lec 7 Flashcards
Eumetazoa who is in there
all animal phyla except Porifera
and Placozoa
what unites eumetazoa
(7)
- presence of true tissues derived from embryonic germ layers
- gap junctions- particular type of intercellular junction
- gonads- organs specialized for making games(ovaries for eggs and testes for sperm
- synaptic nervous system
- epithelium lined gut w digestive enzymes
- primary larva
7.presence of particular opsins
primary larva
ciliated larva bearing a
sensory apical organ
epithelium lined gut w digestive enzymes derived from
embryonic endoderm)
synaptic nervous system derived from
(derived from embryonic ectoderm
opsins
proteins that bind to
light-reactive chemicals
Phylum Cnidaria how many spcs marine and freshwaer
13,300 sps total
mostly marine’
100 freshwater
subphyla of cnidaria
Anthozoa-coral, sea anemone
Medusozoa- jellyfish
Endocnidozoa- morphologically reduced and completely parasitic
two main body forms of free living cnidaria
polyp benthic
medusa pelagic
how do some cnidarians species alternate bw life forms
polyp being for asexual reproduction
medusa for sexual
body axis for cnidaria
oral to aboral
symmetry for cnidaria
radially symmetrical: rarely perfect,
more often have 4-fold radial symmetry
cnidarian gut
gut has one opening: mouth only, no anus
what surrounds oral end of cnidarian
what is their function
tentacles
capture prey and transport food to mouth
water-filled branches or canals that go into different parts of the body
gastrovascular cavity
cnidarian tissues
and layers
true tissue level of organization- diploblastic
epidermis
mesoglea(not true)
gastrodermis
epidermis
outer, from embryonic ectoderm
gastrodermis
inner, from embryonic endoderm
mesoglea
middle layer mostly non-cellular and not a true tissue
do cnidaria have organs
yes
cnidocyte
-a synapomorphy of cnidaria
-derived from gastrodermal interstitial cells
-used for prey capture, defence, and movement to a lesser extent
organelle of cnidocyte
cnida
- capsule w sticky or harpoon like tube
-may contain toxins
what cool about cnidae structure
most complex intracellular structures of all metazoa
nematocysts
type of cnidae, has spines and toxins
where are nematocysts found?
all free living taxa
myoepithelial cell
epithelial cells w basal myofibrils
myoepithelial cell function
functions as skin and muscle
how are myofibrils aranged?
longitudinally in epidermis and circularly in gastrodermis
what acts as a hydrostatic skeleton
muscular contraction against the gastrovascular cavity
myoepithelial cell contraction
mouth open, longitudinal contract
H2O leaves gastrovascular cavity, total volume decrease
tentacle shortens and thickens
myoepithelial cell contraction
circular contract
H2O leaves gastrovascular cavity, total V decrease
tentacle lengthens and thins
Mouth closed, circ and longitudinal contract
-H2O doesnt leave, volume remains
therefore, hydrostatic skeleton
-tentacle stiffens, doesnt change much in diameter
what do nerve cells form in cnidaria
form loosley organized net rather than CNS–> no ganglia and no brainnski
two arrays of nerve net
,
epidermal and gastrodermal separated by mesoglea
planula larva
larva common to almost all
groups of Cnidaria
planula larva features
free-swimming, flattened, ciliated
bilaterally symmetrical
what does planula develop from
fertilized egg of a medusa
planulae of the subphylum Medusozoa
lecithotrophic
have no mouth or digestive tract–> do not eat
planulae of some Anthozoa can be lecithotrophic, others are
planktotrophy- eat smaller orgs
depending on the species, the planula either
1) swim till settling and transforms into a polyp
2) metamorphoses directly into a free-swimming, mini version of the adult
hydrozoa life cycle
medusa–>fert egg–> planula–> polyp–>medusa
actinula larva
tentacled larva develops from planula sometimes
Hydra life cyle weirdness
lacks both a medusa stage
and a planula larva
Class Scyphozoa- aurelia life cycle
scyphistoma buds off more polyps or ephyra
scyphistoma
polyp of aurelia
ephyra
budded off polyp or medusa
all anthozoans lack(life cycle)
a medusa stage
Endocnidozoa (Myxozoa) life cycle lacks
polyp or medusa
molecular data provides support for what hypothesis?
polyp-first
what data supports polyp first hypothesis?
anthozoans and endocnidozoans have ancestral state of circular mitochondrial DNA chromosome.
Medusozoa have a derived state of linear mtDNA
four synapomorphies for cnidaria
(1) polyp stage; (2) cnidae; (3) myoepithelial
cells; (4) planula larva
