Hilda Canter-Lund competition winners 2018

The winner of the 2018 Hilda Canter-Lund competition for algal photography is Rafael Martín-Ledo for “Drifting diatoms”, his phase contrast image of a fragment of a colony of the diatom Licmophora, seen in a sample collected from the Bay of Santander, northern Spain, in March 2018.   There are over twenty cells attached to this branched stem, each just over a 10th of a millimetre in length.   The frond itself was probably originally attached to a seaweed in the littoral zone (see “epiphytes with epiphytes …”) but Rafael found it drifting in open water whilst using a plankton net.

Rafael trained at the University of Extremadura in Spain and started his research career with Biodiversity and Ecology of Marine Invertebrates group at the University of Seville. His primary focus during this period was the taxonomy, symbiosis and biogeography of the ophiuroids (echinoderms, including brittle stars) of Antarctic waters. After that he worked with the British Antarctic Survey in Cambridge, examining thousands of specimens from several expeditions.

Rafael Martín-Ledo: 2018 Hilda Canter-Lund competition winner.

He currently lives in Santander, working as an independent researcher with a particular interest in marine plankton. A personal project to document the larvae of planktonic invertebrates has led to the production of hundreds of images shared through a personal website, a YouTube channel (his videos of marine organisms are also of a very high quality) and a Twitter account (@rmartinledo). The primary motivation is taxonomic but a by-product of this is to make people aware of the great morphological beauty of lesser-known marine organisms.   Some other examples of his work are reproduced below.

 

More examples of Rafael’s photomicroscopy skills:
a. Larva, nectochaete stage, of Glycera alba (polychaete). DIC microscopy, 200x magnification;
b. Pilidium larva, gyrans type, of nemertean worm. DIC microscopy, 200x magnification;
c. Ascidian embryo (tunicate). DIC microscopy, 400x magnification; and,
d. Cymbasoma thompsonii, female with eggs (copepod). Polarization microscopy, 40x magnification.

More examples of Rafael’s photomicroscopy skills:
e. Tripos candelabrus (dinoflagellate). DIC microscopy, 200x magnification; and,
f. Zoothamnium pelagicum (colonial ciliate). Phase Contrast microscopy, 200x magnification.

The second prize this year, awarded to the photographer of an image in a contrasting style, goes to John Huisman, an old friend of the competition who has been on the shortlist several times, winning in 2014.  John is based in Perth, Western Australia and this photograph was taken during a trip to Ashmore Reef off the northern coast of Western Australia.   His motivation is to document the marine flora of this remote region, and the image shows a new species from the red algal genus Ganonema.  Ganonema is a genus of calcified, often mucilaginous red algae, the calcification occurring as granules in the cortex and not forming a firm skeleton. At Ashmore the new species was growing in coarse coral rubble at 12 metres depth. The photograph was taken while SCUBA diving, with a Nikon Coolpix P7100 in a housing with twin Inon strobes providing fill flash.

A new Ganonema: John Huisman’s prize-winning entry for the 2018 Hilda Canter-Lund competition.

You can see these and all other winners and shortlisted images since the competition started in 2009 at the Hilda Canter-Lund pages of the British Phycological Society’s website.

John Huisman: 2014 winner and 2018 second prize winner

 

 

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More pleasures in my own backyard

Back in early July I wrote about a visit to a pond in a local nature reserve (see “Pleasures in my own backyard”) and ended with the hint that there was one other abundant alga there that I was unable to name at the time.  I was reticent about naming it, as it seemed to be a rare alga and the habitat where I had found it did not match the locations where it had been found to live.

I’ve now shown it to Brian Whitton and he has joined me on another excursion to the same pond, and I can confirm that it is, in fact, Chroothece richteriana, a freshwater red alga.   We’ve met (and even eaten) red algae several times over the lifetime of this blog (see “More from the Lemanea cookbook …”), but Chroothece is different in that it does not form filaments or thalli, but lives in mucilaginous masses.   The individual cells, each of which are ovoid, with a single star-shaped chloroplast, live embedded within this mass.

