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Class Scyphozoa
• “true” jellyfish
• medusa & polyp body forms
• thick mesoglea
Class Scyphozoa- life cycle
sperm
ephyra
strobila
egg
Adult medusa
scyphistoma
larva
Jellyfish Diversity
Jellyfish are a major ecological
significance of the plankton.
Found in all oceans and range
from the sea surface to the
abyss. There are about 200
species world wide.
Jellyfish Diversity
Semaeostomae Jellyfish-- the typical jellyfish:
corner of mouth drawn out into four broad gelatinous
frilly lobes.
Aurelia sp.
Cyanea capillata the
Giant Jellyfish or Lion's
Mane Jellyfish can grow
to be one of the largest
of all jellyfishes. Its
disc-shaped bell can be
over 1 meter across and
its trailing tentacles can
reach more than 10
meters in length.
Primitive jellyfish: Stauromedusae
Jellyfish Diversity
Primitive jellyfish: Stauromedusae;
small sessile individuals that develop
directly from benthic planula larvae.
Can change locations, but normally
attached with stalk and adhesive pad to
solid objects like kelp and rocks.
Rizostomae jellyfish: lack a central mouth,
instead they have many suctorial “mouths”
Cassiopea: a small tropical jellyfish is unusual among jellyfish.
It lies on the bottom in shallow waters, with its mouths and tentacles
oriented upwards. Its mouth is much reduced, and is not much used.
Instead, the jellyfish gets most of the nutrition it needs from
symbiotic dinoflagellates (protists) which live inside its body tissues.
Rhizostoma octopus
Class Cubozoa: Sea wasps and box jellyfish
About 3 dozen species almost all are tropical.
medusa & polyp
body forms
thick mesoglea
Unfrilled bell margin
drawn inward to
form a velum-like
structure.
velarial canals
The velarium is at least partly responsible for the great speeds
with which cubozoans are able to swim.
Velarial canals are extensions of the gut and they are important
in telling one species of cubozoan from another.
Manubrium: a tubular extension where the mouth is.
Cubozoan Sensory Structures
Sensory structures called rhopalia.
Cubozoan Sensory Structures
cubozoans have
eyes.
The larger regions
actually contain
lenses, corneas, and
retinas.
Nematocysts are
concentrated in rings
on the tentacles of
cubozoans.
Predominantly two species responsible
• The Box Jelly Chironex fleckeri
• Irukandji Carukia barnesi
The Box Jelly Chironex fleckeri
The Box Jelly Chironex fleckeri
Box Jelly Chironex fleckeri
• Box jellies or sea wasps are thought to be
responsible for about 65-100 deaths over the
past 50 years in Australia.
• The tentacles can be up to 10 feet long.
• In Australia twice as many people die annually
from box jellies as from sharks.
• The toxin of most cubomedusan jellies is more
potent than cobra venom.
Irukandji Carukia barnesi
Stings have been recorded from Australia, and a similar
syndrome has been described elsewhere in the Pacific.
Every summer, more than sixty people are hospitalized with
this potentially fatal syndrome.
Irukandji Carukia barnesi
• The initial sting of the jellyfish is usually not very
painful.
• But about 30 minutes after being stung, the person
starts to have a severe backache or headache and
shooting pains in their muscles, chest and abdomen.
• They may also feel nauseous, anxious, restless and
vomit. In rare cases, the victim suffers pulmonary
aedema (fluid on the lungs) which could be fatal if not
treated.
Cubozoan Life Cycle
• Some species of cubozoans appear to pair
up, male with female, in order to mate.
• The male puts his tentacles into the bell
of the female and appears to pass packets
of sperm. At least one species has been
observed in large mating aggregations.
Cubozoan Life Cycle
• Fertilization takes
place inside the
females. In some
species the fertilized
eggs are released into
the water column
where they develop
into planulae, while
in others
development into
planulae occurs
inside the female.
Cubozoan Life Cycle
• The polyps can move around, and they frequently
bud off additional polyps.
Cubozoan Life Cycle
• During metamorphosis, the
polyp tentacles are resorbed
and four new tentacles and
four rhopalia are formed.
With a couple of contractions,
the entire individual becomes
detached and swims away as a
juvenile medusa.
Class Anthozoa
• polyp body form ONLY
• all marine
Class Anthozoa
• some are colonial
 colonies are formed of individual
zooids
• some are solitary
Class Anthozoa- life cycle
Sexual reproduction
sperm
egg
larva
Class Anthozoa- life cycle
asexual reproduction
fission
pedal laceration
fission