Monthly Archives: March 2019

by | March 31, 2019 · 10:48 pm

New Species: March 2019

by Piter Kehoma Boll

Here is a list of species described this month. It certainly does not include all described species. You can see the list of Journals used in the survey of new species here.

Bacteria

Archaeans

SARs

Liparis napoensis is a new orchid from China. Credits to Li et al. (2019).*

Plants

Microchiritia hairulii is a new flowering plant from Malaysia. Credits to Rahman (2019).*
Neoboletus antillanus is a new mushroom from the Dominican Republic. Credits to Gelardi et al. (2019).*

Excavates

Fungi

Biatora alnetorum is a new lichen from North America. Credits to Ekman & Tønsberg (2019).*

Sponges

Cnidarians

Flatworms

Rotifers

Annelids

Mollusks

Nematodes

Chelicerates

Arrup akiyoshiensis is a new centipede from Japan. Credits to Tsukamoto et al. (2019)*

Myriapods

Antheromorpha nguyeni is a new millepede from Vietnam. Credits to Likhitrakarn et al. (2019).*

Crustaceans

Hexapods

Echinoderms

Tunicates

Ray-finned fishes

Amphibians

Austrobatrachus kurichiyana, a new frog from India. Credits to Vijayakumar et al. (2019).*

Reptiles and Birds

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by | March 29, 2019 · 8:00 am

Friday Fellow: Contractile Gentle-Scaled Centrohelid

by Piter Kehoma Boll

Unicellular eukaryotes, traditionally called protists, come in a variety of shapes and sizes and have a complex classification, especially because many lineages evolved similar features. The centrohelids, for example, have a round cell with several needle-like radially-distributed pseudopods, called actinopods, thus looking like radiolarians, but are only distantly related to them.

A single individual of the contractile gentle-scaled centrohelid. Credits to Wikimedia user NEON_ja.*

A centrohelid that has been considerably well studied recently is Raphidiophrys contractilis, to which I decided to coin the common name contractile gentle-scaled centrohelid. It was described in 1995 from specimens collected from brackish ponds in Hiroshima, Japan. As with other species of the genus Raphidiophrys, the contractile gentle-scaled centrohelid has many structures of silica, called scales, covering the cell and embedded in a gelatinous coat. These scales are more concentrated around the base of the actinopods and extend outward around part of them as well. In the contractile gentle-scaled centrohelid, the scales are oblong, flat and slightly curved, resembling a rubber boat. The convex side of the scale is always directed toward the cell.

The contractile gentle-scaled centrohelid is a predator of other protists, especially flagellates and ciliates. Small protists are captured by the actinopods and pulled quickly toward the cell body by a sudden contraction of the actinopod. This behavior is the reason for the species to be named contractilis. Once the prey is close to the cell body, it is surrounded by pseudopods and stored in a food vacuole, where it gets digested. The capture of prey using the actinopods is aided by a special organelle, called kinetocyst, found in large number below the cell membrane. When the centrohelid touches a prey, it discharges the kinetocysts, which immobilize the prey, working similarly to the cnidocytes of cnidarians.

Raphidiophrys contractilis with several flagellates of the species Chlorogonium elongatum trapped in its actinopods (A) and one of the being swallowed into a food vacuole (B). Extracted from Sakaguchi et al. (2002).

When a gentle-scale centrohelid finds a very large prey, much larger than itself sometimes, such as a ciliate Paramecium, it uses an extreme cooperative behavior. Several individual organisms fuse into a single large cell, pull chunks of the prey off and create a large common food vacuole. Isn’t that bizarre and amazing?

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References:

Kinoshita E, Suzaki T, Shigenaka Y, SugiyamaM (1995) Ultrastructure and rapid axopodial contraction of a Heliozoa, Raphidiophrys contractilis sp. nov. The Journal of Eukaryotic Microbiology 42(3): 283–288. doi: 10.1111/j.1550-7408.1995.tb01581.x

Sakaguchi M, Suzaki T, Khan SMMK, Hausmann K (2002) Food capture by kinetocysts in the heliozoon Raphidiophrys contractilis. European Journal of Protistology 37(4): 453–458. doi: 10.1078/0932-4739-00847

Siemensma FJ, Roijackers MM (1988) The genus Raphidiophrys (Actinopoda, Helozoea): scale morphology and species distinctions. Archiv für Protistenkunde 136(3): 237–248. doi: 10.1016/S0003-9365(88)80023-X

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by | March 28, 2019 · 11:12 am

Becoming a stepfather to get laid: the unusual alloparental care in a small carpenter bee

by Piter Kehoma Boll

Leia em português

Last month, I made some comments on alloparental care, i.e., the act of caring for an offspring that is not yours.

