When real life imitates testates: a 2019 ‘Testate amoebae in the real world’ calendar?!

Contributed by Matt Amesbury and Alex Whittle

(Real!) testate amoeba photos used with the kind permission of Ferry Siemensma, Microworld, www.arcella.nl

Matt:

As testate amoeba analysts, we all spend countless hours staring down the microscope studying and identifying hundreds upon thousands of shells. Perhaps foolishly, I once added up, out of perverse interest, the number of tests I had counted over the course of a three year project developing palaeo records from three Holocene age cores, a couple of shorter cores and developing a regional transfer function. The total was 130,384.

I still can’t quite decide whether this number amazes or sickens me (!), but it certainly does make it understandable that we should all begin to see the familiar shapes and structures of tests when we close our eyes, in our sleep and even in the real world.

Forward on almost a decade from that count-heavy project and I have moved to the University of Helsinki for a year to work on testates from permafrost peatlands. It’s the weekend and I am enjoying a walk in the local forest with my family. We stop for a snack of ruis sippi; circular, bowl-shaped rye crackers that are popular in Finland. My hand delves into the bag and I pull out a freak cracker with the front still attached. The recognition is immediate … keep reading to find out more!

Alex:

In the true collaborative spirit of our community, a photograph of this most unusual ‘specimen’ soon reaches me back at the University of Exeter. Having myself witnessed a curry resembling my second favourite testate amoeba taxa – Certesella certesi – just weeks before, this starts us wondering … how many other testates are hiding in plain sight, surrounding us in the real world? Others soon followed and we share the first three stories below. (I still deeply regret not taking a photo of the curry!)

Of course, the idea of a ‘Testate amoebae in the real world’ calendar was a natural progression, so please regard this blog as part amusing distraction and part call to arms! Go out into the world, friends and colleagues, find and photograph whatever you can that strongly resembles a testate amoeba and send them in to us!

 

1. Centropyxis ‘rye-crackeris’ (Lat: 60.2165°N, Long: 25.0327°E).
Finnish rye crackers generally exhibit a hemispherical boat-shape morphology, adapted to hold some sort of filling. This one obviously had other ideas and preferred to imitate Centropyxis aerophila type, with its test construction of agglutinated rye grains and a sub-terminal aperture. The specimen was found on 13th August 2018 by Matt (and family) whilst stopped for a snack during a walk around the forested tracks and trails near the Viikki campus of the University of Helsinki.

 

2. Difflugia ‘shroomex’ (Lat: 54.5763°N, Long: -5.9356°W)
Many food stuffs that spend their short lives imitating testate amoebae are secretive and prefer to stay out of the limelight, many being digested by unsuspecting members of the public without ever fulfilling their destiny of being recognised for what they really are. However, some are brazen and do everything they can to be found. One such example is this mushroom amoeba with test of agglutinated breadcrumbs (or Difflugia pulex type) who, astonishingly, infiltrated the lunch buffet on day three (13th September 2018) of the 9th International Symposium on Testate Amoebae (ISTA) held at Riddel Hall, Belfast. Found by Matt, who was distinctly peckish at the time and enjoyed the mushroom very much a short while after this photograph was taken.

3. Lagenodifflugia ‘vase’ (Lat: 64.1447 °N, Long: -21.9423°W)
As a word of caution, it is important to consider that not all everyday testates will be disguised as food items. Indeed, I (Alex) believe the stories above may indicate a particular ‘sampling bias’ by their author! Some are a much less ephemeral presence in everyday life and have invested much more energy into creating permanent tests in the hope of being identified – these are the K-strategists of real life testates. This individual was found by Alex, directly after ISTA9 on a wet and windy evening in late September (23^rd) in Reykjavik, Iceland. Considering the location of this record in the Northern Hemisphere, after some initial confusion with Apodera vas, we believe this real-life testate to be imitating Lagenodifflugia vas.

 

Distribution of real-life testates currently reported at the time of writing.

 

Remember that real-life testates may be spotted without warning and when you least expect them so keep your eyes peeled and cameras at the ready. We aim to fill the map with finds across the world and let’s not allow any testate genera to go un-represented!

We cannot wait to hear from you – the hotlines for reporting your real-life testate discoveries are: m.j.amesbury@exeter.ac.uk and aw424@exeter.ac.uk

The Beast of Cors Fochno

Contributed by Evelyn Greeves and Richard Payne

Hi, I’m Evelyn Greeves, a second-year biology undergrad at University of York making a brief foray into the world of testate amoebae as part of a research scholarship. I’ve been looking at a novel morphotype of Hyalosphenia papilio found at Cors Fochno, a raised, estuarine Sphagnum bog in North Wales. This ‘broad form’ morphotype is large (around 130μm wide on average), distinctive and easy to identify – but as yet undocumented anywhere in the world except for at this one location.

We suspect the morphotype may be either a very recently evolved subspecies of H. papilio, or some extreme phenotype which has adapted to the peat conditions at Cors Fochno. It looks a lot like a specimen of H. papilio which has been squashed to give it a fat “bottom” and is unique in that it is broader than it is high. None of the environmental conditions measured indicated anything special about the three sites (of total 36) at which it was found, though water table was typically high and pH low.

We want to find out if this morphotype is present in bogs other than Cors Fochno to build a better picture of what this beastie is, and what on earth it’s doing here. We’re especially interested in bogs with a similar raised, coastal ecology. If you come across a specimen which fits the description above, please contact Richard Payne at richard.payne@york.ac.uk.

Disclaimer: this post is not intended for purposes of nomenclature and is not issued as part of the permanent scientific record – this is not a formal description.

Recent research on testate amoebae in the tropics and other under-studied regions – an almost untapped research Eldorado indeed!

Contributed by Edward Mitchell

Laboratory of Soil Biodiversity, University of Neuchâtel, Switzerland

Vincent Jassey recently reported on tropical testate amoebae and especially those living in tank bromeliads (Jassey, 2017). These habitats are absent from higher latitude regions where winter frost would prevent the growth of such plants. Such “unusual” habitats are likely to house equally unusual testate amoebae and are therefore attractive for collecting samples to discover unknown microbial diversity.

More generally, tropical and higher latitude frost-free (e.g. hyper-oceanic) regions are likely to host a high diversity of testate amoebae. Recently several studies have explored these regions and confirm that indeed there is still a lot to learn regarding the diversity and ecology of testate amoebae.

For example, in a recent latitudinal study in Chile, Fernández et al. (2015, 2016) showed that testate amoeba diversity peaked at mid-latitude (ca. 40° S) corresponding to the Valdivian rain forest, a habitat characterised by high moisture and mild to warm temperatures (Fernández et al., 2015). This habitat is believed to correspond to the climatic conditions under which many lineages evolved, i.e. the need for high humidity and mild temperatures is a phylogenetically conserved trait (Fernández et al., 2016). Conditions further south are less favourable because the climate is harsher. conditions further north towards the tropics, despite being warm becomes increasingly dry up to the Atacama Desert, the driest place on Earth. Chile therefore is an ideal country to conduct research on latitudinal gradients of biodiversity.

However, even in apparently suboptimal conditions such as arid environments, interesting work can be done on testate amoebae. Leonardo Fernández explored the diversity patterns in a desert shrub-land and observed a nested pattern of diversity with communities in open, more exposed soil between bushes representing a sub-set of those living in the more favourable (or should we say less unfavourable) conditions (higher shading and thus likely more often or longer moist) beneath the bushes (Fernández, 2015).

These less studied regions also represent excellent opportunities to discover new testate amoeba species. Several recent examples are listed here:

Recently Horacio Pérez-Juárez studied the testate amoeba communities from an arid environment in Mexico (Pérez-Juárez et al., 2017). Perhaps not surprisingly he discovered a new species. The surprise however was that new species Quadrulella texcalense (Fig. 1), belongs to a genus that is best known from wet habitats such as fens. This illustrates well that when we explore “unusual” habitats we may be in for some surprises!

