Sunday, December 27, 2009

A freshwater ciliate

I am an amateur naturalist trying to discover everything living in my garden.

Some time ago I wrote about the Haematococcus algae I discovered in a puddle in my garden. At the time I enthused about the book Freshwater Microscopy by W.J. Garnett, a guide from another era for the amateur to culturing and identifying pond life. Inspired by the book I recently revisited my puddle and was well rewarded with a number of tiny critters new for me. Photo 1 (click to enlarge) shows three : a) A ciliate (more below) b) what I think may be a cyanobacterium and c) another ciliate that I think may be a paramecium. (As always my identifications come with a health warning. I'm happy to have them corrected).

Photo 2 shows a closeup of 'a' taken at 1000x magnification using my microscope's oil-immersion lens. Features to note about my organism are its large nucleus and the numerous swimming hairs (cilia) covering its body.

Those interested in such arcane matters (those not may like to skip this paragraph) may like to know the specimen here was stained with ~0.01% aqueous Eosin dye then mounted in a mix of water and glycerin with a little added disinfectant (to prevent future growth of mould). In an attempt to render the slide permanent I adopted the 'double cover slip method' . There's a detailed explanation of this here but briefly it involves sandwiching the specimen in its aqueous mountant between two differently sized coverslips, then mounting this sandwich in turn in a solvent based mountant (Permount in my case) thereby sealing in the aqueous mountant against evaporation and hopefully rendering the whole arrangement permanent. (Since acquiring my hobbyists microscope a couple of years ago I've developed a growing passion for making up microscope slides!)

Returning to my specimen itself, I have a couple of basic photoguides to pondlife and from images in these, and the general size (~40um) and form of my ciliate, I was tempted to identify it as a species in the genus Colpidium. You can find some stunning photo's of this and other protozoa here. From the volume of images on the web this seems to be a not uncommon find in pondwater. Unfortunately however, having looked at the equally splendid Protist Images website I'm no longer so confident. The problem is that the phylum Ciliphora (=little organisms like mine with cilia) is broken down into such a large number of superficially similar genera that it's hard for the amateur like me to know that my wee beastie is definitely a Colpidium and not say, a member of the catchily entitled Trithigmostoma, or the Drepanomonas, or the Cinetochilium...or for that matter the Tetrahymena I hear you cry! The Protist Database does give some guidelines for discriminating amongst these genera - typically discrimination involves carefully noting the position of mouth parts, the presence/absence of any stiffer bristles amongst the more whiskery cilia, or the absence of cilia on some parts of the body - but I confess I've not attempted to apply these to my organism since, firstly, the time commitment, my limited number of specimens and my comparatively humble microscope setup would, I'm sure, limit my chances of a successful identification. Secondly, there exists a nagging worry at the back of my mind that the taxonomy ('family tree') of the protozoa may not in fact be correctly established at this time. Certainly, the arrival of DNA sequencing technology is requiring that large amounts of what was assumed to be true about the inter-relationships of different species in other fields of biology is having to be drastically revised. The problem is that what two species look like is not necessarily a guide to how closely related they really are. DNA testing is revealing that superficially similar organisms can sometimes be only distantly related. The opposite is also true. I wrote about this in detail in my previous posting on the Glistening Inkcap Coprinus mushroom. I have no knowledge of the true status for microscopic cilates but I would not be at all surprised to learn that their taxonomy is also undergoing something of an upheaval amongst the professionals. For this reason also I've not attempted a more detailed identification of my ciliate. Of course, my thinking on all this may be entirely wrong. Perhaps someone looking at my photo's can tell immediately what species I have. If so, and you're that person, do please leave a comment.

Friday, December 25, 2009

Fieldfare Turdus pilaris

I am an amateur naturalist trying to learn something about everything living in my garden.

Happy Christmas!

And what better way to enjoy the day than with a photo of one of my favourite visitors to the British garden: the Fieldfare (Turdus pilaris). Photos 1 and 2 show rear and front views (captured using my home-made camera trap incidentally).