Most of the times, when parental care exists in a species, it is performed by the mother only. When there’s a helper, it is usually the father among vertebrates, or siblings among arthropods, especially social insects, such as bees and ants. Males taking care of the offspring in social insects is unlikely to occur in most species because the male usually dies soon after mating.

However, an uncommon situation was recently discovered in Ceratina nigrolabiata, a species of small carpenter bee from the Mediterranean region. In this species, the female is polyandrous, i.e., it mates with several males, so that not all her offspring has the same father.

This is not the unusual part, though. The strange thing is that males of this species do not die after mating and help the female take care of the offspring. While the female leaves the nest to look for food, the male remains and take care of the eggs and larvae, protecting them from natural enemies, such as ants. However, as I said above, females of this species mate with a lot of males, and genetic studies revealed that the male guarding the nest is the father of only about 10% of the offspring.

Parental care in the small carpenter beee Ceratina nigrolabiata:
(A) The female arrives at the nest. A male is flying nearby, looking for a “single lady”
(B) The female greets her helping male
(C) Sectioned nest showing three cells with larvae/eggs and food and a fourth cell being built; the female is to the left and the male to the right.
Credits to Mikát et al. (2019) (See references).

So why do males of Ceratina nigrolabiata take care of the children of another male? What the team who studied this system discovered is that the longer a male takes care of a nest, the larger is the number of offspring that has him as the father. In other words, it seems that helping a female increases the chances of a male to mate with that female, thus increasing the number of descendants he has. Nevertheless, males rarely remained for a long time in the same nest, usually moving to another nest every week or so, which does not increase the amount of his own offspring in the nest.

The team also experimentally removed females from the nests to observe how the males would behave in the absence of a female. What they found out is that males usually abandon the nest when this happens, not giving a damn to the poor babies. Thus, it is likely that this male alloparental care is actually a byproduct of mate guarding, i.e., the male is there to assure that he will have access to the female whenever she is willing to mate. He doesn’t actually care for the young.

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Reference:

Mikát M, Janošik L, Černá K, Matuošková E, Hadrava J, Bureš V, Straka J (2019) Polyandrous bee provides extended offspring care biparentally as an alternative to monandry based eusociality. PNAS 116(13): 6238-6243. doi: 10.1073/pnas.1810092116

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by | March 27, 2019 · 8:00 am

Whose Wednesday: Carl Nägeli

by Piter Kehoma Boll

Sometimes you lack the ability to become a great scientist, so you seek recognition by ruining the career of great names of science. At least that is basically the definition of the man whose birthday we celebrate today.

Carl Wilhelm von Nägeli was born on 27 May 1817 in Kilchberg, near Zurich, as the son of a Physician. In 1836, he started to study medicine at the University of Zurich but soon changed his interest toward botany, having Lorenz Oken and Oswald Heer, among others, as teachers. In 1939 he started to study botany at the University of Geneva under Augustin Pyramus de Candolle and graduated in 1840 with a botanical thesis entitled Die Cirsien der Schweiz (The Cirsium species of Switzerland).

Portrait of Carl Nägeli. Date and author unknown.

In 1842, Nägeli started to work at Jena with the botanist Matthias Jakob Schleiden on the microscopic study of plants. That year, he observed cellular division during the formation of pollen but apparently was unable to understand what he was seeing, different from Robert Remak, who observed cell division at about the same time.

Nägeli coined the terms meristem, xylem and phloem in 1858 and this is probably his main contribution to science. He is more commonly remembered by how he did almost everything wrong, especially regarding evolution and heredity. For example, Nägeli exchanged extensive correspondence with Gregor Mendel, who mentioned to him his works on plants, but Nägeli considered them useless and somewhat discouraged Mendel to go on with his studies.

