Lecture 12 Amoebae
Amoebae
One macronucleus
Most are aerobic
Most are heterotrophic
Some mixotrophic
Asexual reproduction only
No specific fission plane
Some move, some are stationary
Most publicised protozoan
Naked amoebae
Amoeba proteus
Move by cytoplasmic streaming
Produce pseudopodia on surfaces
Feed by direct inception of prey
Raptorial feeding
No specific location for ingestion - can be anywhere
3 cell forms
Trophozoites - the feeding form
Cysts - all produce a resting
stage
Floating form - stiffened
pseudopodia for dispersal
Lecture 12 Amoebae 1
, Shelled amoebae
enclosed in a shell (’test’)
Shell can be made of anything
Intrashellular cytoplasm with in test
Projet extrashellular cytoplasm to move and/or feed
Raptorial or diffusion feeding
can produce cysts
Testate amoebae
freshwater, marine and terrestrial
Raptorial feeding
Foraminiferans
marine only
CaCO3 tests
diffusion feeding
Diffusion feeding
stationary predator captures prey with sticky extrashellular cytoplasm
(’axopodia’)
Radiolarians
marine only
Silica tests
Diffusion feeding
Heliozoans
Freshwater
Silica tests
Diffusion feeding
Ecological impacts
Lecture 12 Amoebae 2
, In the environment - they are everywhere
good = all of the protists
microbes: base of every food chain
keep bacterial populations healthy
Important in nutrient cycling
Bad = mainly amoebae
Allow evolution of new bacterial pathogens
Act as a ‘reservoir’ for them too
Predation stops bacteria reaching stationary phase
predation keeps bacteria in log
phase: bacteria are constantly
feeding and declining so they are
constantly active
Lecture 12 Amoebae 3
, Bad ecological impact - evolution of pathogens
Lecture 12 Amoebae 4
Amoebae
One macronucleus
Most are aerobic
Most are heterotrophic
Some mixotrophic
Asexual reproduction only
No specific fission plane
Some move, some are stationary
Most publicised protozoan
Naked amoebae
Amoeba proteus
Move by cytoplasmic streaming
Produce pseudopodia on surfaces
Feed by direct inception of prey
Raptorial feeding
No specific location for ingestion - can be anywhere
3 cell forms
Trophozoites - the feeding form
Cysts - all produce a resting
stage
Floating form - stiffened
pseudopodia for dispersal
Lecture 12 Amoebae 1
, Shelled amoebae
enclosed in a shell (’test’)
Shell can be made of anything
Intrashellular cytoplasm with in test
Projet extrashellular cytoplasm to move and/or feed
Raptorial or diffusion feeding
can produce cysts
Testate amoebae
freshwater, marine and terrestrial
Raptorial feeding
Foraminiferans
marine only
CaCO3 tests
diffusion feeding
Diffusion feeding
stationary predator captures prey with sticky extrashellular cytoplasm
(’axopodia’)
Radiolarians
marine only
Silica tests
Diffusion feeding
Heliozoans
Freshwater
Silica tests
Diffusion feeding
Ecological impacts
Lecture 12 Amoebae 2
, In the environment - they are everywhere
good = all of the protists
microbes: base of every food chain
keep bacterial populations healthy
Important in nutrient cycling
Bad = mainly amoebae
Allow evolution of new bacterial pathogens
Act as a ‘reservoir’ for them too
Predation stops bacteria reaching stationary phase
predation keeps bacteria in log
phase: bacteria are constantly
feeding and declining so they are
constantly active
Lecture 12 Amoebae 3
, Bad ecological impact - evolution of pathogens
Lecture 12 Amoebae 4
