Friday Fellow: Réaumur’s Desert Woodlouse

by Piter Kehoma Boll

We all know that crustaceans are mainly aquatic animals, but that some species have conquered the land, especially the woodlice. But did you know that some woodlice went as far as to find a way to live in the desert? Today’s Friday Fellow is one of those species. Actually, it is the woodlouse that lives in the driest habitat where a crustacean can be found. Its name is Hemilepistus reaumuri, which I decided to call the Réaumur’s Desert Woodlouse.

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A specimen of Hemilepistus reaumuri in Tunisia. Photo by Ferenc Vilisics.*

Found in the deserts of North Africa and the Middle East, the Réaumur’s Desert Woodlouse is considerably large, reaching up to 22 mm in length. It feeds on leaves and is mainly active at dusk. Being found in great densities, this little fellow is also an important food source for some predators, especially the large-clawed scorpion Scorpio maurus.

In order to tolerate the high temperatures and the low relative humidity of the air in the desert, the Réaumur’s Desert Woodlouse constructs burrows that are at least 40 cm deep, so that it can find an environment in which the relative humidity is of at least 6%, since it cannot survive when it drops below that value. When it gets lost, it usually finds its burrow again in a few minutes by using a systematic search behavior in the environment, exploring regularly the area around the point in which it became lost until its home is located.

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About to enter its burrow. Photo by Ferenc Vilisics.*

One peculiar aspect of the Réaumur’s Desert Woodlouse is that it take care of its offspring. A male and a female form a monogamous couple and construct together a burrow where they live and take care of their young. The female usually bears 50 to 100 live young and those remain in the burrow for 10 to 20 days, being fed by their parents. Members of the same social group are able to recognize each other using pheromones, and when the young leave the burrow they may be captured by adults of other groups, killed and offered as food to that adult’s offspring.

Having a lifespan of only 15 months, the Réaumur’s Desert Woodlouse produces only one brood during their life. Having a long life does not seem to be a privilege for desert crustaceans.

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References:

Hoffmann, G. (1983) The random elements in the systematic search behavior of the desert isopod Hemilepistus reaumuriBehavioral Ecology and Sociobiology 13(2): 81-92.

Linsenmair, K. E. (1985) Individual and family recognition in subsocial arthropods, in particular in the desert isopod Hemilepistus reaumuriFortschritte der Zoologie 31: 411-436.

Wikipedia. Hemilepistus reaumuri. Available at < https://en.wikipedia.org/wiki/Hemilepistus_reaumuri >. Access on March 25, 2018.

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Whose Wednesday: John Hughlings Jackson

by Piter Kehoma Boll

Today we celebrate the birthday of John Hughlings Jackson, an English neurologist. Born in 1835 in Providence Green, Yorkshire, England, he was the youngest son of Samuel Jackson, a brewer, and Sarah Jackson (née Hughlings), the daughter of a Welsh revenue collector. His mother died about a year after he was born.

After being educated in Tadcaster, Yorkshire and Nailsworth, Gloucestershire, he attended the York Medical and Surgical School. He qualified at the St. Bartholomew’s Hospital in 1856 and then became a house physician to the York Dispensary.

Having a wide range of interests, Jackson was ver fond of conceptual issues and almost abandoned medicine to dedicate to philosophy in 1859. However, instead of doing so, he moved to london and started to work at the Metropolitan Free Hospital and the London Hospital.

During his work in London, he became established as a neurologist by studying epilepsy. His name became attached to the specific epileptic phenomenon known as Jacksonian March (or Jacksonian Epilepsy), in which the patient does not lose consciousness and only part of the brain (and therefore part of the body) is affected by the seizures. He is also the main contributor to the understanding of the so-called “dreamy state” caused by psychomotor seizures that originate in the temporal lobe.

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John Hughlings Jackson in 1895, by Lance Calkin.

In 1865, Jackson married Elizabeth Dade Jackson, who was his first cousin. Ironically (or strangely? or coincidentally?) she died in 1865 due to an epileptic condition that happened to be exactly the Jacksonian epilepsy. After her death, he became a recluse person, only leaving his house to continue his work.

