Ch 6-7: Phylum Cnidaria Flashcards
how many epithelial layers do cnidarians have?
2: outer epidermus and inner gastrodermus/endodermus - diploblastic
what do the cells in the epithelia do? (5)
- communication
- movement
- digestion
- internal transport
- reproduction
what is the connective tissue in cnidaria?
jellylike mesoglea
do cnidarians have distinct muscle and nervous tissue?
some do
what type of symmetry do cnidarians have?
superficially, radial
- aboral and oral sides
what are the two types of body forms cnidarians have?
- polyp
2. medusa
are clonal colonies of medusae and polyps common?
yes
polyp properties (2)
- asexual
- benthic
medusa properties (2)
- sexual
- free-swimming
what type of larva do they have?
planktonic (planula)
what does cnidarians gv cavity allow for?
more extracellular digestion
type of diet
carniverous
what do their tentacles do? (2)
catch food and defend
what do cnidocytes contain?
nematocysts (triggered bags of dischargeable threads)
do cnidarians have a brain?
no; may have ganglia
what do the light sensitive cells on their epithelium do? (2)
- gather info
- send out commands
where are cnidarians statosysts located?
btwn tentacle bases
what is the primary function of bell pulsation?
food collection
how do cnidarians respire and excrete?
diffusion
4 anthozoan features
- no medusa stage
- thick mesoglea with many cells
- gv cavity divided by septa/mesenteries
- have siphonoglyphs
anthozoan symmetry
bilateral
how do anthozoans cnidocytes differ from those of other cnidarians?
no operculum and no trigger
hexacorallia features (4)
- many tentacles
- 6 mesenteries
- 2 siphonoglyphs
- some colonial
octacorallia features (4)
- tentacles in groups of 8
- 8 primary mesenteries
- 1 siphonoglyph
- almost all colonial
4 features of actiniaria (sea anenomes)
- use muscles and internal water as hydrostatic skeleton
- can change shape
- move via basal disc crawl
- some ‘swim’
how do actiniaria asexually repro?
can cleave in half
how do actiniaria sexually repro? (4 steps)
- gonads along mesenteries prod gametes
- gametes ejected thru mouth
- planula larvae
- settle and turn into polyp
acrorhagi
bulges of body wall w/ many nematocysts
what is the function of acrorhagi?
territorial fights
Scleractinia features (3)
- colonial
- CaCo3 skeleton surrounds each polyp and extends along mesenteries
- some spp combine to form reefs, some are solitary
- mostly in shallow, clear, tropical water
how do corals eat?
- hunt at night
- prod mucus to help prey capture
- some purely carnivorous deepwater corals
- 90% of food prod by zooxanthellae
how are zooxanthellae acquired?
taken into vesicles via phagocytosis; can be expelled/lost (bleaching)
3 features of Octocorallia
- use chemicals to poison/discourage predators
- tentacles have tiny side-branches (pinnules)
- tolerant of enviro extremes than stony corals
what are Gorgonacea (sea plumes, fans, whips) skeleton made of?
protein; spicles of CaCO3
3 features of Pennatulacea (sea pens)
- colonies of different, specialized polyps
- CaCO3 spicules give support and colour
- usually in deeper water
polyp formation and function
- one polyp forms a central stalk and a root-like penduncle, other form side branches
- others collect food and carry nematosysts
3 ways sea pens can defend themselves?
- taste bad
- can withdraw into penduncle
- bioluminescence
what is unique about medusazoan DNA?
linear mitochondrial DNA
5 defining features of Scyphozoa
- thick mesoglea that may contain cells
- medusa most obvious part of life cycle
- medusa may have 4 mouth lobes as well as tentacles that contain nematocysts and extensions of the gv cavity
- 2 neuron networks; one for swimming, one for everything else
- special sensory organs called rhopalia along bell margin
what type of symmetry to scyphozoa have?
bilateral
what 3 things do rhopalia contain?
- statosysts
- ocelli
- chemosensory cells
5 features if Cubozoa
- 4 tentacles/clusters of them
- reduced bell opening for extra propulsion
- well-developed nerve net
- well-developed rhopalia
- potent nematocysts
what type of symmetry do Cubozoa have?
bilateral
where are Cubozoa most common?
near shore
Cubozoan eyes
- up to 6 eyes per rhopalium
- 4 have a lens and can form images
- may help avoid large obstacles
in their life history, what do Cubozoans NOT have?
strobilization
5 features of Staurozoa
- polyps have a stalk, bearing a 4 sided calyx
- 1-4cm
- no medusa stage
- attach to rocks, seaweed
- known as fossils
how many sets of tentacles to Staurozoa have?
8
where are Staurozoa most common?
- cold northern seas
- near shore
4 stages of annual life cycle
- m/f release eggs into water
- eggs sink to bottom
- larvae crawl along bottom
- metamorphose into polyp
4 features of Class Hydrozoa
- thin mesoglea with no cells
- alternate btwn polyp and hydromedusa
- mostly small
- most morphologically diverse class
Gonionemus features (2)
- hydromedusa most commonly seen
- nerve net and nerve ring at bell margin
life cycle of Gonionemus (5)
- separate sexes perform open fert
- planula larva
- settles to the bottom
- grows tentacles and mouth and becomes polyp
- budding forms more polyps or hydromedusae
what is unique about Turritopsis?
does not die after sexual repro - can turn back into polyps
7 unique features of Hydra
- adapted to freshwater
- no hydromedusa stage
- no statocysts
- can retract into a blob
- has stretch receptors
- somatosensory cells on basal disc and tentacles
- can move towards light
what are 3 ways Hydra can move?
- basal disc crawl
- somersaulting
- detaching and being carried by the current
how do Hydra asexually repro?
when they are well fed, they bud new polyps
how do Hydra sexually repro?
polyps prod free-swimming sperm but hold onto their eggs
- release a gastrula that ‘hatches’ into a polyp
which stages are usually present in colonial Hydroids?
polyp and hydromedusa stages
how are new polyps produced?
via budding
- stay attached to become the colony
- called zooids
zooid specialization (2)
- gastrozooids eat
- gonozooids prod hydromedusae for sexual repro
colonial structure of Hydroids
- share gv and food
- zooids connected by stalk
- colony is rooted by a stolon
- stalks and stolons encased by common perisac
what is a perisac made of?
polysaccharides and proteins
Siphonofore characteristics (2)
- colonies of polyps and medusae
- medusae may jet propel the colony or may act as sails
3 types of zooids in Portuguese man of war polyps
- gastrozooids
- gonozooids
- dactylozooids
Port man of war tentacles length
up to 20m
Myxozoa characteristics (3)
- much reduced body complexity
- parasites of fish and annelids
- consist of only a few cells
