Medaka Fish


LBS 144 Fall '02, Section 3

NMTA 2001:
Sarah Hay
Armon Mahajerin
Chris Sciamanna
Megan VanderZwart

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The Japanese Medaka fish favors springtime reproduction. The methods outline how this setting was created. Once under the conditions the fish create gametes and mate under light. Initially the male holds the spawning female with his fins for approximately 20 - 90 seconds. The male releases sperm, which penetrates the eggs. The egg yolk surrounded by cytoplasm eventually forms a disc-shaped cap at the end of the animal pole. Development then begins.

The lab TAs were very instrumental in the Medaka portion of the lab. The fish were in a tank, surrounded by foil 8 hours per day day to create a 16 hour light/8 hours darkness cycle.
As mentioned before, this helped the fish to mate. As the fish mated, the TAs collected the embryos, placed them in petri dishes, and labeled the approximate time of fertilization. We then viewed specimens ranging from 2-days-old to 4-days-old. We took pictures and used references to identify the stages of development.

Figure 1. (Stage 22: 1 day 23 hours) The brain
region is forming (A), and weak trembles occur
as the heart develops. The eyes also are growing (B).

Figure 2. (Stage 29: 3 days 22 hours) The tail is
beginning to move (A), and the eyes are much
more visible and darkened (B).
Figure 3. (Stage 32: 4 days 23 hours) A
greenish tint is beginning to form in the yolk,
and the blood is becoming reddish (A).
The eyes and brain continue to develop.
Figure 4. (Stage 33: 5 days 22 hours) The
embryo now contains an elongated tail (A) and
completely darkened eyes (B). The embryo
is almost ready to hatch.



Kirchen, R and West, W (??). The Japanese Medaka: Care and Development. Carolina Biological Supply: Burlington, NC.