How an
experiment can be accidentally modified
In a previous article I examined the microfauna
and microflora of a rainwater reservoir in a tree of
Cancún.
. http://www.microscopy-uk.org.uk/mag/artoct04/wdtree.html
The hole had only a diameter of 20 cm x 6-8 cm of depth, but
it supported, in spite of having been filled only a few days before,
a modest but interesting list of species, some with a very high
density of individuals.
Here once lived Astasia, Khawkinia, Euglena,
Dileptus, Halteria, Vorticella, and there were also vestiges
of previous occupants like Centropyxis and a Bdelloidea, prob. Habrotrocha) see the
previous article.
Astasia sp. mounted in GALA, fresh and not stained.
After ten days, without disappearing, the microfauna had a
much lower density, perhaps by competition for the limited existing
resources with a great population of mosquito larvae recently
hatched, or because it was consumed by the same larvae. Fifteen
days later the hollow was completely dry. The cycle, from filling to
dry, was of 30 to 35 days. From the hundreds of hatched mosquito
larvae, probably only a few tens arrived at the adult
stage.
recently hatched mosquito
larvae
These biocenosis are being studied with interest, as much in
nature as in the laboratory, because on one hand they are true
models on scale of more complex, extensive and lasting biocenosis,
and secondly because they really are one of the most difficult to
eradicate sources of annoying and dangerous mosquitoes. In the
neighborhood of Cancún they exist, although they are hardly seen in
the city, the mosquitoes that transmit malaria, and
dengue.
One of the possible experimental approaches is not to depend
on rains to maintain with water the natural holes, and another one
is to even generate manageable artificial “holes” in the
laboratory.
For both tasks it is necessary to have rainwater at hand.
Rain in Cancún is seasonal, with a very extensive dry season, and a
not so long wet season, with heavy rains; so, to have a
permanent source of rainwater it is necessary to gather it with
sufficient anticipation.
With the intention to make some short experiments
(at the amateur level, it is clear) on these micro natural and
artificial biocenosis, I gathered about 60 ltrs of rainwater,
collected on a canvas suspended with that intention. The canvas
formed a sink, which was washed, discarding the water collected the
first two days, and from which water was later drained directly to
three carboys 20 ltrs each. Carboys were of plastic with a very
clear blue color, and their original destiny was to contain purified
commercial drinking water.
The mystery
microbiocenosis
Four months later, already in the dry season, while I
siphoned water to fill some experimental containers, I observed the
presence of small pieces of a green-blackish 'felt' whose origin was,
as it could be verified, a thin and extended bioderme developed over
the container bottom.
Thinking it could be cyanobacteria I examined
some samples with the microscope.
In fact what I found was a quite complex biocenosis. I
verified that it was equal in the three carboys, which allowed me to
suppose that it had been originated in cysts of organisms
contributed by the wind to the rainwater gathered on the
canvas.
Beggiatoa, a filamentous bacteria
conglomerate eubacteria, cyanobacteria and microalgae
rotifers exploring the substrate
Vegetal felt was a thin, but dense and intricate growth
of filamentous bacteria and cyanobacteria. Evidently they also
existed, although no visible directly with the low power, multitude
of small bacteria, denounced by the mucilaginous atmosphere they
produced (see pictures above).
I
believe that observed Cyanobacteria belong to at least 14 different
genera (Anabaena, Beggiatoa, Calothryx,
Scytonema, Microcystis, Gloeocapsa, Chroococus, Aphanotece, Nostoc,
Leptolyngbya, Lyngbya, Oscillatoria, Chlorogloeopsis,
Rivularia and
others
for which it was impossible for me to locate a probable identification….
For some genera there were present more than one species). It must
be understood that I am not a botanist and not, and less, a bacteriologist
or a phycologist, and that my only comparatives images and
information source, on this theme, is the INTERNET, and the reason why, although
I have made my best efforts to determine the genera, except in cases so typical as Nostoc, or Lyngbya , by ex., I must thank very much any corrections that
a specialist who reads this work could contribute to improve this modest
gallery. Those specialists who I tried to consult, did
not respond to my request. So, these identifications are all only
tentative.
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Gomphospheria |
Anabaena |
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Leptolyngbya |
Calothryx |
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Chlorogloeopsis |
cf.
Cyanothece |
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cf.
Gloeocapsa |
cf.
