The blue line artifact (II)
A four episodes' lecture about microscopic deception

Let's continue with our deep dive into - what we think is - microscopic reality. Please remember the cause for this discussion, a photograph as already shown in our previous issue (fig. 1). At first glance it looks like a primitively tampered image - with someone drawing a blue line around the egg! But again - believe it or not - this is an actual image, directly out of the microscope camera.

Fig. 1: The cause for our discussion - a tardigrade egg photomicrograph, with a strange blue contour line!

We are going to continue our discussion with the question: is there any real blue in the tardigrade egg? Well, in fig. 1 the inner volume of the egg doesn't look blue at all. So we tried alternative illumination, namely darkfield (which has a tendency to deliver more saturated color - see fig. 2). But also in dark field there appears to be only some faint blue tinge around the tardigrade body, not markedly stronger within the egg. So our conclusion should be: there appears to be very little or no actual blue within the egg volume!

Fig. 2: A similar situation as in fig. 1, but this time in darkfield illumination.

As a consequence we shouldn't think about the inner egg volume any longer but concentrate on the blue line as a contour line. In a first analysis step we removed the eggs from the cuticula in order to check whether the blue color effect would persist. And it does! Furthermore we tried a completely independent microscope setup: different microscope brand, other objective brand, other illumination - to no avail, the blue contour lines didn't vanish.

Abb. 3: Isolated eggs from the cuticala are still showing the same blue contour line like in fig. 1

So far our (intermediate) resume is as follows:
The blue lines are by no means singularities - instead they persist, also when switching to a completely different microscope and illumination equipment!

Technical annotation: the microscope/camera setup used in order to catch fig. 1
Small mobile microscopic equipment, based on a Hertel&Reuss CN-fl microscope with a monocular tube, original Hertel&Reuss objectives and a Leitz "10x GF Periplan" eyepiece. The light source used was a "Jansjö" LED lamp (sold by IKEA). The image was taken through a Hertel&Reuss 40x/N.A. 0.65 objective by means of a Sony Nex-5N digital camera mounted on the stand by one of those fascinating IHAGEE microscope adapters (cf. our journal issue #229).

© Text, images and video clips by  Martin Mach  (webmaster@baertierchen.de).
The 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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