Monthly Archives: May 2019

Friday Fellow: Common Goose Barnacle

by Piter Kehoma Boll

The open surface of the oceans may at first look like a large lifeless sheet. However, if you look closer, you’ll see that there is much more life there than you could imagine. And it does not only include the microscopic plankton that floats in the water column, but also large organisms that dwell right at the boundary between the water and the air. These creatures are called the neuston and come in several shapes and one of them is Lepas anserifera, or the common goose barnacle.

Several common goose barnacles found growing on a cuttlebone in India’s west coast. Their modified legs (cirri) are out looking for food. Photo by Abhishek Jamalabad.*

The common goose barnacle is found in tropical and subtropical waters all around the world. It belongs to the subclass Cirripedia, a peculiar group of crustaceans commonly known as barnacles. They live attached to the substrate and are hemaphrodites, both features that are uncommon among arthropods. Within the barnacles, the common goose barnacle belongs to the order Pedunculata, or goose barnacles, which are characterized by the presence of a stalk that attaches them to the substrate.

Common goose barnacles in Taiwan. A younger specimen is seen growing on a larger one. Photo by Liu JimFood.*

The substrate chosen by the common goose barnacle is almost exclusively floating material. This material, which includes sea weeds and all sort of debris, such as pieces of wood, coconuts or animal carcasses, rarely remains floating for a long time, either because its decay makes it sink or fall apart or because it ends up on the shore. Thus, the goose barnacle has to find a way to complete its life cycle very quickly, and that is what it does.

Common goose barnacles growing on an apple that must have floated for some time and ended up at the shore in the state of Bahia, Brazil. Photo by iNaturalist user kuroshio.**
Common goose barnacles growing on a light bulb washed ashore in Palau Pinang, Malaysia. Photo by Al Kordesch.

Goose barnacles start their lives as a planktonic one-eyed larva that, after five stages, develops into another larval form known as cyprid. The cyprid’s only purpose is to find a suitable surface to live and, once it finds it, it secretes a glycoproteinaceous substance that attaches it to the substrate by the head. It then develops into the adult animal and secretes a series of calcified plates that surrounds its body. The adults use their feathery legs (cirri) to capture food, mostly plankton, and carry it inside their shell.

Common goose barnacles growing on a brush washed ashore in New Jersey, USA. Photo by Stan Rullman.**

Due to human activities, the amount of floating material on the ocean surfaces increased greatly. Thus, the number of available substrates for the goose barnacle to grow also increased, and so likely did its population. Unfortunately, the human-generated floating material also includes a lot of small plastic particles, and goose barnacles frequently ingest them together with food. Although the harm caused by ingesting plastic particles has not been assessed yet, they certainly do not improve the barnacle’s health.

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Reference:

Goldstein MC, Goodwin DS (2013) Gooseneck barnacles (Lepas spp.) ingest microplastic debris in the North Pacific Subtropical Gyre. PeerJ 1: e184. doi: 10.7717/peerj.184

Inatsuchi A, Yamato S, Yusa Y (2010) Effects of temperature and food availability on growth and reproduction in the neustonic pedunculate barnacle Lepas anserifera. Marine Biology 157(4): 899–905. doi: 10.1007/s00227-009-1373-0

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*Creative Commons License This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.

**Creative Commons License This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.

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Whose Wednesday: Louis-Jean-Marie Daubenton

by Piter Kehoma Boll

After some weeks dealing with researchers of more recent times, today we are going back to ye olde naturalists from the 18th century.

Today we commemorate the birthday of Louis-Jean-Marie Daubenton, who was born on 29 May 1716 in Montbard, Côte-d’Or, France. His father, Jean Daubenton, was a notary and wanted his son to become a priest, thus sending him to Paris to study Theology. Daubenton’s desire, however, was to study medicine. Fortunately for him (I guess), his father died in 1736, when Daubenton was 20, and so he became free to study whatever he wished.

