Japanese Medaka Story

Japanese Medaka Story Jake Godo and Kendall Neal

Introduction – Japanese Medakas Medakas (Oryzias latipes) are small fish, only

growing to be about 4 cm long.

It is a popular pet, and it lives in both salt water

and fresh water environment.

It is commonly used for scientific studies because it

is simple, short lived, easily raised, and easy to ship.

Introduction - Jaws We got our Japanese Medakaon April 16. We

named it Jaws. We observed it every day (except weekends)

until it hatched on April 27.

We also monitored its heartbeat and its growth. We used the booklet to determine what stages

it was in.

First Day – Stage 23  The first day we had our egg we determined that it was in

stage 23.  The heart beat starts to appear.  It beats about 40 to 60 beats per minute, and that is about what we observed.  About fifteen somites are formed, and the head and tail begin lifting of the yolk sac.  The pericardial cavity begins to extend anterior to the forebrain.

Stage 26 This stage is when you can really start to see the

eyes, tail, and fins. Its heart beat was about 100 beats per minute. Black granules speckle the optic cup and the retina darkens.

Stage 30 This picture was taken while the medaka was

in stage 30. During this stage, the urinary bladder forms. The heart beat is 140 beats per minute and the blood is pink or dark pink The tip of the tail is long enough to reach the eye, and golden chromatophores appear on the tail.

Stage 36 Hatching – the fish has hatched. You can now see its organs and its fins. It swims around. There are about 30 somites.

Caring for the Medaka We gave it fresh spring water every day and

observed it under the microscope. We were sure to be gentle with it and not squish it or drop it. We put it back every day. After it hatched, we put it in the tank with the other medaka. They were fed every day and there was a bubbler in the tank.

Structures and Functions Filament – small fibers on the outside of the

egg membrane. Chorion – An outer membrane of the egg, protects the fish. Cytoplasm – The liquid inside the egg surrounding the embryo and everything. Yolk Sac – The sac that the nutrients for the fish are, it is attached to the fish so it can consume the yolk.

Structures and Functions Cont. Oil Globule – Small spheres in the yolk sac that. Heart – This is the cardio muscle that pumps

blood troughout the fish’s body. Fins – They allow the fish to swim by flapping them and making the fish go through water easier. Optic cup/eye – The eye of the fish, it helps the fish see. Brain – The main nervous organ of the fish, controls its movements and helps it sense things (sight, felling, smell, taste, hearing)

Structures and Functions Cont. Mouth/Jaws – The mouth is where the food goes into. The jaws stabilize the mouth and help it open and close. Somites – Division of the body, they look like vertebrae, they are segmented along the neural tube.

References and Resources http://biog-101-104.bio.cornell.edu/BioG101_104/tu html http://en.wikipedia.org/wiki/Oryzias_latipes The Medaka Booklet