As we are amateurs it should be allowed to use our phantasy in order
to comment on our findings:
"We think that those areas are smooth and transparent as they are just
above the eyespots and because a granulated area would spoil the optical properties
of the eyes, similar to a frosted glass"
In order to maintain our hypothesis against potential protests we should
play safe and better prove that the tardigrades have in fact usable eyes and that
some kind of image viewing might be possible by means of those eyes.
In particular a higly developed eye would definitely take profit from
a transparent windowpane.
Therefore let's have a look at the scientific literature first in order to see
what the experts are saying about the existence and properties of tardigrade eyes.
Here is a choice of quotations picked out of some of the best tardigrade monographs:
"There are inverted pigment ocelles on the eye lobes of the upper
parts of the brain which consist of a single eye cell each ... " (translated from:
E. Marcus: Tardigrada. p. 7. Berlin 1936.)
"The cirri and the pigment beaker ocelles serve as sensory organs.
The ocelles are placed on the upper part of the ganglion and consist
of single eye cells" (translated from:
A. Kaestner: Lehrbuch der Speziellen Zoologie. Vol. I: Wirbellose, 1st part. p. 589.
3rd ed. Stuttgart 1969.)
"There is a distinct anterior region which may or may not bear
eyespots and cephalic appendages "
(C.I. Morgan, P.E. King: British Tardigrades. p. 2. London 1976.)
"Eutardigrades and Echiniscoidea have eyes (ocelles) positioned more
or less rostral on the outer lobes of the upper ganglion. The eyes are said to
consist of a single sensory cell in a pigment beaker which is opened towards
the lateral front-end of the tardigrade body. The eye pigment is normally black,
Echiniscidae have red eyes, 'blind' tardigrades have no pigment at all.
... At present there are no ultra-structural investigations about the anatomy
of those organs available."
(H. Greven: Die Bärtierchen. p. 25. Wittenberg Lutherstadt 1980.)
"In molte specie, sia di Etero- che die Eutardigradi, esistono occhi
posti sui lobi esterni del cerebro, e costituiti da una sola cellula
fotosensibile. Spesso (ma non sempre) la cellula fotosensibile è
circondata da macchie pigmentate costituite da granuli più o meno
sparsi, neri negli Eutardigradi, generalmente rossi, ma talora marrone
o neri, negli Eterotardigradi Echiniscidi" (W. Maucci: Tardigrada.
p. 14. Bologna 1986.)
"A pair of cup-shaped pigmented eyespots associated with the lateral lobes
of the cerebral ganglion is also present in many species" (I.M. Kinchin:
The Biology of Tardigrades. p. 52. London 1994.)
In short, the scientists agree that tardigrades have eyes but state at
the same time that these eyes are in fact very primitive and are made up of
a single cell only, sometimes in combination with a little bit of pigment.
Hartmut Greven goes on one step further and mentions the pigment beaker
opened in an angle to the outside world, a construction which would
possibly allow some kind of directional eyesight. So he doesn't completely
destroy our secret hope that the tardigrades might at least be able to
note the direction from which an incident light ray is arriving.
Furthermore Hartmut Greven mentions the obvious lack of scientific work
on the properties of tardigrade eyes.
As we have seen the miraculous miniaturization e.g. of tardigrade claws and
muscles   we might become a little bit depressed
Our fine, highly developed tardigrades which
fight their way though the moss jungles, which are able to combat against bacteria
in the relative size of a sausage and which do survive on the bottom of ice
glaciers - those tardigrades are assumed to have a primitive eyesight only, like a
Depending on your personal temperament you might end up in crying now or
hurry up to the next public library or have intense looks at some more
tardigrades under your microscope. We have decided to adopt one of the less
dramatic pathways (library).
Already 100 years ago the scientists have been
thinking about the eyesight properties of the so-called lower creatures.
In William Carpenter's book of 1891 we even found an image photographed
through (!) an isolated fly eye, illustrating the visual impression
which a fly might have when looking around in the world.
One further fine example is the monograph by Richard Hesse (see literature).
Hesse explains the various degrees of sophistication of eye construction,
starting with a simple light detector, which is just able to tell 'light'
from 'no-light', going over various development stages until to a lens-eye allowing
image views. Hesse's book also helps to come to mental piece with the
given fact that some tardigrades have eye pigment whereas others,
moving and behaving identically, have no eye pigment at all. He simply
states that also human albinos with little or no eye pigment at all are
able to see in an equivalent quality as the rest of us humans.
And, in the end, we were successful and came across a very dusty issue
of an old zoological journal with a very impressive statement concerning
the tardigrade eye (translated):
"I just ... would like to add, that the tardigrade eye ... in contrary
to previous statements by xxx ... is by no means a primitive pigment spot.
The eye is rather complicated and has a homogeneously curved, very
Are we allowed to believe this author who might have been the father of
our grandfather? We will continue exactly at this point in our next issue.