In 1878, Jackson was elected a Fellow of the Royal Society and at the same time he founded, together with the neurologists David Ferrier (1843-1928) and James Crichton-Browne (1840-1938), the Brain journal, which is still being published today. In 1892, he helped to found the National Society for the Employment of Epileptics.

Jackson died in London on October 7, 1911 and was buried in Highgate Cemetery.

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Friday Fellow: Brazilian Dutchman’s Pipe

by Piter Kehoma Boll

When we see plants with large and colorful flowers, they are usually ornamental varieties produced by humans through selected breeding, but sometimes some of those plants exist in all that exuberance in the wild as well and one of them is the Brazilian Dutchman’s Pipe, Aristolochia gigantea.

Native from the Atlantic Forest in Brazil, especially in the states of Bahia and Minas Gerais, the Brazilian Dutchman’s Pipe is a liana that belongs to the widespread genus Aristolochia, commonly known as Dutchman’s Pipe because of another species, Aristolochia durior, which resembles a smoking pipe. The Brazilian Dutchman’s Pipe, however, does not resemble a pipe that much, and some people say that it actually looks like a human’s vulva.

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The flower of the Brazilian Dutchman’s Pipe. Photo by Ken Slade.*

The beauty of the Brazilian Dutchman’s Pipe’s flowers led it to become an ornamental plant. However, it does not tolerate temperatures below 10°C, so in colder countries, such as in Europe or North America, it must be cultivated in Greenhouses or other structures that prevent the temperature from dropping too much.

Most species of Dutchman’s Pipe release a scent of rotting meat that attracts their pollinators, mainly flies. The Brazilian Dutchman’s Pipe, however, releases a pleasant citronella-like odor but is still pollinized by flies.

Due to the widespread occurrence of the genus Aristolochia, the cultivation of the Brazilian Dutchman’s Pipe in the northern hemisphere can also lead to some ecological disasters. The pipevine swallowtail Battus philenor is a butterfly whose caterpillars feed on the leaves of several Neartic species of Aristolochia. When faced with the Brazilian Dutchman’s Pipe, the butterflies mistake it for one of its native hosts and lay their eggs there, but the poor caterpillars cannot survive on this plant and end up dying.

Sometimes our need for beauty can also take some beauty away.

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References:

Hipólito, J.; Viana, B. F.; Selbach-Schnadelbach, A.; Galetto, L.; Kevan, P. G. (2012) Pollination biology and genetic variability of a giant perfumed flower (Aristolochia gigantea Mart. and Zucc., Aristolochiaceae) visited mainly by small Diptera. Botany 90(9): 815-829. https://doi.org/10.1139/b2012-047

Wikipedia. Aristolochia gigantea. Available at < https://en.wikipedia.org/wiki/Aristolochia_gigantea >. Access on March 25, 2018.

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Whose Wednesday: Frederik Ruysch

by Piter Kehoma Boll

Today we celebrate the 380th birthday of the Dutch botanist and anatomist Frederik Ruysch, seen by some as an astonishing artist and by others as a creepy scientist.

Born in 1638 in The Hague, Frederik Ruysch was the son of a government functionary. After the death of his father, he became apprentice to an apothecary. Early in his life, he developed an interest in anatomy and went to the university in Leiden to study anatomy under Franciscus Sylvius (1614-1672). At that time, it was difficult to get corpses to dissect, so Ruysch started to study ways to prepare the organs in order to preserve them.

In 1661, he married Maria Post, the daughter of the architect Pieter Post (1608-1669). In 1664, he graduated with a dissertation on pleuritis. In 1667, he became the praelector of the Amsterdam surgeon’s guild and in 1668 the chief instructor of the city’s midwives, which demanded them to be examined by him before being allowed to practice their profession. About a decade later, in 1879, he became a forensic advisor to the Amsterdam courts.

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Anatomische les van Dr. Frederik Ruysch, by Jan van Neck, 1683.

Another of Ruysch’s interest was botany and in 1685 he was appointed as a professor of botany in the Hortus Botanicus Amsterdam, working with Jan (1629-1692) and Caspar Commelin (1668-1731), specializing on indigenous plants.