Studying medicine at Reims, Daubenton graduated in 1741 and returned to Montbard. His intentions were to work there full time as a physician, but things changed a little bit only one year later. The naturalist Georges-Louis Leclerc de Buffon, also from Montbard, was planning to write a multi-volume work on Natural History, named Histoire naturelle, générale et particulière, and, in 1742, invited Daubenton to help him, especially with anatomical descriptions.

Due to his partnership with Buffon, Daubenton became a member of the French Academy of Sciences in 1744 as an adjunct botanist. During this time, Buffon was the curator of the Jardin du Roi (currently Jardin des plantes), the main botanical garden in France until today, and appointed Daubenton as the keeper and demonstrator of the King’s cabinet.

In 1749, the first volume of Buffon’s Histoire Naturelle was finally published, although most of Daubenton’s contributions only appeared from the fourth volume on, published in 1753. The work included detailed descriptions of 182 quadrupeds (mammals) given by Daubenton and this increased his reputation as a comparative anatomist.

Portrait of Daubenton in 1791 by Alexander Roslin.

Daubenton became one of the contributors of the famous Encyclopédie, the first encyclopedia to be written, writing several articles on natural history. He also published many articles in the memoirs of the Parisian Académie Royale des Sciences, especially on comparative anatomy, but also on agriculture and mineralogy. He became a teacher of mineralogy at the Jardin du Roi and later also taught natural history at the College of Medicine (from 1775 on) and rural economy at the Alfort School (from 1783 on).

The controversial political opinions of the writers of the Encyclopédie, who disregarded Catholicism and the Royalty, helped to prepare the scenario that led to the French Revolution. In December 1799, following the Revolution, Daubenton, who was already 83, was appointed a member of the Senate. However, during the first meeting he attended, he fell from his chair after suffering a stroke and died in Paris on 1 January 1800.

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References:

Wikipedia. Encyclopédie. Available at < https://en.wikipedia.org/wiki/Encyclop%C3%A9die >. Access on 28 May, 2019.

Wikipedia. Louis-Jean-Marie Daubenton. Available at < https://en.wikipedia.org/wiki/Louis-Jean-Marie_Daubenton >. Access on 28 May, 2019.

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Looking like lichens: leaves disguised as tree trunks to avoid being eaten

by Piter Kehoma Boll

We are all familiar with animals of many species that developed interesting mechanisms to avoid being eaten. This includes, for example, animals that look like plant parts:

The famous giant leaf insect, Phyllium giganteum. Photo by Bernard Dupont.**

and animals that merge with the background:

An East African jackal, Canis mesomelas, in the Savanna. Can you spot it? Photo by Nevit Dilmen.***

There are also animals that look like other, unpalatable or dangerous, animals, in order to push predators away:

The edible viceroy butterfly Limenitis archippus (top) mimicks the poisonous monarch butterfly Danaus plexippus (bottom). Credits to Wikimedia user DRosenbach. Photos by D. Gordon E. Robertson and Derek Ramsey.***

But we rarely think that plants also use this sort of mechanisms to avoid being eaten. There are, however, some recorded cases of similar behaviors in plants. One case is that of the plant Corydalis benecincta, whose leaves commonly have the brownish color of the surrounding rocks:

The leaves of Corydalis benecincta look like the rocks found in its natural habitat. Photo extracted from http://www.svenlandrein.com/yunnancollections/10CS2204.html

Recently, a study on plants of the genus Amorphophallus found another interesting case of mimicry. This genus, which includes the famous titan arum, usually develops a single large leaf that in some species can attain the size of a small tree or shrub. Such a gigantic leaf seems to be a perfect meal for some herbivores but, to avoid them, many species of this genus developed a series of marks along the petiole of their leaf that look like lichens or cyanobacteria.

