Medaka Project

Gaea's Journey

Amy Harris & Megan Winters



Jump To:

Day 1
Day 2
Day 3
Day 4
Day 8
Day 9
Day 10
Day 11
Day 14
With the family
Our goodbye

Day 1: May 20

We predict Gaea is 26 hours old. That means we predict it will hatch around June 3.
It is in the Late Neurula stage and that is when the keel has broadened into two divisions of the redimentary brain. The embryo's axis is about a millimeter in length; however, the mesoderm is condensing laterally. The blastopore is reduced to a small opening and the Kupffer's vesicle starts to form.

Words to know:

Keel - maintains organization during neurulation
Mesoderm - forms in embryo of animals; forms during gastrulation when cells move inward to make endoderm
Blastopore - opening into the archenetron during embryotic stages of life
Kupffer's vesicle - small vesicular pocket that forms as blastopore gets smaller

Additional words:

Neurulation - happens in embryo's with vertebrate; steps include the formation of dorsal nerve cord, and the formation of central nerves system later on
Gastrulation - phase in early development in animal embryos where the change in the embryo is changed by cell migration
Endoderm - germ layer which is made during the stages of animal embryos
Archenteron - space made gastrulation caused by the inevolution of cells in the blastopore
Vesicular - made of small sac-like pouches


Chorion - membrane that protects the egg; it is the clear, protective covering over the egg
Projecting Filaments - used to form a cluster of egg's by having these filaments grab onto each other; they are the string-like fibers hanging from the egg
Yolk - provides nutrients for the embryo; it is the circular mass in the center of the egg

Back to the top

Day 2: May 21


We predict that Gaea is about 40 hours old. Megan and I still predict that our Medaka egg, Gaea, will hatch around June 3.
At 40 hours old the optic lens is a small circular object; therefore, the optic lobs are getting bigger and the brain ventricles are forming. The otocyst, or auditory capsule, is present in the back of the brain area and can be hard to find. The neurocoele has extended into the back of the brain and spinal cord; however, the tail bud also is formed. A small gut tube has formed above the periblast in the trunk area and a large cavity appears on the yolk beside the head; therefore, this cavity slowly moves towards the pericardial cavity, joins with it and makes it bigger. The oil globules that were present in earlier stages have condensed into one large drop. Some trembles may be seen, those are knows as weak cardiac contractions and up to 12 somites are present.

Words to know:

Optic Lens - small circular mass in the embryo
Optic Lobes - holds the primary vision center
Otocyst - structure that is made by the embryo's ectodermal tissue, it later develops into the inner ear
Neurocoele - ventricles of the spinal cord and brain
Periblast - matter that surrounds the cell nucleus and goes through segmentation
Somites - division of the body of an animal


Optic Lens - the mass to the right of the yolk; cloudy in appearance
Otocyst - An auditory cyst or vesicle
Periblast - he protoplasmic matter which surrounds the entoblast, or cell nucleus, and undergoes segmentation.
Somites - he paired, blocklike masses of mesoderm, arranged segmentally alongside the neural tube of the embryo, forming the vertebralcolumn and segmental musculature.

Back to top

Day 3: May 22

This video shows the heart pumping colorless blood through the veins of Gaea.

We think Gaea is in the about 52 hours old at this point. At this point in it's life it begins the circulation process. There is colorless blood that holds some cells moving slowly through the aortae and vitelline vessels, as well as the cardinal veins. The latter circumscribe the pericardial cavity. The heart beats at a very strong and synchronized rate of 60 beats per minute. There are contractions that begin in the venous regionchromatophores appear in the brain. The embryo has about 19 or 20 somites in it at this point.

Words to know:
Aortae - The main trunk of the systemic arteries, carrying blood from the left side of the heart to the arteries of all limbs and organs except the lungs.
Cardinal Veins - The major systemic venous channels in adult primitive vertebrates and in the embryos of higher vertebrates;
and move downward. The reddish-brown
pericardial cavity - The potential space between the parietal and the visceral layers of the serous pericardium, in the embryo, that part of the primary celom containing the heart;

Chromatophores - Any pigmentary cell or colour-producing plastid.

Eyes- Structure for seeing.
Heart -
A hollow, muscular organ, which, by contracting rhythmically, keeps up the circulation of the blood.
Brain - One of the two components of the central nervous system, the brain is the centre of thought and emotion.
Somites - The paired, blocklike masses of mesoderm, arranged segmentally alongside the neural tube of the embryo, forming the vertebral column and segmental musculature.

