Lernaean Hydra - Wikipedia, the free encyclopedia

Lernaean Hydra - Wikipedia, the free encyclopedia: In Greek mythology, the Lernaean Hydra (Greek: Λερναία Ὓδρα) was an ancient serpent-like water monster with reptilian traits. It possessed many heads — the poets mention more heads than the vase-painters could paint — and for each head cut off it grew two more. It had poisonous breath and blood so virulent that even its tracks were deadly. The Hydra of Lerna was killed by Heracles as the second of his Twelve Labours. Its lair was the lake of Lerna in the Argolid, though archaeology has borne out the myth that the sacred site was older even than the Mycenaean city of Argos since Lerna was the site of the myth of the Danaids. Beneath the waters was an entrance to the Underworld, and the Hydra was its guardian.

The Hydra was one of the offspring of Typhon and Echidna (Theogony, 313), both of whom were noisome offspring of the earth goddess Gaia.

Eurystheus sent Heracles to slay the Hydra, which Hera had raised just to slay Heracles. Upon reaching the swamp near Lake Lerna, where the Hydra dwelt, Heracles covered his mouth and nose with a cloth to protect himself from the poisonous fumes. He fired flaming arrows into the Hydra's lair, the spring of Amymone, a deep cave that it only came out of to terrorize neighboring villages. He then confronted the Hydra, wielding a harvesting sickle (according to some early vase-paintings), a sword or his famed club. Ruck and Staples (1994: 170) have pointed out that the chthonic creature's reaction was botanical: upon cutting off each of its heads he found that two grew back, an expression of the hopelessness of such a struggle for any but the hero. The weakness of the Hydra was that it was invulnerable only if it retained at least one head.

The details of the struggle are explicit in the Bibliotheca (2.5.2): realizing that he could not defeat the Hydra
in this way, Heracles called on his nephew Iolaus for help. His nephew then came upon the idea (possibly inspired by Athena) of using a firebrand to scorch the neck stumps after each decapitation.

Hera, upset that Heracles had slain the beast she raised to kill him, placed it in the dark blue vault of the sky as the constellation Hydra. She then turned the crab into the Constellation Cancer.

Heracles would later use arrows dipped in the Hydra's poisonous blood to kill other foes during his remaining Labours, such as Stymphalian Birds and the giant Geryon. He later used one to kill the centaur Nessus; and Nessus' tainted blood was applied to the Tunic of Nessus, by which the centaur had his posthumous revenge. Both Strabo and Pausanias report that the stench of the river Anigrus in Elis, making all the fish of the river inedible, was reputed to be due to the Hydra's poison, washed from the arrows Heracles used on the centaur.


When Eurystheus, the agent of ancient Hera who was assigning The Twelve Labors to Heracles, found out that it was Heracles' nephew Iolaus who had handed him the firebrand, he declared that the labor had not been completed alone and as a result did not count towards the 10 Labours set for him. The mythic element is an equivocating attempt to resolve the submerged conflict between an ancient ten Labours and a more recent twelve.

Mythographers relate that the Lernaean Hydra and the crab were put into the sky after Heracles slew them. In an alternative version, Hera's crab was at the site to bite his feet and bother him, hoping to cause his death. Hera set it in the Zodiac to follow the Lion (Eratosthenes, Catasterismi). When the sun is in the sign of Cancer, the crab, the constellation Hydra has its head nearby.

Hydra

may refer to:

Lernaean Hydra,

a many-headed serpent in Greek mythology

or

Hydra (genus),

a genus of simple freshwater animals belonging to the phylum Cnidaria.

Hydra /ˈhaɪdrə/ is a genus

of

small, simple, fresh-water animals

that

possess radial symmetry.

Hydra are predatory animals

belonging to the phylum Cnidaria and the class Hydrozoa.

They can be found 

in

most unpolluted fresh-water ponds, lakes, and streams in the temperate and tropical regions

and can be found by gently sweeping a collecting net through weedy areas. They are multicellular organisms which are usually a few millimetres long and are best studied with a microscope.

Biologists are especially interested in Hydra due to their regenerative ability;

and

that they appear not to age or to die of old age.

Hydra has two main body layers, which makes it "diploblastic". The layers are separated by mesoglea, a gel-like substance. The outer layer is the epidermis, and the inner layer is called the gastrodermis, because it lines the stomach. The cells making up these two body layers are relatively simple.

Hydramacin is a bactericide recently discovered in Hydra; it protects the outer layer against infection.

The nervous system of Hydra is a nerve net, which is structurally simple compared to mammalian nervous systems. Hydra does not have a recognizable brain or true muscles. Nerve nets connect sensory photoreceptors and touch-sensitive nerve cells located in the body wall and tentacles.

Respiration and excretion occur by diffusion everywhere through the epidermis.

Daniel Martinez claimed in a 1998 article in Experimental Gerontology that Hydra are biologically immortal. This publication has been widely cited as evidence that Hydra do not senesce (do not age), and that they are proof of the existence of non-senescing organisms generally. In 2010 Preston Estep published (also in Experimental Gerontology) a letter to the editor arguing that the Martinez data support rather than refute the hypothesis that Hydra senesce.

The controversial unlimited life span of Hydra has attracted the attention of natural scientists for a long time. Research today appears to confirm Martinez' study. Hydra stem cells have a capacity for indefinite self-renewal. The transcription factor, "forkhead box O" (FoxO) has been identified as a critical driver of the continuous self-renewal of Hydra. A drastically reduced population growth resulted from FoxO down-regulation, so research findings do contribute to both a confirmation and an understanding of Hydra immortality.

While Hydra immortality is well-supported today, the implications for human aging are still controversial. There is much optimism; however, it appears that researchers still have a long way to go before they are able to understand how the results of their work might apply to the reduction or elimination of human senescence.

Turritopsis nutricula,
another
cnidarian (a jellyfish) that scientists believe to be immortal.

Turritopsis nutricula
is
a small jellyfish.

Several different species of the genus Turritopsis were formerly classified as T. nutricula, including the "immortal jellyfish" which is now classified
as
T. dohrnii.