Category Archives: History

Laveran’s eye

The military hospital of Constantine, Algeria was a fitting place to view what must have seemed the Devil in microscopic form.

Stages of the malaria parasite drawn by Alphonse Laveran

An interesting look at using skeletal remains and historical reports to reconstruct the geographic distribution of a vector-borne disease.

Contagions

England once looked very different. Much of southern Britain was marshland for most of the island’s occupied history. These bogs, fens, and marshes ensured that areas of virtual wilderness persisted  from before Roman Britain through the Norman period and beyond. Despite the difficulties of using fenlands, these areas were not only occupied throughout the Anglo-Saxon period, but important centers like Croyland, Bardney, and Ely eventually developed in the marsh.

The largest fenland region was known as ‘the Wash’.  This low-lying region drained four rivers into  a square bay of the North Sea that forms the corner between Lincolnshire and Norfolk. In Anglo-Saxon times, this tidal marsh and bog was a vast border region between the region of Lindsey and East Anglia.  Places like Croyland and Ely were islands in the wetlands.  The eighth century Life of Guthlac describes the environment of Croyland when Guthlac arrived:

There is…

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Visualizing trophic interactions in an urban aquatic mesocosm

Variations in how to display the trophic interactions of an ecosystem—the food web, the regulating pressures between organisms of a particular space—have existed since the roots of the idea in community ecology. Nature—or, in particular, the relationships between organisms—has long been described as a web by many. Take, for example, the now-classic food web of Bear Island, the southernmost island of the Norwegian Svalbard archipelago, by Victor Summerhayes and Charles Elton in their seminal 1923 paper. In their illustration below, organisms are grouped into functional clusters, and arrows depict one organism being consumed by another, outlining a basis from which these systemic illustrations would build upon for decades.

Victor Summerhayes and Charles Elton's 1923 food web of Bear Island, Norway.

But this depiction of life wasn’t quite so scientifically until Charles Darwin published his On the Origin of Species in 1859, in which he wrote,

I am tempted to give one more instance showing how plants and animals remote in the scale of nature, are bound together by a web of complex relations. I shall hereafter have occasion to show that the exotic Lobelia fulgens is never visited in my garden by insects, and consequently, from its peculiar structure, never sets a seed. Nearly all our orchidaceous plants absolutely require the visits of insects to remove their pollen-masses and thus to fertilise them. I find from experiments that humblebees are almost indispensable to the fertilisation of the heartsease (Viola tricolor), for other bees do not visit this flower […] Hence we may infer as highly probable that, if the whole genus of humble-bees became extinct or very rare in England, the heartsease and red clover would become very rare, or wholly disappear. The number of humblebees in any district depends in a great measure upon the number of field mice, which destroy their combs and nests; and Col. Newman, who has long attended to the habits of humble-bees, believes that “more than two-thirds of them are thus destroyed all over England.” Now the number of mice is largely dependent, as every one knows, on the number of cats; and Col. Newman says, “Near villages and small towns I have found the nests of humblebees more numerous than elsewhere, which I attribute to the number of cats that destroy the mice.” Hence it is quite credible that the presence of a feline animal in large numbers in a district might determine, through the intervention first of mice and then of bees, the frequency of certain flowers in that district!

Darwin also described this web of complex relations as an entangled bank, “clothed with many plants of many kinds, with birds singing on the bushes, with various insects flitting about, and with worms crawling through the damp earth,” and he reflected on how each of these forms, different they may be, are dependent on one another in direct and indirect pathways while at the same time producing the kinds of ecological pressures that lead to adaptation and the rise—or elimination—of species.

A species web of a slightly different kind: Charles Darwin's 1837 sketch of an evolutionary tree.

On the Origin of Species and Darwin’s subsequent writings were foremost about natural selection, the non-random process by which biological traits become more or less common in a population. But Darwin’s idea can be, and was, applied the same to how organisms themselves become more or less common in an ecosystem—the question became the following: what are those forces and relationships that allow some species to foster in a particular environment, while others only play a minor role? Community ecologists divide these species into two initial groups: autotrophs, which produce organic matter from inorganic substance to compose the primary level of an ecosystem (the first trophic level), and the heterotrophs (1+ trophic levels), which cannot fix carbon and thus must consume organisms from the initial or subsequent trophic bases. In terms of the relationships between the autotrophs and heterotrophs, food web ecology polarizes the dynamic between which group regulates the other. In bottom-up control, also known as donor control, the autotrophs (i.e., plants and algae) produce the primary resources, thereby maintaing the nutrient availability that organisms at higher trophic levels are dependent upon. Contrasting bottom-up control is the top-down dynamic, also known as a trophic cascade, in which predation and herbivory are the factors that dominate whether a species will thrive in an environment. More typically, however, analyses in community ecology strive for some middle ground between the two.

