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Jawad
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Iraq
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يوجد 38 صفحة - انت الآن في الصفحة رقم 1
Jawad Jawad
Learning English
منذ 3 ساعات   نشر في  ٢٠٢٦/٠٧/٢٤ م
By the end of the larval stage, the tadpoles already have limbs and metamorphosis takes place normally. In salamanders, this occurs over a short period of time and involves the closing of the gill slits and the loss of structures such as gills and tail fins that are not required as adults.

At the same time, eyelids develop, the mouth becomes wider, a tongue appears, and teeth are formed. The aqueous larva emerges onto land as a terrestrial adult.
2

Jawad Jawad
Learning English
منذ 1 أيام   نشر في  ٢٠٢٦/٠٧/٢٣ م
The tadpoles are carnivorous and the larval stage may last from days to years, depending on species. Sometimes this stage is completely bypassed, and the eggs of most lungless salamanders (Plethodontidae) develop directly into miniature versions of the adult without an intervening larval stage.

6

Jawad Jawad
Learning English
منذ 2 أيام   نشر في  ٢٠٢٦/٠٧/٢٢ م
Pond-type larvae may have a pair of rod-like balancers on either side of the head, long gill filaments and broad fins. Stream-type larvae are more slender with short gill filaments—in Rhyacotriton and Onychodactylus, and some species in Batrachuperus, the gills and gill rakers are extremely reduced, narrower fins and no balancers, but instead have hind limbs already developed when they hatch.
8

Jawad Jawad
Learning English
منذ 3 أيام   نشر في  ٢٠٢٦/٠٧/٢١ م
In temperate regions, reproduction is usually seasonal and salamanders may migrate to breeding grounds. Males usually arrive first and in some instances set up territories. Typically, a larval stage follows in which the organism is fully aquatic.

The tadpole has three pairs of external gills, no eyelids, a long body, a laterally flattened tail with dorsal and ventral fins and in some species limb-buds or limbs.
10

Jawad Jawad
Learning English
منذ 4 أيام   نشر في  ٢٠٢٦/٠٧/٢٠ م
One species, the Anderson's salamander, is one of the few species of living amphibians to occur in brackish or salt water.

Sierra newt amplexus found in stream at Woolman Semester in Nevada County, California
Many salamanders do not use vocalisations, and in most species the sexes look alike, so they use olfactory and tactile cues to identify potential mates.
14

Jawad Jawad
Learning English
منذ 6 أيام   نشر في  ٢٠٢٦/٠٧/١٨ م
The northern slimy salamander (Plethodon glutinosus) has a wide range and occupies a habitat similar to that of the southern gray-cheeked salamander (Plethodon metcalfi).

The latter is restricted to the slightly cooler and wetter conditions in north-facing cove forests in the southern Appalachians, and to higher elevations above 900 m (3,000 ft), while the former is more adaptable, and would be perfectly able to inhabit these locations.
13

Jawad Jawad
Learning English
منذ 1 أسابيع   نشر في  ٢٠٢٦/٠٧/١٧ م
There are about 760 living species of salamander. One-third of the known salamander species are found in North America. The highest concentration of these is found in the Appalachian Mountains region, where the Plethodontidae are thought to have originated in mountain streams.

Here, vegetation zones and proximity to water are of greater importance than altitude. Only species that adopted a more terrestrial mode of life have been able to disperse to other localities.
17

Jawad Jawad
Learning English
منذ 1 أسابيع   نشر في  ٢٠٢٦/٠٧/١٦ م
They also lived on the Caribbean Islands during the early Miocene epoch, confirmed by the discovery of Palaeoplethodon hispaniolae, found trapped in amber in the Dominican Republic.

Vertebrae fossils recovered from the Murgon fossil site have been tentatively attributed to that of a salamander, though its true identity is disputed. If the vertebrae truly belong to a salamander, they would represent the only salamanders in Australia.
11

Jawad Jawad
Learning English
منذ 1 أسابيع   نشر في  ٢٠٢٦/٠٧/١٥ م
Salamanders are found only in the Holarctic and Neotropical regions, not reaching south of the Mediterranean Basin, the Himalayas, or in South America the Amazon Basin. They do not extend north of the Arctic tree line, with the northernmost Asian species, Salamandrella keyserlingii, which can survive long-term freezing at −55 °C, occurring in the Siberian larch forests of Sakha.
56

Jawad Jawad
Learning English
منذ 1 أسابيع   نشر في  ٢٠٢٦/٠٧/١٤ م
The oldest known total-group (Caudata) salamander is Triassurus from the Triassic of Kyrgyzstan. Further salamander fossils are known from the Middle Jurassic of England, Scotland, China, and Kazakhstan. The oldest known crown-group salamander (Urodela) remains uncertain but recent analyses suggest it is Valdotriton from the Late Jurassic of Spain.
17

Jawad Jawad
Learning English
منذ 2 أسابيع   نشر في  ٢٠٢٦/٠٧/١٣ م
Some salamander species use tail autotomy to escape predators. The tail drops off and wriggles around for a while after an attack, and the salamander either runs away or stays still enough not to be noticed while the predator is distracted.

The tail regrows with time, and salamanders routinely regenerate other complex tissues, including the lens or retina of the eye. Within only a few weeks of losing a piece of a limb, a salamander perfectly reforms the missing structure.
15

Jawad Jawad
Learning English
منذ 2 أسابيع   نشر في  ٢٠٢٦/٠٧/١١ م
A correlation exists between the toxicity of Californian salamander species and diurnal habits: relatively harmless species like the California slender salamander (Batrachoseps attenuatus) are nocturnal and are eaten by snakes, while the California newt has many large poison glands in its skin, is diurnal, and is avoided by snakes.
17

Jawad Jawad
Learning English
منذ 2 أسابيع   نشر في  ٢٠٢٦/٠٧/١٠ م
In California, the palatable yellow-eyed salamander (Ensatina eschscholtzii) closely resembles the toxic California newt (Taricha torosa) and the rough-skinned newt (Taricha granulosa), whereas in other parts of its range, it is cryptically colored.

