Henry the medaka fish develops from an egg over 6 days, progressing through 36 developmental stages. Key developments include the formation of organs like the heart, eyes, swim bladder, and intestines. By day 7, Henry hatches with fins, jaws, and other features fully formed. He is able to swim and interact with his siblings, while the caretakers who observed his development appreciate learning about the fragility and value of life.

1. The Adventures of Henry
the Medaka
By: Cullen Jenary

2. Key
The babysitters
Developmental Steps
Henry (the Medaka fish)

3. Day 1- Stage 23-(46 hours)
Henry is still just an egg, but he has some common
characteristics like the cytoplasm, filaments along
outer layer, and the chorion.
Cytoplasm-is a thick liquid residing between the cell membrane holding all organelles,
except for the nucleus.
Chorion- the outermost membrane around the embryo. It develops from an outer fold on
the surface of the yolk sac.
Filaments- are tiny hairs surrounding the egg, which are used to remain attached to their
mothers.
Henry’s mother has a business meeting out of state so we are baby sitting.
My mom said I have to stay with her friends until she gets back; I’m excited.

4. Day 2- Stage 27-(62 hours)
Henry’s body is becoming more visible as he ages. Nothing major has changed, since
he has had an oil globule and a yolk sac the first day as well.
Oil Globule- A small sphere of oil within the yolk-sac of fish larvae; size, number,
position and color of oil globules is variable and a useful character for identification.
Yolk Sac- is a membranous sac attached to an embryo, providing early nourishment in
the form of yolk.
Henry is so well behaved, he barely even moves. I hope he isn’t always this shy.
They are very nice, but I don’t know them well enough yet.

5. Day 3- Stage 31-(121 hours)
Henry shows his first since of activity. We can now see his heart and his heart beat. His
annual heart rate is 150 beats per minute. His eyes have also become blacker.
Heart- is responsible for pumping blood throughout the blood vessels by repeated,
rhythmic contractions.
He is finally opening up, and getting to know us better. He moves around all day and his
heartbeat reached 150 beats a minute.
I’m getting to know them better, and I’ve had a lot of energy lately.

6. Day 4- Stage 33-(144 hours)
Henry’s body structure has really started to take its
shape. You can now see his swim & urinary bladder.
His heart rate hasn’t changed.
Swim bladder- is an internal gas-filled organ that contributes to the ability of a fish to
control its buoyancy and thus to stay at the current water depth without having to waste
energy in swimming.
Urinary bladder- muscular sac situated in the anterior part of the pelvic cavity in which
urine collects before excretion.
He is growing so fast his mother would be so proud.
I’m getting anxious to swim around, and meet all my brothers and sisters.

7. Day 5- Stage 34-(168 hours)
Henry’s blood circulation has become more visible. His eyes have also blackened even
more. The vitelline membrane can be seen better, but is visible in previous stages.
Optic cup/eye- during development of the eye, the outer wall of the bulb of the optic
vesicles becomes thickened and invaginated, and the bulb is thus converted into a cup.
The eye itself is used by the organism to see.
Vitelline Membrane- a structure directly adjacent to the outer surface of the plasma
membrane of an ovum . It is composed mostly of protein fibers, with protein receptors
needed for sperm binding.
Henry’s mother will be back soon, and we will miss him.
I’m a little restless, and want to take a nap.

8. Day 6- Stage 35-(200 hours)
Henry is at his peak of development, and you can see almost of his vital
organs( spleen, liver, intestine). He will be fully ready to hatch in 1-2 days.
Spleen-produces and destroys red blood cells, filters and stores blood, and produces lymphocytes.
Liver- aids in digestion and removes waste products and worn-out cells from the blood.
Blood Vessel- a vessel in which blood circulates.
Intestine- The long, tubelike organ in the abdomen that furthers the process of digestion.
Henry has shown major activity, and I think he’ll be ready to hatch soon.
I’m almost old enough to come out and see the new world; I can’t wait.

9. Day 7- Stage 36-(224 hours)
Mouth/Jaws- the opening of the digestive tract where food is entered usually broken down by teeth
Brain- the primary receiver, organizer and distributor of information for the body.
Pectoral Fins- pair of fins situated on either side just behind a fish's head, helping to control the direction of movement
during locomotion.
Dorsal Fin- fin on the backs of fishes that helps to maintain balance.
Caudal Fin- the tail fin of fishes used for propulsion during locomotion
Somites- a segmental mass of mesoderm in the vertebrate embryo, occurring in pairs along the notochord and
developing into muscles and vertebrae.

10. Day 7- Stage 36-(224 hours)
Henry has hatched, and is swimming through the water. His fins (dorsal, pectoral,
and caudal), and mouth are moving rapidly. Everything is in order and he is in good
health.
Henry has finally hatched, and we are so happy. We have watched Henry grow up
and it has been fun and a life lesson. It taught us how life is valuable and delicate,
and that it should be shown outermost respect. As Henry grew we noticed
changes in his body, and how everything lead to the next developmental stage.
Henry’s mother has came to pick up Henry and his 30+ siblings. We will miss him.
I have finally hatched and it feels great. I hated being curled up and trapped inside
that egg. I have freedom and a lot of space to swim. I have also been talking to my
brothers and sister, but I’m having a hard time remembering all their names. My
babysitter have been nice to me, and took good care of me. Thank you guys for
being so caring and generous. See you later.

11. What Henry needs to survive
The medaka will eat a variety of foods, from flake and freeze-dried foods to a wide range of frozen foods.
Like many smaller fish, it prefers to have plenty of cover in the tank to hide when stressed.
It also requires some degree of water movement, which can be provided by an air stone or filter.
The medaka is a spring water fish, and if it is placed in regular water it will die.
It also is a small fish making it easy prey for most fish meaning mixture with certain fish could be fatal.

12. Family Portrait