Fig. 1. Vegetation of Cerro Marrubio (San Antonion Texcala, Puebla, Mexico) and one of the barcoded specimen of Quadrulella texcalense (modified from Pérez-Juárez et al., 2017).

 Graeme Swindles and colleagues have recently studied the diversity and ecology of testate amoebae in the Amazon and Central America. Again, not surprisingly they found a new species, Arcella peruviana (Fig. 2), described by Monika Reczuga (Reczuga et al., 2015). This relatively small, but unmistakable species has a highly unusual lobed aperture.

Fig. 2. Arcella peruviana from Reczuga et al. 2015. The diameter (D) is on average 47µm.

 Another highly conspicuous species in genus Arcella was previously reported in this blog when discussing scientific names: Arcella gandalfi (Féres et al., 2016) (Fig. 3) (https://testateamoebaeresearch.wordpress.com/2017/02/17/whats-in-a-name-something-completely-different-to-be-said-about-taxonomic-nomenclature/). It is unclear if genus Arcella is especially diverse in the tropics. These amoebae are obviously easy to spot in a microscopic preparation (unlike smaller taxa such as Cryptodifflugia). To determine the possible existence of regional diversity hotspots and evolutionary radiation we clearly need more systematic inventories. With the growing interest in testate amoeba diversity, evolution and ecology we may hopefully be approaching a day when we will see a global inventory of testate amoebae take place!

Fig. 3. Arcella gandalfi, (modified from Féres et al., 2016). The test is on average 81µm in diameter (i.e. base of “Gandalf’s hat”).

Two new Pontigulasia species were recently described from aquatic habitats China (Fig. 4). The fact that such large species had not been described before suggests that there are indeed still many new species to describe in China as in other under-studied regions of the World.

Pontigulasia pentagulostoma (left) and P. zhangduensis (right) (modified from Qin, Xie, Gu, et al., 2008 and Qin, Xie, et al., 2008b). Scale bars: 100µm (left) and 50µm (right).

Tropical and other less studied regions also represent good opportunities to study the ecology of testate amoebae, either specifically or in relation to other soil or water organisms, ecosystem functioning, human impact and other relevant questions. A few examples are listed here:

Graeme Swindles and colleagues built a transfer function from Peruvian Amazonia (Swindles et al., 2014). They then applied it to a palaeo-environmental study in Peruvian Amazonia (Swindles et al., 2016). Although peat preservation was not optimal a usable palaeo-environmental record could be obtained. Interestingly, the same transfer function was then also used in an ecological study of a coastal peatland in Panama (Swindles et al., 2018). The comparison of measured and transfer function-inferred water table depth and moisture content (Fig. 5) showed that the Peruvian transfer function performed very well indeed, thus showing that this approach holds much promises also in the tropics.

Fig. 5. Biplots of observed water table depth (WTD) and moisture content (MC) in coastal wetland of Panama vs. values predicted using a testate amoeba transfer function from Peruvian Amazonia (modified from Swindles et al., 2018).

In other tropical and subtropical regions, research on testate amoebae is also increasing, such as China (Qin et al., 2011, Li et al., 2010, Bobrov et al., 2015, Qin, Xie, Gu, et al., 2008, Qin, Xie, Swindles, et al., 2008, Qin et al., 2009, Qin et al., 2010, Qin and Xie, 2011, Qin et al., 2012, Qin, Fournier, et al., 2013, Qin, Mitchell, et al., 2013, Qin et al., 2016), Ecuador and Indonesia (Krashevska, 2008, Krashevska et al., 2008, Krashevska, Maraun, Ruess, et al., 2010, Krashevska, Maraun and Scheu, 2010, Krashevska, Maraun, et al., 2012, Krashevska, Sandmann, et al., 2012, Krashevska et al., 2014, Krashevska et al., 2015, Krashevska et al., 2016, Krashevska et al., 2017). These works (and others likely, this report does not aim to be exhaustive!) would deserve to be presented in this blog in more detail! We clearly can expect to learn much more about both diversity patterns and the ecology of testate amoebae beyond the more intensively studied temperate and boreal regions. This is very good news indeed!

Substantial work on testate amoebae has been done over the years in the tropics. But most of this literature is quite old and most of the scientists who conducted them are no longer active, the “Thecamoebian Bibliography” compiled by such scientists provides an very useful compilation of the literature (Medioli et al., 2003). It is therefore a very good signal to see younger researchers working again in these regions.

Working in the tropics can be challenging, and is most often more difficult than nearer the comfort of the higher latitude institutions where most active testate amoeba researchers work. Place or residence and possible logistical or administrative complications result in less research being conducted in the tropics. The payoff if however clearly there. Novel findings are very likely, many new species remain to be described and the community ecology of testate amoebae in different types of ecosystems may either confirm ideas derived from comparable studies in colder climate or else lead us to think differently. Extending our efforts to these regions will help balance the effort and may challenge some long-held opinions. And this of course is essential!

References

Bobrov, A., Qin, Y. & Wilkinson, D.M. (2015) Latitudinal Diversity Gradients in Free-living Microorganisms – Hoogenraadia a Key Genus in Testate Amoebae Biogeography. Acta Protozoologica, 54, 1-8.

Féres, J.C., Porfírio-Sousa, A.L., Ribeiro, G.M., Rocha, G.M., Sterza, J.M., Souza, M.B.G., Soares, C.E.A. & Lahr, D.J.G. (2016) Morphological and Morphometric Description of a Novel Shelled Amoeba Arcella gandalfi sp. nov. (Amoebozoa: Arcellinida) from Brazilian Continental Waters Acta Protozoologica, 55(4).

Fernández, L.D. (2015) Source-sink dynamics shapes the spatial distribution of soil protists in an arid shrubland of northern Chile. Journal of Arid Environments, 113, 121-125.

Fernández, L.D., Fournier, B., Rivera, R., Lara, E., Mitchell, E.A.D. & Hernández, C.E. (2016) Water–energy balance, past ecological perturbations and evolutionary constraints shape the latitudinal diversity gradient of soil testate amoebae in southwestern South America. Global Ecology and Biogeography, 25, 1216–1227.

Fernández, L.D., Lara, E. & Mitchell, E.A.D. (2015) Checklist, diversity and distribution of testate amoebae in Chile. European Journal of Protistology, 51, 409-424.

Jassey, V.E.J. (2017) Why living in the tropics is Awesome? From inside the shell – Blog of the International Society for Testate Amoeba Research (eds R. K. Booth, D. J. G. Lahr, E. A. D. Mitchell & J. E. J. Jassey).

Krashevska, V. (2008) Diversity and community structure of testate amoebae (Protista) in tropical montane rain forests of southern Ecuador: altitudinal gradient, aboveground habitats and nutrient limitation. Ph.D. Ph.D., Technischen Universität Darmstadt, Darmstadt.

Krashevska, V., Bonkowski, M., Maraun, M., Ruess, L., Kandeler, E. & Scheu, S. (2008) Microorganisms as driving factors for the community structure of testate amoebae along an altitudinal transect in tropical mountain rain forests Soil Biology & Biochemistry, 40, 2427–2433.

Krashevska, V., Klarner, B., Widyastuti, R., Maraun, M. & Scheu, S. (2015) Impact of tropical lowland rainforest conversion into rubber and oil palm plantations on soil microbial communities. Biology and Fertility of Soils, 51, 697-705.

Krashevska, V., Klarner, B., Widyastuti, R., Maraun, M. & Scheu, S. (2016) Changes in Structure and Functioning of Protist (Testate Amoebae) Communities Due to Conversion of Lowland Rainforest into Rubber and Oil Palm Plantations. PLoS ONE, 11, e0160179.

Krashevska, V., Maraun, M., Ruess, L. & Scheu, S. (2010) Carbon and nutrient limitation of soil microorganisms and microbial grazers in a tropical montane rain forest. Oikos, 119, 1020-1028.

