Due to its unique look, the olm salamander (Proteus anguinas) is one of the strangest amphibians. This species is distantly related to the axolotl. It is born, lives, and then dies in the water. Let’s have a look at some cave salamander facts to see how fascinating they are!
Phylum: Chordata
Class: Amphibia
Order: Urodela
Genus: Proteus
1. The olm has an unusual appearance
The olm is the only member of the genus Proteus and it has a distinctive appearance. The species features pale skin like humans. That’s why it’s called ‘human fish’. Its skin is so thin and translucent that you can see the animal’s organs through its abdomen. A layer of mucus also protects the skin.
This human fish has a snake-like body with folds at the borders of the voluntary muscles. It has an average size of about 8–12 in (20-30 cm) in length, some individuals are bigger with 16 in (40 cm). It has a short, flattened tail wrapped by a tiny fin that supports it to swim.
When compared to other amphibians, the olm salamander has smaller and slender limbs with fewer digits. Its front limbs contain 3 digits rather than 4, and the back legs have 2 digits rather than 5.
The creature has a pear shape, a blunt snout, a little mouth with tiny teeth, and mini nostrils that are nearly unnoticeable. Due to a little riboflavin in the skin, the species has enough pigment to be yellow or pink.
Its eyes are undeveloped and have a skin layer on top. However, the subspecies black olm (Proteus anguinus parkelj) has better vision and skin with more pigments.
Although males are smaller than females, you can’t distinguish between two genders without flipping them over. The male cloaca is bigger.
2. They live underwater
Olm salamanders, unlike other amphibians, are fully aquatic. They only live in watery caves in the Dinaric Alps near the Adriatic Sea. These species are found in Southeastern and Southern Europe, including Croatia, Bosnia and Herzegovina, Italy, and other Dinaric Alps regions.
The caves the species locate are limestone caves. The water here is quite acidic, has high oxygen concentrations and a temperature that range from 41 – 59°F (5 – 15 °C). These blind aquatic salamanders live deep within cave networks because they are adapted to an aphotic habitat. They are typically found more than 985 feet (300 meters) below the surface.
The black olm salamander lives in slightly warmer waters. They have also been observed to reach the cave’s surface.
3. They can move and hunt with blind eyes
Olms are sociable animals. They like to live together in the crevices and cracks of rocks that humans can’t reach. However, at mating time, males will become territorial. These creatures don’t appear to be migrating. These human fish are usually calm, they don’t want to fight or have a battle.
They have lungs, but these lungs are just for show. They don’t breathe through their lungs, but through the red frilly gills on the back of its head. Lungs are only used in low-oxygen conditions.
The olm is blind, and it doesn’t need to see in its continuously dark surroundings. To live an aphotic life, this species has evolved non-visual sensory systems.
It navigates the depths of a cave by using its powerful sense of smell, which can detect even the tiniest organic materials in the water and even determine whose prey it belongs to. This is because the head of the olm salamander has mechano-, sensitive chemo-, and electroreceptors.
This olm cave salamander has great hearing, both in and out of the water. Its lateral line on the side also picks up on the sounds. The line aids the animal in sensing motion, pressure changes, and vibrations. It also features a sense of taste and electrosensitive organs in their heads that can detect electrical fields.
Despite being regressive, the eyes maintain a light sensitivity. Some researchers believe that its skin has light sensors.
These amazing abilities allow them to move and hunt prey in dark environments.
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4. They can go without food for 10 years
One of many special abilities of olm salamanders is that they can survive without food for years. Just by relying solely on glycogen and fats in their bodies, the species can starve themselves for 10 years. It will eat if it becomes hungry. When getting hungry, they will devour available food nearby.
The olm salamander mostly feeds on insects and their larvae, particularly those that emerge from the water, like stoneflies, caddisflies, or mayflies. It will, however, consume any species it can grab and retain. Their diet can be worms, freshwater snails, amphipods such as Niphargus, little fish, eggs, and mollusks. They also willingly accept raw meat.