Chroothece_Crowtrees_July16

A colony of Chroothece richteriana growing on marl-encrusted rocks from Crowtrees Pond, County Durham, July 2016.  Scale bar: 10 micrometres (= 1/100th of a millimetre).

This is a species that was, until recently, known only from two very old records. However, searches over the past few years have found it growing at a number of different locations.  There are now half a dozen locations in the UK, plus one in the Isle of Man.   Interestingly, the population at Crowtrees matches these other records in respect to the underlying geology – limestone – which yields very hard water, but differs in being permanently submerged.  The other records are from seepages and other semi-aerial habitats.   The population at Crowtrees formed a thin film that was firm to the touch due to the deposition of calcite crystals within the matrix.   There were also some cyanobacterial filaments mixed in amongst the Chroothece, as well as the diatoms that I mentioned in the previous post.  I suspect that the snails that I observed on my earlier visit were scraping up a mixture of all these species from the thin surface layer that had not yet had time to become hardened by calcite crystals.

One theory for the success of Chroothece here is that habitats such as this are naturally low in phosphorus, an essential nutrient that is naturally scarce but which is relatively insoluble and consequently is precipitated out of the water along with the calcite.   Studies in Spain (in a river, rather than a seepage or pond) showed that Chroothece shares the characteristic of several other algae from this type of habitat, of producing enzymes that can scavenge phosphorus from tiny particles that are suspended in the water.  The enzymes are thought to be concentrated in the mass of mucilage (which is actually formed from the organism’s stalks)

Ironically, our excursions to Crowtrees Nature Reserve have become more frequent over the past year or so as our usual running and walking beats in the countryside around Bowburn have been changed as a local quarry expands its activity (seen in the gouge in the skyline in the picture below).  The pond, itself, looks natural, but local drainage is strongly influenced by mining and quarrying.  The area around here, especially associated with the Permian limestone, abounds in nature.   But whether or not this nature is natural is a topic for another day …

view_from_Crowtrees_July16

The view from Crowtrees Nature Reserve towards the Tarmac quarry, July 2016.

References

Aboal, M., García-Fernández, M.E., Roldán, M. & Whitton, B.A. (2014).  Ecology, morphology and physiology of Chroothece richteriana (Rhodophyta, Stylonematophyceae) in the highly calcareous Río Chícamo, south-east Spain.  European Journal of Phycology 49: 83-96.

Pentecost, A., Whitton, B.A. & Carter, C.F. (2013).  Ecology and morphology of the freshwater red alga Chroothece in the British Isles.  Algological Studies 143: 51-63.

The complicated life of simple plants …

I have a theory, which I have touched on before in these posts, that the success in conveying the wonders of nature to non-biologists is easiest when the audience can relate what they see directly to their own experiences.   You only have to watch a typical David Attenborough documentary to see this principle at work: it may feature sumptuous photography in glorious landscapes, but the events portrayed are not so different to a typical Friday evening at the Bigg Market in Newcastle.   The BBC Natural History Unit would find plenty of courtship activities, territoriality and several kinds of violence here, much of it set around watering holes.   Who needs a plane ticket to an exotic location?

As we lose that sense of empathy, so nature becomes “weird”.  A few of us find fascination in the weird but we are a minority.   Strangeness, however, brings problems, as I have commented before (see “Reflections from the trailing edge of science”) as stories cannot be conveyed using familiar metaphors drawn from our own experience.   The example I used in that earlier post was the concept of “alternation of generations” in plants and my recent encounter with the red alga Lemanea a couple of weeks ago (see “Spaghetti Carbonara con Lemanea”) reminded me of a set of wonderful photographs by Chris Carter that illustrate this concept very well.

That post contained a photograph of Lemanea from the River Ehen in Cumbria which shows some of the wiry filaments growing on the stream bed.   These filaments are, actually, hollow tubes of cells (see photograph in “The River Ehen in April”) along which there are a series of nodes.   The nodes, in this case, bear sexual cells at certain times of the year (see “Lemanea in the River Ehen”).

Lemanea-Rede-crosssection

A cross section of a filament of Lemanea from the River Rede, Northumberland (photo: Chris Carter).

