Zeamnature: Amphibians

Salamanders ( Urodela ) - What is special about salamanders?

Phylum: Chordata
Class: Amphibia
Clade: Caudata
Order: Urodela

Salamanders are amphibians with lizard-like bodies, blunt snouts, small limbs that protrude at right angles to the body, and the presence of a tail in both larvae and adults. The order Urodela encompasses all 10 extant salamander families. Salamanders come in a variety of sizes and shapes; some have four legs, while others only have two. Some have lungs, some have gills, while yet others breathe via their skin.

Salamandridae members are primarily recognized as newts, and they lack the costal grooves on the sides of their bodies that other families have. Salamanders are members of the order Caudata, which is one of three Amphibia orders, along with Anura (frogs and toads) and Gymnophiona (frogs and toads) (caecilians, which have no legs and resemble large worms). According to the San Diego Zoo, Caudata has nine families, 60 taxa, and over 600 species. Salamanders include newts, mudpuppies, sirens, and Congo eels (amphiumas). Some salamander species have the potent poison tetrodotoxin in their skin; these salamanders are slow-moving and have brilliant warning coloring to warn of their toxicity.

Description

A Small species of salamanders Eastern newt
( Notophthalmus viridescens )

A large species, Chinese giant salamander ( Andrias davidianus )

There are hundreds of distinct varieties of salamanders, all of which come in a variety of sizes. Salamanders range in size from tiny salamanders with a total length of 27 mm (1+18 in) including the tail to the 1.8 m (6 ft) Chinese giant salamander that may weigh up to 65 kg (145 lb). The majority, on the other hand, are between 10 and 20 cm (4 and 8 in) long.

Except in Salamandridae newts, which have velvety or warty skin that is moist and silky to the touch, the skin lacks scales and is moist and smooth. The skin might be dull or vibrant, with stripes, bars, spots, blotches, or dots in a variety of designs. During the mating season, male newts change colors considerably. Cave species with no pigmentation and a transparent pink or iridescent look are found in the dark.

Habitat and Distribution

Salamanders may be found all around the world, but according to the University of Michigan's Animal Diversity Web, the United States contains the most salamander families (ADW). Except for Hynobiidae (Asian salamanders), all known families are located in the United States. Salamanders broke from the rest of the amphibians in the mid-to-late Permian, and they looked a lot like contemporary Cryptobranchoidea members at first.

Their lizard-like appearance is due to symplesiomorphy, or the shared retention of the original tetrapod body plan, although they are not related to lizards any more than mammals are. Frogs and toads are their closest cousins in Batrachia. Salamander fossils dating back to the middle Jurassic era, roughly 164 million years ago, have been discovered in geological layers in China and Kazakhstan.

Salamanders are exclusively found in the Holarctic and Neotropical zones, with the exception of the Mediterranean Basin, the Himalayas, and the Amazon Basin in South America. They do not extend north of the Arctic tree line, with the northernmost Asian species, Salamandrella keyserlingii, found in the Siberian larch forests of Sakha, and the most northerly North American species, Ambystoma laterale, reaching no further north than Labrador and Taricha granulosa not beyond the Alaska Panhandle. Salamanders come in 760 different species. North America is home to one-third of all known salamander species. The Appalachian Mountains, where the Plethodontidae are considered to have evolved in mountain streams, contain the largest concentration of them.

The majority of species, with a few exceptions, dwell in humid woods. The Iranian harlequin newt dwells in western Iran's Zagros Mountains, where water is only available for three or four months of the year. During the wet season, it mates and eats, then rests in a burrow during the dry season.

Reproduction

Because many salamanders lack vocalizations and the sexes in most species appear identical, they rely on smell and tactile clues to identify possible mates, and sexual selection occurs. Pheromones are generated by the abdominal gland in men and the cloacal glands and skin in both sexes and play a vital role in the process. Males have been known to use their snouts to investigate possible mates. Males of Triturus spp., Old World newts, are sexually dimorphic and exhibit in front of females. In some Plethodont species, visual signals are also regarded to be crucial.