Gloeocapsa |
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cf.
Gloecapsa |
cf.
Gloeocapsa |
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Nostoc |
Nostoc |
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Chlorococcus |
Chroococcus |
Oscillatoria
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Lyngbya |
Lyngbia |
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Aphanothece,
colony |
Aphanothece,
individuals |
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Rivularia,
base of the trichoma |
Rivularia, apex |
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Scytonema |
Scytonema |
The microfauna
Consuming mainly the bacteria and the detritus that cover or surround this material, were 4 species of rotifers (a species of Rotaria, another one of
Philodina, an Adineta, and a Phylodinavidae). Cysts of
them, as the ones shown in the two following pictures surely are
dragged by the wind, when the habitat is dry.
When the habitat is wet the species are active and reproducing,
as shown by the eggs in its interior, or the ones deposited between
the vegetation.
Rotaria, 2 rostral eyes, 1 young
embryo
Philodina, 2 brain eyes
Samples of this biocenosis, transferred to the laboratory in
covered containers, to avoid contamination and mosquitoes, stayed
stable for more than a year, with later aggregates of some
contaminating agents (a Cephalodella, and later
some small ciliates)
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Philodinavidae |
Adineta |
At
least the species of Phylodinavidae seems to be new. The most
similar genus seems Abrochta. If it would
be, it would be easily distinguished from the other two now
recognized in this genus. It seems also that the Adineta species is
a new one.
ROTIFER’S
BEHAVIOR
Genera
can be easily identified even at low power.
Philodina
swims rarely. It stays clinging permanently to substrate while it
extends all its length, and unfolds its absolutely typical
trochae. Most of the time, it is filtering bacteria suspended in the
water, as their trochal activity, their oscillating movements, and
their frequent contractions demonstrate. At 100 powers their eyes
can be easily distinguished, over the brain. Ovovitelogens are
clearly visible, and often an egg almost mature, with a big
nucleus.
Rotaria
can fasten itself to vegetation and act more or less like Philodina;
but even fixed and extended, its characteristic proboscis identifies
it. Very frequently it loosens its attachment, and uses its trochae to
swim and to collect food, as the tireless activity of its mastax
demonstrates. During swimming it bears the rostrum extended with its
characteristic eyes at the end (visible with 100x, but most clearly
with 400x) and the lamelas unfolded.
It
is also common that it closes the corona, and crawl on the
substrate, giving to its head a long tapered profile where the
retracted ciliated discs are clearly distinguished at the base of
the always extended rostrum. Their ovovitelogenes are small.
Normally it has in its interior a small, rather cylindrical egg,
with blunt ends, and a bigger developed and movable
embryo.
Adineta
has a size smaller than the two previous species, and a special
shape and mobility. It remains generally extended, running on the
substrate at great speed, propelled by its cephalic ventrally
ciliated field, sweeping food from it at the same time. The flat tape-like
head and trunk, the narrow neck, and the always extended foot of
medium length with two small spurs laterally open, makes it
unmistakable. When eating, it flattens on the substrate, showing its
flexible and depressed profile, with tapered shape, not a cylindrical
one like the two previous species.
The
Phyllodinavidae (whose
taxonomic position is still uncertain) is a species whose atypical
behavior immediately distinguishes it.
It
is small but robust, and normally it crawls, permanent and
untiringly, between the handfuls of cyanobacteria of the substrate,
which makes photography almost impossible. In order to
move, it extends and retracts its relatively short foot, which
generally forms a strong angle with the trunk.
This
is quite rigid, and inclines like a unit due to the existence of
rectangular cuticular plates. Uniting this to the gross head,
crowned by the big rostrum, with strong cilia at
its end, also inclined to explore and to scrape the substrate with
an alternative movement of capture and traction, it is difficult not
to find that it has a comical aspect. Aside from the zoological
distance, the movement closely remembers a chicken pecking for its
food.
NATURAL PLUVIAL BIOCENOSIS
It
is commonplace in Cancún that after rains, there form little pools
in the ground, the sidewalks, and even in the street, that could
maintain water for a couple of days, and that often will be filled
again with the following rain, before they are dried up. Also it is
common that at their bottom a mud layer forms, in whose surface
cyanobacteria develops, easily detectable by its black-greenish
color. There are also cyanobacteria in places that receive permanent
(or at least very frequent) dripping, from some water pump, or from a failing faucet, installed to feed hoses for garden
irrigation, etc.
