Phylum ctenophora Flashcards
adhesive cells
colloblast
8 rows of comb like plates
ctenes
clade bilateria
all exhibit primary bilateral symmetry
also see cephalization
Why do we see cephalization in bilateria?
more active lifestyle requires a different form
all are triploblastic
Nervous system (platyhelminth)
- cephalization but vary in complexity
- most simple is subepidermal nerve net plexus (seen in some Turbellarians)
- others additionally have 1-5 pairs of
longitudinal nerve cords (“ladder”) - “brain” – mass of ganglion cells
- differentiation of neurons into types
Sense organs ? (platyhelminth)
- abundant tactile & chemoreceptive cells
- form organs (auricles ) in planarians
- statocysts for equilibrium
- eyespots ( ocelli ) in some members
Nutrition & digestion
- mouth, intestine & pharynx (muscular & protruding in turbellarians)
- extracellular digestion via intestinal secretions
- intracellular digestion after phagocytosis by intestinal cells
- undigested food expelled via pharynx( blind gut)
rhabdites
form protective mucous sheath
eyespots
ocelli
from organs in planarians
auricles
Excretion & osmoregulation( platyhelminthes )
- canals with tubules ending in flame cells (protonephridia)
- flagella beat to create negative pressure to draw in fluid
- collecting ducts open to outside via pores
- metabolic waste removed via diffusion through body wall
Reproduction
- many via asexual and sexual means
-asexual reproduction can be via regeneration
-parent constricts in middle
-each half generates missing end
-parasitic flukes reproduce asexually in
mollusc intermediate host
also sexual reproduction - cross fertilization even though monoecious (hermaphroditic)
protonephridia
canals with tubules ending in flame cells.
hermaphroditic
cross-fertilization even though monoecious
clamp using hooked attachment organs called
opisthaptor
proglottids
long flat bodies of repeating segments for tapeworms
scolex
something for attaching to host (tapeworms)
strobila
body for tapeworms
Locomotion of Phylum Nemertea
circular & longitudinal muscle
usually glide over slime track
Feeding & digestion of Phylum Nemertea
- seize prey with proboscis contained within rhyncocoel
- cavity entirely within mesoderm – true coelomate
- eversion exposes sharp barb (stylet) that stabs & injects neurotoxins
- esophagus thrust through mouth to engulf prey
- digestive tract is complete (mouth & anus)
- cilia move food through intestine
Circulation & excretion of Phylum Nemertea
- have a true circulatory system with blood
- vessels contract to keep up flow
- flame-bulb protonephridia are associated
- true excretion vs. osmoregulation
Sensory of Phylum Nemertea
Pair of nerve ganglia & longitudinal nerve cords connected by transverse nerves
Reproduction of Phylum Nemertea
some asexually by fragmentation & regeneration
- others sexually
- most are dioecious
