Question 1

How do you identify male and female zebrafish for breeding?

Accepted Answer

Male zebrafish have slimmer bodies with a slightly red hue, while females have bigger, silver bellies full of eggs. Recognizing these physical differences is essential for setting up successful breeding crosses. Periodic mating keeps eggs healthy, but individual females should only be mated once per week to ensure their wellbeing.

Question 2

What is the purpose of a removable insert in zebrafish breeding tanks?

Accepted Answer

Breeding tanks feature a removable insert with holes that allow eggs to fall through, protecting embryos from being eaten by adult fish. This design is critical for successful embryo collection. The insert can be lifted to remove adults after spawning, making the entire breeding process more efficient and reliable.

Question 3

How long should you wait after removing the divider before collecting zebrafish embryos?

Accepted Answer

Wait approximately 15 to 30 minutes after pulling the divider to give the fish time to mate and spawn. During this period, males chase females around the tank, stimulating spawning while releasing sperm for fertilization. After this time, remove the adults and collect embryos by pouring water and embryos through a mesh tea strainer.

Question 4

What is PTU and why is it used in zebrafish embryo culture?

Accepted Answer

PTU is a chemical that inhibits production of the pigment melanin in zebrafish embryos. Zebrafish begin developing pigment by 24 hours, which can interfere with microscopy observations. By supplementing embryo water with PTU, researchers can maintain transparency and improve visualization of developmental processes during live imaging studies.

Question 5

What is dechorionation and when is it necessary for zebrafish embryos?

Accepted Answer

Dechorionation is the removal of the chorion, a shell-like membrane surrounding the embryo that can impede manipulation. For the first three days of life, zebrafish embryos develop inside this protective chorion. The chorion can be removed using the proteolytic enzyme pronase or manually with forceps, depending on experimental requirements.

Question 6

How can zebrafish embryos be used for genetic manipulation in research?

Accepted Answer

The external development and transparency of zebrafish embryos allow for genetic manipulation through introduction microinjection early zebrafish embryos of DNA, RNA, or gene knockdown reagents. This method produces uniform distribution of injected material and can generate visible phenotypes from protein overexpression or loss. Transgenic fish with fluorescent protein markers can also be created for cell-type-specific visualization.

Question 7

What daily care practices keep zebrafish embryos healthy in the laboratory?

Accepted Answer

Keep water in petri dishes clean and free of debris, and remove dead opaque embryos daily. Methylene blue can be added to prevent fungal growth. Maintain optimal embryo density at 50 to 100 per dish, and place dishes in an incubator at 28.5 degrees Celsius. Use a transfer pipet to move embryos between dishes, swirling the dish first to concentrate them in the center.

Zebrafish Breeding and Embryo Handling - Assessment Quiz