Krashevska, V., Maraun, M. & Scheu, S. (2010) Micro- and Macroscale Changes in Density and Diversity of Testate Amoebae of Tropical Montane Rain Forests of Southern Ecuador. Acta Protozoologica, 49, 17-28.

Krashevska, V., Maraun, M. & Scheu, S. (2012) How does litter quality affect the community of soil protists (testate amoebae) of tropical montane rainforests? FEMS Microbiology Ecology, 80, 603-607.

Krashevska, V., Sandmann, D., Maraun, M. & Scheu, S. (2012) Consequences of exclusion of precipitation on microorganisms and microbial consumers in montane tropical rainforests. Oecologia, 170, 1067-1076.

Krashevska, V., Sandmann, D., Maraun, M. & Scheu, S. (2014) Moderate changes in nutrient input alter tropical microbial and protist communities and belowground linkages. ISME Journal, 8, 1126–1134

Krashevska, V., Sandmann, D., Marian, F., Maraun, M. & Scheu, S. (2017) Leaf Litter Chemistry Drives the Structure and Composition of Soil Testate Amoeba Communities in a Tropical Montane Rainforest of the Ecuadorian Andes. Microbial Ecology, 74, 681-690.

Li, H.K., Wang, S.Z., Bu, Z.J., Zhao, H.Y., An, Z.S., Mitchell, E.A.D. & Ma, Y.Y. (2010) The testate amoebae in Sphagnum peatlands in Changbai Mountains. Wetland Science, 8, 249-255.

Medioli, F.S., Bonnet, L., Scott, D.B. & Medioli, B.E. (2003) The Thecamoebian Bibliography, 2nd edition. Palaeontologia Electronica, 6, 107.

Pérez-Juárez, H., Serrano-Vázquez, A., Kosakyan, A., Mitchell, E.A.D., Rivera Aguilar, V.M., Lahr, D.J.G., Hernández Moreno, M.M., Cuellar, H.M., Eguiarte, L.E. & Lara, E. (2017) Quadrulella texcalense sp. nov. from a Mexican desert: An unexpected new environment for hyalospheniid testate amoebae. European Journal of Protistology, 61, 253-264.

Qin, Y., Booth, R.K., Gu, Y., Wang, Y. & Xie, S. (2009) Testate amoebae as indicators of 20th century environmental change in Lake Zhangdu, China Fundamental and Applied Limnology, 175, 29-38.

Qin, Y., Fournier, B., Lara, E., Gu, Y., Wang, H., Cui, Y., Zhang, X. & Mitchell, E.A.D. (2013) Relationships between testate amoeba communities and water quality in Lake Donghu, a large alkaline lake in Wuhan, China. Frontiers of Earth Science, 7, 182-190.

Qin, Y., Mitchell, E.A.D., Lamentowicz, M., Payne, R.J., Lara, E., Gu, Y., Huang, X. & Wang, H. (2013) Ecology of testate amoebae in peatlands of central China and development of a transfer function for paleohydrological reconstruction. Journal of Paleolimnology, 50, 319-330.

Qin, Y., Payne, R.J., Gu, Y., Huang, X. & Wang, H. (2012) Ecology of testate amoebae in Dajiuhu peatland of Shennongjia Mountains, China, in relation to hydrology. Frontiers of Earth Science, 6, 57-65.

Qin, Y., Wang, J., Xie, S., Huang, X., Yang, H., Tan, K. & Zhang, Z. (2010) Morphological Variation and Habitat Selection of Testate Amoebae in Dajiuhu Peatland, Central China. Journal of Earth Science, 21, 253-256.

Qin, Y. & Xie, S. (2011) Moss-dwelling testate amoebae and their community in Dajiuhu peatland of Shennongjia Mountains, China. Journal of Freshwater Ecology, 26, 3-9.

Qin, Y., Xie, S., Gu, Y. & Zhou, X. (2008) Pontigulasia pentangulostoma nov spec., a New Testate Amoeba from the Da Jiuhu Peatland of the Shennongjia Mountains, China. Acta Protozoologica, 47, 155-160.

Qin, Y., Xie, S., Smith, H.G., Swindles, G.T. & Gu, Y. (2011) Diversity, distribution and biogeography of testate amoebae in China: Implications for ecological studies in Asia. European Journal of Protistology, 47, 1-9.

Qin, Y., Xie, S., Swindles, G.T., Gu, Y. & Zhou, X. (2008) Pentagonia zhangduensis nov spec. (Lobosea, Arcellinida), a new freshwater species from China. European Journal of Protistology, 44, 287-290.

Qin, Y.M., Man, B.Y., Kosakyan, A., Lara, E., Gu, Y.S., Wang, H.M. & Mitchell, E.A.D. (2016) Nebela jiuhuensis nov sp (Amoebozoa; Arcellinida; Hyalospheniidae): A New Member of the Nebela saccifera – equicalceus – ansata Group Described from Sphagnum Peatlands in South-Central China. Journal of Eukaryotic Microbiology, 63, 558-566.

Reczuga, M.K., Swindles, G.T., Grewling, L. & Lamentowicz, M. (2015) Arcella peruviana sp nov (Amoebozoa: Arcellinida, Arcellidae), a new species from a tropical peatland in Amazonia. European Journal of Protistology, 51, 437-449.

Swindles, G.T., Baird, A.J., Kilbride, E., Low, R. & Lopez, O. (2018) Testing the relationship between testate amoeba community composition and environmental variables in a coastal tropical peatland. Ecological Indicators, 91, 636-644.

Swindles, G.T., Lamentowicz, M., Reczuga, M. & Galloway, J.M. (2016) Palaeoecology of testate amoebae in a tropical peatland. European Journal of Protistology, 55, 181-189.

Swindles, G.T., Reczuga, M., Lamentowicz, M., Raby, C.L., Turner, T.E., Charman, D.J., Gallego-Sala, A., Valderrama, E., Williams, C., Draper, F., Coronado, E.N.H., Roucoux, K.H., Baker, T. & Mullan, D.J. (2014) Ecology of Testate Amoebae in an Amazonian Peatland and Development of a Transfer Function for Palaeohydrological Reconstruction. Microbial Ecology, 68, 284-298.

Why living in the tropics is Awesome?

Living in the tropics, surrounded by jungle-covered hills, corals, picture-perfect beaches and cocktails sounds like a dream. Imagine listening the gentle music of the waves, bird songs, or the characteristic ‘zzzzzzzzzz’ of mosquitoes while enjoying a cup of coffee at the sun set. Walk along the beach, go for a swim to cool off from the sun’s warmth and do some snorkeling. This is paradise.

This is a dream that comes true for testate amoebae.

Travelling through tropical countries is such an experience that most people dream of returning; the same holds true for testate amoebae. Visiting tropics is one thing but by actually accumulating down some shells, testate amoebae gained a much better perspective on just how awesome the warmer part of the world is compared to the cold and dark side of the world. With the sun, sand and sea at your pseudostome-door and a relaxed way of life, the tropics has it all.

Tropics are so diverse that testate amoebae can enjoy various and nice places to live in. Sphagnum mosses in the Galapagos is an obvious spot to enjoy the tropics (Fournier et al. 2015), but why always live in a moss while you can experience other habitats? Living in the tropics also means sometimes living differently from what you already know. In such purpose, the jungle seems appropriate! The jungle is a great place to go hiking and trekking, and incidentally see how diverse and valuable these ecosystems are. Plus, it’s usually the best place to spot new habitats, particularly if you are an amoebae. Pseudopoding through the dense and muddy vegetation gives a sense of true exploration, you never know what you’ll find. That’s what happened to testate amoebae when they ended up in tank-bromeliads as they wanted to cool off after a hike through the humid jungle.

