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Emotions
are one of the things that make humans so complex.
Memories
attached to associations, stimulated by
individualized
brain chemistry makes it so you can’t predict
how
any one person might feel about a particular stimulus.
But
perhaps we are not so complex. A new study suggests that
there
are really only four human emotions, happy, sad, afraid,
and
mad. The other two commonly held states, disgusted and
surprised
are just sides of mad and afraid, respectively. Read
the
study and feel…… something.
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Indeed, this makes us complex and hard to understand,
especially when we mumble. But on the other hand, wouldn’t it be more amazing
if an organism could do complex things without
the benefit of all that organization and without all those trillions of cells
doing different jobs?
What if an organism did many complex things but was only
made of one cell? I think this blog has shown on many occasions that bacteria
are capable of some pretty astounding feats, and they don’t even have a
nucleus! True, they don’t have structures as complex as ours, most of their
behaviors are responses to chemical signals from other cells, and they can’t
make doughnuts.
But there are other single celled organisms that might match
us for complexity, or even exceed our level of complexity, and they do it all
within the confines of a single cell. Of course I’m talking about the ciliate
protists. If don't know them, stick around and meet them and their kin. Sometimes, less is more.
We have been talking about the undulipodia in the last few weeks, and our last story started to
describe the great catch-all kingdom, the protists.
They use cilia and eukaryotic flagella (these being the undulupodia), but this
is just one characteristic that can be used to separate them into groups.
The last post talked about the plant-like protists and how
they can use flagella to either move around or to have their gamete cells move
around. Today let’s discuss the animal-like protists; they use undulipodia in
more ways.
There are six phylums of animal-like protists, just like there
were six phylums of plant-like protists – but I think that was just a happy
accident. The animal-like protists have more diversity amongst their phyla than
did the plant-like protists; some use flagella, some use cilia, some use neither.
Each phylum is amazing, but we’ll save the most complex – or is that most
simple – for last.
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The
radiolaria are counted amongst the actinopoda. They
have
intricate mineral skeletons. What you can’t appreciate from
these
photomicrographs is that also have an inner skeleton that
divides
them into an endoplasm and ectoplasm. Some house
algae
in there ectoplasm to harvest their photosynthetically-
produced
carbohydrates.
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The radiolaria are amongst the actinopoda and are quite
complex. They're one celled, but the cell has two parts, an
endoplasm that contains the nucleus and organelles, and the ectoplasm, that has
frothy bubbles to control their buoyancy.
Radiolaria are floaters, which would suggest that they don’t use
undulipodia for motility. In fact, the only time that flagella have been
observed in radiolarians is in some swarmer cells. Scientists think these represent sexual
reproductive gametes that might be
released from a swelling in the adult cell. Sexual reproduction has not been
confirmed; scientists must be too embarrassed to ask them about it.
The swarmers are very small, as a new study shows and can
move in the water column. This may be why we often find radiolarian DNA at
depths where they don’t live – it’s their swarmers. And they do seem to get
around. A Russian cosmonaut just reported having sampled the windows on the space station and found plankton! They think they have escaped the atmosphere
on the wind. If true, that certainly
changes our post about life moving from Earth to space.
Phylum Foraminifera – these organisms have
tests, shells of calcium carbonate with little holes in them from which they
stick out a pseudopod (we'll see more of this below) and walk. The foarminifera look like and are closely
related to the actinopoda. Some wonder if they shouldn’t be lumped together, but we all know that arguments about protist classification are the rule, not the exception.
Like actinopoda, they only show flagella on their gametes, and like actinopoda,
the gametes are biflagellated.
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The
foraminifera are protists with calcium carbonate shells. I
wonder
if the RAF pilots returning during WWII knew that the
White
Cliffs of Dover are chalk formed from these protists.
Likewise,
the limestone quarries in Bloomington, IN where they
filmed
Breaking Away in 1979 are also made from the tests
of
these protists.
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Oil spills and other such disasters are having an effect on
the ability of foraminifera to maintain their calcium tests, and this affects
us beyond just having some pretty cliffs to look at. We may be using foraminifera
in the future to repair bone injuries.
A 2014 study showed that using foraminifera exoskeletons is
a good way to promote bone growth in skull defects in rats. The hope is that we
can use these for bone grafts and for bone repair in the future. As long as we
don’t destroy all the formanifera.
