Daphnia Downloads & RevenueDaphnia: Ecosystem Simulator · App Store

A tiny ecosystem on your wrist.

Daphnia is an ecological simulation game for Apple Watch where you can raise and observe the life and reproduction of Daphnia magna.

This is more than a virtual pet whose numbers rise when you feed it.

Algae, dissolved oxygen, water temperature, water movement, and population density interact to shape the lives of the organisms inside your tiny aquatic world.

■ Walking supports the food chain

Your steps do not turn directly into experience points.

Instead, they provide energy for algae growth. The daphnia feed on those algae, store energy, grow, molt, and reproduce.

Steps
↓
Algae grow
↓
Daphnia feed
↓
Growth, molting, and reproduction

Walking helps produce food inside the tank and supports the ecosystem.

■ Your wrist moves the water

While the app is open, the movement of your wrist affects the mixing of the water.

Gentle movement helps distribute sinking algae and supports oxygen circulation.

Movement that is too strong creates turbulence, temporarily disturbing swimming and filter feeding.

There is no need to shake your arm. Small movements are enough to influence the environment.

■ Zoom in with the Digital Crown

Turn the Digital Crown to zoom continuously from a view of the entire tank to a detailed view of an individual daphnia.

Tap an individual to select it and keep it in view.

At higher magnification, you can observe the transparent carapace, compound eye, digestive tract, brood chamber, eggs, embryos, antennae, and filtering limbs.

■ Follow the daphnia life cycle

Inspired by the biological characteristics of Daphnia magna, the simulation includes:

• Growth from juvenile to adult
• Molting
• Eggs entering the brood chamber
• Development from eggs to embryos
• Birth of juveniles
• Reproduction mainly by females in favorable conditions
• Appearance of males when conditions worsen
• Formation of ephippia and resting eggs
• Death caused by age or environmental decline
• Hatching of resting eggs after conditions recover

Even when all ordinary individuals disappear, the ecosystem may not be finished.

If resting eggs remain, daphnia can hatch again when the environment improves, allowing life to return.

■ Watch their distinctive swimming

Daphnia do not swim like fish at a constant speed.

They strike their large second antennae to move forward, then glide and sink before the next stroke.

Each individual has its own timing for body movements, turns, short pauses, antenna motions, filtering movements, and bursts of swimming.

The inhabitants of the tank do not all move in the same way at the same time.

■ Observe the aquatic environment

You can check information including:

• Total population
• Adults and juveniles
• Number of males
• Resting eggs
• Algae concentration
• Dissolved oxygen
• Water temperature
• Water mixing
• Selected individual’s sex
• Growth stage
• Body length
• Scientific name

Food shortages, low oxygen, unsuitable temperatures, and overcrowding can change activity, feedin