In 1884, Nägeli published a work entitled Mechanisch-physiologische Theorie der Abstammungslehre (A mechanico-physiological theory of organic evolution) in which he proposes the concept of idioplasm, which would be a special part of a plant’s cytoplasm that transmitted inherited characters. Mendel, who died that same year, was not even mentioned in this work, which makes it clear how Nägeli despised Mendel’s work.

Likewise, Nägeli rejected Darwin’s theory of Natural Selection as a force guiding evolution. Instead of this, he defended the idea of orthogenesis, developing the concept of an inner perfecting principle that he considered to direct evolution.

He died on 10 May 1891 in Munich, aged 74.

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References:

Wikipedia. Carl Nägeli. Available at <
https://en.wikipedia.org/wiki/Carl_N%C3%A4geli >. Access on 26 March 2019.

Wikipedia (in German). Carl Wilhelm von Nägeli. Available at <
https://de.wikipedia.org/wiki/Carl_Wilhelm_von_N%C3%A4geli >. Access on 26 March 2019.

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by | March 25, 2019 · 1:10 am

Hagfish: Another Phylogenetic Headache

by Piter Kehoma Boll

Years ago, I wrote a post about the problematic Acoelomorpha and their controversial position among bilaterian animals. Now I am going to talk about another headache: hagfish.

Hagfish are primitive chordates that make up the class Myxini. They are marine animals that live at the bottom of the sea and feed mainly on polychaete worms that they pull out of the substrate. However, they are also scavengers and have a peculiar behavior in which they perforate the body of dead fish and enter it, eating the dead animal from inside out.

Specimen of the Pacific hagfish Eptatretus stoutii. Photo by Jeanette Bham.*

Morphologically, hagfish are characterized by the presence of a cartilaginous skull, like vertebrates, but lack a vertebral column, keeping the notochord, the dorsal cartilage-like structure of chordates, during their whole lives. Due to this lack of vertebrae, the hagfish were classified outside of the vertebrates, but united to them due to the presence of the skull. Thus, Myxini was seen as the sister-group of Vertebrata and both together formed the clade Craniata.

Among the vertebrates, most extant groups have a jaw that evolved from modified gill arches, making up the clade Gnathostomata. The only animals with a vertebral column that lack jaws are the lampreys (Petromyzontiformes) and, although this lack of jaws is shared with hagfish, it is not usually seen as a synapomorphy uniting these groups. In hagfish, the jawless mouth have lateral keratin plates with tooth-like structures that act somewhat like the true jaws of Gnathostomata, but working from the sides and not from above and below. In lampreys, on the other hand, the mouth is circular and have keratin tooth-like structures arranged circularly.

General organization of the head of hagfish, lampreys and jawed vertebrates, with special attention to the mouths. Extracted from Oisi et al. (2012).

There are a lot of morphological features that unite lampreys to vertebrates and separate them from hagfish, the main one being the already mentioned vertebrate column. Likewise, lampreys and jawed vertebrates have dorsal fins while hagfish lack them. Lampreys also have lensed eyes in common with jawed vertebrates, while hagfish have simple eyesposts without lenses or even associated muscles.

Some of the traits shared between hagfish and lampreys, just as the lack of jaws, are usually seen as a primitive state that changed in jawed vertebrates, or have clearly evolved independently. For example, both hagfish and lampreys have only a single nostril, while jawed vertebrates have two, but this is likely a primitive character. Adult hagfish and lampreys have also a single gonad, but this appears in hagfish by an atrophy of the left gonad, so that only the right one develops, while in lampreys the left and right gonads fuse into a single organ.

Specimens of the least brook lamprey Lampetra aepyptera. Photo by Jerry Reynolds.*

Therefore, morphologically, it seems logical to consider hagfish as a sister group of vertebrates, which include lampreys and jawed vertebrates. It is also important to mention that there are more groups of jawless vertebrates that are currently extinct, such as the class Osteostraci, one of several fossil groups traditionally called ostracoderms. Although lacking a jaw as well, these vertebrates had paired fins just like jawed vertebrates. Thus, the phylogenetic organization of these major groups based on morphology would be as shown in the figure below:

The craniate hypothesis, where hagfish are a sister-group to vertebrates.