24

Jawad Jawad
Learning English
منذ 2 أسابيع   نشر في  ٢٠٢٦/٠٧/٠٩ م
the eastern newt is avoided by birds and snakes, and can survive for up to 30 minutes after being swallowed (later being regurgitated).
The red salamander (Pseudotriton ruber) is a palatable species with a similar coloring to the red eft. Predators that previously fed on it have been shown to avoid it after encountering red efts, an example of Batesian mimicry.
24

Jawad Jawad
Learning English
منذ 3 أسابيع   نشر في  ٢٠٢٦/٠٧/٠٤ م
Although many salamanders have cryptic colors so as to be unnoticeable, others signal their toxicity by their vivid coloring. Yellow, orange, and red are the colors generally used, often with black for greater contrast. Sometimes, the animal postures if attacked, revealing a flash of warning hue on its underside.

The red eft, the brightly colored terrestrial juvenile form of the eastern newt (Notophthalmus viridescens), is highly poisonous.
24

Jawad Jawad
Learning English
منذ 3 أسابيع   نشر في  ٢٠٢٦/٠٧/٠٣ م
The Iberian ribbed newt (Pleurodeles waltl) has another method of deterring aggressors. Its skin exudes a poisonous, viscous fluid and at the same time, the newt rotates its sharply pointed ribs through an angle between 27 and 92°, and adopts an inflated posture.

This action causes the ribs to puncture the body wall, each rib protruding through an orange wart arranged in a lateral row.
When the danger has passed, the ribs retract and the skin heals.
19

Jawad Jawad
Learning English
منذ 3 أسابيع   نشر في  ٢٠٢٦/٠٧/٠٢ م
Skin secretions of the tiger salamander (Ambystoma tigrinum) fed to rats have been shown to produce aversion to the flavor, and the rats avoided the presentational medium when it was offered to them again.

The fire salamander (Salamandra salamandra) has a ridge of large granular glands down its spine which are able to squirt a fine jet of toxic fluid at its attacker. By angling its body appropriately, it can accurately direct the spray for a distance of up to 80 cm (30 in).
16

Jawad Jawad
Learning English
منذ 3 أسابيع   نشر في  ٢٠٢٦/٠٧/٠١ م
When attacked by a predator, a salamander may position itself to make the main poison glands face the aggressor. Often, these are on the tail, which may be waggled or turned up and arched over the animal's back.

The sacrifice of the tail may be a worthwhile strategy, if the salamander escapes with its life and the predator learns to avoid that species of salamander in the future.
20

Jawad Jawad
Learning English
منذ 3 أسابيع   نشر في  ٢٠٢٦/٠٦/٣٠ م
Salamanders have thin skins and soft bodies, move rather slowly and might appear vulnerable to opportunistic predation, but have several effective lines of defense.
Mucus coating on damp skin makes them difficult to grasp, and the slimy coating may have an offensive taste or be toxic.
18

Jawad Jawad
Learning English
منذ 4 أسابيع   نشر في  ٢٠٢٦/٠٦/٢٩ م
Though frequently feeding on slow-moving animals like snails, shrimps and worms, sirenids are unique among salamanders for having developed herbivory speciations, such as beak-like jaw ends and extensive intestines. They feed on algae and other soft-plants in the wild, and easily eat offered lettuce.
18

Jawad Jawad
Learning English
منذ 4 أسابيع   نشر في  ٢٠٢٦/٠٦/٢٧ م
An aquatic salamander lacks muscles in the tongue, and captures its prey in an entirely different manner. It grabs the food item, grasps it with its teeth, and adopts a kind of inertial feeding.

This involves tossing its head about, drawing water sharply in and out of its mouth, and snapping its jaws, all of which tend to tear and macerate the prey, which is then swallowed.
30

Jawad Jawad
Learning English
منذ 4 أسابيع   نشر في  ٢٠٢٦/٠٦/٢٦ م
High-speed cinematography shows how the tiger salamander (Ambystoma tigrinum) positions itself with its snout close to its prey. Its mouth then gapes widely, the lower jaw remains stationary, and the tongue bulges and changes shape as it shoots forward.

The protruded tongue has a central depression, and the rim of this collapses inward as the target is struck, trapping the prey in a mucus-laden trough. Here it is held while the animal's neck is flexed, the tongue retracted and jaws…
Read more read more
34

Jawad Jawad
Learning English
منذ 4 أسابيع   نشر في  ٢٠٢٦/٠٦/٢٥ م
A terrestrial salamander catches its prey by flicking out its sticky tongue in an action that takes less than half a second. In some species, the tongue is attached anteriorly to the floor of the mouth, while in others, it is mounted on a pedicel.

It is rendered sticky by secretions of mucus from glands in its tip and on the roof of the mouth.
33

Jawad Jawad
Learning English
منذ 4 أسابيع   نشر في  ٢٠٢٦/٠٦/٢٤ م
When struggling prey is advanced into the salamander's mouth, the teeth tips relax and bend in the same direction, encouraging movement toward the throat, and resisting the prey's escape.

Many salamanders have patches of teeth attached to the vomer and the palatine bones in the roof of the mouth, and these help to retain prey. All types of teeth are resorbed and replaced at intervals throughout the animal's life.
16

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