Pond Life: Algae

Diatoms, Desmids and Other Algae

Strictly speaking, these are protists, rather than plants, but many people still think of them as plants: after all they do possess chlorophyll for photosynthesis. Of course many have the disconcerting habit of moving around, often quite rapidly, and not very plant-like...

Diatom Circle slide

Such slides were especially popular in the 19th century as exhibition pieces to show of both the beauty of the diatoms and also the prowess of the slide maker. It has been said that the ideal tool for arranging diatoms is a tiger's whisker.

Zeiss GFL Microscope
Objective: Zeiss x10 plan
Ocular: Watson x8 Compensating
Darkground: substage wheelstop
Camera: Canon Powershot S50
ISO50, F4.0, 1/640 sec

 

Diatoms

Diatoms have long been a favourite subject for microscopists, both for aesthetic and utilitarian reasons. The patterns resulting from their cell-wall structure can be very beautiful, especially if you have a love of patterns and geometry. These patterns can be so fine that they have also provided microscopists with a readily available and cheap means of testing the ability of their instuments to resolve fine detail. The pictures on this page of diatoms are of a mixture of marine and freshwater species.

Diatoms are unusual in that as single celled algae they possess cell wals impregnated with silica - effectively the cell walls are made of glass. The cells are made of two halves, "frustules" held together by a kind of belt, called a "girdle". To appreciate the fine patterning, the frustules have to be specially cleaned and mounted for viewing in a highly refractive mountant. The patterns are only poorly visible in live diatoms, largely being obscured by chlorophyll and also by the fact that the refractive index of water is too low for really good resolution.

Moiré pattern formed by fine markings in a centric diatom

Zeiss GFL Microscope
Objective: Zeiss x40 plan achromat
Ocular: Watson x8 compensating
COL with Zeiss 0.9 NA substage condenser
Camera: Canon Powershot S50
ISO100, F4.9. 1/13 sec
Sample from Dunkirk, USA, kindly provided by Frez

Colouration caused by diffraction effects due to the very fine patterns

Zeiss GFL Microscope
Objective: Zeiss x25 plan achromat
Ocular: Watson x8 compensating
Darkground with Zeiss 0.9 NA substage condenser + wheelstop
Camera: Canon Powershot S50
ISO100, F4.9. 1/8 sec
Sample from Dunkirk, USA, kindly provided by Frez

Coscinodiscus

Zeiss GFL microscope
Objective: x25 plan achromat
Ocular: Watson x8 compensating
Zeiss dark field substage condenser
Light source: 8000 mcd LED
Camera: Canon Powershot S50
F4.9, 0.5 sec, ISO50

and at greater magnification: -

Zeiss GFL Microscope
Objective: Zeiss x100 oel
Ocular: Watson x8 compensating
Substage: Zeiss brightfield NA 1.3
Camera: Canon Powershot S50
ISO100, F4.9, 1/160 sec

Another species:

Zeiss GFL Microscope
Objective: Zeiss x40 plan achromat
Ocular: Zeiss x10 Kpl
Brightfield, flash

 

 

Synedra

A live sample from Dipping Pond 1, Warnham Millpond 25-Apr-2004

Watson Bactil Binocular Microscope
Ocular: x10 Huygenian
Objective: x10 parachromat
DG illumination (wheelstop)
Camera: Canon Powershot S50

 

 

Gyrosigma sp

A common freshwater species

Microscope: Zeiss Standard GFL
Objective: Leitz x40 NPL Fluotar ICT
Ocular: Olympus P15
Substage: Leitz ICT
Sample from Warnham Mill Pond mud

 

Pleurosigma sp (prepared specimen)

A marine species

Showing detail of fine markings (inset)

Specimen from Dunkirk, USA (thanks, Frez!)

Zeiss GFL Microscope
Objective: Zeiss x40 plan achromat
Ocular: Watson x8 compensating
Circular oblique lighting: Zeis 0.9 NA condenser with substage wheelstop
Camera: Canon Powershot S50
ISO100, F4.9, 1/8 sec

 

Unidentified diatom

Girdle and plan views (but which is which?)

Zeiss GFL Microscope
Objective: Zeiss x40 Plan achromat
Ocular: Watson x8 compensating
Brightfield
Sample from Warnham Millpond (main body) 03-Jan-2005

 

Sceptroneis sp.