Bromeliads include mainly epiphytic rosette plants occurring mostly in Central and South America. They collect rain water and particulate materials in tanks (cisterns) formed by the coalescing leaf axils. These tanks form micro-ecosystems above the ground where groups of freshwater organisms ranging from algae, fungi, bacteria and protozoa through insects to frogs are represented and constitute considerable populations (Frank 1983, Laessle 1961, Maguire 1971, Picado 1913, Richardson 1999). Of special interest to us, these tanks are inhabited by many characteristic protists and small metazoans (Picado 1913; Maguire 1971; Martinelli 2000; Schönborn 2003). The only way for Nebela tincta, a widely distributed species, to meet Polyplaca globosa (Figure 1), P. monocornica and P. invaginata is to visit a Brazilian tank-bromeliad (Torres-Stolzenberg 2000).

 

Figure 1: Polyplaca globosa; an endemic testate amoebae from tank-bromeliads (Picture from Torres and Schwarzbold, 2000)

 

The vibe is unbelievable in the tropics! The common view is that no one seems to be in a hurry for anything. Such a cliché is obviously false; this includes testate amoebae in tank-bromeliads. Life in tank-bromeliads is not so quiet but rather dangerous. The aquatic food web inhabiting tank-bromeliads consists of micro- and macroinvertebrates (Kitching 2000) and microorganisms such as bacteria, algae, flagellates, fungi and protozoa (Carrias et al. 2001). While testate amoebae can be fearsome predators (Gilbert et al. 2000, Geisen et al. 2015) in mosses and soils, they are neither the largest nor the most dangerous in tank-bromeliads (Carrias et al. 2001). Micro- and macroinvertebrates can be very interested to feed on testate amoebae, and when you’re trapped in a tank, your chance to escape a predator are very low. This may explain why testate amoebae abundance is so low in tank-bromeliads compared to other protists such as ciliates (Carrias et al. 2012).

Tank-bromeliads are fascinating to me. Recent studies showed that microbial communities in bromeliads are highly distinct from the surrounding environments, for example soil, with sometimes a strong shift towards crucial ecosystem functions such as methanogens (Goffredi et al. 2011a, b; Mattinson et al. 2010, Louca et al. 2016). In temperate and subarctic ecosystems, testate amoebae are abundant and suggested to be key in ecosystem processes such as decomposition (Lamentowicz et al. 2013; Geisen et al. 2015; Jassey et al. 2016) or carbon uptake (Jassey et al. 2015). The low abundance of testate amoebae in tank-bromeliads suggest either they are not key species in microbial interactions and connected ecosystem processes, or they are a key trophic-link between microorganisms and micro- and macro-invertebrates as preferential food resource.

Clearly, more studies focusing on the role of testate amoebae in tank-bromeliads are needed. There are so many reasons to go and live in the tropics. If you need a good excuse to go in the tropics and see how living there is awesome, I hope this post will give you a good one. For the others who hate warm temperatures, corals, picture-perfect beaches, and rather love winters, but who would like to study testate amoebae in tank-bromeliads, I heard that some testate amoebae found an alternative to the tropics by living in bromeliads…from florist wholesalers (Kolicka et al. 2016).

References

Carrias et al. A preliminary study of freshwater protozoa in tank bromeliads. Journal of Tropical Ecology, 17, 611–617 (2001).

Carrias et al. An ant–plant mutualism induces shifts in the protist community structure of a tank-bromeliad. Basic and Applied Ecology. 13, 698–705 (2012).

Fournier et al. A legacy of human‐induced ecosystem changes: spatial processes drive the taxonomic and functional diversities of testate amoebae in Sphagnum peatlands of the Galápagos. Journal of Biogeography 43, 533-543 (2015).

Frank. Bromeliad phytotelmata and their biota, especially mosquitoes. Pp. 101–128 in  Frank, J. H. & Lounibos, L. P. (eds). Phytotelmata: terrestrial plants as hosts for aquatic insect communities. Plexus Publishing Inc., Medford (1983).

Goffredi, Kantor & Woodside. Aquatic microbial habitats within a neotropical rainforest: bromeliads and pH­associated trends in bacterial diversity and composition. Microbial Ecology 61, 529–542 (2011a).

Goffredi et al. Bromeliad catchments as habitats for methanogenesis in tropical rainforest canopies. Frontiers in Microbiology 2, 256 (2011b).

Jassey et al.. An unexpected role for mixotrophs in the response of peatland carbon cycling to climate warming. Scientific Reports, 1–10 (2015).

Jassey et al.. Loss of testate amoeba functional diversity with increasing frost intensity across a continental gradient reduces microbial activity in peatlands. European Journal of Protistology, 55, 190–202 (2016).

Kitching. Food Webs and Container Habitats: The Natural History and Ecology of Phytotelmata. Cambridge University Press, Cambridge (2000).

Kolicka et al. Hidden invertebrate diversity – Phytotelmata in Bromeliaceae from palm houses and florist wholesalers (Poland). Biologia 71, 194-203 (2016).

Laessle.  A micro-limnological study of Jamaican bromeliads. Ecology 42:499–517 (1961)

Louca et al. High taxonomic variability despite stable functional structure across microbial communities. Nature Ecology & Evolution, 1, 1–12. (2016).

Maguire. Phytotelmata: biota and community structure determination in plant-held waters. Annual Review of Ecology and Systematics 2:439–464 (1971).

Martinelli. Gefährdete Raritäten. Bromelien im at- lantischen Regenwald. Spektrum der Wissenschaft 6/2000, 66–73 (2000).

Martinson et al. Methane emissions from tank bromeliads in neotropical forests. Nature Geoscience 3, 766–769 (2010).

Picado. Les Broméliacées epiphytes considérées comme milieu biologique. Bulletin Scientifique de la France et de la Belgique 47:215–360 (1913).

Richardson. The bromeliad microcosm and the assessment of faunal diversity in a neotropical forest. Biotropica 31:321–336 (1999).

Schönborn. Lehrbuch der Limnologie. Schweitzerbart, Stuttgart (2003).

Torres and Schwarzbold. Procta em associacao com Vriesea sp. (Bromeliaceae): tres novos taxa de amebas tes- taceas (Protoctista: Rhizopoda, Testacealobosea). Not. Faun. Gembloux 41, 105–113 (2000).

Who is hiding behind these square scales? or The mystery of the origin of square shell plates in testate amoebae

Contributed by Anush Kosakyan

 

It would be hard to find a testate amoeba lover who does not know the genus Quadrulella. These vase-shaped species are a very unique group within family Hyalospheniidae (Arcellinida) since they are capable of secreting their own square or rectangular shell scales (or plates). These scales are characterisstic only for this genus, while most other members of the family are predators that build their shell by using mainly recycled plates taken or scavenged from other testate amoebae (i.e. kleptosquamy, Lahr et al. 2015).

***

My story started in the summer of 2013, when Edward Mitchell returned from his holiday in South Africa with a bag of Sphagnum samples. The samples were full of Quadrulella shells, including species that had never been seen since their original description back in 1957. And that was it….”the right time” for single-cell barcoding of this group. From this material, we obtained very interesting results that have been published recently (Kosakyan et al., 2016).

The most surprising result was that organisms presenting square shell plates appeared not to be monophyletic: two different groups of taxa with square scales (genus Quadrulella and newly established genus Mrabella) were indeed placed far from each other on the mtCOI-based phylogenetic tree. We thought of two possible evolutionary scenarios to explain this situation. These two hypotheses depend on whether the square-shaped plates in an organism have an autogenous or exogenous origin. This is a relevant aspect because hyalospheniids are known to engage in the behaviour of kleptosquamy, or recycling of shell plates produced by other organisms (Lahr et al., 2015).

Assuming that all amoebae that present square-shaped plates in their shells have produced them autogenously, the phylogenetic hypothesis presented here indicates homoplasy:

1) either the ability to produce square plates is an ancestral character that has been lost in a number of lineages (reversion); or

2) this character has evolved more than once independently (convergence).

