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.
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.
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…
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):
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.
All of the following use Zeiss condenser NA 1.4 and low NA Leitz 25x objective (NA 0.22).
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:
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.
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.
I have created a pond at home using a very large plastic pot from Homebase. It even obtained a new resident yesterday (a fish) who has joined the frogspawn and Elodea and some other water plants obtained from a friend’s pond – whence the fish also originated. The friend in question insists that the fish should not be lonely so another will be joining it later in the week!
The photos below are of an algal sample from the pot pond. 18 x Eppendorf 1.5ml centrifuge tubes were centrifuged at 10000 revolutions/minute for 10 minutes. I pipetted off excess water above the centrifuge pellet. I then combined the pellets into a single Eppendorf tube and centrifuged again using the same settings. This concentrated the algae to make microscopic observation easier.
The main findings today are of cilia on most of the algal cells. I have annotated the photos below to show whether these can be seen. In some cells the green chloroplasts are bunched up at one end and I suspect this is due to the centrifuging process.
Finally bacteria abound – not sure why I used to have such difficulty seeing bacteria initially but now I see them all the time – I suspect it is a bit like training yourself to observe faint fuzzies in the night sky – once it clicks it becomes a lot easier – perhaps it is also just about knowing what to look for!