Ruysch made significant scientific contributions to the field of anatomy, having discovered, for example, the vomeronasal organ in snakes and the valves in the lymphatic system.

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Frederik Ruysch in 1694, by Juriaen Pool.

However, what really made Ruysch famous was his anatomical museum created in the late 1600s. Known simply as the Cabinet, the museum consisted of a series of small houses that Ruysch filled with more than 2000 preserved specimens, including many human embryos and fetuses.

The preservation techniques used were of different types, but the most sofisticated ones consisted of injecting the vascular systems of the corpses with a special red-tinted wax and then submerging them in an embalming fluid. This technique allowed him to manipulate the specimens more easily and arrange them in ways that were anatomically accurate and to give the impression of life. As the museum was open to both scientists and laypeople, he considered the impact that the material would have on people and tried to give it an artistic look. He was helped by his daughter, the painter Rachel Ruysch (1664-1750). Some of his specimens were organized in elaborate scenes using pieces of plants, animals or even body parts such as bones and kidney stones.

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One of Ruysch’s scenes drawn by Cornelius Huyberts in 1721.

In 1697, the Russian tsar Peter the Great (1672-1725) visited Ruysch’s collection and became fascinated by it. Later, in 1717, during a second visit, the tsar bought the entire collection and took it with him to Russia. Ruysch refused to help packing and labeling everything, possibly as a way to reduce the emotional struggle caused by having to give his entire work away, but soon after he began anew.

Ruysch died in 1731, aged 92. About 900 of his displays have survived until the present, being considered pieces of art.

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References:

The Embryo Project Encyclopedia. The Cabinet of Frederik Ruysch. Available at < https://embryo.asu.edu/pages/cabinet-frederik-ruysch >. Access on March 26, 2018.

Wikipedia. Frederik Ruysch. Available at < https://en.wikipedia.org/wiki/Frederik_Ruysch >. Access on March 26, 2018.

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Planarian: a living vessel built by unicellular organisms?

by Piter Kehoma Boll

Not long ago I talked about the peculiar genome of the freshwater planarian Schmidtea mediterranea and how it challenges our view of many cellular processes. Now what if I told you that planarians also challenge our view of what a multicellular organism is?

We all know that organisms may be either unicellular or multicellular, but sometimes it is hard to tell them apart, especially in what are called colonial organisms, in which clones of unicellular individuals may live together.

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Green algae of the genus Volvox are somehow at the boundary between unicellular and multicellular organisms. Although usually considered a colony of unicellular organisms, they behave somewhat like a multicellular organism. Photo by Frank Fox.*

So where lies the boundary between gathered unicellular organisms and true multicellular organisms? One of the ideas is that for a group of cells to be considered a single unit (an organism) they must have high levels of cooperation and low levels of conflict between each other and, perhaps more important than that, they have to be dependent on the association in order to survive.

As most recent evolutionary theories predict, cooperation increases with genetic similarity. As a result, multicellular organisms are (almost) always composed of cells having the exact same genetic material, i.e., they are all clones. We know, however, that during DNA replication mutations may occur, so that eventually at least some cells of an adult and many-celled organism may have become genetically distinct. This leads to a need to find a way to fix this problem by reincreasing genetic similarity, and the way most organisms found to do that is by allowing only one lineage of their cells, the germ cells (which produce the gametes) to generate the next generation. Thus, each transition from one generation to the next passes through a “zygotic bottleneck”, i.e., a new organism is always generated from a single original cell, the zygote, which assures that the genetic similarity is always brought back.

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A developing new egg, with an embryo that is created from a single original cell, the zygot, assuring a higher genetic similarity of the cells in the whole organism. Photo by Stéphanie Bret.**

The zygotic bottleneck is not a rule for a lot of species though. Many animals and plants are able to reproduce asexually by budding, fission or many other ways. In such cases, the new organism usually is built from several different lineages of the parent organism. For example, some succulent plants may generate a new organism from a dettached leaf and several cells of the original leaf start to reproduce and together they build the new plant and, as each lineage may have suffered different mutations, the offspring is not necessarily composed of genetically identical cells. Nevertheless, even such organisms, which are able to reproduce asexually, still retain the ability to generate zygotes through sexual reproduction, which eventually “cleans that mess”.