Cyanobacteria-like marks on the petiole of Amorphophallus gigas (A); Cyanobacteria-like plus lichen-like marks also on A. gigas (B); And lichen-like marks on A. hewittii (C) and A. dactylifer (D). Extracted from Claudel et al. (2019).

With this mimicry, the petioles, which are quite tender, end up looking like a hard and old trunk that does not look that interesting as a meal for most herbivores. The lichen marks are so well represented that they can even be associated with real lichen genera. For example, the marks seen on the figures B and C above look like lichens of the genus Cryptothecia.

Lichen of the species Cryptothecia striata, which seems to be mimicked by the marks in Amorphophallus gigas and A. hewittii. Photo by Jason Hollinger.*

How and why this marks evolved across Amorphophallus species is still not well understood. Despite the hypothesis that they help the plant mimic a tree trunk, some species with small leaves also have those marks, while some with large leaves do not have any marks or have them in simpler patterns. The titan arum Amorphophallus titanum is a good example of the latter:

Amorphophallus titanum is the largest species of Amorphophallus but displays a considerably simple lichen-like pattern. Photo by flickr user Björn S.**

For a long time, plants were regarded as less dynamic organisms than animals, but in recent years our knowledge about them is increasing and showing that they are actually very versatile creatures that developed similar creative and complex strategies.

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Reference:

Claudel C, Lev-Yadun S, Hetterscheid W, & Schultz M 2019. Mimicry of lichens and cyanobacteria on tree-sized Amorphophallus petioles results in their masquerade as inedible tree trunks. Bot J Linn Soc 190: 192–214.

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*Creative Commons License This work is licensed under a Creative Commons Attribution 2.0 Generic License.

**Creative Commons License This work is licensed under a Creative Commons Attribution-Share Alike 2.0 Generic License.

***Creative Commons License This work is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License.

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Friday Fellow: Venus’ Flower Basket

by Piter Kehoma Boll

Sponges are the weirdest of all animals but also some of the most beautiful. One species of special beauty that is considerably popular is Euplectella aspergillum, popularly known as the Venus’ flower basket.

Venus’ flower basket in the Pacific Ocean.

Growing on the Ocean floor of tropical waters, the Venus’ flower basket is common around the Philippines and this may be the only place where it occurs. Other similar species are found in nearby areas such as Japan, Indonesia and Australia and are often mistaken for the Venus’ flower basket. There are, indeed, populations of this species identified in Australia and Indonesia, among other areas near the Philippines, but are considered subspecies due to subtle morphological differences and may in fact be complete separate species.

The Venus’ flower basket is a medium-sized sponge, measuring up to 1.3 m in height, althout most specimens measure between 10 and 30 cm. The body is white and has several large pores that make it look like an elongate basket, hence the common name. The osculum, the large opening at the top, is covered by a mesh of fibers that makes its interior inaccessible to large organisms.

Skeleton of the Venus’ flower basket. Credits to the Auckland Museum.*

Recently, the Venus’ flower basket has called the attention of scientists because of the structural complexity of its skeleton, which is composed of silica (i.e., glass). Studies have shown that the anchor spicules, i.e., those that attach the sponge to the substrate, are similar to man-mane optical fibers regarding optical properties but are better regarding fracture resistance. Understanding the detailed pathway used by the sponge to build these spicules could lead to the development of easier ways to build optical fibers and even increase their quality.

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References:

Monn MA, Weaver JC, Zhang T, Aizenberg J, Kesari H (2015) New functional insights into the internal architecture of the laminated anchor spicules of Euplectella aspergillum. PNAS 1112(16): 4976-498. doi: 10.1073/pnas.1415502112

Shimizu K, Amano T, Bari MR, Weaver JC, Arima J, Mori N (2015) Glassin, a histidine-rich protein from the siliceous skeletal system of the marine sponge Euplectella, directs silica polycondensation. PNAS 112(37): 11449-11454. doi: 10.1073/pnas.1506968112

Tabachnick KR, Janussen D, Menschenina LL (2008) New Australian Hexactinellida (Porifera) with a revision of Euplectella aspergillum. Zootaxa 1866: 7–68.

