Pond, lake, stream and river water (fresh water) microscopy

Bright field vs. crossed polarisation views of microscope slide of material from LRO pot pond 28/5/2018

I used the centrifuge to concentrate down material from “open water” in the pot pond (i.e. not near edge or bottom or plants) and views the result in the LOMO Polam P-113 microscope, by bright field & crossed polarisation.

Note that such open water samples do not contain diatoms – which are famously birefringent.

Andy

Birefringement material pot pond slide 280518@1642, x20 objective:

Birefringent material slide from pot pond 280518@1703, x20 objective:

Insect on slide pot pond water 280518@1626 panorama, x20 objective:

Slide from pot pond: birefringent material shown in sequence as I moved the second polarised filter from 0-90 degrees so that the sample moved between crossed polarisation and bright field, 280518@1639 (below):

Slide from pot pond highly birefringent organisms brightfield x20 obj 280518@1635:

Cross-polarised views of mosquito larva from pot pond

For the last few weeks, I have created myself a garden pond in a large plastic pot about 80cm across and similar height. Today, I noticed a large population of mosquito and other larvae.

I sacrificed one of these larvae today to view its structure under crossed polarisation on my LOMO Polam P-113 polarising microscope.

I had read online that muscle shows up on crossed polarisation. Certainly, the photos below show birefringence which might be muscle.

I am particularly pleased with the photo at the bottom. I managed to work out how to use layers in GIMP2 and change relative transparency between the layers and consequently combine the bright field and crossed polarisation images so that you can see where the colourful polarised tissue is located.

Andy

Bright field view of larva, x3.5 objective:

Crossed polarisation views x3.5 objective mosquito larva:

Combined bright field and crossed polar image:

The strips of birefringence follows down the side of the larval body. The photo above this one shows this follows the organism around. From http://www.sciencephoto.com/media/74993/view/mosquito-larva-light-micrograph, it would appear that this represents muscle bundles down the side of the insect.

Bright field vs. Crossed Polarisation filters of slide cultured in pot pond at LRO 27/5/2018

LOMO Polam P-113 microscope.

Microscopy forum posts discuss using polarisation to view microscopic slides of pond life – apparently it can be quite spectacular! Well, my observations today were not spectacular but I had some success – see below…

Andy

x11 objective, bright field – a piece of pond weed (below):

This is the most successful observation today. The above field of view after introducing crossed polar filters (below, showing bi-refringence in the plant material) (x11 objective):

The following is a little weird – bi-refringence at the edge of the cover slip! (Below, again x11 objective):

However other parts of the slide do not show bi-refringence, such as this collection of material (below, x11) – bright field followed by crossed polars (there is a tiny amount of bi-refringence only at the lower right):

I had hoped to get more luck at higher magnifications – here is a slide at x20 – crossed polars followed by bright field (below):

Observing commercial slide of Hydra spp. through crossed polarisation filters on LOMO Polam P-113 Polarising Microscope

I had a go today at observing a commercial slide of Hydra spp. through crossed polarisation filters on LOMO Polam P-113 Polarising Microscope. The first picture shows the slide with plain polarisation (effectively bright field). The second is where the one filter is rotated nearly 90 degrees. Initially, I thought the bright dots were some birefringence (small bright dots) from the mountant used on the slide, but now I think they are hot pixels on the camera! The specimen interesting becomes nearly invisible – in fact if I rotated to 90 degrees exactly, it did become invisible – this is a little short of that so that you can see specimen in background. Much longer exposure required.

Andy

Circular Oblique Lighting (COL) on microscopic images of bacteria and algae

Using the slide from my previous post http://roslistonastronomy.uk/algae-superfood-after-two-days-in-water, I tried out Circular Oblique Lighting on the Zeiss IM today using appropriate COL annuli.

All of the following use Zeiss condenser NA 1.4 and low NA Leitz 25x objective (NA 0.22).

Andy

The following photo is a BRIGHT FIELD image of part of the slide – the bacteria are just visible as the blue/black mottling top right/and at bottom left:

The following picture is of the same field of field of view with same condenser and objective but adding in COL annulus – I don’t think there is a deep sky astronomy filter that works quite as well as this!

The following photo uses a COL filter with smaller hole for light to pass through – do you think there is a meaningful difference between the two?

I think there a difference – the bacteria stand out a bit more BUT so do the larger hill-like mounds in the background – these are due to dust on the slide or optics.

The following is a dark field photo (changed to greyscale in GIMP2) – again the contaminants stand out as well as the bacteria which is a real nuisance, although the bacteria are easily seen – same condenser and objective as above:

 

Algae superfood after two days in water

Ean Ean has bought for me a “superfood” based on Spirulina algae – apparently Kate Middleton eats it! It is sold as dry powder and I wondered if it was dead or alive. I put some in a cup of water for two days in the sun. In the photos below you can see algae cells – however lots of bacteria too which suggests that the algae are killed and the bacteria quickly take up residence with plenty of food available.

[You may also wish to view a following post where further work was done on this slide using COL, http://roslistonastronomy.uk/circular-oblique-lighting-col-on-microscopic-images-of-bacteria-and-algae]

Andy

Four algae cells showing cilia around edge from Hopwas Canal

Ean Ean and I collected the sample of water from Hopwas canal 19/4/2018 and today I viewed it in the Zeiss IM microscope using 40x objective. The picture below shows multiple cilia (hair-like structures) around edge of the cells which the cells use to move around. I have used Curves function in GIMP2 to enhance the image to demonstrate these cilia more effectively.

Andy

Ean Ean collecting sample from canal:

Attempts at dark field microscopy using x50 infinity-corrected objective with diaphragm

I still can’t seem to get dark field to work well!

Photos below using infinity-corrected 50x objective with iris diaphragm, curves adjusted in GIMP2.

Andy

Algae from my pot pond 12/4/2018:

Volvox on commercial slide viewed by myself today using same setup as above: