Batillipes egg!
As reported previously, the sea water micro aquarium is a fascinating system:
though possibly slightly smaller than a real ocean it may still serve as
a perfectly working sea life equilibrium for 12 months or even longer.
All its components are easily available: a toothbrush tumbler, a few soupspoon
portions of fresh, wet sea sand and 100 ml of sea water from the same site.
In addition you might make use of a cover plate (in order to hinder the water from
evaporating, thus preserving its natural salt content) and some spare ocean water, e.g.
kept in a 1 liter plastic bottle. You don't even have to go to the ocean
yourself but instead can ask a friend to pick up a small seasand/water sample for you.
Just tell him or her to use a small plastic film container (from those analogue
films, some of you will remember) and to fill its volume with 2/3 of sand and 1/3
of water. The sand should contain as little bigger organisms as possible (no algae,
no living shells, no fishes and no crocodiles). Instead, some shell fragments and a
slightly coarse sand are welcome - remember that tardigrades would suffocate in fine mud.
Of course the film container should be kept in a dark and rather cool environment
during transport. At home you might place it on a window sill, slightly dark. Sun is
allowed by no means!
At first one might think that such a tootbrush tumbler size aquarium should be
clearly inferior to a big sea water aquarium - but this is wrong. By means of the
micro aquarium in combination with your microscope you will be able to
study many organisms in their infancy - with the advantage of an increased
transparency! As an example you might have a look at the following video clip of
a living baby seashell. Due to the transparency you will be able to look
inside the shell without making use of some more brute human investigation tool, like e.g. a knife.
Note how the shell is moving on the slide. It is feeling uneasy there because
there is an annoying lack of sand. At the end of the clip we present a close-up
which shows how the gills are working in order to pump oxygen into the shell:
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