Weaver JC, Aizenberg J, Fantner GE, Kisailus D, Woesz A, Allen P, Fields K, Porter MJ, Zok FW, Hansma PK, Fratzl P, Morse DE (2007) Hierarchical assembly of the siliceous skeletal lattice of the hexactinellid sponge Euplectella aspergillum. Journal of Structural Biology 158: 93–106. doi: 10.1016/j.jsb.2006.10.027

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*Creative Commons License This work is licensed under a Creative Commons Attribution 4.0 International License.

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Whose Wednesday: Patricia Louise Dudley

by Piter Kehoma Boll

Today we celebrate the birthday of an important figure in the study of the fascinating copepod crustaceans.

Patricia Louise Dudley, often called Pat Dudley, was born on 22 May 1929 in Denver, Colorado, USA, the daughter of David C. Dudley, a salesman for State and School supply, and Carolyn Dudley (née Latas). Her father died in 1932, when she was only 3 years old.

During her childhood, Dudley lived with her mother and maternal grandparents in Colorado Springs. She studied in Colorado Springs High School and graduated in 1947. Soon after, she started her undergraduate studies at the University of Colorado, where she studied with the limnologist Robert William Pennak. She earned her Bachelor’s degree in 1951 and stayed in the same university for her Master’s degree, having Pennak as her advisor. Her master’s thesis was a research on the aquatic fauna of four brooks in Boulder County, Colorado.

Finishing her Master’s in 1953, she pursued a PhD Degree at the University of Washington in Seattle. Her initial intention was to continue to do limnological studies, but ended up meeting the carcinologist Paul Louis Illg, who studied copepods. At the University of Washington and its marine biological station at Friday Harbor, Dudley turned her attention to marine copepods that are associated with ascidians. This copepod group has a huge variety of forms and Dudley dedicated her doctorate to study the developmental stages of this small comensal crustaceans. She defended her thesis in 1957.

In 1959, Dudley joined the Columbia University and started to teach zoology at Barnard College. She remained there until her retirement in 1994 and dedicated her research to the study of comensal copepods, mostly those associated with ascidians, but later also those comensal on other marine invertebrates, especially polychaetes. She was one of the first researchers to use electronic microscopy for the study of copepod structures.

Pat Dudley in her later years in Seattle. Extracted from https://fhl.uw.edu/wp-content/uploads/sites/17/2015/10/Patricia-L.-Dudley-Endowment.pdf

After her retirement, Dudley moved back to Seattle and planned to continue her research on copepods there. Unfortunately, she started to have health problems soon after, which forced her to abandon her research. She became very ill during the following years and died on 30 September 2004, aged 75.

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References:

Damkaer DM (2004) Patricia Louise Dudley (22 May 1929 – 30 September 2004). Monoculus: Copepod Newsletter 48: 10.

Wikipedia. Patricia Louise Dudley. Available at < https://en.wikipedia.org/wiki/Patricia_Louise_Dudley >. Access on 21 May, 2019.

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Friday Fellow: Turnip Sawfly

by Piter Kehoma Boll

After beetles, which make up the order Coleoptera, the second most diverse group of insects is the order Lepidoptera, which includes butterflies and moths. However, the order Hymenoptera has the potential to eventually surpass Lepidoptera and get closer to the beetles because a lot of new species are being constantly described.

The most widely known hymenopterans are bees, ants and wasps, but a huge part of their diversity is made up by the so-called sawflies. One of these species is commonly known as the turnip sawfly and scientifically named Athalia rosae.

Turnip sawfly in the Netherlands. Photo by Herman Berteler.*

The turnip sawfly is found throughout the Paleartic Ecozone, from western Europe to Japan, and his common name comes from the fact that its larvae feed on plants of the family Brassicaceae, which includes the turnip, as well as the cabbage, among others. The larvae is considerably large and resembles a caterpillar, having a dark gray, almost black dorsal color, and is lighter close to the feet. When they are about to turn into a pupa, they dig into the ground, build a cocoon and remain there until they become adults.

