Salamanders- JN

Salamanders

What are they?

Salamanders are an endangered group of species within the order, Caudata and are found in the northern hemisphere. There are roughly 400 species of salamanders worldwide but unfortunately, around 40% of them are considered to be at risk. They are usually born as larvae in water and generally stay there until they die but there are species that chose to live to water or in cool damp places.

The amphibian looks very similar to a lizard and have 4 toes on their front legs and 5 on their rear legs but this can vary between species. As well as being permeable, their skin also contain lethal toxins called tetrodotoxin and display very bright warning colours to frighten off predators.

Anatomy

There are some aquatic species that do not have limbs but most do have short limbs that vary in size according to their habitat. For example, the Tree climbing salamander has webbed feet which allows it to grip onto the rocks when it is climbing. Sometimes, the tail can also be used to hold up the body up or propel it upwards when it is jumping. In certain species, this is also used to attract partners and store proteins and lipids.

The skin of salamanders is very thin and permeable and is essential in its role as an ectotherm as it allows their body temperature to be heavily influenced by its environment. The skin is a respiratory membrane which has many glands. These glands are controlled by the pituitary and thyroid glands. When these glands are activated, mucus is released to reduce infection and keep the skin moist to assist in skin respiration and thermoregulation.

Salamanders also have a very advanced sense of smell and olfaction (sense of smell) to detect predators and prey in order to allow it to feed. The sensory areas include:

·        Olfactory epithelim= picks up airborne aquatic odours

·        Vomeronasal organs= detect non-volatile chemical cues

Most salamanders are also very well adapted to seeing in the dark as they spend so much time under water. There are even certain species that don’t have eyes at all and use lateral lines to detect changes in water pressure. The lateral line is a system which uses specialised epithelial cells and hair cells to detect movement in order to gauge the surrounding environment.

As well as this, they also lack eardrums but use 2 ossicles to detect low frequency vibrations that can used to detect predators. Generally, most species are also unable to make voices but there are species that are able to make rattling or hissing sounds.

Hunting and Defence'''

Most salamanders have teeth but there are some that live on land that uses its tongue to secrete sticky mucus onto its prey and pull it towards the mouth. The tongue is projected when the hyoid bone contracts to create pressure which causes the hyoid bone to elongate. The salamander are opportunistic predators which means that they are generally able to eat a wide range of foods.

Even though they move relatively slowly, the salamander has several adaptations which helps protect itself. For example, its skin is coated with a toxic and slipper substance which will cause the predator to avoid it in the future. The skin can also have very vivid colouring which frightens other animals and warn of its toxicity. Its tail is also very strong and if necessary, it is able to sacrifice its limbs or tail to avoid a predator. After the tail has dropped off, the tail remains to wriggle around to create the perception that the salamander is still attached and this distracts the predator whilst the salamander escapes. This generally grows back within a few weeks.

Conservation

During the last century, the number of salamanders have fallen significantly mainly due to the extensive deforestation and contamination of streams. They have also been hunted to create Chinese medicines.

Medical interest

The salamander’s ability to regenerate parts of its body has been gaining a lot of interest during the last few years and there are hopes that this property can also be replicated in humans. The Mexican axoloti in particular has been researched extensively by scientists at Birmingham University who have suggested that if this mechanism could be understood by humans, we could use it to prompt the body to regenerate itself. This puts a lot less pressure on organ donation banks.

The salamander's ability to regenerate tissue has been associated with the ERK pathway which sends a signal from the receptors on the surface of a cell to the nucleus. In mammals, this is not always active which is why we are unable to reprogramme and regenrate our cells.