But in planarians things get really strange. First of all, let’s explain some basic things about planarians. They have, as you know, a remarkable regeneration ability. This happens due to the presence of stem cells called neoblasts that fill their bodies. Those neoblasts are able to generate all cell types that make up the planarian’s body. In fact, all cells in a planarian must come from neoblasts, because, as weird as it may be, all differentiated cells in a planarian body ARE UNABLE TO UNDERGO MITOSIS! Once a neoblast differentiates into any kind of cell, it is condemned to die in a few days without ever letting descendants. All cells in a planarian body are therefore constantly replaced by new ones coming from neoblasts. The only lineage of differentiated cells that is still able to reproduce is that of the germ cells, which, as in other multicellular organisms, assure that the next generation will consist of organisms with genetically homogeneous cells.

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Girardia tigrina, a freshwater planarian. Photo by Wikimedia user Slimguy.**

Several freshwater planarians, however, have lost their ability to generate sexual organs and, as a result, germ cells. In order to reproduce, they must rely on a form of asexual reproduction, which in this case happens by transversal fission of the body and posterior regeneration of the missing parts. In these populations, the zygotic bottleneck disappeared completely and, as a result, any non-lethal mutation in the neoblasts is retained in the organism, leading to a population of genetically distinct neoblasts inside a planarian.

Therefore, considering the fact that asexual planarians are not genetically homogeneous, having several different neoblast lineages in the same body, and that the neoblasts are the only cells able to reproduce and continue the species, a recent publication by Fields and Levin (see references) suggests that asexual planarians are nothing more than a very complex environment built by neoblasts in order to survive. Considering that each neoblast is an independent cell, which only needs the environment (the planarian) to survive, but does not need other neoblasts, planarians, at least the asexual ones, do not seem to have reached completely the requirements of high internal cooperation and low internal competition to be considered multicellular organisms.

We could interpret the neoblasts as unicellular organisms that live together, cooperating to build a complex environment, the planarian body, with their own sterile descendants (the differentiated cells), as if they were a group of queen ants living among sterile castes. Kind of mind blowing, huh? But it actually makes sense.

If you want to read more about it and understand every detail in this theory, read the references below.

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Maybe you’d like:

Endosperm: the pivot of the sexual conflict in flowering plants

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References:

Fields, C; Levin, M. (2018) Are Planaria Individuals? What Regenerative Biology is Telling Us About the Nature of Multicellularity. Evolutionary Biology: 1–11.

West, S. A.; Fisher, R. M.; Gardner, A.; Kiers, E. T. (2015) Major evolutionary transitions in individuality. PNAS 112 (33): 10112-10119. https://doi.org/10.1073/pnas.1421402112

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Friday Fellow: Savigny’s Brittle Star

by Piter Kehoma Boll

It is time to present the second echinoderm here, and for that I have chosen a brittle star, actually the most widespread brittlestar in the world. Known scientifically as Ophiactis savigny and populary as Savigny’s brittle star or simply little brittle star, this species occurs in tropical and subtropical waters of all the world’s oceans.

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One tiny specimen of Ophiactis savignyi. Photo by Ria Tan.*

The Savigny’s brittle star is very small, having a disc measuring between 0.5 and 11 mm in diameter and usually six long segmented arms. It can live from the intertidal zone to about 500 meters below the surface and is often found living inside sponges in a possible commensal association, sometimes occurring in very high densities.

The reproduction of the Savigny’s brittle star can be sexual or asexual. During sexual reproduction, both males and females release gametes into the water, where they are fertilized, while asexual reproduction occurs by fission of the discs, literally splitting the animal in half and then each half regenerates the missing parts. Males seem to be more prone to engage in asexual reproduction, which leads to a higher rate of males in the population in relation to females.