Various photos of extreme microhabitats
The
previous experience took me to investigate these sites, and I
verified in all of them biocenosis very similar to the one developed
in my carboys. I even identified on the roof of a nearby house the
one that, by its specific composition, surely was the source of the
cysts that were seeded by the rain in my carboys. During the rains a
layer of water from 2 to 3 cm collects in this ceiling, and
evaporates in a couple of days. The white reflecting bottom, and the
heavy direct sunlight must raise the water temperature, around 2pm
(14: 00) to a very high
level.
The
list of rotifers species although always included some of those
already found, reached a greater diversity, incorporating two Habrotrochidae (mainly Habrotrocha and cf. Otostephanus), a Mniobia, one second Philodinavidae (Abrochta) and another
pair of bdelloids difficult so far to identify, although they
probably are also Habrotrochidae.
The
Habrotrochidae family,
characterizes itself by an apparently sincitial stomach, without the
ciliated lumen which the Philodinida or the Philodinavida have, and in
which the food is included in spherical vacuoles that give to the
stomach the aspect of a bag filled with small greenish
balls.
Habrotrocha
moves like a Philodinida, but it has a
very short foot, a wide and oblong belly, and a longer and thinne
neck (as also is the buccal tube), with a corona of hardly a little
greater diameter. These characteristics make it almost immediately
differentiable from the Philodinidae. The species found so far produces
no capsule or housing, as described in other species. Their behavior
is similar to that of Philodina: it remains
stretched and feeding most of the time, but seldom swims. I could
not take an acceptable picture of this
species
Otostephanus
(or what is a very close genus) differs because its corona seems to
have one double troca, and by a longer and differentiable neck. It
has a morphology and behavior very similar to that of Habrotrocha. But is
more sedentary.
Mniobia
surprised
me at first by its general aspect during swimming, with its two
dorsal eyes behind the antenna, which made it seem a Philodina. But a few
moments of observation differentiate it quickly. The first segments
of their torso are distinctly separated from the neck, are more
rigid and the whole cuticle of the torso is more rigid. In addition,
unmistakably, does not have toes in the foot but an adhesive
disc.
Abrochta is a small, agile species, with the typical
genus organization, but this population has individuals much more
thin those Abrochta intermedia
, the species whereupon it must be
compared, and to which it probably belongs.
cf.
Otostephanus
Mniobia
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cf.
Abrochtha
This is an exceptional picture because
the
species rarely swims out of the
vegetation and
when it does, does it swiftly, making
imaging
difficult, and does not extend
himself so
freely. |
The unidentified specimens (at least two other species) are also Habrotrochidae, but I have
not been able to define the number of fingers, nor the position and
forms of spurs in the foot. They are shy species, generally hidden
inside the vegetal mass. I could not obtain good comparative
images.
In all these natural biocenosis they are also some
monogononta rotifers, (Cephalodella, Colurella)
in much smaller quantity, and several small ciliates species.
Colurella
In one of the samples I found vestiges of a quite dense
population of a tardigrade (Echiniscus). But the
population was dead, leaving only his empty cuirasses, as the one
shown below, before I could see them alive.
Until now I have altogether identified 8 (perhaps 9) genus of
Bdelloidea adapted to
survive in an extremely hostile medium, plus a tardigrade and a couple of
Monogononta
genus.
Due to the location of all these biocenosis and to the substrate
in which they are based, it is evident that, although I could
not measure pH, this must be very high and the water must have a
high calcium content. The action of the wind and the intense sunlight,
dry in a few hours most of the investigated habitats. All
this microfauna, and the microflora that provides them with food and
shelter has a few hours to develop and complete their vital cycles.
Their bodies support enormous biochemical
tensions.
Then it is not strange that species like all those here
mentioned can be cultivated for very long periods, even in the
relatively crude conditions of my laboratory. All of them are
candidates to become laboratory models for the biology of their
genus.
NOTE: All cultures, which were established for more than a year, and maintained the identity and abundance of species of
the original biocenosis, were lost during Hurricane Wilma in 2005. I
hope to recover some populations in the rainy season that just
started this year, to publish the new species, and to distribute
some samples to laboratories qualified to fully utilize the
experimental potential of these
populations.
Comments to the author,
Walter
Dioni
, are welcomed.
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