Dr. Tanguay makes observations of the fish experiment. After about five days, he notices that the zebrafish embryos in the experimental treatment are deformed. The experimental treatment adult zebrafish are unaffected as are fish and embryos in the two control tanks.

Adult zebrafish, control treatment

Adult zebrafish, experimental treatment

The deformed embryos do not survive to become adults. When too many embryos are deformed and die, the fish population decreases.

Five-day old zebrafish embryo,
control treatment

Five-day old zebrafish embryo,
experimental treatment

Luckily, Dr. Tanguay and his research team specialize in the field of developmental toxicology.

What is Developmental Toxicology?

Toxicology is the study of harmful substances. Developmental toxicology is the study of how those substances affect organisms during early stages of growth.

In all animals, the development stage begins when an egg is fertilized and lasts until the egg hatches (in the case of zebrafish) or until birth (in the case of mammals like humans and mice.)

If an embryo is exposed to a developmental toxin —a chemical that harms a developing organism—it can suffer physical changes (also called morphological changes; “morph“-means shape or form) and become deformed. These developmental toxins change the body’s normal gene expression, or the way the body reads its instructions from genes in DNA.

What is Gene Expression?