In around 90 percent of all organisms, fertilization is internal. The male normally drops a spermatophore on the ground or in the water depending on the species, and the female takes this up with her vent. The spermatophore consists of a packet of sperm supported on a conical gelatinous base, and its deposition and collecting are frequently accompanied by complex wooing activity. The spermatozoa enter the cloaca and go to the spermatheca, one or more chambers in the cloaca's ceiling, where they are kept for often long periods until the eggs are deposited. External fertilization is used instead in the most primitive salamanders, such as Asiatic salamanders and gigantic salamanders. In a reproductive process similar to that of normal frogs, the male discharges sperm onto the egg mass in these species. In some species, the females keep the eggs inside her body until they hatch into larva bodies or fully developed juveniles.

Diet and feeding

Salamanders are predators who take advantage of opportunities. This implies they eat meat rather than plants. Worms, slugs, and snails are among their favorite slow-moving prey. Fish, tiny crustaceans, and insects are eaten by some of the bigger species. Frogs, mice, and even other salamanders are eaten by some salamanders. They aren't picky about what they eat and will eat practically any creature of a suitable size. Crabs, fish, small animals, amphibians, and aquatic invertebrates are eaten by large species like the Japanese giant salamander (Andrias japonicus).

The upper and lower jaws of most salamander species contain tiny teeth. Even the larvae of salamanders, unlike frogs, have these teeth. Many salamanders have tooth patches linked to the vomer and palatine bones at the roof of the mouth, which aid in the retention of prey. Throughout the animal's life, all types of teeth are resorbed and replaced at regular periods. A terrestrial salamander captures its food by flicking out its sticky tongue in less than a half-second motion. The tongue is linked anteriorly to the mouth floor in certain species, whereas it is fixed on a pedicel in others. Because an aquatic salamander's tongue is devoid of muscles, it uniquely grabs its prey. It takes the food item with its teeth and feeds in a sort of inertial manner. Tossing its head around, pulling water in and out of its mouth quickly, and snapping its jaws are all used to rip and macerate the prey, which is subsequently ingested.

Type/Species Of Some Salamanders

EASTERN HELLBENDER (Cryptobranchus alleganiensis alleganiensis )

MUDPUPPY ( Necturus maculosus maculosus )

JEFFERSON SALAMANDER ( Ambystoma jeffersonianum )

SPOTTED SALAMANDER ( Ambystoma maculatum )

MARBLED SALAMANDER ( Ambystoma opacum)

RED-SPOTTED NEWT ( Notophthalmus viridescens viridescens )

GREEN SALAMANDER ( Aneides aeneus )

NORTHERN DUSKY SALAMANDER ( Desmognathus fuscus fuscus )

APPALACHIAN DUSKY SALAMANDER ( Desmognathus monticola monticola )

MOUNTAIN DUSKY SALAMANDER ( Desmognathus ochrophaeus )

NORTHERN TWO-LINED SALAMANDER ( Eurycea bislineata bislineata )

LONGTAIL SALAMANDER ( Eurycea longicauda longicauda )

NORTHERN SPRING SALAMANDER ( Gyrinophilus porphyriticus porphyriticus )

FOUR-TOED SALAMANDER ( Hemidactylium scutatum )

REDBACK SALAMANDER ( Plethodon cinereus )

SLIMY SALAMANDER ( Plethodon glutinosus glutinosus )

WEHRLE'S SALAMANDER ( Plethodon wehrlei )

NORTHERN RED SALAMANDER ( Pseudotriton ruber ruber )

Conservation status

Hundreds of species are included on the Red List of Threatened Species by the International Union for Conservation of Nature (IUCN). While some species are classified as Least Concern for extinction due to stable populations, the majority of the species on the list are vulnerable, endangered, or critically endangered.

Because the species is highly fragmented and the population is on the decline, the blunthead salamander, located in a restricted region of northern Mexico, is designated as critically endangered. There is currently no estimate of the population. Similarly, Anderson's salamander, which dwells in a lake in northwestern Mexico, is critically threatened to owe to pollution.
As a result of climate change, several salamander species are diminishing from generation to generation. According to University of Maryland researchers, salamanders in the Appalachian Mountains are diminishing as the local environment becomes hotter and drier, forcing them to expend more energy.

