protective molecules.<ref name="DE MEESTER-2020" /> Nonetheless, the alpine salamander has been relatively lucky in avoiding infection with amphian chytrid fungus<ref name="R-2012" /> compared to other amphibian species.<ref name="R-2012" /><ref>Template:Cite journal</ref> This dangerous fungal infection, caused by Batrachochytrium dendrobatidis (Bd) has decimated amphibian populations on every continent.<ref name="R-2012" /> Bd is present in the Alps where alpine salamanders live, but in a study performed in 2012, there were no salamanders who tested positive when swabbed.<ref name="R-2012" /> This may be because Bd infections are more common in species who spend more of their time in water, and since the alpine salamanders are terrestrial, they are less susceptible.<ref name="R-2012" /> An alternate hypothesis proposes that S. atra are resistant via their skin microbiome or a produced molecule, thus granting them immunity.<ref name="R-2012" /><ref name="Woodhams-2007">Template:Cite journal</ref> This theory is untested, but considering how many salamanders excrete biological toxins, plausible.<ref name="R-2012" /><ref name="Woodhams-2007" />
ReferencesEdit
External linksEdit
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