10 years Water Bear Web Base: the Echiniscus Finder!

With respect to our 10 years' jubilee we would like to share an interesting discovery with you: the Echiniscus Finder.

Basically we are talking about a loupe, but a kind of extraordinary loupe. All of us are aware of the fact that not every Ebay item is exactly what it appears to be. We have learned that today's 10fold loupes might be offered "erroneously" under the label of a 20fold or 30fold magnification etc. Most of the strongly magnifying Ebay loupes are praised in addition for extraordinary lens diameters. Of course this is nonsense as high loupe magnifications are always limited to a small usable visual cross-section (e.g. 40x loupe must have extremely small lenses). That is the difference between selling and physics. Furthermore, high magnifications always require a very small working distance. And because of this small working distance special attention must be taken to an appropriate illumination. Just have a look at one of those old good quality Leitz loupes where the high magnification lens housing has conical geometry in order to let at least some light pass from outside on to the object under investigation:

Old folding Leitz double loupe with high magnification (left side, conical lens housing) and lower magnification (right side, cylindrical housing). The yellow areas indicate the light cones that will reach the object. Illustration from Henry Scherren's book "Through a Pocket Lens "(1897), modified.

The conical geometry of the lens housing allows ambient light to reach the object area under investigation even though the working distance is very low. Otherwise the high loupe magnification would become unusable, due to insufficient illumination. Obviously, LED illumination was not available around 1900.
Now, with todays low power consumption white LEDs it has become possible to incorporate a really perfect LED light into a small housing. Some early loupe models of this type had poor optics and poor colour characteristics (a really terrible blue) with disfiguering shadows. But there are modern follow-ups, in particular the "6 LED" folding loupes which offer a nice, bright and homogeneous light in combination with achromatic true triplet optics (three lens optics, cf. warning of false triplets below).

The illumination construction of the "6 LED"" loupes can be seen on the following photograph which depicts the 6 LED ring and the diffusor ring, everything positioned neatly around the lens glass:

"6 LED" loupe with diffuse light, as seen from below in order to show the diffuse light of the LEDs under a shared diffusor ring. International Ebay, Chinese quality product.

And besides, as a kind of goodie, the LED lights is rendering our Echiniscus "tuns" in blue! They are still very small, of course, but the blue colour will turn out as a tremendous advantage when searching for tardigrades in dry state. Remember, when seen under ordinary light, they appear camouflaged as grey or whitish shapes without distinctive visual characteristics.

What might be the reason? We are not perfectly sure but tend to assume that the effect is same as with the "coulours of thin leaves", well-known from school physics. It appears that the ultra-thin tardigrade cuticula has the proper thickness in order to produce this miraculous blue light just by means of interference from the incoming white light.

Single Echiniscus tardigrade, seen at medium magnification under LED light. The cuticula looks intensively blue!

Even at a rather low 10fold magnification this marvelous blue light is an excellent marker indicating the degree of Echiniscus population density.

Moss plant, as seen through a "6 LED" loupe with diffuse light. All those tiny blue spots are dry Echiniscus "tuns", measuring 50 µm in length at best. Normally it would be difficult to tell that they are present, but the intensively blue colour is extremely helpful.

The "6 LED" loupe is a Chinese product. It appears that there is no western equivalent, so we think that it is not just a copy but instead a kind of Chinese innovation. Please note that those loupes contain true triplets which must not be confused with those many fake "Triplet" loupes on Ebay (loupes which are simply named "Triplet" but do not contain three lenses). The 6 LED true triplet loupe is an excellent product. Thanks to brute international competition and globalization you will get it for about 25 US$ - which is a very low price. Ridiculous on one side, tragical in the eyes of western optical factories.

© Text, images and video clips by  Martin Mach  (webmaster@baertierchen.de).
Water Bear web base is a licensed and revised version of the German language monthly magazine  Bärtierchen-Journal . Style and grammar amendments by native speakers are warmly welcomed.

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