Transcript Protozoa - Dr Magrann

MARINE
Invertebrates
BIOL 505
Understanding Marine
Invertebrates,
Their Environments
and Processes
The Protozoans = “first animals”
Unicellular eukaryotes.
Between animals and plants.
Lack collagen.
Lack chitinous cell walls.
Have different modes of existence:
some heterotrophic
some photosynthetic (although not in
primitive forms)
some detritivorous
some parasitic
The Protozoans
~38,000 extant spp. ~44,000 fossil spp.
Have wide range of sizes, shapes, ultrastructure,
nutrition, behavior, physiology, genetic diversity.
Of scientific and economic importance.
Many free-living forms – marine.
Most microscopic - ~5 – 20 um (but some new
spp 0.5 – 2um).
Since unicellular, each cell must do all basic
functions multi-cellular organisms do.
The Protozoans
Organelles, rather than cells, specialize to increase
complexity.
No specialized circulatory, respiratory or excretory
structures.
How is gas exchange and excretion accomplished?
Mainly across body wall due to high SA:V ratio.
Whole body has cell membrane (plasmolemma) –
same as multicellular cells.
Cytoplasm differentiated into ecto- and endoplasm.
The Protozoans
Organelles include nuclei, nucleoli, chromosomes,
Golgi, ER (smooth and rough), lysosomes,
centrioles, mt, and sometimes chloroplasts.
Some organelles not found in metazoan cells are:
contractile vacuoles – help regulate volume
trichocysts – serve in defense or anchoring.
toxicysts - serve in prey capture.
The Protozoans
Locomotion
Most protozoans move by:
1. using cilia
2. using flagella
3. using psuedopodia
Some spp use different forms at different life
history stages.
Protozoans
Protozoan Anatomy
Protozoans
Protozoan Anatomy
Protozoans
Protozoan Anatomy
Protozoans
Ciliophoran Ciliation
Individual cilia associated below cell membrane with
other cilia through infraciliature.
Kinetodesmos – striated fibers extending from each
kinetosome (basal body of cilia).
The Kinetodesmata – cord of fibers running along side
each row of basal bodies.
This infraciliature is not only found in Ciliophora, but
also in all adult ciliates, even if adults lack external cilia.
Structure of infraciliature is a primary tool in identifying
different ciliate spp.
Protozoans
Ciliophoran Ciliation
membranelles
marginal
cirrus
Cilia usually cover entire body of
some spp., but modified or reduced in
others.
In some spp. cilia form specific
organelles.
Undulating membrane – a flat sheet
of cilia that moves as a single unit.
Membranelle – small number of cilia
in neighboring rows lean toward each
other making a 2-D pointed tooth.
Oxyticha marcili
Protozoans
membranelles
Ciliophoran Ciliation
marginal
cirrus
Cirrus – cilia gather together to form a
bundle, pointed at tip.
Cytostome – oral opening, has specific
arrangement and ultrastructure of cilia
for different spp.
Cillia that form structures are same as
other cilia with no permanent
attachment between them. No known
mechanisms of association of cilia.
Oxyticha marcili
Protozoans
Ciliophoran Ciliation
Pellicle - complex series of membranes often covering
body. May be rigid or flexible. May be for support in
some spp. Trichocysts often associated with it.
Plasmalemma – outer surface of the body membrane.
Alveoli – series of
flattened vesicles
beneath plasmalemma.
Cilia project to outside
from between alveoli.
Paramecium
tetraurelia
Protozoans
Ciliophoran Reproduction
All ciliates have one or more
macronuclei (less abundant) and
one or more micronuclei (more
abundant).
Thus nuclei are dimorphic (and
thus, heterokaryotic).
Macronuclei – polyploid
(contains DNA and RNA), is
involved with differentiation,
regeneration and daily activities
of cell. No role in sexual repro.
Protozoans
Ciliophoran Reproduction
Micronuclei – critical for sexual
repro., but not involved with
daily activities.
Sex repro in ciliates does not
involve gamete formation
(why?).
Instead involves process of
conjugation, in which 2
individuals exchange genetic
material through a conjugation
tube.
Protozoans
Ciliophoran Reproduction
Conjugation Steps (Sexual Reproduction)
1. Macronuclei disintegrate.
2. Diploid micronuclei divide by meiosis  4 haploid
pronuclei form from each micronuclei.
3. All but one pronuclei break down. Remaining
undergoes mitosis  2 identical haploid pronuclei.
4. One of these migrates through conjugation tube to
other individual.
5. Migratory pronuclei fuses with stationary pronuclei to
form 2N synkaryon.
Protozoans
Ciliophoran Reproduction
Conjugation Steps (Sexual Reproduction)
6. Conjugates separate and synkaryon of each conjugate
divides several times by mitosis.
7. Some products form micronuclei, others form
macronuclei.
8. Cytoplasmic division may follow  several
individuals genetically distinct from parents.
Protozoans
Ciliophoran Reproduction
Protozoans
Ciliophoran Reproduction
Autogamy (Special Case of INDIVIDUAL Sexual
Reproduction)
1. Much like the first stages of conjugation.
2. Macronuclei degenerate.
3. Micronuclei undergo meiosis  pronuclei.
4. Meiosis followed by several mitotic divisions of
pronuclei.