However, in the last decades, the use of molecular phylogenetics has challenged this view by grouping hagfish and lampreys into a monophyletic clade that is sister-group of jawed vertebrates. But how could this be possible? Such a relationship would imply that the primitive state of hagfish is the result of secondary loss.

The cyclostome hypothesis. Hagfish are a sister-group to lampreys.

Evidence from fossils could help clarify this issue, but most fossils that have been associated with hagfish have not good enough morphological characters preserved to assess their correct phylogenetic position. Recently, however, a well preserved hagfish fossil from the Cretaceous helped to elucidate part of the hagfish phylogeny. The divergence between lampreys and hagfish, considering previous knowledge, was usually put around the early Cambrian period, just after the beginning of the divergence of most animal phyla, but with data of the new fossil, it is pushed to a more recent point in time, around the Early Silurian, more than 130 million years after. This new fossil, named Tethymyxine tapirostrum, clearly lacks a skeleton or dorsal fins as seen in lampreys and jawed vertebrates, but has several characters shared with extant hagfish.

Fossil of Tethymyxine tapirostrum found in Lebanon. Extracted from Miyashita et al. (2019).

At least two synapomorphies can be found uniting hagfish and lampreys and separating them from jawed vertebrates. The first one are the teeth, which in these two groups are composed of keratin plates. The second one is the organization of the myomeres, the series of muscles arranged along the body of chordates in a somewhat segmented fashion, that in both hagfish and lampreys begin right around the eyes.

Considering the evidence from molecular data, the new fossil that makes it likely that hagfish and lampreys diverged more recently if they form a monophyletic group, and the likely true synapomorphies uniting these two jawless vertebrate groups, it seems that hagfish and lampreys are indeed sister-groups, forming a clade called Cyclostomata and sister-group of the jawed vertebrates Gnathostomata. If this is really the case, then the apparently more primitive features of hagfish are in fact the result of secondary losses and its ancestor likely had a more vertebrate look, with a vertebral column, dorsal fins and lensed eyes.

But let’s keep watching. Things may change again in the future as new data become available.

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References:

Miyashita T, Coates MI, Farrar R, Larson P, Manning PL, Wogelius RA, Edwards NP, Anné J, Bergmann U, Palmer AR, Currie PJ (2019) Hagfish from the Cretaceous Tethys Sea and a reconciliation of the morphological–molecular conflict in early vertebrate phylogeny. PNAS 116(6): 2146–2151. doi: 10.1073/pnas.1814794116

Oisi Y, Ota KG, Kuraku S, Fujimoto S, Kuratani S (2012) Craniofacial development of hagfishes and the evolution of vertebrates. Nature 493: 175–180. doi: 10.1038/nature11794

Wikipedia. Cyclostomata. Available at <
https://en.wikipedia.org/wiki/Cyclostomata >. Access on March 25, 2019;

Wikipedia. Hagfish. Available at <
https://en.wikipedia.org/wiki/Hagfish >. Access on March 25, 2019.

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by | March 22, 2019 · 8:00 am

Friday Fellow: Red-Rust Bryozoan

by Piter Kehoma Boll

It is time for our second bryozoan fellow, and this time I am bringing you a problematic species that can become a serious nuisance, the red-rust bryozoan Watersipora subtorquata.

The red-rust bryozoan is a colonial bryozoan that lives in tropical and temperate waters and grows on hard surfaces such as rocks or eventually on other colonial organisms. Each individual in the colony, called a zooid, lives inside an elongate structure of mineralized material, mainly calcium carbonate with an oval-shaped opening through which the mouth protrudes. The colony begins spreading over a surface and forming a thin plate of mineralized material that has a dark-red color, hence the common name red-rust. As the colonies become larger, the central parts tend to change to a grayish or blackish color. Older colonies tend to overgrow themselves and turn into leaf-like structures, especially when growing on irregular surfaces.

