Survival of the fittest (2) …

As well as the bright green flocs of Tribonema, the stream draining the Hadjipavlou chromite mine also had bright orange-red growths on some of the pebbles on its bed.  These seemed to be composed primarily of the Cyanobacterium Chamaesiphonthough I am still not sure what species.   Using the limited literature I have, from the UK and Germany, I would opt for either Chamaesiphon polymorphusor C. polonicus.   This particular alga was very easy to remove from stones, compared to other epilithic Chamaesiphon species (see “A bigger splash …”).  This is a feature of C. polymorphus, though the colour is more typical of C. polonicus*.  On the other hand, that bright colour could be the response to high solar radiation, so maybe my north European guides are not that reliable.  It could be something else altogether.

Chamaesiphon_polonicus_Troodos

Chamaesiphon growths on pebbles in the stream draining Hadjipavlou chromite mine in the Troodos mountains, Cyprus, March 2019.

Chamaesiphon_Troodos_Mar19

Colonies of Chamaesiphon from Hadjipavlou chromite mine under the microscope.   Scale bar: 10 micrometres (= 1/100thof a millimetre). 

In addition to the Chamaesiphon, there were a few diatoms, mostly Achnanthidium minutissimumand Meridion circulare.   These are typical species of metal-rich streams, as is the general lack of diversity that was evident.   There were also a few filaments of the cyanobacterium Phormidium, along with quite a few Paramecium and Vorticella.  As these are both heterotrophs that feed on organic matter, their abundance is probably at least partly a reflection of the long time that the sample spent in my suitcase between collection and analysis.  The latter is a fascinating organism to watch: it is a goblet-shaped cell with a fringe of cilia around the lip (or “peristome”).  These beat in unison to create water currents that draw small particles towards the cell.   These particles mostly at least an order of magnitude smaller than the algae)  are then collected in food vacuoles where they are digested.   A few of these vacuoles can be seen in the image of Vorticella below.

Vorticella is attached to its substrate by a stalk which contains contractile filaments, giving it spring-like qualities.  Watching a Vorticella is a beguiling experience, with the undulating rows of cilia drawing food into the vestibule (as the opening is known).  At intervals, the whole cell lurched across the field of view as the “spring” in the stalk suddenly contracted, shortening the stalk.  After this, the stalk would gradually extend again, the cilia not having missed a beat meanwhile.   This process may simply be a device that enables the Vorticellato exploit its locality to the full, as well as creating some additional turbulence to keep a steady flow of particles towards the peristome.  To be honest, I haven’t seen a more convincing explanation but, even if we don’t know why it does what it does, Vorticella is a fascinating organism to watch, whether or not I understand what is going on.

I’ll be coming back to talk more about the diatoms in a future post, and writing these posts has also reminded me that I’ve never written about the interesting mine sites almost on my own doorstep.  I cut my ecological teeth looking at these habitats back in the 1980s and they are striking examples of natural selection in action.   So, plenty of potential for more left-field natural history …

Hadjipavlou_organisims_Mar19

Other organisms present in the Hadjipavlou chromite mine. a. – d.: Meridion circulare; e. Phormidiumsp.; f. Vorticellasp.   Scale bar: 10 micrometres (= 1/100thof a millimetre). 

* Note: after I had written this post Brian Whitton confirmed that it was, most likely, Chamaesiphon polonicus.

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