Chris’ photographs shows how the Lemanea filaments are actually composed of a hollow tube of cells with an outer cortex.  However, the centre of this tube is not completely empty, and the clusters of cells that we can see inside the tube are spore-producing organs called “carposporophytes”.   At some point during the development of the carpospores, two cells fuse so that the carpospores is diploid (2n), rather than haploid (n).   The carpospores are released when the Lemanea filament dies back in late Spring and these then germinate into a filamentous sporophyte (2n) phase, called the “chantransia”.  At some point during the winter, these chantransia undergo meiosis, and the resultant haploid cells grow, still attached to the chantransia, into the next generation of gametophytes.

Lemanea-transp_CFC

Transapical view of a Lemanea filament; the arrows show the sporophytes (“carposporophytes”) inside (photo: Chris Carter).

Finally, I have included Chris’ high magnification photograph of some of the cells of this carposporophyte plant, looking very similar to simple red algal genera such as Audouinella, which prompted my original series of posts on alternation of generations.

These photographs capture my fascination with the algae: apparently simple, easily overlooked, but actually presenting sophisticated, highly-evolved solutions to survival under tough circumstances.   The constant current in rivers makes establishing and maintaining a population at one place hard enough, more so when a “population” actually consists of two discrete stages.   This has led some to suggest that the complexities of the red alga life cycle may be a form of “bet hedging”, spreading the risk of mortality between the life stages.   Having a large gametophyte phase, for example, gives the plants access to more light, making them more productive, but they are also exposed to the strong currents in the river, increasing their risk of loss due to scour.   On the other hand, the smaller sporophytes (the “chantransia”) are protected from the ravages of the current because they live close to rock surfaces, within a “boundary layer” where current velocity falls off due to drag.  It could be seen to be roughly parallel to the metamorphosis of butterflies and other insects, with phases of the life cycle optimised for different activities.

Lemanea faces a particular challenge: the gametophytes have “solved” (excuse the teleology) the challenge of living in very fast current speeds, where they have little competition from other plants and algae and, I would guess, little threat from grazing invertebrates.   This gives the genus plenty of scope to thrive in fast-flowing upland rivers.   There is normally a benefit to an organism of releasing spores and gametes into their immediate environment, as this encourages dispersal and cross-breeding. Were Lemanea to do this, the spores and gametes would be washed quickly downstream, away from their ideal habitat.  The practice of keeping the carposporophyte inside the thallus, rather than on the outside, increases the chances of some of the carpospores finding their way to the rocks in the immediate vicinity of the gametophyte and, thereby, ensuring that the chantransia are well-placed to produce a new gametophyte generation the following year.

It is all very complicated.  This is, I suspect, partly because systematic biologists have a fondness for obscure terminology that makes it hard for the non-initiate to follow the twists and turns of life cycles.  But it also, I suspect, a consequence of dealing with habits and life cycles that are unfamiliar and, more importantly, cannot be distilled down to simple, anthropomorphic metaphors.

Lemanea_Carpospores_CFC

High magnification view of carpospores of Lemanea (photo: Chris Carter).

Reference

Sheath, R.G. (1984).  The biology of freshwater red algae.  Progress in Phycological Research 3: 89-157.

Something else we forgot to remember …

The story of the mysterious red alga that I wrote about a couple of weeks ago (see “More than just an insignificant dot?”) has taken another intriguing turn.   Having decided that the alga was probably Audouinella pygmaea, I was shown a paper from 2011 by Orlando Necchi and Marianna Oliveira in which they consider the affinities of Audouinella species and came to the conclusion that Audouinella pygmaea only really exists in the imaginations of people who write identification guides. I’ve written before about the complicated life history of red algae (see “The schizophrenic life of red algae …”) and commented that it can be hard to differentiate between simple red algae such as Audouinella and stages in the life history of more complicated red algae.

