Fifteen molts between hatching and adulthood
A brine shrimp's life can begin twice: once when it's laid, and again — possibly years later — when its dried cyst finally touches water. From there it's a fast, well-documented march through larval stages to a swimming, breeding adult.
Cyst to adult
A dry cyst meets salt water
The cup-shaped, dormant cyst absorbs water and swells into a sphere. Inside, an embryo that had paused all development — a state called cryptobiosis — begins reactivating its metabolism.
The shell splits: the "umbrella stage"
The outer shell ruptures and the embryo emerges still wrapped in a thin hatching membrane, hanging just beneath the empty cyst like it's sheltering under an umbrella, while it finishes developing.
Instar I: the free-swimming nauplius hatches
The hatching membrane breaks and a nauplius — the first larval stage, under half a millimeter long — swims free. It's brownish-orange, colored by the yolk reserves it's still living off; its gut isn't connected yet, so it can't eat.
The digestive tract opens
After its first molt, the nauplius's gut connects and it starts filtering algae and bacteria from the water. If food isn't available around now, larvae commonly die at this stage — the yolk reserves only carry them so far.
About 15 molts to maturity
Across roughly 14 to 17 distinct stages, the animal keeps outgrowing and shedding its exoskeleton. Compound eyes on stalks develop, along with the paired swimming/feeding limbs (thoracopods) that line the thorax. Under ideal warmth, food, and oxygen, this whole process can finish in as little as 8 days; in a real lake it more commonly takes 3 to 6 weeks.
Reproduction begins
Adults reach about 8–15mm. Males have a paired reproductive organ near the tail; females carry a visible brood pouch. A fertilized female can release up to roughly 75 free-swimming nauplii a day when conditions are good, in broods every few days for the rest of her life.
Live young, or a cyst built to wait
The same female can choose between two very different strategies, depending on how good conditions currently are.
Ovoviviparous — live nauplii
Fertilized eggs develop directly inside the female's brood pouch and are released as active, free-swimming nauplii, ready to start feeding immediately.
Oviparous — dormant cysts
If salinity spikes, oxygen drops, or the water is about to dry up, development instead halts at an early embryonic stage. The embryo is sealed inside a tough, dark cyst shell and released into the water, where it may drift, dry out, and wait — sometimes for years — until conditions improve.
Many brine shrimp populations skip males altogether: parthenogenetic females produce viable, all-female broods on their own, generation after generation, without ever mating.