Poison dart frogs (Dendrobatidae) - Can you touch a poison dart frog?

Kingdom - Animalia
Phylum - Chordata
Class - Amphibia
Order - Anura
Family - Dendrobatidae

The poison dart frog (also known as a dart-poison frog, poison frog, or poison arrow frog) is the common name for a family of amphibians endemic to tropical Central and South America. These species are diurnal, and their bodies are frequently brilliantly colored. The species' toxicity is linked to their vivid color, making them aposematic. Some Dendrobatidae species have exceptionally vivid colors and High toxicity, whereas others have cryptic colors and little to no toxicity. The toxicity of the species that consume ants, mites, and termites comes from their food. Other species, on the other hand, with cryptic colors and minimal to no toxicity, consume a considerably wider range of prey. Human infrastructure is intruding on the habitats of several species in this family, putting them in jeopardy.

Because Native Americans used their toxic secretions to poison the points of blowdarts, these amphibians are commonly referred to as "dart frogs." Only four species from the Phyllobates genus have been reported as being used for this purpose (curare plants being more regularly utilized), and they are all from the genus Phyllobates, which is known for its huge size and high levels of toxicity.

Dendrobates tinctorius "azureus

Behavior

These frogs prefer to reside in the trees closest to the ground or in the leaf litter of the forest floor, according to certain facts about their habits. They love to rest on tree branches and leaves.

These frogs, like other frog species, croak and squeak in order to establish their homes and attract mates. They are mostly diurnal animals, meaning they are active throughout the day.

These frogs don't try to hide from predators since their skin is enough of a deterrent. If their toxins don't kill a predator, they will certainly make it unappealing to eat them. Predators will remember how horrible this frog tasted and will most likely avoid eating another one.

Dendrobates leucomelas

Characteristics

The majority of poison dart frog species are tiny, with adults measuring less than 1.5 cm (0.59 in) in length, while a handful reach 6 cm (2.4 in) in length. On average, they weigh 1 oz. To alert prospective predators, most poison dart frogs are brilliantly coloured and feature aposematic patterns. Their brilliant colour is linked to their toxicity and alkaloids levels. Dendrobates frogs, for example, have high alkaloids levels, but Colostethus species are cryptically coloured and not lethal.

An example of an aposematic organism is poison dart frogs. To potential predators, their brilliant colour signals unpalatability. According to evolutionary trees, aposematism is considered to have developed at least four times within the poison dart family, and dendrobatid frogs' aposematic colouring has subsequently experienced substantial interspecific and intraspecific divergences. Given the frequency-dependent nature of this sort of protection mechanism, this is surprising.

Adult frogs lay their eggs in damp areas such as leaves, plants, exposed roots, and other locations. When the eggs hatch, the adult piggybacks the tadpoles to a suitable water source, such as a pool or the water collected in the throats of bromeliads or other plants, one at a time. The tadpoles stay there until they metamorphosis, and are nourished by unfertilized eggs deposited by the mother at regular intervals in some species.

Poison Dart Frog Habitat

These frogs are found in Central and South America's moist jungles. Also these frogs are found in tropical rainforests all throughout the world, including Bolivia, Costa Rica, Brazil, Colombia, Ecuador, Venezuela, Suriname, French Guiana, Peru, Panama, Guyana, Nicaragua, and Hawaii (introduced) They are occasionally mistaken with the Mantella, a tiny, vividly coloured frog species that is exclusively found in Madagascar.

They used to be imported in large quantities to the United States for the pet trade, but this has since decreased. Frogs from other parts of the world are smuggled into Europe.

These frogs do not thrive in extremely polluted places due to their sensitivity to the environment.

Diet

To catch insects, these frogs utilize their long, sticky tongue. The frog becomes a carnivore as a result of its diet. Termites, flies, ants, and a variety of other insects make up its food, which is abundant in the poison dart frog's environment. Tadpoles are omnivorous and will consume algae on occasion. They are also given unfertilized eggs from their parents on occasion. Some frog species are cannibals, eating the tadpoles of other species.