Despite tiny teeth, the white salamander doesn’t chew its prey. Instead of that, it consumes it whole, as the caecilian does.
If food is available, the cave-dwelling salamander will eat as much as it can to keep food to the degree that it can live for years without eating anything. When food is scared, the blind cave salamander will reduce its metabolism. It may even begin to consume its tissues. It can occasionally eat its own kind too.
5. They are the longest-living amphibians
Olm salamanders do not mate until they reach the age of 14. Males establish and protect territories during this period while waiting for a female to go by.
These salamander olms have a distinct and one-of-a-kind mating ritual that might last for hours. After winning over other rivals, the male creates a smell to entice the female. Once the female goes to his territory, he will discharge a sperm packet. The female puts the packet into her cloaca and keeps it in a spermatheca. The sperm then fertilizes her eggs.
The olms only mate every 12 years. Males can breed with multiple partners, while females exclusively mate with an only male.
After mating, the female creates her own zone separate from the male’s. She then lay 35 – 70 eggs beneath rocks and this could last for 25 days. The mother will protect her eggs till they hatch, which takes around two to six months.
The time the eggs will hatch depends on the water temperature. Warmer temperature means their eggs will hatch sooner (about 86 days) than the colder temperature incubated eggs. After hatching, the larvae are on their own. In the first 4 months, they still can see things. From the 4th month onwards, their vision weakens. They’re blind by the time they become adults.
The olm salamander never matures. Unlike other amphibians, their larvae don’t experience a separate metamorphosis phase. They will go straight to the adults at 4 months old but still maintain some juvenile traits such as frilly gills and tail fins.
The water temperature also influences how fast or slow they will grow. Usually, it will take them 4 months to have a size of an adult body.
These cave salamanders are believed to have 2 reproduction methods: lay eggs and give birth to live offspring. Some scientists said that they will lay eggs in warm water and give birth in cold water. However, this is unreliable and unproven.
Among other amphibians in the wild, olms have the longest lifespan. Their average age is 58 years old, but they can live up to 100 years. This is because they don’t have many predators in their habitats.
6. Olm vs axolotl
Olms and axolotls are very similar in appearance, but these two salamanders are different species. In fact, they are distant relatives.
– Similarities:
Olms and axolotls both have the same size and gills behind their heads. However, axolotls feature more robust legs that they utilize more frequently, as well as a distinct tail and hind part, whereas the olm salamander has a more eel-like body. They are carnivorous.
They do not go through the transformation process. As a result, they retain juvenile characteristics like external gills and a tail. They both spend their whole lives underwater and breathe through their gills, although they have lungs.
– Differences:
They are native to two different continents. While olm salamanders are found in middle Europe, axolotls live in South America – Mexico. You can keep an axolotl as an exotic pet, but you can’t do this to an olm. This proteus salamander can’t live in captivity.
They both have pinkish and black colors. However, axolotls have more colors since they are bred in captivity. Axolotls have poor eyesight, while the olms are blind.
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The lifespan of axolotls is about 10 – 15 years. On the other hand, the average lifespan of the olm salamander is 60 years, some specimens can live up to 100 years. The conservation status of axolotls and olms are critically endangered and vulnerable, respectively.
7. Olm Salamander Threats
Scientists estimate that there are at least a few hundred of these species on the planet. It’s very hard to study them because of their secret home. They are classified as vulnerable on the IUCN Red List due to their fragmented and restricted location and rapidly declining population.
The European cave salamander has no natural predators in its limited area. They are only consumed by fish or other animals that have become lost in their cave, or by their own species. However, they are threatened by human activities.
Although the olm salamander are protected by law for nearly a century, their population still decreases. They are affected by water pollution due to toxic substances, fertilizers, pesticides, and microplastics. They are also poached for the pet trade.
The olms in Slovenia are extremely threatened, while in Croatia they are classified as critically endangered.
References:
- Olm – https://a-z-animals.com/animals/olm/
- Fun Olm Facts For Kids – https://kidadl.com/facts/animals/olm-facts
