Life-History Characteristics of Japanese Medaka (Oryzias latipes)

A simplified guide based on the 2011 Copeia study by Leaf et al.

Overview

This study examined the full life cycle of Japanese medaka, including how they grow, reproduce, and how their eggs hatch. Medaka are a widely used model organism in biology, toxicology, and environmental science. Understanding their natural patterns helps researchers design more accurate experiments.

Lab Conditions

• Water temperature: 77°F (25°C)
• Light cycle: 16 hours light, 8 hours dark
• Feeding: Twice daily
• Sample size: 300 individuals monitored from hatch to death

Growth

• Maximum length: About 1.95 inches (49.5 mm)
• Estimated lifespan: 347 to 485 days (approximately 1 to 1.3 years)
• Growth pattern: Rapid early growth, slower as they age

Survivorship

Most medaka died early in life, and mortality increased again after they started reproducing. This pattern is called a Type III survivorship curve, which is common among small fish species.

Reproduction (Fecundity)

• Age at first spawning: Around 68 days
• Peak daily egg production: Up to 48 eggs per day, typically around 92 days old
• Total eggs per female: Between 38 and 141
• Spawning duration: Around 57 days
• Average egg diameter: 0.043 inches (1.08 mm)

Fish that laid more eggs tended to have smaller eggs, suggesting a tradeoff between quantity and size.

Egg Hatching

• 50% of eggs hatched by: 3.5 days
• 99% of eggs hatched by: 7.5 days
• Average hatching success rate: 73% (range: 53% to 93%)

Conclusion

This research provides valuable baseline data on medaka development and reproduction. Their rapid maturity, small size, and high reproductive rate make them ideal for laboratory studies, especially in environmental and chemical research.

Reference

Leaf, R.T., Jiao, Y., Murphy, B.R., et al. (2011).
Life-History Characteristics of Japanese Medaka (Oryzias latipes). Copeia, 2011(4), 559–565.

Tags: medaka, oryzias latipes, fish breeding, growth rate, fecundity, egg hatching, model organism, life history traits, ecotoxicology