We have assumed that convergence is the most parsimonious alternative (see the detailed discussion in the paper for further detail), with only two steps required – one event in genus Quadrulella and another independent event in genus Mrabella. Although we should not forget another unrelated group of organisms that are capable of producing square plates: the shelled amoeba Paraquadrulla is capable of producing calcareous square plates (the genus has not been sequenced yet, but while it is almost certainly an Arcellinid it is most likely unrelated to hyalosphenids or at best branches in a basal position to the whole group).

Alternatively, considering the fact that majority of hyalosphenids have the ability to scavenge plates from prey and use them to make the shell (kleptosquamy), a possible scenario is that Mrabella is in fact using scales from preyed Quadrulella, or scavenging these scales from the environment to construct the shell. And indeed, this was our first guess when we saw the description of Nebela galeata (current name Gibbocarina galeata) from Africa by Gauthier-Lièvre (1957). It is almost identical to Q. subcarinata in general shape and dimensions of the test (L=180-200, B=98-144, A=31-41 μm) (see Figure). Gauthier-Lièvre, 1957 (in her Fig. 10A) showed that square plates typical for Quadrulella can be integrated in the shell of N. galeata.  This is very easy to explain since Gauthier-Lièvre (1957) documented other Quadrulella species from the same locality where she found N. galeata and Q. subcarinata. Thus, other Quadrulella species could have provided the square plates use by these two species.

 

Legend: A- Line drawing of Gibbocarina (Nebela) galeata from Congo by Gauthier-Lievre, 1957. B and C– Scanning electron microscopy and light microscopy micrographs of Mrabella subcarinata from South Africa. Scale bars =50 µm (in A) and 20 µm (in B). Modified from Kosakyan et al. 2016.

 

However,  things are not that easy in our case for two reasons:

1) Mrabella would specifically select these plates, a trait that is not known for any other hyalosphenid presenting kleptosquamy; these species generally use a mixture of plates from different origins to build their shell (see for instance: Apodera vas in Fig. 69 in Meisterfeld 2002);

2) if not specifically selecting, then Quadrulella would have to be the most abundant prey organism, or Quadrulella plates would have to be the most abundant in the environment, both options are likely not true since Quadrulella tends to be present in low abundance in comparison to Euglypha (although Euglypha was not abundant in our sample where we found Mrabella subcarinata), a genus of filose testate amoebae which is generally abundant and produces oval and ornamented siliceous plates.

Additionally, there are a number of other described species in genus Quadrulella that differ from the tear-shaped morphology of Quadrulella s.str. These also present similar shapes to other genera: Quadrulella vas, Q. constricta – Apodera vas, Q. lageniformis – Padaungiella lageniformis, Q. tubulata – P. tubulata. These “mirror” species could either be a result of convergent evolution or alternatively represent cases of the “classical” hyalosphenids (A. vas, Padaungiella ssp.) that live in environments where euglyphids are rare but Quadrulella are abundant enough to provide material for building their shells. We have suggested that at this point these Quadrulella species must be treated as incertae sedis, and their sequencing will certainly illuminate the conundrum of the evolution of square-shaped plates.

References

Gauther-Lievre L. 1957.  Additions aux Nebela d’Afrique. Bull. Soc. Hist. Nat. l’Afrique du Nord 48, 494-523.

Kosakyan, A., Lahr, D. J. G., Mulot, M., Meisterfeld, R., Mitchell, E. A. D. and Lara, E. 2016. Phylogenetic reconstruction based on COI reshuffles the taxonomy of hyalosphenid shelled (testate) amoebae and reveals the convoluted evolution of shell plate shapes. Cladistics, 32: 606-623. doi:10.1111/cla.12167

 

What’s in a name? Something (completely different) to be said about taxonomic nomenclature

By Edward A. D. Mitchell,

Laboratory of Soil Biodiversity, University of Neuchâtel, Switzerland

With the advent of high throughput sequencing, estimates of global diversity are being totally revised.  For us protistologists – arguably much more importantly – so is the picture of how diversity is distributed among the different branches of the tree of life. The image that emerges is one that shows a huge unknown diversity among protists, at all levels, from major groups (i.e. “environmental clades”) and within known groups (i.e. from more or less divergent groups to complexes of cryptic and pseudo-cryptic species). This is fascinating and to say the least mind-boggling and a much welcome development for making a case about the need to study protists more intensively. It is indeed impossible today to ignore this diversity and the many functional roles that protists play in all ecosystems.

But this unknown diversity also calls for a massive investment in taxonomy. And as we all know there are only few active protist taxonomists. We therefore need to train a new generation of taxonomists to meet the huge challenge of keeping up with the novel discoveries resulting from molecular studies. And indeed, combining molecular and traditional microscopy approaches is the key to doing this job properly.

But there is also an often overlooked but important aspect of taxonomy, besides the critically important fact that descriptions need to be done correctly in order not to make a huge mess of nomenclature: naming a species. Choosing an appropriate name is indeed not always easy. Should we name a species after an esteemed colleague, the geographical location where the species was found, a morphological feature of the species, or should we try to find a name that also allows non-specialists to relate to the species – thus providing an excellent opportunity to increase the impact of the finding and making a broader audience aware of the sheer existence of our beloved amoebae?

I firmly believe that witty names are useful. They make us happy, allow many lively discussions to take place among colleagues and are much appreciated by journalists always keen to report on “something completely different” (Monty Python, 1971).

The choice of names tells a lot about the personality and cultural references of the author. Here are three recent examples among testate amoebae:

Padaungiella Lara & Todorov 2012.

This genus of hyalosphenid testate amoebae is characterised by an elongated neck (Kosakyan et al., 2012). The idea for this name came to me while riding my bicycle (a great source of inspiration!). I knew about the existence of some African tribes that used metal necklaces to elongate the necks of woman (allegedly, if the woman cheated on her man he would remove the necklaces and she would die due to cervical spine injury). I did a bit of research on this and found out that there were two unrelated tribes using such necklaces, one in Africa, with independent circular necklaces piled on top of each other and one in Asia (Padaung – https://en.wikipedia.org/wiki/Kayan_people_(Myanmar)), with a single spiral necklace. The latter corresponded much better to the shape of the amoeba shell and hence we decided to choose this name.

At the time of writing this post there were 1’110 hits for Padaungiella in Google.

Padaungiella wailesii (left, picture by E. Mitchell) and a Padaung woman (right, source: http://www.chiangdao.com/chiangmai/karenlongneck.htm)

Nebela gimlii Singer & Lara 2015.

This species was named after Gimli (http://lotr.wikia.com/wiki/Gimli), a dwarf in Tolkien’s Lord of the Rings saga (Singer et al., 2015). This dwarf wanders in forests during the saga, something dwarfs are not supposed to do much. This species being the smallest of the species complex and being found in forested bogs the name seemed appropriate. Newspapers as far as Austria wrote about this. http://www.krone.at/wissen/amoebenart-nach-figur-aus-herr-der-ringe-benannt-in-torfmoor-entdeckt-story-497678.

At the time of writing this post there were 188 hits for “Nebela gimlii” in Google.

Arcella gandalfi Féres, Porfírio-Sousa, Ribeiro, Rocha, Sterza, Souza, Soares & Lahr 2016.

This large Arcella species bears striking resemblance to Gandalf’s hat and thus logically was named after this even more famous character of the Lord of the Rings (Féres et al., 2016; Tolkien, 1954) (http://lotr.wikia.com/wiki/Gandalf).

Arcella gandalfi (left, from Féres et al., 2016) and Gandalf, as played by Ian McKellen in The Lord of the Rings triology, (right, source: http://lotr.wikia.com/wiki/Gandalf).

The media picked up on this story even more and this illustrates again how a well-chosen name can significantly contribute to making our field of research more visible.

“Arcella gandalfi” has 31’600 hits on Google at the time of writing this post. To this date, news agencies in more than 15 countries reported on this, including: Brazil, USA, Germany, France, Russia, India, Mexico, Spain, Turkey, Argentina, Hungary, Indonesia, Croatia, South Korea, Ukraine.

Gandalf clearly wins! Well done fellows!

Who’s next? There’s no end to the fun!