While the organization of a food web is inherently more complex—incorporating the movement of energy and mineral nutrients; dividing the heterotrophs into carnivores, herbivores, decomposers; delineating even further between competitor species, generalist consumers, specialist predators, etc—this basic model holds steady. Because this organization is predominantly a visual one—spatial and temporal patterns and variations are a large part of community dynamics in ecological research, as outlined in a recent review by Massol et al.—an interesting aspect of studying trophic interactions lies in the possibilities for visualizing data. The first graphical interpretation of a food web was published in 1880 by Lorenzo Camerano, in a manuscript entitled “On the equilibrium of living beings by means of reciprocal destruction.” Frustrated by his time’s scientific divide over which animals are useful or beneficial to agriculture, Camerano wrote the following.

To have an exact and clear idea, I repeat, of the relations between, for example, insectivorous birds and phytophagous insects, and between these and plants, these groups cannot be studied separately. Rather it is necessary to study each in relation to all other animals to see the general laws governing the equilibrium of animal and plant species.

While Camerano’s reasoning for the paper, published in the Accademia delle Scienze di Torino, was particular and applied towards the practical, his ultimate goal in the article and its resulting visualization was of general and theoretical concern.

Plate 1, Camerano 1880. Theoretical web of plant and animal interactions.

Compare that template of trophic relationships among organism groups—including primary producers, predators, ectoparasites, endoparasites, and carnivores—with a particular illustration of an ecological community of individual species with regard to enemies of a specific phylogenetic order, Coleoptera.

Plate 2, Camerano 1880. Web of interactions between Coleoptera, enemies of Coleoptera, and ecological enemies of those enemies.

In the former, more-theoretical visualization, Camerano sides with the theory of bottom-up control—vegetation is the base layer of the trophic sphere, with interactions between higher trophic levels expanding in outward rings. In the latter, allying with top-down ideas of control, complex relations are derived not from primary production, but rather from multiple pressures of predation, forming direct and indirect influences between heterotrophs. It is the latter depiction—with its emphasis on predator–prey relationships and linear–nonlinear associations between species—that has most influenced how many visualizations of trophic dynamics are drawn. In Summerhayes and Elton’s depiction of Bear Island, the first illustration in this article, the ecologists organized the biota with priority on that relationship between predator and prey—protozoa eat the bacteria, polar bears eat seals. Even where nutrients and zooplankton entered the situation, their connection to the rest of the system was given within the framework of consumption dynamics—bacteria consume nitrogen, worms eat dead plants, algae take in mineral salts.

And nor is this choice of visualization a poor or incorrect one. However, an interesting note lies in the shift between how to organize a food web in the 19th and early 20th centuries  and what kind of information should and can be included in more sophisticated images now. When one adds in the more quantitative turn in food web analysis—such as with ecological pyramids and trophic dynamics, both of which incorporate the second law of thermodynamics to consider how energy is conserved or lost as it passes between organisms—the complexity inherent in the early food webs above exponentially increases in magnitude.

The question in producing a food web is, then, how to produce a visualization of that complexity without overwhelming our perception of reality. Sacrifice quantitative rigor, and the illustration instead appears as illusion, an over-simplification. Introduce too much information, and the traceable dissolves into surplus. Such are the balancing acts Edward Tufte outlines in his 1983 The Visual Display of Quantitative Information. In the book, the statistician argues that good information design reveals the greatest number of ideas in the shortest time, with the least ink, in the smallest amount space, akin to what Italo Calvino described as lightness in literary prose—both must, in the end, tell not only a good story, but a proper one, without sacrificing either extreme of this information equilibrium.

