Cnidaria Flashcards
Cnidaria are part of what domain?
Eumetazoa
what are the unique features?
cellular differentiation is elaborate with the formation of muscle cells, nerve cells and sensory cells
defining characteristic of Cnidarians?
- secretion of complex intracellular organelles called cnidae (nematocysts)
- planula larva in the life cycle
how many species of Cnidaria?
10,000 species (only some FW, all marine
What is their reproductive process?
forming colonies by asexual reproduction
define dimorphic?
two different adult morphologies during lifecycle = polyp and medusa
3 things all Cnidarians have?
- radial symmetry (oral/aboral)
- only 2 layers of living tissue (epidermis and gastrodermis) with non living mesoglea = diploblastic
- tentacles surrounding mouth - single opening to digestive system
where does waste come out?
mounth - they have an incomplete digestive system - lacking an anus
define Cnidae
- nettle / stinging thread,
protein capsule with opening (operculum) + coiled tube. secreted by golgi apparatus in a cnidoblast
chemical/ tactle stimulation.
how do Nematocysts attack?
pierce, wrap or stick to prey
as food collection, defence, locomotion,
fires once
Cnidarians are carnivorous true or false?
true but they do feed on Phytoplankton with symbiotic algae (corals)
do Cnidarians have gills?
no
after fertilisation what is created?
planula larvae
what are the simple characteristics of phylum Cnidaria
no head
2 cell layer
tissues but very few
no organs
no brain
no seperate muscles
what are the 4 classes of Cnidaria?
- Hydrozoa
- Anthozoa
- Scyphozoa
- Cubozoa
define Class Hydrozoa
polyp + medusa (with velum)
define class Anthozoa
polyps with mesentries . no medusa
define class Scyphozoa
medusa dominant (no velum) transient polyp
define class Cubozoa
medusa with 4 sides + velum - tiny polyp
what is a free floating hydrozoan colonie withere medusa and polyps are present simultaneously?
class Hydrozoa, Order Siphonophora
what is a Hydrocoral?
a small number of colonal species that secrete a calcareous skeleton. mainly in warm waters “fire coral” = dactylozooids
define the characteristics of the Class Anthozoa
absense of a medusa, absense of operculum and cnidocil, circular mtDNA rather than linear , presence of ciliated grooves (siphonoglyph) in the pharyngeal wall leading from the mouth
coelenteron partitioned by distinct sheets of tissue (mesentries/septa)
how many species of Anthozoa?
6000 - all marine
what are the species of Anthozoa?
sea anenomes, sea fans, corals , sea pens
how does a sea anenome eat?
nematocysts/ tentacles for capture
what is Acrorhagi
appendages under the tentacles for defence = very potent nemotocysts
Class Anthozoa has two sub classes, what are they?
- Zoantharia (Hexacorallia) = sea anenomes. hard coral
- Alcyonaria (octocorallia) = sea fans, soft corals, seapens
define Zoantharia characteristics
numurous tentacles around mouth (usually in multiples of six) and 6 pairs of primary mesentries . 1 pair siphonoglyphs
define Alcyonaria characteristics
8 tentacles around mouth and 8 pairs of primary mesentries, genrally single siphonoglyph
reef building corals are:
hermatypic scleractinian corals
non-reef building corals are
Ahermatypic
hermatypic corals can live in water less than 18 degrees true or false?
false. water must be over 18
loss of Zooxanthellae causes
coral bleaching - caused by prolonged temperature change and increased UV
defining characteristic of Scyphozoa - jellyfish
asexual reproduction by strobiliation, a few hundred species, all marine, can get up to 2m across, medusoid body
what are the three sensory receptors in jellyfish?
- Statocysts (balance,
- ocelli ( light)
- lappets (touch)
what is a statocyst?
each rhopalia adjacent to a sensory cilia - each tube weighted with statolith.
what is a rhopalium (a)?
houses the sensory structures
how do the sensory structures work?
when the jelly is upright everything is hanging downwards, when the medusae tilts -> statocyst presses against cilia -> nerve generate action potentials -> orientation occurs
what does an ocellus detect?
only light, not real images
are polyps ight sensitive?
no, they have no ocelli
define Cubozoa
medusa with box like body
rhopalia bear complex lensed eyes.
how long can the tentacles of a box jelly be?
30cm - waspsting
can kill a human in 3 minutes
what is an Irukandji?
Carukia barnesi - small 2.5cm jelly with a venom neurotoxin similar to funnel web spiders and scorpion
Cubozoa have pupils true or flase?
true but severaly under focused
what is the defining characteristics of Ctenophora?
- plates f fused cilia arranged in rows
- adhesive prey capturing cells (colloblasts)
how many species of Ctenophores are there?
100 - all marine and most planktonic
distinguishing feature of a ctenophore?
their comb “ctenes” in rows , they beat simultaneously and can give off bright colours
and colloblasts (sticky structures that capture food)