Audouinella hermanii, the red alga that I was writing about in those earlier posts, does not present us with any serious problems, as it is possible to see all the reproductive structures, which enables us to distinguish between the (haploid) gametophyte filaments and the (diploid) sporophytes. However, reproductive organs have not been observed on populations of A. pygmaea, which presents us with some problems. Is this really an independent species of Audouinella or just a “chantransia” (gametophyte) stage of another red alga? Necchi and Oliveria took a number of populations of A. pygmaea and another species, A. macrospora (which has not been recorded from Britain or Ireland) and compared their genetic composition with other freshwater algae. What they found was that these chantransia stages were more closely related to known species from other red algal genera than they were to each other.   Their conclusion: “Audouinella pygmaea” does not exist in any meaningful sense. Rather, the populations we describe as A. pygmaea represent life history stages of other red algae. These life history stages are impossible to tell apart from one another using morphological criteria.   However, there is a good chance that a thorough search of the Anghidi Fawr stream upstream of where the sonde was placed will reveal another red alga – most likely Batrachospermum or Thorea – that was releasing the carpospores that produced the filaments that we named Audouinella pygmaea.

Curiously, this brings us back close to the situation almost 100 years ago as, reading my trusty old copy of West and Fritsch I read that the freshwater species we now call Audouinella were then placed in the genus Chantransia and that “C. pygmaea is probably a stage in the life-history of Batrachospermum moniliforme Roth.”   Another case, perhaps, of things we forgot to remember?

Reference

Neechi, O. Jr. & Oliveira, M.C. (2011). Phylogenetic affinities of “chantransia” stages in members of the Batrachospermales and Thoreales (Rhodophyta). Journal of Phycology 47: 680-686.

West, G.S. & Fritsch F.E. (1927). A Treatise on the British Freshwater Algae.   Cambridge University Press, Cambridge.

More about red algae

One other alga that we saw at Burn Head (the location near Whitbarrow Quarry) was tucked away in a shaded area close to where the spring bubbled out from the base of a limestone cliff. At first glance, this was barely recognisable as a plant, as it looked more like a splash of red paint on a rock. It is, however, a thin crust of red algal cells, called Hildenbrandia rivularis. This is the only freshwater representative of the genus, although other species can be found on the seashore. Under the microscope, you can see polygonal cells, though we are actually looking here at the top of a short stack of cells.

I generally associate Hildenbrandia with good ecological conditions although, as for Batrachospermum, there are exceptions, as I have seen it growing at quite high nutrient concentrations in chalk streams and, I daresay, it thrives in enriched waters elsewhere. Here it was growing in very shaded conditions, and I have also seen it growing under quite thick patches of moss, which must also have trapped much of the light. However, I often see it growing in shallow, well-lit places as well.

Whitbarrow_Hildenbrandia

Hildenbrandia rivularis from Burn Head, southern Cumbria, May 2014.

So why are some red algae red and others not? The answer to this question lies in the pigments that they contain. Red algae, like Cyanobacteria, contain chlorophyll a (the common green pigment), plus two protein-based pigments, phycoerythrin (red) and phycocyanin (blue). The balance of these two pigments influences the final colour of the organism: those with more phycyoerythrin tend to be red; those with more phycocyanin have a blue-green or grey-green colour. Red-coloured algae have an advantage in deep water as it can absorb those wavelengths of light that penetrate furthest. Being able to absorb over a broader range of the light spectrum than would be possible if it just had green chlorophyll means that a plant is able to use the limited light more efficiently. Why we find some red-coloured algae in shallow, freshwater situations is a mystery. It may simply reflect the evolutionary history of the genera concerned. It may be significant that two of the reddest freshwater red algae (see also “At last … a red alga that really is red”) both come from genera that can be found in both freshwater and marine locations whereas the two olive-green genera we’ve met (Lemanea and Batrachospermum) are found exclusively in freshwaters.

Hildenbrandia_ChrisCarterr

Looking down on a crust of Hildenbrandia rivularis, showing the tops of the polygonal cells. Photograph: Chris Carter.

Algae … cunningly disguised as frog spawn?