As some of the first illustrations of food webs came from aquatic systems, bodies of water, as simultaneously self-contained microcosms and hubs in ecological networks, are good places to look for growing trends in data visualizations. An interesting and successful  update on the classic food web comes from a paper by Kevin Caillouët et al. in a 2008 paper on enclosed aquatic communities in New Orleans, Louisiana. After Hurricane Katrina flooded 80% of the city in August of 2005, floodwater from Lake Pontchartrain to the north inundated the urban terrain for over three weeks. By completely covering most regions of the city in brackish water, flooding resulted in the production of novel aquatic habitats in lowlands, depressions, and artificial containers, to name a few. Much as a forest fire produces a blank template from which previously occupied niches can be reclaimed and monocultures overthrown, Hurricane Katrina produced a blank template from which new food webs—new trophic interactions, in new magnitudes and organizations—could be drawn. In particular, on the back of research suggesting correlations between flooding and increased mosquito populations, Caillouët et al. sought to examine how these new aquatic communities would work for or against local mosquito populations, and how this in turn could influence the human risk of mosquito-borne diseases such as that caused by West Nile virus. In particular, the team examined the quasi-contained ecosystem of abandoned swimming pools, the largest of artificial containers and one of the most prone habitats to support mosquito larval development.

Caillouët et al. sample a flooded abandoned swimming pool in the Lakeview neighborhood of New Orleans.

By sampling pools in two flooded neighborhoods of New Orleans near the 17th Street Canal levee breach, the researchers were looking at this artificial environment as a mesocosm of sorts. Unlike the simplified microcosm, a controlled, laboratory-based ecosystem used to simulate and predict the behavior of its natural counterpart, a mesocosm instead brings the natural under controlled conditions, providing a link between observational field study and the artificiality of the laboratory. These mesocosms, which were being colonized by various invertebrates, fish, and mosquito species, allowed the team to ask the following questions about the composition of these new and temporary environments: if mosquito larvae were using the pools for development; if fish moved in from Lake Pontchartrain and were able to establish populations; if predatory invertebrates migrated to and colonized pools; and, lastly, if and to what extend these latter organism groups regulated mosquito populations.  To explore how these questions translate into science, Caillouët et al. relied on a conceptual model, the first step in transforming idea into design, the prerequisite for collecting and interpreting data.

Models and interpretations of aquatic community colonization post-Hurricane Katrina. Caillouët et al. 2008.

The conceptual model (A) of Caillouët et al. is not all too different, as a theoretical insight, from the initial plate by Camerano in 1880. Just as Camerano endeavored to clearly illustrate the relationships that draw together insectivorous birds and phytophagous insects, and between these and plants, the modern model food web illustrates the general relations between four main groups of organisms: the top predators, the specialist predators, the competitor species, and the prey. Much as Summerhayes and Elton used arrows in their 1923 depiction of an aquatic food web to illustrate the direction of the relationship between two or more organisms, the above model demonstrates a direct (and negative) effect of one group on another with solid lines, while dotted lines indicate an indirect (and therefore positive) effect. Continue reading

Beetles, form, art

In Emerging Infectious Diseases, each issue of the peer-reviewed journal contains a short essay that connects and contextualizes the artwork of the cover to the content of the issue (for a brief but interesting discussion of cover art on scientific journals, take a look at a post by biocreativity, another blog exploring the nexus of art, biology, creativity, science, design, and nature). The Centers for Disease Control and Prevention, the producing body of the journal, writes that the cover art is selected on the basis of “artistic quality, technical reproducibility, stylistic continuity, communication effectiveness, and audience appeal.” The cover story, on the other hand,

has evolved by popular demand, literally out of the journal readers’ wish to know the art and how it relates to them and to what they do. A sketch of the artist, period, and work, provides contextual knowledge, and a brief interpretation offers a link between the art and the human elements and goals of public health. The reader becomes familiar with the work, and in the end is surprised and, we hope, enlightened.

A rather dry description of these clips, but the author, Cyprus-born Polyxeni Potter, is rather anything but. Potter’s contextualization of the art and artists of which she writes is lyrical and informative. For a 2005 issue of EID, containing research on Staphylococcus aureus infection in football teams, bed bug infestations, Lyssavirus prevalence in Scottish bats, and other outbreaks,  Potter chose a watercolor painting of a stag beetle, most likely the Europe-dominated member of the Lucanidae family, Lucanus cervus. Of her selection of this organism, this “tribute to the minutest in nature,” Potter writes:

Other critters, not so benign or visible, are also easy to ignore, their pestiferous history relegated to the past and quickly forgotten. Blood-thirsty ticks, bed bugs, and other insects, as if caught in some Gothic time machine, continue to torment humans, still claiming their lives, if not their souls. Renewed infestations of ticks causing meningoencephalitis in Germany and of bed bugs compromising health in Canada and elsewhere warn against ignorance and neglect regarding visible or invisible tiny creatures of nature.