It is assumed that the poison dart frog's toxicity is caused by its food. Scientists aren't sure which insects the frogs consume that causes them to become poisonous. Toxins are not released from the skin of frogs grown in captivity and fed crickets and fruit flies.

Their long, sticky tongues

Reproduction and Lifespan

Poison dart frogs reproduce at various times throughout the year, frequently in combination with rainy seasons. Males and females vie for the best perches from which to call for mates, while females compete for nesting places during this period. Female frogs have been known to eat other frogs' eggs. After the male has made his mating call and found a female to procreate with, the mating procedure begins.

The male uses an elaborate wooing ceremony to entice the female to a location where he wants to mate. Wrestling, caressing, and leading the female around are all part of this courting. Before the two decide to settle down and the female may lay her eggs, the ritual might run for several hours.

Ranitomeya amazonica

The females will lay their eggs in the wet leaf litter. The number of eggs varies from one to forty, with an average of 10 eggs each clutch. After the female has lay, the male will fertilize the eggs. Both parents will keep an eye on the eggs, making sure they don't dry up.

The parents will carry the young tadpoles on their backs until they hatch, roughly 10 to 18 days after the eggs have been fertilized. When a parent frog sits in the middle of a clump of young tadpoles, the tadpoles might wiggle their way onto the back of the parents. Parents transport their young to little pools where they can develop and mature, either all at once or a few at a time. After several months, tadpoles will mature into adult frogs. They are extremely vulnerable to predators in this stage of development.

The lifetime of the poison dart frog has not been thoroughly studied. According to some biologists, they can survive as little as three years in the wild. Some species have been recorded to live to be 25 years old in captivity.

In the poison dart frog family, the operational sex ratio is mostly female. This results in a few distinct behaviours and features in creatures with unequal sex ratios. Females, in general, have a choice of partners. Males, on the other hand, have more vibrant colour, are territorial, and hostile against other males. Females choose their partners based on dorsal colouring, calling perch position, and territory.

Toxicity , Medicine

Lipophilic alkaloid poisons such as allopumiliotoxin 267A, batrachotoxin, epibatidine, histrionic toxin, and pumiliotoxin 251D are secreted by several poison dart frogs via their skin. Poison frogs' skin glands contain alkaloids that act as a chemical defence against predation, allowing them to stay active throughout the day alongside possible predators. In poison frogs, there are approximately 28 structural classes of alkaloids. Phyllobates terribly is the most deadly of the poison dart frog species. The diet-toxicity theory claims that dart frogs do not produce their poisons, but rather sequester them from arthropod prey such as ants, centipedes, and mites.

As a result, captive-bred animals do not have large amounts of poisons because they are fed diets that do not include the alkaloids that wild populations sequester. In fact, new research suggests that some species' maternal frogs deposit unfertilized eggs laced with tiny levels of alkaloids to nourish the tadpoles. This conduct indicates that toxins are introduced at an early age. When the captive-bred frogs are given an alkaloidal diet again, they retain their capacity to collect alkaloids. Some predators have gained the capacity to survive the poisons employed by some poison dart frog. The snake Erythrolamprus epinephalus, for example, has acquired resistance to the venom.

It's possible that chemicals derived from the skin of Epipedobates tricolor have medical potential. This poison is used to create a painkiller by scientists. Epibatidine, a painkiller 200 times more powerful than morphine, is one such molecule; unfortunately, the therapeutic dose is extremely near to the deadly amount.

The venom of the golden poison frog (Phyllobates terribilis) is enough to kill ten to twenty men or ten thousand mice on average. While most other dendrobatids are bright and poisonous enough to deter predators, they offer significantly less of a threat to humans and other big animals.When handling potentially poisonous species, it is critical to ensure that there are no cuts or open wounds. It also relies on the nutrition of the frog. Poison dart frogs in the wild consume insects that increase their toxicity. Most frogs in captivity do not have the right diet to produce lethal toxins in their skin.

The golden poison frog (Phyllobates terribilis)

Conservation

Many poison dart frog species have lately faced habitat degradation, chytrid infections, and pet trade collecting. As a result, some are classified as threatened or endangered. Zoos have attempted to combat the condition by administering an antifungal medication similar to that used to treat athlete's foot in people to caged frogs.

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