References

Féres, J.C., Porfírio-Sousa, A.L., Ribeiro, G.M., Rocha, G.M., Sterza, J.M., Souza, M.B.G., Soares, C.E.A., Lahr, D.J.G., 2016. Morphological and Morphometric Description of a Novel Shelled Amoeba Arcella gandalfi sp. nov. (Amoebozoa: Arcellinida) from Brazilian Continental Waters Acta Protozool. 55(4).

Kosakyan, A., Heger, T.J., Leander, B.S., Todorov, M., Mitchell, E.A.D., Lara, E., 2012. COI Barcoding of Nebelid Testate Amoebae (Amoebozoa: Arcellinida): Extensive Cryptic Diversity and Redefinition of the Hyalospheniidae Schultze. Protist 163, 415-434.

Monty Python, 1971. And Now for Something Completely Different, in: MacNaughton, I. (Ed.), Monty Python’s Flying Circus. Columbia Pictures, United Kingdom, p. 95 minutes.

Singer, D., Kosakyan, A., Pillonel, A., Mitchell, E.A.D., Lara, E., 2015. Eight species in the Nebela collaris complex: Nebela gimlii (Arcellinida, Hyalospheniidae), a new species described from a Swiss raised bog. European Journal of Protistology 51, 79-85.

Tolkien, J.R.R., 1954. The Fellowship of the Ring, The Lord of the Rings, Boston. Ballantine Books, New York.

A new approach to testate amoeba paleoecology: reconstructing past environmental conditions from morpholological traits

Contributed by Edward A. D. Mitchell

Laboratory of Soil Biodiversity, University of Neuchâtel, Switzerland

Testate amoebae are well known to be good indicators of micro-environmental gradients and especially soil moisture, water table depth and pH. This has been known since the early 20th century (Harnisch, 1925). The predictable distribution patterns of many species not only systematically result in seeing these variables emerge as being significantly correlated to testate amoeba community data in ecological studies but also allow the development of inference models – so called “transfer functions” – based on testate amoeba community data to reconstruct (infer) these variables either from modern samples or more generally from subfossil communities extracted from peat deposits or lake sediments. As there are few proxies to reconstruct past hydrological changes, testate amoebae have become part of the standard toolbox of palaeoecologists (Charman, 2001; Mitchell et al., 2008). Indeed, developing and using such transfer function has been the main reason to study testate amoebae and indeed most papers dealing with testate amoebae published in the last couple of decades. These organisms were thus being used as tools using correlative approaches rather than considered as study subjects in their own right.
Simon van Bellen and colleagues have just published a paper in which they present a new approach for palaeo-environmental inference based on testate amoeba morphological traits rather than community data (van Bellen et al., 2017). They used nine different traits and related them to the depth to the water table (DWT), the variable most commonly inferred from testate amoebae. Their data set is from Tierra-del-Fuego, but could almost be from anywhere in the World where Sphagnum peatlands occur. The list of traits includes morphological traits such as biovolume, aperture position, test compression, aperture size and test composition, a binary physiological trait (mixotrophy vs. heterotrophy) and two phylogenetic traits (Arcellinida and Euglyphida – there were no Amphitremids in the data). Most traits showed a relationship to DWT. For example, Arcellinida show an almost perfect negative linear correlation to DWT (i.e. the propostion of Arcellinida decreases with increasing DWT, in other words, the wetter the habitat, the more Arcelinida dominate the community). By contrast Euglyphida show a positive correlation to DWT (so the drier it gets the more the testate amoeba community is dominated by Euglyphida).

An extract from Figure 3 of van Bellen et al. 2017. Relationship between the community weighed means of Arcellinida (top) and Euglyphida (bottom) vs depth to water table (DWT, horizontal axis – left is wet, right is dry). The two phylogenetic groups clearly show opposite responses to the humidity gradient.

Interestingly this pattern corresponds to a ratio used in mineral soil, the LF index (Bonnet, 1976), where “L” stands for Lobosea (Arcellinida) and “F” stands for Filosa (Euglyphida). By analogy to MacArthur and Wilson’s concept of r (ruderal) and K (competitors) life history classification (MacArthur and Wilson, 1967), Euglyphida are considered as r strategists while Arcellinida are on average more K strategists. Euglyphids are on average smaller and thus more likely to feed on smaller prey such as bacteria. Being smaller also means that they may tolerate dry conditions better than the generally larger arcellinids that require a thicker water film to move.

The study of testate amoebae functional traits is clearly rapidly becoming a dynamic field of research within our community (Arrieira et al., 2015; Fournier et al., 2016; Fournier et al., 2015; Fournier et al., 2012; Jassey et al., 2016; Jassey et al., 2015; Lamentowicz et al., 2015; Marcisz et al., 2016; Marcisz et al., 2014). It will be interesting to follow the next developments in this area!

References

Arrieira, R.L., Schwind, L.T.F., Bonecker, C.C., Lansac-Toha, F.A., 2015. Use of functional diversity to assess determinant assembly processes of testate amoebae community. Aquatic Ecology 49, 561-571.

Bonnet, L., 1976. Le peuplement thécamoebien édaphique de la Côte-d’Ivoire. Sols de la région de Lamto. Protistologica 12, 539-554.

Charman, D.J., 2001. Biostratigraphic and palaeoenvironmental applications of testate amoebae. Quaternary Science Reviews 20, 1753-1764.

Fournier, B., Coffey, E.E.D., van der Knaap, W.O., Fernandez, L.D., Bobrov, A., Mitchell, E.A.D., 2016. A legacy of human-induced ecosystem changes: spatial processes drive the taxonomic and functional diversities of testate amoebae in Sphagnum peatlands of the Galapagos. Journal of Biogeography 43, 533-543.

Fournier, B., Lara, E., Jassey, V.E.J., Mitchell, E.A.D., 2015. Functional traits as a new approach for interpreting testate amoeba palaeo-records in peatlands and assessing the causes and consequences of past changes in species composition. Holocene 25, 1375-1383.

Fournier, B., Malysheva, E., Mazei, Y., Moretti, M., Mitchell, E.A.D., 2012. Toward the use of testate amoeba functional traits as indicator of floodplain restoration success. Eur. J. Soil Biol. 49, 85-91.

Harnisch, O., 1925. Studien zur Ökologie und Tiergeographie der Moore. Zoologisch Jahrbuch (Abteilung Systematik) 51, 1-166.

Jassey, V.E.J., Lamentowicz, M., Bragazza, L., Hofsommer, M.L., Mills, R.T.E., Buttler, A., Signarbieux, C., Robroek, B.J.M., 2016. Loss of testate amoeba functional diversity with increasing frost intensity across a continental gradient reduces microbial activity in peatlands. European Journal of Protistology 55, Part B, 190-202.

Jassey, V.E.J., Signarbieux, C., Haettenschwiler, S., Bragazza, L., Buttler, A., Delarue, F., Fournier, B., Gilbert, D., Laggoun-Defarge, F., Lara, E., Mills, R.T.E., Mitchell, E.A.D., Payne, R.J., Robroek, B.J.M., 2015. An unexpected role for mixotrophs in the response of peatland carbon cycling to climate warming. Scientific Reports 5, 16931.

Lamentowicz, M., Gałka, M., Lamentowicz, Ł., Obremska, M., Kühl, N., Lücke, A., Jassey, V.E.J., 2015. Reconstructing climate change and ombrotrophic bog development during the last 4000 years in northern Poland using biotic proxies, stable isotopes and trait-based approach. Palaeogeography, Palaeoclimatology, Palaeoecology 418, 261-277.

MacArthur, R.H., Wilson, E.O., 1967. The Theory of Island Biogeography. Princeton University Press.

Marcisz, K., Colombaroli, D., Jassey, V.E.J., Tinner, W., Kołaczek, P., Gałka, M., Karpińska-Kołaczek, M., Słowiński, M., Lamentowicz, M., 2016. A novel testate amoebae trait-based approach to infer environmental disturbance in Sphagnum peatlands. Scientific Reports 6, 33907.