5. Two pronuclei form synkaryon and remaining
products disintegrate.
Protozoans
Ciliophoran Reproduction
Autogamy (Special Case of INDIVIDUAL Sexual
Reproduction)
6. Synkaryon divides several times by mitosis.
7. Some products form micronuclei, others form
macronuclei.
8. Cytoplasmic division may follow  several
individuals genetically distinct from parents.
Protozoans
Ciliophoran Reproduction
Binary Fission Steps (Asexual
Reproduction)
1. Micronuclei divide by mitosis and
redistribute through cytoplasm.
2. Macronuclei elongate but don’t
undergo mitosis.
3. Macronuclei develops cleavage
furrow and divides.
Protozoans
Ciliophoran Reproduction
Binary Fission Steps (Asexual Reproduction)
4. Cell develops cleavage furrow. If
perpendicular to long axis – transverse
binary fission. Divides into anterior and
posterior halves. If longitudinal (as in other
protozoans) – binary fission.
5. Each half must develop the opposite section
lost during division.
6. Unicellular individuals “daughter cells”
genetically identical and mirror images of
each other.
WHAT HAVE YOU
LEARNED TODAY?
Protozoans
Protozoan Diversity
Phylum Dinozoa (Dinoflagellata).
~2500 extant spp.
Occur in both freshwater and marine habitats.
All dinoflagellates have two flagella. One in a
longitudinal groove (sulcus) and the other in a transverse
groove (girdle or cingulum) around the body.
Position and orientation of grooves is spp specific and
used for ID.
Protozoans
Protozoan Diversity
Orientation of flagella cause the organism to whirl in
distinctive movement patterns.
Individual covered by cellulose plates secreted within
alveolar sacs just beneath cell membrane.
Protozoans
Protozoan Diversity
Phylum Dinozoa (Dinoflagellata).
Protozoans
Protozoan Diversity
Phylum Dinozoa (Dinoflagellata).
Most are bioluminescent.
Many are known to produce highly toxic “red tides”
that cause dense aggregations of dinoflagellates that
produce neurotoxins (saxitoxins and relatives) that kill
fish, crustaceans and bioaccumulate in clams, oysters,
mussels and cause diarrhetic shellfish poisoning.
Ciguatera poisoning – neurotoxin that accumulates in
certain tropical fish. Can kill people that eat the fish, but
fish unaffected by toxin.
Protozoans
Protozoan Diversity
Pfiesteria piscicida – dinoflagellate
responsible for massive fish kills in
estuaries.
Protozoans
Protozoan Diversity
Phylum Dinozoa (Dinoflagellata).
About half of all dinoflagellates have chlorophyll and
are autotrophs.
Some are important symbionts with some forams, and
various multicellular invertebrates, such as ???. These
are called zooxanthellae and are mainly from the genus
Symnodinium.
Zooxannthellae greatly contribute to the nutritional
needs of the host.
Protozoans
Protozoan Diversity
Some lack chlorophyll and are only
heterotrophic, but are bioluminescent –
Noctiluca = “night light”. Ingests
particulate matter through phagocytosis.
Some are parasitic on invertebrates,
vertebrates and other protozoans.
Noctiluca
Protozoans
Protozoan Diversity
Phylum Granuloreticulosa; Class Foraminiferans.
Pseudopodia form granular reticulopods with bidirectional streaming.
Reticulopodia form intricate, intercommunicating
networks.
Forams comprise the test-forming spp. and are among
most abundant protozoans in marine systems.
Secrete multi-chambered tests usually made of CaCO3.
Reticulopodia emerge through pores in test and form
branched networks. (Fig. 3.28g
Protozoans
Protozoan Diversity
Of the 4,000 extant spp. About 40 are planktonic. The
rest are benthic.
No parasitic spp. Although are hosts to symbiotic algae.
Most are heterotrophic feeding on other protists, small
metazoans, fungi, bacteria and detritus.
Manys spp. Found in fossil record. Some up to 15 cm
diameter.
Fossil forams usually good indication of oil deposits.
Protozoans
Protozoan Diversity
Phylum Granuloreticulosa; Class Foraminiferans.
Bolivina subaenariensis – planktonic
foraminifera approximately 1mm long.
Polystomella strigillata
Protozoans
Protozoan Diversity
Phylum Granuloreticulosa; Class Foraminiferans.
Protozoans
Protozoan Diversity
Phylum Radiozoa (Radiolarians).
Body divided into distinct intra- and extra capsular
zones separated by a perforated membrane or capsule.
Have pseudopodia supported by radiating microtubules axopodia. Give a spiny appearance to most spp.
Have rigid endoskeletons made of silica.
Many representatives in fossil record due to siliceous
test; approx. 7,700 of ~11,000 described spp.
All radiolarians are planktonic.
Protozoans
Protozoan Diversity
Many spp. Have symbiotic algae and thus meet some
nutrition needs through photosynthesis. But also are
carnivorous spp. that use axopodia to capture
microscopic prey.
Body plan is generally spherical and divided into intra –
and extracapsular zones by a perforated membrane, or
capsule.
Digestion occur in food vacuoles in extracapsular
region. Nucleus contained in intracapsular region.
Protozoans
Protozoan Diversity
Phylum Radiozoa (Radiolarians).
WHAT HAVE YOU
LEARNED TODAY?