A Miniature World in Beucha: Hydras, the Animals That Don’t Senesce

4 hours ago

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A fascinating discovery of hundreds of hydras living on an ordinary submerged stick.

On a beautiful late-summer day, I decided to snorkel at Beucha’s Kirchbruch quarry. Best known for its majestic stone cliff crowned by a white church, this picturesque place has remarkably clear water and has long been popular with young people for cliff jumping.

View across the water of Kirchbruch quarry in Beucha, with a white church standing above the high rocky cliff beneath a blue, cloud-filled sky. — *The Kirchbruch quarry in Beucha, with the Bergkirche rising above its distinctive rock wall.*

What I didn’t know was just how much life the quarry held. Alongside aquatic birds such as Great Crested Grebes and fish including European perch, roach and tench, I found an incredible miniature world on an old submerged stick. Covered in algae, sediment and small mussels, it also held dense aggregations of hydras — tiny animals that are almost impossible to see clearly with the naked eye underwater.

What first appeared to be an ordinary submerged stick was covered by an entire community of aquatic
Algae, biofilm, sediment and tiny bubbles covering one of the stick's upper branches.

The first thing that made me stop was a cluster of tiny, shiny bubbles forming in and around the algae. They looked like perfectly round pearls trapped underwater. But when I checked the photos on the camera, I noticed several strange, greyish shapes among them — so small that I hadn’t even seen them with my own eyes.

Close underwater view of an algae-covered stick with clusters of tiny reflective bubbles and faint translucent hydras against green water. — *Tiny oxygen bubbles gather among algae and sediment on the submerged stick, with almost invisible hydras hidden among them.*

That was when I realised there were lots of these tiny creatures, and I became completely fascinated by them. They were hydras.

Small translucent hydra with fine tentacles growing from an algae-covered underwater surface dotted with round reflective bubbles. — *A tiny hydra rises among algae, sediment and bubbles that glisten like underwater pearls.*

A microhabitat on an ordinary stick

The more I explored the old stick, the more rewarding it became. It was covered with clusters of zebra mussels (Dreissena polymorpha). With their siphons open, they were actively filter-feeding, and when the sunlight hit them directly, I could even glimpse some of their soft internal tissues.

Zebra mussels and hydras crowded together on a small section of the submerged stick.
An open zebra mussel (Dreissena polymorpha), with its soft tissues visible inside the siphon opening

But the mussels were not alone. Hundreds of hydras were living on and around the mussels, all sharing the same tiny habitat.

Dozens of pale freshwater hydras with long thread-like tentacles densely covering algae and mussel shells underwater. — *A dense aggregation of hydras occupying the same tiny habitat as the zebra mussels.*

Microscopic neighbours

A tiny mass of white dots suspended on almost invisible filaments also caught my attention. They were probably Vorticella or closely related peritrich ciliates. Their bell-shaped bodies are only a few tens of micrometres across, yet they feed on even smaller particles such as bacteria.

Each individual consists of a tiny inverted bell attached to a long, slender stalk. Their superpower lies in that stalk: when disturbed, it contracts almost instantly, coiling like a microscopic spring and pulling the animal rapidly back toward the surface it is attached to.

*Probable Vorticella ciliates forming minute white colonies within the same underwater microhabitat.*

Finding these microscopic beings reminded me how much life exists all around us — most of it passing completely unnoticed.

The amazing capabilities of hydras

As I looked closer, I noticed something remarkable: some of the hydras were growing another hydra directly from their body column.

Close-up of a freshwater hydra attached to an algae-covered surface, with a clearly visible young bud growing from the side of its body. — *A developing hydra grows directly from the body column of its parent through asexual budding.*

It is called budding, an asexual form of reproduction in which a bulge forms on the parent’s body, develops a mouth and tentacles, and eventually detaches as an independent genetic clone.

The more I researched hydras, the more fascinating they became. They are often described as “biologically immortal”. They can still die — for example if eaten by a predator — but some species show almost no senescence: they do not seem to age or physically decline in the way most animals do. One study estimated that, under laboratory conditions, around 5% could theoretically still be alive after 1,400 years.

As if that were not astonishing enough, some hydras can even survive being cut in half: each half rebuilds what is missing, resulting in two complete animals. Even when broken down into individual cells in laboratory experiments, those cells can reorganise themselves and form new hydras.

Hydra: a tiny but extremely powerful animal

Translucent hydra with long tentacles and a small developing bud extending from its body, photographed against pale green water and algae. — *A hydra carrying a developing bud, surrounded by the muted colours of its underwater habitat.*

What seemed like an ordinary snorkelling exploration at Beucha’s Kirchbruch became an unexpectedly fascinating discovery.

Hydras are tiny, intriguing animals that possess abilities we humans have only dreamed of for millennia. Finding them reminded me how extraordinary even the smallest and most easily overlooked forms of life can be.

Text by Ana Mano · Photography by Ana Mano