Marcisz, K., Lamentowicz, L., Slowinska, S., Slowinski, M., Muszak, W., Lamentowicz, M., 2014. Seasonal changes in Sphagnum peatland testate amoeba communities along a hydrological gradient. European Journal of Protistology 50, 445-455.

Mitchell, E.A.D., Charman, D.J., Warner, B.G., 2008. Testate amoebae analysis in ecological and paleoecological studies of wetlands: past, present and future. Biodivers. Conserv. 17, 2115-2137.

van Bellen, S., Mauquoy, D., Payne, R.J., Roland, T.P., Hughes, P.D.M., Daley, T.J., Loader, N.J., Street-Perrott, F.A., Rice, E.M., Pancotto, V.A., 2017. An alternative approach to transfer functions? Testing the performance of a functional trait-based model for testate amoebae. Palaeogeography, Palaeoclimatology, Palaeoecology 468, 173-183.

Fashionable testate amoebae!

Fashion phenomena strongly influence our societies. These phenomena mostly affect young people and can be very worrysome. Many sociological studies seek to understand these phenomena, based on community background, culture and society tendencies but none seem to have considered a simple possibility: are our young people not just copying nature?

Recently, a very interesting study highlighted an intriguing fashion phenomenon within the testate amoeba community. Gomaa et al. (1) indeed revealed that all mixotrophic testate amoebae dressed up with the same algal-underwear!

Mixotrophic testate amoebae are species able to combine two nutrition modes; phototrophy and phagotrophy (predation). Using light energy thanks to their algal symbionts, mixotrophic testate amoebae are able to fix inorganic carbon through photosynthesis, whilst in parallel they are also able to assimilate organic carbon by feeding on prey items such as bacteria, fungi and other protists (2-5). This mixotrophic energetic mode thus gives them an important trophic advantage when food resources are low.

Figure 1| Some mixotrophic testate amoebae we can find in mosses : Placocista spinosa (A), Archerella flavum (B), Amphitrema wrigthianum (C), Hyalosphenia papilio (D) and Heleopera sphagni (E). Scale bar on E = 50 μm

Most mixotrophic testate amoebae show different characteristics, with for instance, different body sizes, shape and test composition. However, visually under the microscope, it seems that all of these species choose their algal symbionts in the same shop, copying each other! Probably intrigued by such fashion phenomena, Gomaa et al. (1) investigated the genetic diversity of the algal symbionts harboured by several mixotrophic testate amoeba species such as Archerella flavum, Hyalosphenia papilio, Heleopera sphagni and Placocista spinosa. These analyses showed that most algae found in testate shells shared the same kind of gene sequence (ribulose- 1,5-bisphosphate carboxylase/oxidase), thus revealing a close genetic proximity (1). The phylogenetic analysis further placed all surveyed testate amoebae symbionts close to Chlorella variabilis, a species known for forming symbiotic relationships with the ciliate Paramecium bursar (6). However, the authors also underlined that it is probable that some other endosymbiotic species occur in mixotrophic testate amoebae. Some symbionts morphologically clearly differ from C. variabilis in shape and colour, in particular within genus Placocista (Figure 1).

The modalities of symbiont acquisition by mixotrophic testate amoebae are still poorly kown and would require more investigations. Who is copying whom? Did Archerella flavum make Hyalosphenia papilio jealous with such nice colours in its shell leading the latter to feed on it to steal these nice coloured symbionts (Figure 2)? Is Placocista spinosa a weak copy of Archerella flavum and Hyalosphenia papilio, selecting its symbionts from a cheaper shop? Many questions remain unanswered. Could some of these require a sociological approach?

 

Figure 2 | Hyalosphenia papilio taking its revenge on Archerella flavum.

 

References

1. Gomaa, F. et al. One alga to rule them all: unrelated mixotrophic testate amoebae (amoebozoa, rhizaria and stramenopiles) share the same symbiont (trebouxiophyceae). Protist 165, 161–176 (2014).
2. Gilbert, D., Amblard, C., Bourdier, G., Francez, A.-J. & Mitchell E. A. D. Le régime alimentaire des thécamoebiens (Protista, Sarcodina). L’année Biologique 39, 57–68 (2000).
3. Gilbert, D., Mitchell, E. A. D., Amblard, C., Bourdier, G. & Francez, A.-J. Population dynamics and food preferences of the testate amoeba Nebela tincta major-bohemica-collaris complex (Protozoa) in a Sphagnum peatland. Acta protozoologica 42, 99–104 (2003).
4. Jassey, V. E. J., Shimano, S., Dupuy, C., Toussaint, M.-L. & Gilbert, D. Characterizing the feeding habits of the testate amoebae Hyalosphenia papilio and Nebela tincta along a narrow ‘fen-bog’ gradient using digestive vacuole content and 13C and 15N isotopic analyses. Protist 163, 451–464 (2012).
5. Wilkinson, D. M. & Mitchell, E. A. D. Testate Amoebae and Nutrient Cycling with Particular Reference to Soils. Geomicrobiology Journal 27, 520–533 (2010).
6. Hoshina, R., Iwataki, M. and Imamura, N. (2010) Chlorella variabilis and Micractinium reisseri sp nov (Chlorellaceae, Trebouxiophyceae): Redescription of the endosymbiotic green algae of Paramecium bursaria (Peniculia, Oligohymenophorea) in the 120th year. Phycological Research, 58, 188-201.

Testate amoebae on fire

Contributed by Katarzyna Marcisz

How do testate amoeba communities respond to fire? How does burning affect this group of microorganisms and the environment where they occur in exceptionally high abundance – Sphagnum peatlands?

Answering these questions is crucial, as fire has a significant impact on peatland ecosystems. Peatlands are an important carbon pool, containing 1/3 of the global soil carbon (Parish et al., 2008). It has been shown that even a moderate drop in water table influences vegetation composition in peatlands and disturbs carbon accumulation (Kettridge et al., 2015). Peatlands experiencing drying are also more often ignited, and the frequency of fire and the extent of peat fires often increases (Turetsky et al., 2015). Peat fires can be deceptive: peat often burns by smouldering combustion that can persist for long periods of time rather than by more visible large fires as in the case of forests. The consequence is nevertheless that this burning affects the peat carbon stock.

The relationships between testate amoebae and fire are still quite a mystery. In studies from North America, Clifford and Booth (2013) and Clifford and Booth (2015) revealed peaks in microscopic charcoal accumulation rates that corresponded to drought periods as reconstructed with the use of a testate amoeba-based transfer function. However, these charcoal peaks were likely primarily derived from regional, upland fires rather than fire on the peatlands themselves. The effects of peatland fires on testate amoeba communities, and the response of individual species, have not been adequately examined. For example, Trigonopyxis arcula was suggested to be a possible fire indicator by Warner (1990) and Turner et al. (2014), and Hyalosphenia subflava was correlated with fire in the work by Turner and Swindles (2012). However, Turner et al. (2014) later suggested it should rather not be regarded as a reliable local fire indicator.

Fig. 1. Linje mire in the spring 2013.

Recently the relationships between individual testate amoeba species and fire were examined in a study by Marcisz et al. (2015), which was conducted within the RE-FIRE Sciex project (http://www.swissuniversities.ch/en/topics/sciex) and CLIMPEAT project (www.climpeat.pl), in northern Poland at a beautiful Linje mire (Fig. 1).

The analyses revealed that the peatland was wet before the onset of the Little Ice Age (ca. AD 1300-1850), when a rapid drop in water table occurred. Drying was also correlated with human migrations in the region, and with changing agricultural practices. Anthropogenic fires preceded hydrological changes on the mire; the response of the mire recorded as hydrological changes towards drier conditions was delayed in relation to the surrounding fire-related vegetation changes.

