﻿Jellyfish Explained #13. Jellyfish are the oldest multicellular
When people think about the oldest organisms ever, their minds typically drift towards dinosaurs.
However, there are several other organisms alive today that predate dinosaurs by many years.
Some of these organisms include sharks, sea turtles, and lobsters. As it turns out,
Jellyfishes may be the oldest multicellular organisms on the planet. This follows from a
discovery of jellyfish fossils found in rocks believed to be over 500 million years old.
Further research has shown that they may, in fact, be up to 700 million years old. This makes them
the oldest multi-organ animal group. #12. Jellyfish don’t have brains
The brain is one of the most important organs in the body of any complex organism. It is a key part
of the central nervous system, responsible for coordinating all other major systems
like the cardiac system, endocrine system, and digestive system. Most creatures can’t survive
when their brain is damaged. As it turns out, jellyfish don’t have brains at all. Neither
do they have hearts or lungs. External nervous stimulus is perceived by a thin layer of cells
within the skin. In addition, they have no blood and as such don’t need a heart to pump anything.
And lastly, they absorb oxygen from their skin and as such, don’t need lungs.
#11. Jellyfish can clone themselves When it comes to jellyfish, their
regenerative abilities are next level. If you split a jellyfish clean in half,
both halves can regenerate completely. And so, similar to cell division, two new creatures
will be created where there used to be one. It has been revealed though that the extent to which they
can regenerate depends on their diet. #10. Jellyfish are mostly composed of water
When it comes to the composition of jellyfish, there really isn’t much to them. Humans may
be composed of 70 percent of water, but for jellyfish, the figure is much higher. Jellyfish
are composed of between 85 percent to 98 percent water. And so, if a jellyfish washes up on a
beach, chances are, within hours, they will get completely dried up, leaving very little behind.
Remember, they are invertebrates that don’t have brains, hearts, or lungs. They do have some sort
of digestive system and an elementary nervous system. They have a single opening in their bodies
that acts as both a mouth and an anus. #9. Jellyfish can get as big as blue whales
There are over 200 species of jellyfish in existence. Although they have the same
general appearance, these species sometimes vary widely from each other in terms of size,
color, and so on. The largest jellyfish in the world is a lion’s mane jellyfish. They can
typically be found in the waters of the arctic. The largest ever specimen of this species was
discovered in Massachusetts had a bell with a diameter of 7 feet and tentacles around120 feet
long. This species can also grow up to 12,000 tentacles per individual. All these factors
combined make them as large as blue whales. #8. Some species of jellyfish are really venomous
Certain species of jellyfish have venom. This allows them to kill prey as well as
protect themselves from predators. One of the most dangerous species of jellyfish to exist
is the box jellyfish. The box jellyfish has venom which is so potent that it can kill 50
people. When human beings are stung, they usually die from shock or drowning before they can get
medical attention. Jellyfish kill 20 to 40 people a year in the Philippines alone. Vinegar can help
counteract the effects if the box jellyfish venom, but it isn’t effective for other species such as
the Portuguese Man O’ War. #7. Some jellyfish species are immortal
There are certain species of jellyfish that could live forever if they were not killed by predators
or interfered with by human beings. One of these species is known as Turritopsis dohrnii jellyfish.
The way the immortality of this species works is unique. It basically reverses its life cycle. You
see, when the Turritopsis dohrnii grows old, gets injured, or gets too hungry, it simply reverts
from its adult form to the baby form known as the “polyps”. From there, it clones itself,
becoming multiple jellyfish that are genetically identical to the first version. Therefore,
this is technically immortality and this jellyfish behaves kind of like the mythical phoenix.
#6. Jellyfish have traveled into space To prepare for mankind’s interstellar future,
space agencies such as NASA, ESA, and JAXA have been performing experiments with Earth
life in space for decades now. One of those such experiments, performed by NASA, happened when they
took a couple of jellyfish up in space in 1991. The goal of the experiment was to see if these
jellyfish could breed appropriately in space and determine if the results would apply to humans.
As it happened, the jellyfish were able to breed just fine. However,
when the newborn jellyfish were brought to Earth, they started to act strangely. And so,
this casts some doubts on whether humans could breed appropriately in space.
#5. Jellyfish reproduce quite rapidly Jellyfish are experiencing a population
boom. So much so that they are beginning to cause disruption and are making scientists
really worried. Their high population growth rate is mostly due to the fact that most of their
natural predators, such as turtles, sea birds, sharks, and whales, have declining populations.
Another reason is global warming. Since the oceans are getting warmer, acidic content is rising and
jellyfish are great at surviving in conditions of pollution. An example of the disruption their high
numbers cause can be seen from the power outage they caused in the Philippines after being sucked
in into a power plant’s cooling pipes. #4. Jellyfish are not really fish
This might come as a surprise to most people, given their name. However, jellyfish are
not really fish. This should be obvious from their appearance, as they look quite different
from most other organisms we call fish. In reality, jellyfish are classified as gelatinous
zooplankton. They belong to the phylum Cnidaria and are incredibly varied in their taxonomic group
that defining what they are is really difficult. Beyond some general and loose definitions,
different scientific communities argue about how to classify them.
Some scientists say that there are about 200,000 species of jellyfish yet to be discovered.
#3. The jellyfish lifecycle has two distinct stages
The lifecycle of a jellyfish has five main stages. However, two of those stages are quite visually
distinct from each other. The five main stages are Planula, Polyp, Strobila, Ephyra, and Medusa. Of
those five stages, the two which are most visually distinct from each other are the adult stage or
the medusa and the polyps or the young jellyfish. The medusa tends to look like a bell with several
tentacles attached. However, the polyps tends to look like sea anemones, with shorter tentacles
that flow up above the main body. Interestingly, both the polyps and the medusa can reproduce. The
medusa reproduces using eggs and sperm while the polyps reproduces by cloning itself.
#2. Some jellyfish have teeth One jellyfish species that is known
for having teeth is the beroid comb jellyfish. This unique species of jellyfish has hundreds of
rows of “teeth” made of tiny hairs that can pierce, tear and pull their prey into their
stomachs. This helps them digest their food quicker. When it comes to the jellyfish diet,
they are typically carnivorous. Sometimes, though, they are parasitic. They typically
feed on planktonic organisms, crustaceans, small fish, fish eggs and larvae,
and other jellyfish. #1. They are bioluminescent
It is estimated that over 50% of jellyfish species are bioluminescent. This means they have the
ability to emit brilliant displays of light from their tissues. Bioluminescence can have many uses,
depending on the organism. In some organisms, it’s used to attract prey. In other organisms, it’s
used to attract mates. However, where jellyfish are concerned bioluminescence is mostly used to
ward off predators and this manifests itself in different ways based on the species. For example,
jellyfish such as comb jellies produce bright flashes to startle a predator
and then make their escape. However, other species such as siphonophores can produce a chain of light
or release thousands of glowing particles into the water as a mimic of small plankton to confuse
the predator. And then, some other species can also produce glowing goo which they can stick to
predators so as to confuse them. …