Specimen from Dunkirk, USA (also from Frez)

Zeiss GFL Microscope
Objective: Zeiss x40 plan achromat
Ocular: Watson x8 compensating
Circular oblique lighting: Zeis 0.9 NA condenser with substage wheelstop
Camera: Canon Powershot S50
ISO100, F4.9, 1/8 sec

Triceratium sp (?)

Zeiss GFL microscope
Objective: Zeiss x100 oel
Ocular: Watson x8 compensating
Substage: Zeiss NA 1.3 brightfield
Camera: Canon Powershot S50
ISO100, F4.9, 1/160 sec
Combination of 4 images manually

Sample from Dunkirk, Maryland

Actinoptychus

This is a composite of 30 images. A rough template was first composed using CombineZ, then each of the in-focus parts of the original images was cloned onto the template using Paint Shop Pro 9. The original specimen is on a slide, provided by Frez, of diatoms from Dunkirk, Maryland. This particular individual was in the mounting medium at an angle, thus permitting a composite image showing the 3D layout of the diatom.

Zeiss GFL Microscope
Objective: Zeiss x40 plan achromat
Ocular: Watson x8 compensating
Substage condenser: Zeiss 0.9 NA brightfield
Camera: Canon Powershot S50
ISO100, F4.9

...and in plan view:

Zeiss GFL Microscope
Objective: Zeiss 40/0.63 plan achromat
Ocular: Zeiss Kpl W 10x/18
Brightfield
Stack of 15 images/Helicon Focus

 

... and finally for Actinoptychus, here is a 3D view again, but this time created using Helicon Focus to combine 92 differential interference contrast images:

Microscope: Zeiss Standard GFL
Objective: Leitz 40/0.7 NPL ICT Fluotar
Substage: Leitz ICT
Ocular: Watson x8 Compensating
Stack of 92 images

 

A selection of diatoms in a strew slide of a sample from the Bosphorus Sea

Zeiss GFL microscope
Objective: Zeiss x40 PH2
Ocular: Watson x8 compensating
Phase contrast
Camera: Canon Powershot S50
ISO200, F4.9, 1/13 sec

 

Desmids

These are another type of single celled algae, and again they come in many beautiful forms.

Closterium

Projectina Microscope
Ocular: x10 phot
Objective: x10 achromat
DG illumination: wheelstop

Collected from my garden pond

Other Algae

Pandorina

Zeiss GFL Microscope
Ocular: Watson x8 compensating
Objective: Zeiss x40 plan achromat
Brightfield flash
Camera: Canon Powershot S50
ISO100, F4.9, Flash

Sample from Boldings Brook surface film (Warnham Millpond, Hosrham, UK) 10 July 2005

Spyrogyra

Zeiss Standard GFL Microscope
Objective: Zeiss x10 Plan achromat
Ocular: Watson x8 compensating
Brightfield
Sample from Warnham Millpond
1/250 sec, F8, ISO100
Stack of 15 images/Helicon Focus

 

Synura uvella(?)

This is a rather like a spherical cluster of grapes, each one of which has a flagellum. The whole colony swims with a rolling motion, tumbling through the water.

Microscope: Zeiss Standard 18
Ocular: Zarf G9 Photo-adapter
Objective: Leica EF L 20/0.3
COL
Camera: Canon Powershot G9/Flash
Sample: Wimbledon Common 31 May 2008
Stack of 12 images, CombineZP

 

Phacus, a Euglenid alga

Microscope: Zeiss Standard 18
Ocular: Zarf G9 Photo-adapter
Objective: Leica EF L 20/0.3
COL
Camera: Canon Powershot G9/Flash
Sample: Quekett Microscopical Club excursion to Wimbledon Common 31 May 2008

The dark spot at the left end of the organism is in fact a red eye spot


Gonium pectorale

This is a free swimming algal colony, usually of 16 cells, the inset shows the colony in motion, and the flagella can be seen that provide propulsion

Microscope: Zeiss Standard GFL
Ocular: Zeiss Kpl W 10x/18
Objective: Leitz x40 NPL Fluotar ICT
Substage: Leitz ICT
Sample from garden pond 11 Aug 2007

 

Coleochaete scutata

Microscope: Zeiss Standard GFL
Ocular: Olympus P15
Objective: Leitz x40 NPL Fluotar ICT
Substage: Leitz ICT
Sample grown in microtube in Pond at Warnham LNR

 

 

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