The rain made me start thinking about rain pools and all that is living in it. Especially when rain is combined with sediment, mosses and other plants. A small film of water started to form in my garden pots. So I decided to wait a few days and sample the tiny pools in my garden. I squeezed leaves from the begonia and small mosses in the miniscule pools. The first interesting organisms that I discovered were desmids.
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| Cosmarium holmiense var. integrum at 600x immersion-oil. Sample: My home Goirle. |
In the first photograph you will find Cosmarium holmiense var. integrum. It’s a distinctive desmid, recognizable by the semicells being rounded like tum-tum candy (high-trapeziform), but with a little kink in it. The desmid has ribbon-like chloroplasts in each semicell, which can be clearly seen with a light microscope. The cell wall is smooth.
Cell dimensions are approximately 55 x 30 µm; variation in length (36-) 45-62 (-76) µm, variation in breadth (23-) 28-40 (-44) µm. Cosmarium holmiense is mainly found in arctic-alpine ecosystems, though shallow Dutch dune pools and rain pools on sediment or mosses are also known for the distibution of Cosmarium holmiense (Coesel & Meesters 2007, http://www.desmids.nl/).
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| Staurastrum striatum at 600x immersion-oil. Sample: My home Goirle. |
The second photograph shows Staurastrum striatum. This desmid has tiny bumbs on its semicell(delicately granulated, granules arranged in concentric patterns around the lateral angles), and has a radiated structure. The semicells are (sub)rhomboid in outline, like diamonds, only the angles are rounded-truncate. Cell dimensions: length 25-35 µm, breadth 24-36 µm. This species is mainly found in fen hollows, moorland pools and rain pools.
The third photograph doesn’t show desmids. These are cyanobacteria called Nostoc (genus), the filaments with spherical cells, and Leptolyngbya (genus), the very thin almost colourless filaments. I found these cyanobacteria in a vase that has been standing on my balcony for some time, while organic compost of leaves were left there in a pool of rain.
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| Nostoc and Leptolyngbya at 100x without immersion-oil. Sample: My home Goirle. |
Some Nostoc species grow symbiotically* within plant tissues or endophytically^ in mosses and fungi; add some rain to degenerating tissues and Nostoc will swell up like a yellowish-brown heap of gelatine. Leptolyngbya also forms clusters and mats, which were almost ‘weaved through’ the slimy Nostoc. Leptolyngbya is very common in soils and freshwater biotopes.
You can find more information in the Cyanobacteria Database, click here
It was an exciting experience to discover so many interesting organisms almost 'on my doorstep', while rain drops gently brushed the leaves of my begonia's and the tiny mosses in simple garden pots.
*Symbiosis: a close, prolonged association between two or more different organisms of different species that may, but does not necessarily, benefit each member.
^Endophyte: an organism, especially a fungus or microorganism, that lives inside a plant, in a parasitic or mutualistic relationship.
Photocredits
All microscopic photographs were taken with Olympus IX81, DP72 and cellSens Dimension at 100x-600x magnification, with/without immersion oil. Photographs and samples: Marta Demarteau © Orbica/Aquon. Species found verified by expert AMT Joosten.
Literature
Coesel PFM & Meesters KJ (2007) Desmids (Desmidiaceae) in the Netherlands http://www.desmids.nl/
Coesel PFM & Meesters KJ (2007) Desmids of the Lowlands - Mesotaeniaceae and Desmidiaceae of the European Lowlands, KNNV Publishing Zeist
