Deadly Jewels of the Sea
Cnidaria Report • Academic Biology Period 5 • November 5, 2009
Deadly Jewels of the Sea
Picture sources (left to right) Jellyﬁsh 3, Jellyﬁsh, Jellyﬁsh (ﬂickr user: MotoMo); Eruption (ﬂickr user:
pokpok313); 2008-013-16 Camden 013 New Jersey State Aquarium (ﬂickr user: Allie_Cauliﬁelds)
Fact: The Turritopsis nutricula is immortal. This breed of jellyﬁsh rejuvenates
after becoming an adult.
The internal transport of a jellyfish is very simple. On the inside of the jellyfish exists a gastro-
vascular cavity. This functions as a gullet, stomach, and intestine all in one. Respiration is car-
ried out by means of gas diffusion that occurs on all surfaces of the body. The regulation of a jel-
lyfish is easy and simple. The prey is “swallowed”, then travels to the gastrovascular cavity where
it is digested. The nutrients from the digested food simply travels to the various cells where they
The epidermis, or the outside surface, of the jellyfish protects the inner organs. It is made up of a
loose network of nerves. The mesoglea is the jelly-like substance that makes up the jellyfish’s
“skin”. The gastrodermis is the inner layer of cells lining the gastrovascular cavity. The tenta-
cles are used as weapons and a method of self defense.
Cnidarians can produce both asexually and sexually; however, the jellyfish reproduces sexually by
producing eggs and sperm. The jellyfish life cycle consist of 7 different phases. The first phase is
fertilization. In this step fertilization occurs in open water, producing many diploid zygotes. In
the following step, the zygote grows into a larvae. The next step is the Planula Larvae stage. The
larvae swims throughout the ocean and will eventually attach itself to rocks or coral. From there
the larvae will develop into a polyp. In the next step the polyp buds. Budding occurs when one
side of the polyp swells, eventually the swelling grows into a new polyp which will, in time, grow
into a new young medusa, jellyfish. This leads us to the next step in the cycle, the young medusa
step. As a young medusa, the jellyfish
have yet to develop tentacles or any
means of self defense. And finally the
young medusa matures into an adult.
As an adult the jellyfish, the medusa is
fully grown and can defend itself and
catch prey. Adult medusa’s can repro-
duce sexually by releasing gametes
into the water, which causes the cycles
jellyfish by Flickr user: to restart. The life length of a jellyfish
is one year.
Jellyfish are carnivorous, meaning that they eat other organisms whether they are living or dead.
The diet of a jellyfish includes small fish, eggs, and other invertebrates. The jellyfish rank with
octopi and squids near the top of the food chain. Jellyfish paralyze the prey that gets caught in
their tentacles. Then they ingest the food through their mouth which also functions as an anus.
That is disgusting!
The jellyfish doesn’t adapt well in captivity because there is a lack of ocean current. Without
these vital current the jellyfish fall to the bottom of the tank and die. In these situations jellyfish
don’t live for even a year. Now aquariums are
creating a fake ocean current that help jellyfish
jellyfish by Flickr user: baxterclaus
swim and survive. Recent discoveries show
that jellyfish have small sensory organs around
its bell. These eye spots detect light and some
scientist believe they can even detect odor.
Jellyfish communicate by means of biolumines-
cence. Jellyfish are found in oceans and seas
around the world, some even exist in rivers or
lakes. Jellyfish have adapted so that they can
survive in both salt water and fresh water. Jelly-
fish move by means of propulsion. As the bell
expands it collects water. When the jellyfish
squeezes this water out, it propels forward.
The only means of self defense that jellyfish are capable of are the tentacles that are located
around the outside of the bell. Each of the tentacles have stinging cells called cnidocytes located
all over the tentacle. Within each cnidocytes is a nematocyst. A nematocyst is a small structure
which contains the barb and filament. When a fish or other form of prey comes into contact with
the a small trigger on the cnidocytes the barb and filament is injected into the victim. The fila-
ment paralyzes the prey.
The group Cnidaria consist of other 9,000 species. The earliest fossil that resemble modern
Cnidarians was from possibly around 580 million years ago.
Importance to Humans
The jellyfish has many important uses among humans. Jellyfish have many bio-technical uses.
Mainly scientist study the green fluorescent protein along with other bioluminescent proteins.
These proteins give jellyfish the ability to glow and communicate. Scientist recently discovered
that the collagen that comes from jellyfish can help heal rhuematiod arthritis. Along with bio-
technical uses, the jellyfish also has many culinary uses. Jellyfish is a delicacy in many counties in
Oddballs that Exsist
It was recently discovered that the Box Jellyfish has 4 stomachs, 4 cluster of 6 eyes, and 4 brains.
Each brain competes for dominance. The Box Jellyfish can also propel through water. This abil-
ity, along with having so many eyes, enables the Box Jellyfish to have 360 degree vision.
Are Jellyﬁsh Going Extinct?
There are no jellyfish that have recently gone extinct; however, the Peach Blossom jellyfish is on
the threatened species list. Meaning they haven’t made it to the endangered species list yet.