Back to top

Day 4: May 23

I made the prediction that Gaea is about 62 hours old. The pectoral fin bud is starting to appear as a broad swelling that is behind the anterior vitelline artery. The fin will soon grow into a round protuberance. The body movements have became more frequent and the blood circulation is strong. The arterial end of the heart has moved to the right and the end of the ail is bent. There are about 26 somites that can be found. Otoliths are small but also distinct.

Words to know:
Protuberance - That which is protuberant swelled or pushed beyond the surrounding or adjacent surface

Vitelline Artery -
An artery carrying blood to the yolk sac from the embryo
Tail - The terminal, and usually flexible, posterior appendage of an animal.

Back to top

Day 8: May 27

We think that Gaea is about 144 hours old. The rudiments of several internal organs have developed. The liver is composed of colorless globules and nearly covers the greenish urinary bladder on the left side of the animal. The intestine is a transparent, elongated structure mostly to the right of the midline. The swim bladder now appears as a clear vesicle mesial to the urinary bladder. This vesicle may soon become larger than the urinary bladder or remain small until after hatching. A ventral fin has widened, along he entire ventral edge of the tail. The lower jaw is forming. The pectoral fin is membranous and may flutter.

Today we counted the heart beat is 128 beats per minute. When we were counting the heart beat, Amy saw Gaea's fin moving. We predict that it is in stage 33, and 144 hours old. Maybe a little earlier because we are measuring at an earlier time in the day, but it is close. We are a little skeptical about the age exactly, but we are pretty sure that Gaea is going to hatch on June 3.
The tail is pretty apparent today. We can see it moving clearly and the heart beat is easy to distinguish.

Words to know:

Urinary Bladder: A musculomembranous elastic bag serving as a storage place for the urine.
Intestine: This is a general term often used to describe both the small and large intestine.
Swim bladder: An air sac, sometimes double or variously lobed, in the visceral cavity of many fishes.
Mesial: Forward or front.
Pectoral Fin: Either of the anterior pair of fins attached to the pectoral girdle of fishes, corresponding to the forelimbs of higher vertebrates.

Back to top

Day 9: May 28

We think Gaea is about 168 hours old. There is some jaw movement and yellow clor to her. Upon careful obsevation of the region beneath the olfactory lobes, the lower jaw is seen to twitch very infrequently. There is a yellowish cast to the dorsal aspect of the head and trunk. The eye may be capable of slight movement, but this is usually observed later. The cornea has lifted well off the lens. The tral reaches back to the hindbrain. A dorsal fin is present but it is not as extensive as the ventral fin.

Today the heart beat 123 beats per minute. We think Gaea is about 168 hours old. In this stage, the jaw starts to move and twitch infrequently. There is a bit of yellow near the head and trunk. The tail reaches back to the hindbrain during this stage, also. The dorsal fin is present.

Words to know:

Hindbrain: The posterior of the three principal divisions of the brain, including the epencephalon and metencephalon.
Dorsal Fin: Fin located on the back of most fishes.

Back to top

Day 10: May 29

We predict that Gaea is about 200 hours old. The spleen arises as a small crimson-colored rudiment between the urinary and swim bladders. Its color intensity and initial shape are cariable. The liver is conspicuous. As the head flexure begins to straighten out, the mouth is moved upward and becomes visible in dorsal view. the mouth moves acively and will soon open. Posterior margin of the operculum can be seen below the otocyst. Golden chromatophores are scattered over the dorsal surface of the animal and melanophores spot the head. The yolk sac is devoid of pigment cells and markedly diminish in size. The embryo thrashes.

The heart beat today was 92 beats per minute. Gaea is about 200 hours old today. The spleen and mouth begin to appear. The mouth also becomes visible throughout this stage, and is about to open. The yolk is beginning to diminish.

Words to know:

Spleen: An organ that produces lymphocytes, filters the blood, stores blood cells and destroys those that are aging.
Mouth: The opening through which an animal receives food.

Back to top

Day 11: May 30


The heart beat today was over 170. We've changed our prediction that Gaea will hatch sometime this weekend - possibly tomorrow. She's shaking a lot so we assume that it means she's getting ready to hatch.

Back to top

Day 14: June 2

She hatched! We assume she hatched over the weekend like we expected, most likely saturday/sunday morning.

Our prediction from the beginning was only a day off. The mouth opened, as you can see in the video. Most of the inner organs are present now, and are remotely visible through Gaea's transparent outer body.


Back to top

Gaea with her brothers and sisters.


Our farewell...


Kudos on the definitions to this site.

Back to top