An Insight into Daphnia biology

Daphnia are truly amazing. They are often called ‘water fleas’ as they look like tiny fleas swimming around in lakes and ponds. However, they are harmless and fascinating to observe. You can easily find some at home – just scoop a bit of water out of your pond with a pot and hopefully there’ll be plenty of these complex organisms bobbing about!

Believe it or not, Daphnia are actually tiny crustaceans, related to crabs, lobsters and woodlice. The reason they don’t look very similar is that the shell of Daphnia is uncalcified (not hard). This means they’re see through, and so great to put under a microscope. Yesterday and today I collected a few Daphnia from the pond with my pipette (like a small turkey baster), put a drop of water containing the Daphnia on a microscope slide and placed a cover slip gently on top so that the Daphnia wouldn’t be squashed.

Looking at them under a microscope reveals a whole new view on their lives, which we could never see with the naked eye. This photo I took yesterday and I find it most intriguing, Daphnia obtusa giving birth!

Daphnia giving birth!

Daphnia giving birth!

In the photo you can make out a smaller version of the adult Daphnia just below it’s rear end, at the bottom. Look for the black eye. To add to that, as the Daphnia is see through, you can also see its twin still inside the adult!

With the Daphnia collected today, I could also see their tiny heart beating. This short video I recorded shows it well:

To help give an idea of where the heart is on a Daphnia, this is the image of the pregnant Daphnia with most of its anatomy labelled:

Simple Daphnia Anatomy

Simple Daphnia Anatomy

The antennules – These are antennae, but instead of being sensory organs, they have evolved to be used to propel the Daphnia through the water. The ‘proper’ antennae are found beneath the rostrum, and are tiny. The mound on which the ‘proper’ antennae are born, sensibly called the antennal mound, is an important identification feature of Daphnia obtusa and is just visible in the image above. Daphnia obtusa has a noticeably larger antennal mound than similar species like Daphnia pulex.

I hope you’ve enjoyed this post on Daphnia. Hopefully this has inspired you to look for Daphnia in your own local pond or lake. Daphnia are incredibly unrecorded for such an abundant animal, which is probably present in nearly all squares in the UK:  >>CLICK<<


A Microscopy Workshop: a great day out!

On the way to Wales this summer (see Teifi Marshes, home to the Welsh Wildlife Centre) I stopped off at Brunel Microscopes Ltd.’s HQ in Chippenham to look for a microscope that would suit me best. I bought a microscope mainly for looking at fungi spores and other fungal structures, but I also look at other things like the leaves of Fissidens spp., a genus of mosses which are absolutely tiny. I’m still getting used to using the microscope, so today I went to a beginner’s microscope workshop in Great Bookham run by the West Weald Fungus Recording Group.

I was asked to bring my microscope to the workshop, so I did, but I left the stuff like the prepared slides, pipettes, coverslips etc. behind thinking that I wouldn’t need them. However, that turned out to be a mistake as I took just a few minutes to set myself up, whereas others started unloading whole dissection kits, oil immersion, all the chemicals and stains… at least there was a plate of Jaffa cakes to keep me busy!

The day started with a talk by Maurice Moss, who used to be a professor at Guildford University. He brought in two microscopes, one a dissecting microscope for larger objects like feathers and moths and the other a standard one like the one I have to look at fungi. He taught us all about how polarising filters can be used to look at colours in crystals and the colours the filters produced were phenomenal. He also let us look at some of his prepared slides, such as a peacock head feather, which again had superb colour.

After Maurice’s talk we chatted amongst ourselves about fungi (and other things!) and some people were able to recommend some useful tools and books. Many were quite surprised that I had no books whatsoever, and they had no hesitation in recommending “Mushrooms” by Roger Phillips. This looks really good and I think it will be a good purchase if I can find a copy , as well as a key to the genus Russula (a tricky genus) by Geoffrey Kibby, who regularly comes along to WWFG meetings.

After lunch was a talk by Barry Hughes, the author and photographer behind the Collins Fungi Guide. Many of the photos included in the book are taken in Surrey and West Sussex! He did a talk on spores and he handed out a few spore prints for us all to look at. He then asked us to look at them under the microscope and decide what shape they were using a sheet he handed out. My spores were from the genus Inocybe and almond-shaped! I learnt that there are a few tests you can do on spores to help identify it. You can see if the spores are amyloid, dextrinoid or neither by applying iodine using Melzer’s reagent or Lugol’s solution. If the spores turn black to blue-black when exposed to the substance then they are amyloid and if they turn reddish-brown then they are dextrinoid.

Other tests you can do include:

  • Putting a few drops of household ammonia onto the flesh of the fungus. The fungus might or might not have a reaction; if it does then the colour the flesh turns aids an identification.
  • A fun one: the gills of the genus Lyophyllum turn blue with Paradimethylaminobenzaldehyde.
  • When potassium hydroxide (KOH) is applied there is a colour change in some fungi, including agarics and boletes.

At the end of the afternoon, I had a really informative day. I learnt lots of new skills which hopefully I will soon be applying back home. I also had the chance to meet some really great people who love to share their interests.

One of my spore photos, taken earlier in the year.

One of my spore photos, taken earlier in the year.