A larva in Denmark. Photo by Donald Hobern.**

The adults measure about 6 to 8 mm in length, the females being larger than the males. The body and the legs have a yellow to orange color, darker on the dorsal surface of the thorax, which also has two large black spots. The head and the antennae are black.

An adult in Germany. Photo by Martin Grimm.*

Hymenopterans in general are characterized by a unique sexual determination in which females are diploid, i.e., have two sets of chromosomes, and males are haploid, having only one set. Matings conducted in the laboratory with the turnip sawfly, however, were able to produce anomalous combinations, including diploid males and triploid females and males. Apparently this is possible due to sex being determined by one allele in one chromosome, so that males are always homozygous and females always heterozygous, but this must be explained in another post. The fact is that the study of this peculiar system in this species is helping to understand how sex determination evolved in hymenopterans.

In adult in Russia. Photo by Roman Providuhin.*

One last interesting thing to mention about the turnip sawfly is that it is able to bypass the defense mechanisms of the plants on which its larva feeds. Plants in the family Brassicaceae produce a group of compounds called glucosinolates that give them their characteristic pungency and bitterness, such as in mustard and horseradish. These compounds are used by the plant as a defense against pests that feed on them. However, the turnip sawfly is resistant to this compounds and is able to sequestrate them and store them in their hemolymph, i.e., their “blood” in concentrations much higher than found in the plants. When attacked by a predators, such as ants, the larva releases drops of its hemolymph in a sort of defensive bleeding and can stop the attack.

The turnip sawfly may be a nuisance for humans and their crops, but it is certainly a fascinating animal.

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References:

Müller C, Agerbirk N, Olsen CE, Boevé JL, Schaffner U, Brakefield PM (2001) Sequestration of host plant glucosinolates in the defensive hemolymph of the sawfly Athala rosae. Journal of Chemical Ecology 27(12): 2505–2516. doi: 10.1023/A:1013631616141

Müller C, Boevé JL, Brakefield PM (2002) Host plant derived feeding deterrence towards ants in the turnip sawfly Athalia rosae. In: Nielsen J.K., Kjær C., Schoonhoven L.M. (eds) Proceedings of the 11th International Symposium on Insect-Plant Relationships. Series Entomologica, vol 57. Springer, Dordrecht. doi: 10.1007/978-94-017-2776-1_18

Naito T, Suzuki H (1991) Sex determination in the sawfly, Athalia rosae ruficornis (Hymenoptera): occurrence of triploid males. Journal of Heredity 82(2): 101–104. 10.1093/oxfordjournals.jhered.a111042

Oishi K, Sawa M, Hatakeyama M, Kageyama Y (1993) Genetics and biology of the sawfly, Athalia rosae (Hymenoptera). Genetica 88(2–3): 119–127. doi: 10.1007/BF02424468

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*Creative Commons License This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.

**Creative Commons License This work is licensed under a Creative Commons Attribution 2.0 Generic License.

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Whose Wednesday: Élie Metchnikoff

by Piter Kehoma Boll

For the third week in a row, our featured scientist is a Nobel laureate!

Ilya Ilyich Mechnikov (in Russian: Илья Ильич Мечников), also known as Élie Metchnikoff, was born on 15 May 1845 in the village of Ivanovka in Ukraine. His father, Ilya Ivanovich Mechnikov was a Russian officer of the Imperial Guard and his mother, Emilia Lvovna Nevakhovich was the daughter of the writer Leo Nevakhovich.

Metchnikoff ca. 1862.