A couple of kilometres from Whitbarrow Quarry there is a spring that we always visit during the “Introducing Macroalgae” course because it usually yields a range of larger algae that we like to ensure that all the students can recognise. One of these forms tufts of filaments that are very slippery to the touch. There is a slight resemblance to frog spawn in both appearance and texture: under a hand lens the filaments can be seen to have a beaded appearance and this plus the texture creates a superficial resemblance to frog spawn. It is, in fact, another red alga, Batrachospermum which, like Lemanea (see “Lemanea in the River Ehen”) has an olive-green rather than red colour. I’ll explain more about that in the next post. I have also included one of Chris Carter’s photographs to show the structrure of Batrachospermum at higher magnification: the “beads” are composed of tufts of branchlets arising from a central filament.

Whitbarrow_Batrachospermum

Left hand image: Batrachospermum sp. growing at Burn Head, near Whitbarrow in Cumbria; right-hand image: filaments of Batrachospermum in the palm of my hand. Each of the “beads” is about half a millimetre across.

Batrachospermum_Bodmin_Chri

Batrachospermum sp. from Bodmin, Cornwall. Photograph by Chris Carter

I usually associate Batrachospermum with healthy ecological conditions: low nutrients, clear, cool water and diverse invertebrate communities. However, when I told the group on our course this, one of the participants said that he sometimes found it in quite polluted conditions. Interestingly, the same thing happened on a presentation of the course a few years ago and both the contradictory examples were from chalk streams in southern England. I went back to the published literature to reassure myself and, sure enough, these also referred to Batrachospermum as a species associated with good ecological conditions. There must be, however, some rare combination of conditions that enables Batrachospermum to occasionally proliferate in very enriched conditions. What we have, I suspect, is a common situation in ecology: we base our inferences about preferences on statistics rather than ecophysiology. This means that we assume that an association between a genus or species and a set of environmental conditions represents the realised niche of the species, without always understanding the nuances of ecology and physiology that determine these niches.

Next time: a red alga that really is red.

Lemanea in the River Ehen

The rocks in the fastest-flowing sections of the lowermost of our four sample sites on the River Ehen were all smothered with the coarse filaments of Lemanea fluviatilis. Lemanea is another red alga (see “The schizophrenic life of red algae …”) but one that grows to a much larger size than Audouinella which I wrote about back in early February. I wrote about Lemanea last year (“The River Ehen in April”) but that was before I had an underwater camera. However, most of the Lemanea is attached to large, stable boulders located in sections of the river where the fast current made it almost impossible to photograph safely. Instead, I hunted around and found a smaller stone that was wedged in amongst these, and moved this to a shallow area where it was easier to photograph.

Lemanea_fluviatilis_in_Ehen

Lemanea fluviatilis from the River Ehen in March 2014. Scale bar: one centimetre.
If you look closely you will see that each of the filaments has a series of nodes along its length. Under the microscope, these nodes form darker patches, composed of smaller cells than the rest of the filament. These are, in fact, the reproductive structures, spermatangia, of the plant as Lemanea has a similar life-cycle to that of Audouniella, which I described in my earlier post. There is also a closely-related genus, Paralemanea, which looks like Lemanea but which has these spermatangia in rings rather than in patches. Older books do not recognise the distinction between Lemanea and Paralemanea.

Lemanea_fluviatilis_stack

Lemanea fluviatilis from the River Ehen, March 2014. a. low-power image showing the knobbly stems; b. close-up of a single stem showing the spermatangia patches associated with these protruberences (scale bar: 20 micrometres; 1/50th of a millimetre); c. close-up of a patch of spermatangia.
Lemanea is, in my experience, a very useful indicator of good quality aquatic ecosystems. Looking back through my own records, I see 88 per cent are associated with “high status” or “good status” conditions and the few instances where it is found associated with poorer quality conditions, it is always quite sparse. There is a site quite close to Durham where we used to find Lemanea despite the water being quite enriched with nutrients: though low down in the catchment there was an extensive riffle area with fast currents and, I suspect, few other organisms able to compete for Lemanea’s favourite conditions. Remember, too, that there are enormous reserves of Lemanea in the upper catchment of the River Wear, and plenty of opportunities for this to be scoured off boulders and carried downstream. The wise ecologist always works on “balance of evidence”, rather than making categorical judgements on the presence or absence of a single organism. There is, simply, too much that we still don’t know about the biology of these species.