Fig. 2. Cross-correlation diagrams between testate amoeba species and macroscopic charcoal particles (from Marcisz et al., 2015)

Individual testate amoeba species were correlated with macroscopic charcoal particles recorded in the peat profile (Fig. 2). Testate amoebae indirectly responded to vegetation removal in the catchment driven by fire. While all the wet indicator species were negatively correlated with fire activity, most of the dry indicators (as well as Arcella discoides) were positively correlated. Although no explicit local fire indicator was found, from all the testate amoeba species Nebela tincta s.l. had the highest positive correlation recorded (Fig. 3)…..

https://www.youtube.com/watch?v=J91ti_MpdHA&feature=youtu.be&t=46s

Fig. 3. Nebela tincta s.l. on fire.

Additional work is needed to better quantify the relationships between testate amoebae, hydrological change, and fire, and experimental work is needed to assess the causes of these relationships. Such work may provide insight into the underlying processes controlling microbial community responses to fire and hydrological change. However, fire activity likely affects peatland microbial food webs, both directly (combustion of surface Sphagnum and peat layers) and indirectly (surrounding vegetation and surface run-off changes).

Literature cited

Clifford, M.J., Booth, R.K., 2013. Increased probability of fire during late Holocene droughts in northern New England. Climatic Change 119, 693–704.

Clifford, M.J., Booth, R.K., 2015. Late-Holocene drought and fire drove a widespread change in forest community composition in eastern North America. The Holocene 25, 1102-1110.

Kettridge, N., Turetsky, M.R., Sherwood, J.H., Thompson, D.K., Miller, C.A., Benscoter, B.W., Flannigan, M.D., Wotton, B.M., Waddington, J.M., 2015. Moderate drop in water table increases peatland vulnerability to post-fire regime shift. Scientific Reports 5.

Marcisz, K., Tinner, W., Colombaroli, D., Kołaczek, P., Słowiński, M., Fiałkiewicz-Kozieł, B., Łokas, E., Lamentowicz, M., 2015. Long-term hydrological dynamics and fire history over the last 2000 years in CE Europe reconstructed from a high-resolution peat archive. Quaternary Science Reviews 112, 138-152.

Parish, F., Sirin, A., Charman, D.J., Joosten, H., Minayeva, T., Silvius, M., Stringer, L., 2008. Assessment on peatlands, biodiversity and climate change: main report. Global Environment Centre, Kuala Lumpur and Wetlands International, Wageningen 179 pp.

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Testate amoebae and their influence on (global) silicon cycling

Contributed by Daniel Puppe

Silicon is the second most common element in the Earth’s crust (after oxygen) and the seventh most abundant element in the universe. That means we can find silicon almost everywhere. Silicon plays a pivotal role in diverse living organisms comprising pro- and eukaryotes accumulating biogenic silicon in various siliceous structures (= biosilicification) – like idiosomic testate amoeba shells. In soils of terrestrial ecosystems we can find a lot of biogenic silicon forming different silicon pools. These pools can be separated into zoogenic, phytogenic, microbial and protistic ones (Fig. 1).

Fig. 1: Biogenic silicon (Si) pools in terrestrial ecosystems (from Puppe et al. 2015).

While scientific research has been focused especially on the phytogenic silicon pool (represented by so-called phytoliths), little is known about zoogenic, microbial and protistic silicon pools. The protistic silicon pool in soils comprises mainly terrestrial diatoms and idiosomic testate amoebae (some testates are shown in Fig. 2).

Fig. 2: Scanning electron microscope (SEM) micrographs of various idiosomic (a – c) and xenosomic (d) testate amoebae: a) Euglypha rotunda-like amoeba, b) Puytoracia bonneti (first record for Germany), c) Corythion dubium and d) two individuals of Centropyxis sphagnicola. Scale bars in all micrographs = 20 µm. Source: Puppe et al. 2014.

However, what is the relevance of biogenic silicon pools for silicon cycling? To understand this, we have to look at biogeochemical cycles at a global scale. Globally, silicon and carbon cycles are connected by weathering processes and fluxes of dissolved silicon from terrestrial to aquatic ecosystems (e.g. Sommer et al. 2006). When silicon is washed away into the oceans, it is used by marine diatoms for frustule synthesis (frustules are the siliceous cell walls of diatoms). Due to their worldwide distribution in very high abundances, diatoms are able to fix carbon dioxide (CO₂) on a large scale (about 20 % of the photosynthesis on Earth is carried out by diatoms! See, e.g., Armbrust 2009). By consuming atmospheric CO₂, diatoms thus have an effect on climate change, which is mainly caused by increasing atmospheric concentrations of the greenhouse gas CO₂ since 1750 (IPCC 2013). The fluxes of dissolved silicon are affected by organisms that synthesize siliceous structures and consequently accumulate and recycle biogenic silicon in soils. In other words, the more silicon that is fixed in terrestrial ecosystems, the less silicon that arrives in the oceans, and as a consequence diatom production in the oceans decreases. Let´s visualize the main aspects of the processes described so far (Fig. 3).

Fig. 3: Connections of global silicon (Si) and carbon (C) cycles and the influence of biogenic silicon pools (see descriptions in the text).

In two recent publications we analyzed protozoic silicon pools (represented by idiosomic testate amoebae) in initial (Puppe et al. 2014) and forested (Puppe et al. 2015) ecosystems. We found, that after (only!) 10 years of development idiosomic silicon pools in initial ecosystem states become comparable to the ones in forested ecosystems. In forest soils idiosomic silicon pools were relatively small (0.2 kg – 4.7 kg silicon per hectare in the upper 5 cm). Due to the fact that only intact shells were enumerated in our studies idiosomic silicon pools might be larger than calculated. However, there is no information on the quantity of this “platelet silicon pool”.

At the forested sites we further analyzed potential influences of abiotic factors (e.g. soil pH) and earthworms on idiosomic silicon pools. Surprisingly, no relationship between silicon supply (readily-available silicon in soils) and idiosomic silicon pools could be found, thus no silicon limitation for shell synthesis appeared in the field. Instead, idiosomic silicon pools showed a strong, negative relationship to earthworm biomasses. We concluded that earthworms control idiosomic silicon pools by direct (e.g. competition in the soil food web) and/or indirect mechanisms (e.g. change of habitat structure through burrowing activities). Earthworms themselves were strongly influenced by soil pH. Due to the fact that soil pH is a result of weathering and acidification, idiosomic silicon pools are indirectly, but ultimately controlled by soil forming factors, mainly parent material and climate. These results point to the potential relationships between soil fauna and the storage of biogenic silicon in terrestrial ecosystems. However, further research is needed to enlighten the complex biotic linkages in terrestrial biogeochemical silicon cycling and their importance for global silicon fluxes.

Annual biosilicification rates of living testate amoebae (17 kg – 80 kg silicon per hectare) in forested ecosystems were comparable to or even exceeded reported data of annual silicon uptake by trees. Just imagine it! Unicellular, microscopic organisms can out-compete multicellular, macroscopic ones in terms of annual silicon uptake. Given the worldwide distribution of testate amoebae, the importance of idiosomic silicon pools and corresponding biosilicification for (global) silicon cycling becomes clear.

Literature Cited

Armbrust, E.V. (2009). The life of diatoms in the world’s oceans. Nature, 459, 185-192.

IPCC, 2013: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex & P.M. Midgley (eds.). Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, 1535 pp.

Puppe, D., D. Kaczorek, M. Wanner & M. Sommer (2014). Dynamics and drivers of the protozoic Si pool along a 10-year chronosequence of initial ecosystem states. Ecological Engineering 70, 477-482.

Puppe, D., O. Ehrmann, D. Kaczorek, M. Wanner & M. Sommer (2015). The protozoic Si pool in temperate forest ecosystems – Quantification, abiotic controls and interactions with earthworms. Geoderma 243-244, 196-204.

Sommer, M., D. Kaczorek, Y. Kuzyakov & J. Breuer (2006). Silicon pools and fluxes in soils and landscapes – a review. Journal of Plant Nutrition and Soil Science 169, 310-329.