A leaf-like colony of the red-rust bryozoan. The small dots are the openings of each zooid. Photo by Alison Young.*

With a cosmopolitan distribution, the original location of the red-rust bryozoan is unknown but it was most likely spread throughout the oceans by human activities and soon became a nuisance to humans. The red-rust bryozoan, as a species that grows on hard substrates, found ideal habitats in human structures, such as pipes and ships, which end up covered by colonies, a process called biofouling. Some anti-fouling substances, such as copper-based paint used on ships hulls to prevent biofouling are unable to prevent its growth, as the red-rust bryozoan is a copper-resistant species. And after covering the anti-fouling paint with its colonies, the red-rust bryozoan creates a habitat that allows copper-sensitive creatures to grow.

A closer look in which the individual structures of each zooid are clearly visible. Photo by Damon Tighe.*

On a positive side for humans, the red-rust bryozoan is known to produce bryoanthrathiophene, a substance with antiangiogenic properties, i.e., it prevents the growth of new blood vessels, which may be useful in the treatment of some types of cancer.

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References:

Jeong S-J, Higuchi R, Miyamoto T, Ono M, Kuwano M, Mawatari SF (2002) Bryoanthrathiophene, a New Antiangiogenic Constituent from the Bryozoan Watersipora subtorquata (d’Orbigny, 1852). Journal of Natural Products 65(9): 1344–1345. doi: 10.1021/np010577+

Mackie HA, Keough MJ, Christidis L (2006) Invasion patterns inferred from cytochrome oxidase I sequences in three bryozoans, Bugula neritina, Watersipora subtorquata and Watersipora arcuata. Marine Biology 149(2): 285-295. doi: 10.1007/s00227-005-0196-x

Ryland JS, De Blauwe H, Lord R, Mackie JA (2009) Recent discoveries of alien Watersipora (Bryozoa) in Western Europe, with redescription of species. Zootaxa 2093: 43–59.

Vieira LM, Jones MS, Taylor PD (2014) The identity of the invasive fouling bryozoan Watersipora subtorquata (d’Orbigny) and some other congeneric species. Zootaxa 3857: 151–182. doi: 10.11646/zootaxa.3857.2.1

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by | March 20, 2019 · 1:46 pm

Whose Wednesday: Torbern Bergman

by Piter Kehoma Boll

Today I am presenting a 18th century scientist who worked on several areas of the natural sciences.

Torbern Olaf Bergman was born on 20 March 1735 in Låstad parish, Sweden, the son of Barthold Bergman and Sara Hägg. His interest in botany was raised by his teacher Sven Hof at Katedralskolan in Skara.

At the age of 17, he enrolled at the University of Uppsala. He wanted to study mathematics and natural science, but his father wanted him to study law or divinity. Trying to please both his father and himself, he overworked himself and became ill, which forced him to stay some time away from study. During this period, he entertained himself with field botany and entomology.

Portrait of Torbern Bergman by Ulrika Pasch.

Through his entomological collections, Bergman became acquainted with Linnaeus and sent him several insects of new species. In 1756, he succeeded in proving that, contrary to Linnaeus’ opinion, the species called Coccus aquaticus was simply the ovum of a leech, which Linnaeus recognized as correct. Due to this discovery, as well as because he developed a method to capture the wingless females of winter moths, Bergman was awarded a prize by the Swedish Academy of Sciences, being elected a member of the Academy in 1764. The next year he was ellected a Fellow of the Royal Society of London.

Bergman also defended a thesis in astronomy and founded the Cosmography Society in Uppsala, through which the published, in 1766, his work Physisk beskrifning öfver jordklotet (Physical description over the globe), which was one of the first books of modern geography. He then became an associate professor of physics and studied the electrical properties of tourmaline, as well as meteorological phenomena such as the northern lights, thunder and rainbow.

In 1767, the chemist Johan Gottschalk Wallerius resigned from his position as professor of chemistry and mineralogy at the University of Uppsala and Bergman was decided to be a candidate. However, he did not have previous experience in publishing works on chemistry and his competitors charged him with ignorance on the subject. To refute them, he isolated himself in a laboratory for some time and wrote a treatise on the manufacture of alum and it became a standard work. Nevertheless, he still faced strong opposition and only got the chair of chemistry through the influence of the prince Gustavus III, who was also chancellor of the university. He kept this position until his death.

