Zebrafish Larva
Danio rerio
Type: freshwater
Physical Characteristics
Translucent, elongated body shape during the larval stage with prominent large eyes and a visible yolk sac. The body displays early development of the notochord and lack of adult pigmentation patterns (stripes).
Habitat & Distribution
Found in slow-moving or stagnant waters, such as rice paddies, ponds, and streams across South Asia, specifically India, Pakistan, Bangladesh, and Nepal.
Size & Weight
Larvae are approximately 3-4 mm in length; adults reach 3-5 cm. Weight is negligible at this stage, with adults weighing only a few grams.
Similar Looking Species
Larvae of other Danio species or small cyprinids. Identification at this stage often requires genetic testing or observing development because many teleost larvae look alike.
Ecological Role
Acts as primary consumers of phytoplankton and microscopic zooplankton, while serving as a fundamental prey base for larger aquatic invertebrates and fish.
Diet
Initially relies on the yolk sac for nutrition, transitioning to feeding on microscopic organisms like rotifers, paramecia, and small zooplankton.
Behavior
Exhibits early swimming movements and phototactic responses (reaction to light). Larvae tend to hang near the water surface to access oxygen and micro-prey.
Reproduction
Adults are prolific spawners; eggs hatch 48-72 hours after fertilization. Larvae undergo rapid morphogenesis, becoming free-swimming within days.
Conservation Status
Least Concern (IUCN); populations in the wild are generally stable, though highly valued in laboratory settings.
Identification Tips
Look for the large, dark eyes relative to the clear body, the presence of a ventral yolk sac, and a slender, tapering tail characteristic of cyprinid larvae.
Interesting Facts
Zebrafish are a premier model organism in genetics and developmental biology because their embryos and larvae are transparent, allowing scientists to see organs grow in real-time.
Identified on: 5/20/2026
Mode: Standard