In 1856, at the age of 11, Metchnikoff entered the Kharkiv Lycée school and developed an interest in biology. Due to his mother’s influence, he was interested in science since and early age. She also convinced him to study natural sciences instead of medicine. Thus, in 1862, he tried study biology at the University of Würzburg, in Germany but, as the academic year there would only begin by the end of the year, he ended up enrolled at the Kharkiv University to study natural sciences. In 1863, he married Ludmila Feodorovitch and, in 1864, graduated at the age of 19, completing the four-year degree of natural sciences in only two. That same year, he went to Germany to study the marine fauna on the island of Heligoland in the North Sea.

After meeting the botanist Ferdinand Cohn, Metchnikoff was advised by him to work with the zoologist Rudolf Leuckart at the University of Giessen. Together with Leuckart, he studied the reproduction of nematodes and discovered intracellular digestion in flatworms. In 1866, he moved to Naples and worked on a doctoral thesis on the embryonic development of cuttlefish of the genus Sepiola. In 1867, he moved to Russia and received his doctorate degree with Alexander Kovalevsky from the University of St. Petersburg. For their work on the development of germ layers of invertebrate embryos, Metchnikoff and Kovalevsky won the Karl Ernst von Baer prize.

Due to his competence, Metchnikoff was appointed, still in 1867, professor of the new Imperial Novorossiya University (currently Odessa University). He was only 22 years old, being younger than most of his students. The next year, due to a conflict with a senior colleague, he was transferred to the University of St. Petersburg but the professional environment there was even worse. He returned to Odessa in 1870 as professor of Zoology and Comparative Anatomy.

On April 20, 1873, Metchnikoff’s wife died of tuberculosis. This event, combined with his professional problems, made him attempt suicide taking a large dose of opium. He survived and eventually recovered and, in 1875, married his student Olga Belokopytova.

The assassination of Alexander II in 1881 led to political turmoils in Russia, which made Metchnikoff resign from Odessa University in 1882. He moved to Sicily and set up a private laboratory in Messina. There, while studying starfish larvae, he noticed that, by inserting a small citrus thorn in the larvae, a group of cells started to surround the thorn. He suggested that some white cells in the blood are able to attack and kill pathogens, and the zoologist Carl Friedrich Wilhelm Claus, with whom he discussed his hypothesis, suggested the name “phagocyte” to such cells.

Élie Metchnikov ca. 1908.

Metchnikoff presented his findings on phagocytes at Odessa in 1883, but his idea was met with skepticism from many specialists, including Louis Pasteur. The idea at that time was that white blood cells carried pathogens away from the infection place and delivered them elsewhere, spreading them instead of destroying them. His main supporter was the pathologist Rudolf Virchow. Back to Odessa, Metchnikoff was appointed director of an institute created to produce Louis Pasteur’s vaccine against rabies.

In 1885, Metchnikoff’s second wife suffered from severe typhoid fever. As a result, he attempted suicide once more, this time by injecting himself with spirochaete bacteria that cause relapsing fever. He survived again, and his wife survived as well.

In 1888, Metchnikoff left Odessa again due to new difficulties and went to Paris to seek the advice of Pasteur, who gave him an appointment at the Pasteur Institute. Metchnikoff remained there for the rest of his life. In 1908, he won the Nobel prize in physiology or medicine due to his discovery of phagocytes. During his last years, he developed a theory that aging was a disease caused by toxic bacteria in the gut and that lactic acid produced by Lactobacillus could prolong life.

He died on 15 July 1916 of heart failure in Paris, aged 71.

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Reference:

Goldstein BI (1916) Elie Metchnikoff. The Canadian Jewish Chronicle. Available at < https://news.google.com/newspapers?id=BQodAAAAIBAJ&sjid=xGEEAAAAIBAJ&pg=6460,5413902&dq=%C3%A9lie+metchnikoff&hl=en >. Access on 14 May, 2019.

Wikipedia. Élie Metchnikoff. Available at <
https://en.wikipedia.org/wiki/%C3%89lie_Metchnikoff >. Access on May 14, 2019.

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