Bergman married his wife, Margareta Catharina Trast, in 1771. In 1772, he was one of the first to receive the Royal Order of Vasa, which was awarded to Swedish citizens for their service to the state and society, especially in the fields of agriculture, mining and commerce.

In 1775, Bergman published his most important chemical paper, Essay on Elective Attractions, a study of chemical affinity. In March 1782, he was elected a foreign associate of the French Academy of Sciences.

He died prematurely on 8 July 1784, aged 49, in Medevi, Sweden, due to a stroke. The radiactive uranium mineral torbernite was named in his honor.

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References:

Encyclopædia Brittanica (1991) Bergman, Torbern Olof. Available at < https://en.wikisource.org/wiki/1911_Encyclop%C3%A6dia_Britannica/Bergman,_Torbern_Olof >. Acess on 20 March 2019.

Wikipedia. Torbern Bergman. Available at < https://en.wikipedia.org/wiki/Torbern_Bergman >. Access on 20 March 2019.

Wikipedia (in Swedish). Torbern Bergman. Available at < https://sv.wikipedia.org/wiki/Torbern_Bergman >. Access on 20 March 2019.

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by | March 15, 2019 · 8:00 am

Friday Fellow: Imperial Fritillary

by Piter Kehoma Boll

Let’s bring a high dose of beauty into today’s Friday Fellow with a wonderful species that may sometimes be found in your garden.

Imperial fritillary growing in its natural environment in Kurdistan. Photo by Wikipedia user A2raya07.*

Fritillaria imperialis, the imperial fritillary or crown imperial, is native from Asian highlands between Turkey and the Himalayas but is cultivated worldwide, having a series of artificially selected cultivars. The plant reaches a height of about 1 m and has a series of lance-shaped leaves along its stem, similarly to what is found in other species of the lily family, Liliaceae, to which it belongs. The flowers appear in a whorl close to the top of the stem and face downwards. A crown of small leaves tops the flowers, hence its name imperialis. The bell-shaped flowers are usually orange in the wild but, in cultivars, they vary between red and yellow.

A cultivar named ‘Rubra Maxima’. Photo by Hendry Heatly.**

The imperial fritillary has been used in traditional medicine for centuries by people living around its native range. Recent studies revealed that the plant contains a series of alkaloids, mostly anticholinergic steroidal alkaloids, which have the potential to be used for the development of new medicines to treat several conditions.

Despite its popularity as an ornamental plant, wild populations of the imperial fritillary are endangered in many countries in which it occurs, especially due to habitat loss. In order to aid in the preservation and restoration of wild populations, some laboratory techniques have been developed to generate clones that could help increase population size in the wild.

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References:

Akhtar MN, Rahman A, Choudhary MI, Sener B, Erdogan I, Tsuda Y (2003) New class of steroidal alkaloids from Fritillaria imperialis. Phytochemistry 63: 115–122. doi: 10.1016/S0031-9422(02)00569-1

Gilani AH, Shaheen F, Christopoulos A, Mitchelson F (1997) Interaction of ebeinone, an alkaloid from Fritillaria imperialis, at two muscarinic acetylcholine receptor subtypes. Life Sciences 60 (8): 535–544. doi:
10.1016/S0024-3205(96)00691-1

Kiani M, Mohammadi S, Babaei A, Sefidkon F, Naghavi MR, Ranjbar M, Razavi SA, Saeidi K, Jafari H, Asgardi D, Potter D (2017) Iran supports a great share of biodiversity and floristic endemism for Fritillaria spp. (Liliaceae): A review. Plant Diversity 39(5): 245–262. doi: 10.1016/j.pld.2017.09.002

Mohammadi-Dehcheshmeh M, Khalighi A, Naderi R, Sardari M, Ebrahimie E (2008) Petal: a reliable explant for direct bulblet regeneration of endangered wild populations of Fritillaria imperialis L. Acta Physiologiae Plantarum 30(3): 395–399. doi: 10.1007/s11738-007-0126-2

Wikipedia. Fritillaria imperialis. Available at < https://en.wikipedia.org/wiki/Fritillaria_imperialis >. Access on 11 February 2019.

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by | March 13, 2019 · 2:23 pm

Whose Wednesday: Jean-Louis Petit

by Piter Kehoma Boll

Today we celebrate the birthday of a French scientist and surgeon that achieved a great renown during his time.