Phylum Apicomplexa – We could talk about
the best known apicomplexans for years and just touch the surface of their
biology. Why do we know so much about them? Because they kill us. Plasmodium falciparum is an apicomplexan
– it causes malaria. Toxoplasma gondii
is an apicomplexan; it causes toxoplasmosis that can chew holes in your brain
and kill you as well.
Apicomplexans are immotile, a lot like the planktonic
foraminifera and actinopoda. But in this case they're usually carried around from place to
place inside a living host. The vast majority of them are parasites. Since they get
carried around, they don’t need flagella to move, but some of the species have
gametes that have three flagella on their back ends. Even though I’m breaking
my parasitology friend Bill’s heart, I am going to leave the apicomplexa here and move on.
Don’t worry Bill, we’ll come back to them soon.
Phylum Rhizopoda - These are the amoebas; most don’t have cilia or
flagella. They move by pseudopodia (pseudo = false, podia = feet), oozing their membrane and
cytoplasm in one direction and then pulling the rest along. Of course, this
means they need a surface to move across, you don’t use pseudopodia to move in
water. But this phylum also includes the ameoboflagellates,
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Naegleria
fowleri lives in warm waters. It enters the body
through
the nose and travels straight to the brain. The
feeding
structures look like a clown face, which makes it
double
frightening for my daughter. The infection is almost
always
fatal. Must be a sad clown.
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Naegleria fowleri
is the brain-eating protozoan that is transmitted through contaminated drinking or swimming
water. It may not happen often, but I hate to think about something swimming
(or would they crawl?) around my brain and feasting. Primary amoebic
meningioencephalitis from N. fowleri
is fatal in about 95% of cases, and though it is rare worldwide, most cases
occur in the U.S.
A 2014 study in Arizona found that N. fowleri in five of 33 lakes studied. That’s scary enough, but
the researchers also found that the protozoa were present in the cooler months,
when it had been supposed that the cooler water temperatures were lethal to the
organism. I am not retiring to Arizona.
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Choanoflagellates
look so much like the choanocyte cell
type
in sponges. They are both collared and have a
flagellum
sticking out. Since sponges are the basal phylum
of
kingdom Animalia, it is believed that choanocyte protists
are
the ancestor to all animal cells. But a new study says don’t
be
so hasty. They resemble each other, but it could be parallel
evolution
not straight descent.
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Phylum Ciliophora – The ciliates are
those “less is more” organisms we described at the beginning of this post. These
organisms have cilia all over their bodies, and they use them for feeding,
motility (swimming and crawling), attachment and for sensing chemicals and
perhaps sensing mates. These are all very complex behaviors for single-celled organisms. But wait, they do more.
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Vorticella
is one of the ciliates. It uses it’s cilia to shovel prey into
its
oral groove, but the adult doesn’t use cilia to move. They
anchor
to one spot and duck predators. The myoneme doesn’t
spring
them up, it coils them down when something tries to eat them.
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They have a complex cytoskeleton, made of connections
between all those cilia. They have contractile vacuoles that control their
water content. They even carry spears called trichocysts for defense against
predators. These are like the cnidocytes of the jellyfish, and are a trick that we, with all our complexity, can't come close to matching
So do they go beyond us, even though they only have one
cell? Yep, you have seen anything yet. Ciliates have up to six life cycle stages, they all have two nuclei, and they
go through an insanely complex sexual reproduction that uses seven different
sexes – with all our complexity, we only manage two - or are there more? That could be a good series of posts as well.
Ciliates are free living and cause us no problem. But
in a great show of disrespect to their inferiors, Balantidium coli can be a horrible problem for us. It's the exception
among ciliates in that it causes a disease, Balantidiasis, in primates. The
organism usually lives in the guts of pigs, but if it gets into our gut, and we
then become immunocompromised – watch out.
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This
is B. coli, the only know ciliate to
cause disease in mammals.
You
see all the cilia, that is how it moves around. It is transmitted
via
the oral-fecal route, but might also be transmitted by
undercooked
pork. Some people say fecal-oral, but that sounds
more
gross to me.
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We haven’t talked about the fungus-like protists. We’ll
include them when we talka bout the undulipodia of the plants and fungi. Some plants cells have flagella for
movement. Is my salad going to crawl off my plate?
But next week we'll start some Thanksgiving posts. Should we really be eating goat for Thanksgiving?
But next week we'll start some Thanksgiving posts. Should we really be eating goat for Thanksgiving?
For
more information or classroom activities, see:
Plankton
–
N.
fowleri –
Ciliates
–
