Much of the pioneering work on the fungal parasites of algae such as Asterionella was performed by Hilda Canter-Lund during her time at the Freshwater Biological Association, which makes a nice link with this post, as the winner of the 2013 Hilda Canter-Lund photography award has just been announced on the British Phycological Society website. Hilda Canter-Lund was an extremely accomplished photographer of the microscopic world, producing pictures that combined high technical and aesthetic merits and was a Fellow of the Royal Photographic Society. The award was set up in her memory by the British Phycological Society.
I was extremely pleased that Chris Carter won this year. He made it to the shortlists in 2010 and 2011 and, as readers of this blog will already know produces pictures of an extremely high standard (see posts of 1 March and 14 May). Chris’ winning entry shows the reproductive organs of a stonewort, Chara virgata from a pond in Northamptonshire, where he lives. The visual focus s the bright orange antheridium, about 0.4 millimetres across, with interlocking shield cells caught just before they rupture.
Chara virgata: Chris Carter’s winning image in the 2013 Hilda Canter-Lund photography award.
Chris’ career was spent developing infra-red sensors in the electronics industry, with natural history and photomicroscopy as spare-time enthusiasms. Now he has retired from the electronics industry he has more time to spend on these enthusiasms, with some spectacular results. Despite all the advances in optical technology and digital imaging over the last decades, good microscopic images require an extraordinary amount of patience and technical know-how. His winning image encapsulates perfectly the standards that Hilda Canter-Lund set herself.
Chris Carter, out in the field collecting algae.
My post about John Snow pointed out that he made the link between contaminated water and disease without actually knowing what we now know about germs. In effect, Snow had made an inference based on the association between cases of cholera and the closest pump but correlation, as we tell our students, is not the same as causation. Elsewhere in London and beyond, others were desperately searching to identify the culprit itself.
Various theories had been put forward, dividing roughly into those suggesting a chemical origin and those suggesting a biological cause. One of the proponents of the latter was a doctor called Arthur Hill Hassall who looked down his microscope at samples he had collected from the reservoirs which supplied London’s drinking water and thought he had found the answer. The drawings he published in The Lancet show water teeming with algae and if this sounds preposterous, remember that this was still 20 years before Pasteur and Koch discovered bacteria, a group of organisms far too small to be seen with the microscopes available to Hassall.
Hassall published the first authoritive guide to the freshwater algae of Britain and described several new species including a diatom called Asterionella formosa which is very common in the plankton of lakes in the spring. The Latin name translates as “beautiful little star” and finding it in a sample always brings a wry smile to my face, as I recall the walk-on part this and other algae played in the story of the struggle to unravel the causes of cholera.
Asterionella formosa collected from Dannemarche Reservoir in Jersey in June 2013 by Dave John. The scale bar indicates 10 micrometres (1/100th of a millimetre).
The individuals photographed here come from a reservoir in Jersey. I spend a day each year teaching on an algal identification course based in Durham. It relies on water samples brought along by the tutors and participants which means that there is always a rich assortment of material from all over the country to examine. I was checking this sample before the class when I noticed the beaded appearance of the Asterionella. Under higher magnification, these “beads” resolved into yet tinier organisms, unicellular fungi called “chytrids” which had infected the alga.
Just as cholera was able to spread rapidly through the densely-populated regions of London in the nineteenth century, so chytrids thrive when Asterionella is most abundant. It is a reminder that diseases and infections are a natural feature of animal and plant populations, not just human scourges and, indeed, are an entirely natural way of regulating population numbers:
Little bugs have littler bugs
upon their backs to bite ‘em.
And littler ones have littler ones,
and so on, ad infinitum …