Hydras, according to meriam-webster, are “any of small tubular hydrozoan polyps” they are found everywhere imaginable, and consists of a hollow tube and tentacles, the hydra, and its mythological counterpart, have regenerative properties, this allows both of them to recover from injuries and even live ‘forever’, but, before we delve into the question as to whether they can live or not, we must first dive deep into its structure.
Hydras are small jellyfish like creatures, their body parts consists of a body, a mouth, and tentacles, its body is a hollow column, composed of two layers of cells separated by connective tissue called “mesoglea”, their bodies are 10-20 millimeters, and half of its compositions is made up of stem cells, which enable them to regenerate, which means that if one is cut, it can regenerate into two new hydras, their bodies can also contract when needed. Their bodies are usually of different colors, width, and length but are often translucent.
they don't often have mouths, and usually tear one open whenever they are ready to eat, their mouths can also be wider than their bodies, thus allowing them to consume larger foods.
They usually have 4-25 tentacles which contain nematocysts, these have multiple nematocysts, stinging cells which are ready to attack, these nematocysts compose of two main types, one wraps around the hydra and the other injects neurotoxins, these nematocysts are harmless to humans, and is replaced every 48 hours
Ok so now we know what they’re made of, but, how do they eat?
Hydras eat by stinging their prey with their tentacles, like jellyfish, but, unlike jellies, these hydras often make a new mouth, due to the fact that their bodies are closed when not eating, hydras like to eat crustaceans, insects, and small fish, and their prey usually experiences millions of Gs of force in nanoseconds, and the prey is then broken up by special cells.
Their wastes are excreted out of the same hole.
Now we know how they eat, but, what do they do when they want to expend that energy?
Hydras move by looping (tentacles attach to substrate, then, the base releases which allows the body to somersault, thus allowing the base to attach to a new surface), or by creeping.
Moving allows the hydra to move away from predators or unsavory conditions, and also allows them to migrate long distance through plant barks riding along the waves of rivers.
Ok, so hydras expend their energy through moving, but, what do they do with the rest?
They ,of course, make little hydra children. hydras reproduce through sexual and asexual methods, the sexual method involves seperate gonads containing sperm and eggs, the gonad releases the sperm while the other absorbs the sperm, but does not release the egg, afterwards, the egg becomes hard and falls off, once it falls, it is thought to be resistant to dehydration, this egg soon develops into a fully grown hydra.
Most hydras are either male or female, but some can be hermaphroditic.
The asexual route is done by budding, five finger shaped outpushings turn into mouths and tentacles, then, once the bud is fully grown, it nips itself off at the base.
Hydras replace their stem cells every 20 days, which allows the hydra to keep and maintain a steady source of stem cells for regenerative purposes.
Hydras are part of the genus hydrozoa, a genus of freshwater invertebrate animals, this genus has more than 25 species, classified by appearance, the two common types are the brown hydra and the green hydra, the brown hydra is found in waters in early spring to late autumn in the northern temperate area, it is found attached to plants
Meanwhile, the green hydra, is found in still waters, they contain algae within the vacuoles of their cells, these algae are chlorella vulgaris, and give energy in exchange for shelter and nutrients.
The green hydra is carnivorous and eats crustaceans.
ok, so we know who and what they are, but, where do they live?
Hydras live in freshwater, either in freshwater lakes, slow moving rivers, or ponds, they are mostly sessile and are found attached to hard stuff like rock and wood.
They usually prefer temperate and tropical climates, and do not like cold areas.
Hydras may or may not be the fathers of experimental zoology, back in the 1700’s Abraham Trembley, a genevan naturalist, published a book called “Mémoires pour servir à l'histoire d'un genre de polypes d'eau douce” in 1744, this groundbreaking book includes his experimentation and observations in detail, this book was made after he came across a strange organism in his pond.
He thought that this organism was a plant, due to its irregular number of arms which varied per polyp, still, he felt as though this thing was an animal.
So, in order to see if it was a plant or an animal, he decided to cut it in half, he thought that if this thing regenerated, it must be a plant, since animals cannot regenerate completely. During his experiment, he noticed that this thing moved like an inchworm, further suggesting it was an animal, he was surprised when the severed hydra turned into two new polyps, thus further suggesting that it was a plant.
He soon noticed that the polyps were exact carbon copies of each other, however, this did not convince him that these were plants, he instead concluded that these were animals.
This discovery soon lead to not just the birth of a groundbreaking memoir, but it also birthed experimental zoology and lead to further studies on hydras
Now that we know all about the hydra, it is now time to answer the question, “are they truly immortal?”
Well, short answer, no, the hydra is susceptible to changing conditions and can die if food sources become low, and if they’re eaten.
Though they have the ability to regenerate due to their constant supply of stem cells, and the inability to age and to repair DNA, they are still under the mercy of their environment and larger predators.
What i like about the hydra is their ability to regrow and repair, they taught me that you must always find ways to repair and rebuild yourself, i also like them because of their ability to sting their prey much like jellyfish, i have always wondered as to how they ate and captured prey, and, now that i know all about it, i feel complete
See you on the other side!
-ralf