The Fascinating Upside-Down Jellyfish: Cassiopea sp.
The Upside-down
Jellyfish
Cassiopea sp.
Phylum Cnideria
Class Scyphozoa
The upside-down jellyfish belongs to order
Scyphozoa, the “true jellyfish”.
As most Scyphozoan jellyfish do, the upside-down
jellyfish has two life phases: the medusa form and
the bottom-dwelling polyp form.
Scyphozoans exhibit both asexual and sexual
reproduction; usually asexual as a polyp through
budding or strobilation, and sexual as a medusa
with gametes.
Order Rhizostomeae
The upside-down jellyfish belongs to order
Rhizostomeae.
The jellyfish in this order, unlike others in Class
Scyphozoa, have no tentacles of structures on the
edges of their bell, but have 4 to 8 highly branched
oral arms.
It is also common for the organisms in this order to
have multiple mouths, one primary and many
secondary, often distributed all along the oral arms.
Common Name
The common name for
Cassiopea sp., the Upside-
down jellyfish, comes from
their tendencies to settle
upside-down on the ocean
floor in shallow, muddy
water.
They are also sometimes
called Mangrove jellyfish
because they are often
found in mangroves.
The upside-down
jellyfish doesn
’
t look
like a typical
Scyphozoan jellyfish,
but more like an
Anthozoan, like a sea
anemone. This
appearance is
beneficial to the
jellyfishes survival.
The upside-
down jellyfish
release their
stinging cells in
a layer of
mucus that
floats in the
water. Their
sting is not
harmful to
humans but
can cause an
itchy rash.
Like most jellyfish, the upside-down jellyfish hunts for food and
wards off predators using stinging cells (nematocysts). These
nematocysts are used to feed on plankton and zooplankton.
These jellyfish also
have multiple
mouths. They have a
primary mouth and
then many
secondary mouths
(up to 40) located on
their arms to quickly
capture and eat
food.
The upside-down
jellyfish is a filter
feeder and they use
pulsations of their
bell to bring in
planktonic food.
In addition to their nematocysts, the upside-down jellyfish gets
most of its nutrition from its symbiotic relationship with
photosynthesizing zooxanthellae that are housed in the bell of the
jellyfish. This is why these jellyfish spend their time upside-down
on the bottom of the ocean soaking up sunlight for their
photosynthesizing golden algae. They aren’t born with the
symbiotic algae, but rather they acquire it infectiously.
Life Cycle
Sexual Reproduction: The
upside-down jellyfish starts
its life out as a free
swimming planula larvae,
which they remain until they
are about 2 cm. Then they
invert their bell and land
upside-down on the ocean
floor in shallow water.
Like most jellyfish, they
alternate between polyp and
medusa stages. In the polyp
stage new jellyfish can be
produced asexually through
budding and strobilation.
The upside-down
jellyfish share a
relationship with
a family of crabs
called
Dorippidae. The
crabs will put the
jellyfish onto
their back and
carry it around
for protection
from predators
although the
jellyfish doesn
’
t
seem to get
anything out of
it.
Phylum Cnideria
Class Hydrozoa
Some Hydrozoans are solitary and some
are colonial. Colonial Hydrozoans can get
to be very large and sometimes the
specialized individuals in the colony
cannot survive outside of the colony.
The Portuguese man of war (
Physalia
physalis
) is an example of a colonial
Hydrozoan
Order Siphonophorae
The Portuguese man-of-war
belongs to Order
Siphonophorae.
Siphonophores are colonial
Hydrozoans and are
generally long, thin,
transparent pelagic floaters.
Some Siphonophores, like
the Portuguese man-of-war,
resemble Scyphozoan
jellyfish.
Each zooid that makes up
the organism is an
individual, but they are so
strongly integrated that they
cannot live on their own.
Some Siphonophores can
emit light
Physalia Physalis
Portuguese man-of-war
The Portuguese man of
war lives at the surface
of the ocean. They float
using their gas-filled
pneumatophore and
the remainder of the
organism is
submerged.
Portuguese man of war
are usually found in
more tropical waters
Portuguese man of
war are composed of
four different types of
polyp.
