Aquatic Health Program

Medaka Embryos

Endocrine Disrupting Chemicals

Toxicity studies using model fish species, Medaka (Oryzias latipes)

Medaka is a small (2-4 cm in total body length) fish native in Japan, Taiwan and other areas of Southeast Asia.  Because of their characteristic biology, the fish species is widely used in various research fields in biology, such as development, endocrinology and toxicology.  In our laboratory we are analyzing biological effects on medaka due to chemical exposure and developing statistical tools for screening endocrine disrupting chemicals in ambient water in accordance to US EPA standard protocol.

Advantages of Medaka for EDC studies:

  • Easy to breed and maintain in large numbers under laboratory conditions
  • High growth rate and maturation in a relatively short period (8-10 weeks)
  • High fecundity (single female medaka lays up to 40 eggs everyday)
  • XY-XX genetic sex determination system (zebrafish larvae have an ovary-like undifferentiated gonad)
  • Gender specific analysis is capable using Qurt strain medaka (develop sex-linked coloration of leucophores at embryonic stage)
  • Genetic information is available for whole genome sequences, cDNA sequences, microarrays, development of transgenic fish, and whole mount in situ hybridization

Current Projects:

  • Development of statistical modeling for screening EDCs in ambient water based on medaka gene expression profiles
  • Investigation of biological responses and adverse outcome effects due to EDC exposure
  • Analysis of bioconcentration and elimination of chemical in fish body

Photo: Tomofumi Kurobe, Assistant Project Molecular Taxonomist

Tomofumi Kurobe, Assistant Project Molecular Taxonomist

Molecular biology, specializing in gene expression analysis using medaka cDNA microarray to predict endocrine disrupting chemicals in ambient water.  Currently working on developing species identification system based on standardized DNA regions (DNA barcoding) for zooplankton and cyanobacteria.