I have an apple tree in my garden, which, besides providing a home for various lichens and mosses (not to mention a resting post for beeflies!) yields a bumper crop of cooking apples. So many in fact that that I have given up trying to collect them all and lots are left to lie on my lawn where they fall. They may look a bit untidy but this is more than made up for by the large numbers of Blackbirds, Fieldfares, Song Thrushes and other birds they attract come winter. In my garden, it is not unusual to find fifty birds at a time feeding upon them .

At 26cm in length and 100g, Fieldfares are a little larger and stockier than Song Thrushes (the BTO site has a host of biometric data). They eat invertebrates and berries (and apples!).
Fieldfares are not really resident in Britain. I say 'not really' since, as I learn from my copy of the RSPB Handbook (Holden and Cleeves) in fact a first British breeding pair was recorded here in the Orkney Isles in 1967. Over subsequent decades the number climbed to a peak of 13, but has since fallen back to less than five pairs a year. Of the population of one million individuals in Britain and Ireland, the overwhelming number are winter migrants, arriving here from late October from Scandinavia and Northern Russia.

Attempting to learn something further about Fieldfares I did a quick internet search and came across an interesting online paper by O. Hogstadt Nest Defence Strategies in the Fieldfare (Ardea 92(1), 79-84) in which the author reports studies of the response of nesting Fieldfares to effigies of crows and stoats - common egg predators of the Fieldfare. The Fieldfare's under study showed a distinct and rather well optimised reaction to these two predators. With crows, the reaction was to try to deter the attackers by defecating on them. This makes sense as fecal matter would certainly be detrimental to the performance of a crow's feathers. With stoats however, the reaction of the Fieldfares was to silently slip away from the nest and delay their return - eminently sensible when faced with a predator that hunts mainly by smell and is an equal danger to eggs and adults alike.

To end why not a few lines of poetry. These from the Cornthwaite by the British poet, Norman Nicholson (1914-1987):

Granite and black pines, where the migrant fieldfare breeds
And the ungregarious, one-flowered cloudberry
Is commoner than the crowding bramble.

Saturday, December 12, 2009

A mushroom Psathyrella lutensis

I am an amateur naturalist trying to identify everything living in my garden.

Photo 1 shows a small troop of mushrooms I found growing in some damp grass beneath my garden hedge.
From its general appearance my first thought was that these were a type of ink cap mushroom (see my previous posting here), but after watching them for a week there was no sign of any of the caps dissolving into an inky mess and it was clear further investigation would be needed.

The first thing to do when seeking to identify a mushroom is to take a spore print. This is extremely easy: place a cap, gills down, on any suitable surface, wait twenty minutes, remove, and hey presto - a spore print. That of my mushroom is shown in photo 2. Knowing spore colour (here, black) will typically allow you to rule out at least half the species in the average mushroom guide.

If you have a microscope it can also be valuable to ascertain spore shape and size. Mine were ovoid and around 12x6micron (photo 3).

Other features I noted for my mushroom were the the grooved (the technical term being striate) mostly brown cap, fading to white at the edge, and the 'flakey stem' (a.k.a. floccose stipe) in photo 1.

With these features in mind it was time to turn to the guide books. Unfortunately, such is the number of species of mushroom in Britain (more than 3000, with others, new to these shores, being recorded regularly) that no single guide book can cover them all. This proved the case for my mushroom. I failed to find it in the first three books I tried, the floccose stipe proving a rather troublesome feature, ruling out a number of otherwise similar small brown mushrooms in the books. It wasn't until I turned to my copy of Mushrooms and Toadstools (Cortecuisse and Duhem) that I found a picture of Psathyrella lutesnsis. All the features were there and I'm fairly confident in this indentification.

Cortecuisse describes P. lutensis as growing on damp ground (a fit with my location) and being scare-to-rare.

I have learnt in the course of writing this blog that almost any life form I come across will have some unique and curious aspect to its lifestyle (for example, its relationships with other creatures, its chemistry, or its means of reproduction). No doubt this is true of P.lutensis. Unfortunately my searches have failed to turn up any information about it whatsoever. Perhaps I have merely looked in the wrong places. On the other hand, so sporadic and fleeting may be its appearance that perhaps no one has ever studied my enigmatic little mushroom. If anyone knows more any more about it than merely its name, do please leave a comment.