The pneumatophore
Dactylozooid
(stinging/feeding)
Gonozooid
(reproductive)
Gastrozooid (feeding)

Exploring the unique characteristics of the upside-down jellyfish, Cassiopea sp., which belongs to the order Rhizostomeae within the class Scyphozoa. Often found in mangroves, these jellyfish exhibit a distinctive appearance resembling sea anemones. Despite their atypical traits for a Scyphozoan jellyfish, they thrive using stinging cells to hunt for food. Their symbiotic relationship with zooxanthellae provides vital nutrition, showcasing their remarkable adaptation strategies for survival.
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Presentation Transcript
The Upside-down Jellyfish Cassiopea sp.
Phylum Cnideria Class Scyphozoa The upside-down jellyfish belongs to order Scyphozoa, the true jellyfish . As most Scyphozoan jellyfish do, the upside-down jellyfish has two life phases: the medusa form and the bottom-dwelling polyp form. Scyphozoans exhibit both asexual and sexual reproduction; usually asexual as a polyp through budding or strobilation, and sexual as a medusa with gametes.
Order Rhizostomeae The upside-down jellyfish belongs to order Rhizostomeae. The jellyfish in this order, unlike others in Class Scyphozoa, have no tentacles of structures on the edges of their bell, but have 4 to 8 highly branched oral arms. It is also common for the organisms in this order to have multiple mouths, one primary and many secondary, often distributed all along the oral arms.
Common Name The common name for Cassiopea sp., the Upside- down jellyfish, comes from their tendencies to settle upside-down on the ocean floor in shallow, muddy water. They are also sometimes called Mangrove jellyfish because they are often found in mangroves.
The upside-down jellyfish doesn t look like a typical Scyphozoan jellyfish, but more like an Anthozoan, like a sea anemone. This appearance is beneficial to the jellyfishes survival.
Like most jellyfish, the upside-down jellyfish hunts for food and wards off predators using stinging cells (nematocysts). These nematocysts are used to feed on plankton and zooplankton. The upside- down jellyfish release their stinging cells in a layer of mucus that floats in the water. Their sting is not harmful to humans but can cause an itchy rash.
These jellyfish also have multiple mouths. They have a primary mouth and then many secondary mouths (up to 40) located on their arms to quickly capture and eat food. The upside-down jellyfish is a filter feeder and they use pulsations of their bell to bring in planktonic food.
In addition to their nematocysts, the upside-down jellyfish gets most of its nutrition from its symbiotic relationship with photosynthesizing zooxanthellae that are housed in the bell of the jellyfish. This is why these jellyfish spend their time upside-down on the bottom of the ocean soaking up sunlight for their photosynthesizing golden algae. They aren t born with the symbiotic algae, but rather they acquire it infectiously.
Life Cycle Sexual Reproduction: The upside-down jellyfish starts its life out as a free swimming planula larvae, which they remain until they are about 2 cm. Then they invert their bell and land upside-down on the ocean floor in shallow water. Like most jellyfish, they alternate between polyp and medusa stages. In the polyp stage new jellyfish can be produced asexually through budding and strobilation.
The upside-down jellyfish share a relationship with a family of crabs called Dorippidae. The crabs will put the jellyfish onto their back and carry it around for protection from predators although the jellyfish doesn t seem to get anything out of it.
Phylum Cnideria Class Hydrozoa Some Hydrozoans are solitary and some are colonial. Colonial Hydrozoans can get to be very large and sometimes the specialized individuals in the colony cannot survive outside of the colony. The Portuguese man of war (Physalia physalis) is an example of a colonial Hydrozoan
Order Siphonophorae The Portuguese man-of-war belongs to Order Siphonophorae. Siphonophores are colonial Hydrozoans and are generally long, thin, transparent pelagic floaters. Some Siphonophores, like the Portuguese man-of-war, resemble Scyphozoan jellyfish. Each zooid that makes up the organism is an individual, but they are so strongly integrated that they cannot live on their own. Some Siphonophores can emit light
Physalia Physalis Portuguese man-of-war The Portuguese man of war lives at the surface of the ocean. They float using their gas-filled pneumatophore and the remainder of the organism is submerged. Portuguese man of war are composed of four different types of polyp. The pneumatophore Dactylozooid (stinging/feeding) Gonozooid (reproductive) Gastrozooid (feeding) Portuguese man of war are usually found in more tropical waters