Albrecht Dürer (1471–1528). Stag Beetle (1505).

L. cervus, most simply known as the stag beetle, was named as such—lucanus—by Publius Nigidius Figulus, a scholar of the Late Roman Republic and friend to Cicero, due to its ornamental use in the Lucania region of Italy. The latter end of the creature’s binomial nomenclature, cervus, the direct Latin for deer, the stag. The naming is gender-biased, typical of sexual dimorphism, as the reference to the stag—which itself refers to a male red deer—is more applicable to the males of the beetle, themselves characterized by the mammal’s antlers.

Stag beetle, Pavel Krasensky (2007).

It was in Italy, home of Nigidius, the lucanus label, and the Latin for stag, writes Potter, that Albrecht Dürer, the painter responsible for the above work, was drawn. But it was in Venice to the northeast, rather than the linguistic homeland of L. cervus, that the artist found inspiration and welcome. Of Venice, Dürer reflected, “In Venice, I am treated as a nobleman…. I really am somebody, whereas at home I am just a hack.” This home was Nürnberg, Germany, where Dürer had been trained in Gothic traditions, metallurgy, and mathematics. His move to Italy brought him to the Northern Renaissance, to the work of Leonardo da Vinci, to printmaking. Like other polymaths of his day, Dürer asserted that “art must be based upon science,” and, in agreement with da Vinci, on mathematics, on geometric form, on the golden ratio.

Ratios and antlers held a special place to mathematicians and artists of the day. Named by the Greeks—Dürer held a special reverence for Aristotle—the golden ratio has been considered the proportion of length to width of a rectangle most objectively pleasing to the eye.  The golden ratio draws from the Fibonacci sequence, introduced to the West by Leonardo Fibonacci in the 1100s and utilized to solve an issue of the growth of a population of rabbits . In the Fibonacci sequence, one produces a sequence of numbers by starting with 1 and 1 and adding the two together—the product is, of course, 2. Obtaining the subsequent number involves adding the latter two integers—the result is 3. Follow the natural pattern and the integers appear as 5, 8, 13, 21, 34, 55, etc. The role of the golden ratio is in taking from Fibonacci’s order of numbers and dividing each pair (2 by 1, 3 by 2, 5 by 3, 8 by 5, etc.). The resulting quotients are, respectively, 2.0, 1.5, 1.67, and 1.6. Continue making these divisions, and one number will begin to hold as a constant quotient—1.618. Continue reading

A gallery and a drawing

A recent gallery review in the New York Times asked the following question: are killer viruses, rendered in glass, also things of beauty? The exhibit, by Britain’s Luke Jerram, is showing in Manhattan from June 4th to July 31st, 2010. In it, Jerram has produced several infectious microbes out of glass, a step that the reviewer, the science journalist Donald G. McNeil Jr., questions and feels troubled by. As someone who reports on the global impact of infectious diseases, McNeil Jr. and his review both find troublesome depicting death as art and attempt to reconcile this bias. From the view of the artist, Jerram’s work attempts to reconcile the arts and the sciences, to illuminate cultural biases in biology and medicine’s depiction of pathogens, and to showcase his own agenda and position. I found the exhibit a success. But to get there, I need to stop, reflect, and return to the work of Ernst Haeckel and others if I wish to problematize McNeil Jr.’s critique.

Can art and science meet? Robert Hooke’s Micrographia serves as one example of this merger, and I can think of no better progression of the kind of polymath Robert Hooke embodied than in Ernst Haeckel. If Hooke had begun bridging the arts (drawings and sketches) with scientific rigor (microscopy), then it was Haeckel who took this task to another level. His Kunstformen der Natur, images of which were shown in an earlier post, not only was popular, but also embodied what Haeckel saw as scientific truths. If anything else, the prints of various organisms embody Haeckel’s scientific beliefs, his view of the world, which was often contested by the wider scientific community. In line with other mergers of art and science in 16th to 19th century Europe, Haeckel’s prints are about symmetry, about perfection, about order. Much like Robert Hooke’s Micrographia, in Kunstformen der Natur, something Platonic, some higher ideal, perhaps unobtainable by humans, existed in the natural world.
Continue reading