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Hundreds of arms of many individuals of Ophiactis savignyi poking out from a spong Spheciospongia cf. vagabunda. Photo by Ria Tan.**

The diet of the Savigny’s brittle star is composed mainly of detrites or dead animals. Its association with sponges may be related to the fact that sponges pump water that carries particles that may also serve as food for the brittle stars. It is common to found the cavities of certain sponges completely filled by individuals of the brittle star, some of them already too large to be able to leave the sponge.

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References:

McGovern, T. M. (2002) Sex-ratio bias and clonal reproduction in the brittle star Ophiactis savignyEvolution 56(3): 511-517. https://doi.org/10.1554/0014-3820(2002)056[0511:SRBACR]2.0.CO;2

Wikipedia. Ophiactis savigny. Available at < https://en.wikipedia.org/wiki/Ophiactis_savignyi >. Access on March 22, 2018.

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Whose Wednesday: David Keilin

by Piter Kehoma Boll

Today we celebrate the birthday of a Russian-British entomologist, David Keilin, whose work had important outcomes not only in entomology, but also in parasitology, biochemistry and even, indirectly, in molecular phylogeny.

Born on March 21, 1887 in Moscow, David Keilin was the son of Polish parents, his father being a small businessman. The family returned to Warsaw, Poland, when Keilin was still very young.

Since childhood, Keilin was a kid of poor health and who suffered from asthma. As a result, he was taught at home by a governess and only started to attend school at the age of 10. From this time until he was 17, he attended the Gorski school and showed an aptitude for mathematics, languages and literature.

After finishing school, he went to the University of Leige in Belgium, where he studied natural sciences, completing the two-year program in a single year. As he continued to have health issues at this time of his life, he was advised not to engage in medical studies, so in 1905 he moved to Paris where he attended philosophy lectures at the College de France and spent a lot of his time reading books at the Bibliotheque St. Genevieve.

One day, after having left a lecture by the philosopher Henri Bergson (1859-1941), Keilin was caught in a heavy rain and, seeking refuge, he ended up in a building that housed the Laboratoire d’Évolution des Êtres Organisés. There, the biologist Maurice Caullery (1868-1958) was giving a lecture and, having to wait the rain to give a break, Keilin watched the lecture and became impressed by it. As a result, he started to attend Caullery’s class three times a week and both became good friends. Caullery eventually offered him a position at the Laboratoire d’Évolution, where he worked as a parasitologist, and convinced him to enroll at the Sorbonne, where Keilin began classes in zoology, botany, embryology and geology.

Keilin published his first paper, on the life cycle of the fly Pollenia rudis, in 1909, and in 1915 he finished his doctorate. Soon after, he was recruted to Cambridge in the United Kingdom as an assistant to American-British bacteriologist George Nuttall (1862-1937) and spent the rest of his career there.

Up until 1920, most of Keilin’s work was descriptive, after which it became more experimental. While studying the life cycle of the horse bot fly, he observed a disappearance of the red color of the larva in later stages. By performing direct-vision spectroscopy on the pigments, he found a four-banded pattern in adult flies which he later also found in other organisms, including other insects, yeasts and even bacteria. By more detailed observations he found out that these pigments were oxidized by atmospheric oxigen, but in its absence were re-reduced. He decided to call this pigments cytochromes, and spent the rest of his career studying this pigments, discovering their function in cellular respiration.

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David Keilin in 1931. Author unknown.

Keilin succeeded Nuttall in 1931 and retired in 1965, but continued an active researcher until his death. During his work, Keilin studied several molecules and shed a lot of light on the mechanisms of cellular respiration.

On the afternoon of February 27, 1963, aged 75, Keilin died suddenly after a morning engaged in his usual activities in the laboratory.

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References:

Dead Scientist of the Week. David Keilin. Available at < http://deadscientistoftheweek.blogspot.com.br/2010/03/david-keilin.html>. Access on March 20, 2018.

Dixon, M.; Tate, P. (1966) Obituary Notice: David Keilin, 1887-1963Journal of General Microbiology 45: 159-185.

Erling, N. (2016) Nobel Prizes and Notable Discoveries. 580 pp.

Wikipedia. David Keilin. Available at < https://en.wikipedia.org/wiki/David_Keilin >. Access on March 20, 2018.

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