Proteus anguinus embryonic expansion usually takes 140 days and it may take another 14 years in order to arrive at complete sexual maturity. The larvae obtain grown-up form after approximately four months, with the period of complete maturity robustly relating with water temperature. Unverified chronological examinations of vivipary do subsist, but it has been illustrated that females have a peculiar gland that creates the egg covering, comparable to those of fish and egg-hatching amphibians. It was observed that female Proteus anguinus gave birth to young ones at lesser temperatures and hatch eggs at elevated temperature, but meticulous examinations have not verified that. The olm tend to be oviparous. The female Olm gives up to 70 eggs, approximately about 12 millimetres in width, and puts them between boulders where the eggs remain under Olms fortification. The resultant tadpoles are roughly two centimetres long when they emerge and survive on yolk saved in the body of the digestive area for at least a month. Growth of the Proteus anguinus and erstwhile troglobite amphibians is categorized by heterochrony – the creature does not experience metamorphosis and rather involves larval characteristics. The appearance of heterochrony in the Proteus anguinus is considered to be neoteny – deferred somatic adulthood with gifted reproductive ripeness, i.e. reproductive development is reached whilst sustaining the larval peripheral morphology.
However, in other amphibians, the process of metamorphosis is controlled by the inner hormone thyroxine that is emitted by the thyroid gland. The Thyroid gland typically develops and functions in Human fish in the most ideal manner and therefore, the absence of metamorphosis may be due to the insensitivity of main tissues. This amphibian swims like eel by winding its overall body. Nevertheless, inadequately developed legs help this amphibian while swimming. It is usually a predatory amphibian, eating little crabs, insects and even very small fishes as well. It swallows its entire food rather than chewing. At the same time, Proteus anguinus is considered to have long term resistance to hunger. Therefore, it can live without adequate food for at least 2-3 days without any health problems. Human fish can easily eat large quantities of food immediately and can save advantageous nutrients in the form of glycogen and proteins in its liver without any difficulties. These nutrients supply adequate strength and power to Olm for its survival under water. Nevertheless, when the quantity of food is very less it decreases its overall metabolic rate in order to consume energy and power.
It has been observed that males are not very sexually active trying to protect their respective regions where they try to draw attention of females. The absence of food may lead to fighting between Olms under water and hence, fighting is only done for display. Reproduction has been noticed in confinement only. Sexually grown-up males tend to have inflamed cloacas, vivid skin shade, double lines at the surface of the appendage, and somewhat bent fins. No such alterations have been noticed in females. Prolonged existence is approximately up to 58 years. Personal samples have been stored under semi-natural environments in solid containers till 70 years.