Jean-Louis Petit, usually known as Petit the surgeon, was born on 13 May 1674 in Paris. He was interested in anatomy since childhood and received lessons on the subject from the anatomist Alexis Littré, who lived in his house. When Petit was only 12 years old, Littré trusted him his anatomical theater.

After studying surgery with the surgeon Georges Mareschal, Petit obtained the title of master in surgery in 1700. In 1705, he published a work entitled L’Art de guérir les maladies des os (The art of curing bone diseases), which would be translated into English in 1726.

Portrait of Jean-Louis Petit by Ambroise Tardieu.

In 1715, he became a member of the French Royal Academy of Sciences and, in 1731, was named, by the King Louis XV, director of the Royal Academy of Surgery after its foundation.

Petit’s reputation was achieved due to his talent and experience, especially because of his case reports of bleeding, lacrimal fistulas and operations on the frenum of the penis, as well as his work on bone diseases. Due to his fame, he was invited to Poland in 1726 to treat King Augustus II, and to Spain in 1735 to treat Prince Ferdinand VI. Both offered great advantages for him to stay in their countries, but he decided to return to France.

Petit is also acknowledged for the first broad clinical description of an epidural hematoma and its treatment by trepanning at the opposite side of the beginning of neurological signs.

Petit died in Paris on 20 April 1750, aged 76.

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Reference:

Wikipédia (in French). Jean-Louis Petit (anatomiste). Available at < https://fr.wikipedia.org/wiki/Jean-Louis_Petit_(anatomiste) >. Access on 13 March, 2019.

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by | March 8, 2019 · 8:00 am

Friday Fellow: Platine Shield Harvestman

by Piter Kehoma Boll

Beneath fallen logs and rocks or in the leaf litter of forests and gardens around the La Plata River in Argentina and Uruguay, you may find today’s fellow. Scientifically known as Discocyrtus prospicuus, it is a harvestman, a member of a group of arachnids that resemble spiders. As usual among small hidden invertebrates, it lacks a common name, so I coined the term Platine shield harvestman to refer to it.

Discocyrtus prospicuus in Buenos Aires, Argentina. Photo by Nicolas Olejnik.*

The Platine shield harvestman belongs to the family Gonyleptidae, which includes harvestmen with astonishing armored bodies and a prosoma (or cephalothorax) with a triangular shape resembling some sort of shield. It has a dark reddish brown color and two powerful hindlegs armed with several spines.

The Platine shield harvestman is found in several localities of Argentina and Uruguay, but especially in forested areas around the La Plata River and its tributaries. As usually among gonyleptid harvestmen, the Platine shield harvestman is dependent on environments with a considerable degree of humidity.

Different from most arachnids, harvestmen are usually omnivorous scavengers, feeding on dead animal and plant material, and the Platine shield harvestman is not different. In predator-prey relationships, they are usually the prey of other animals, especially spiders, such as wolf spiders that share the same habitat. When facing a large spider that is about to hunt it, the Platine shield harvestman can use a series of defense mechanisms. One of the simplest ways to avoid being eaten is remaining motionless or playing dead, a behavior called thanatosis. When facing an apparently dead harvestman, a wolf spider usually ignores it completely, as if it wasn’t even there. When this is not enough to stop the attack, the harvestman can use additional strategies, such as “showing its butt” to the spider by lifting its abdomen toward the predator and sometimes kicking the spider with its hind legs. Another common defense mechanism in harvestmen is releasing chemicals with a strong and repulsive scent but the Platine shield harvestman does not seem to use it often, at least not against spiders.

Little is known about the natural history of the Platine shield harvestman or of any of its close relatives. As I said several times before, we need more people studying the small creatures that live all around us.

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References:

Costa LE, Guerrero EL (2011) Geographical distribution of Discocyrtus prospicuus (Arachnida: Opiliones: Gonyleptidae): Is there a pattern? Zootaxa 2043: 1–24.

Fernandes NS, Stanley E, Costa FG, Toscano-Gadea CA, Willemart RH (2017) Chemical sex recognition in the harvestman Discocyrtus prospicuus (Arachnida: Opiliones). Acta Ethologica 20(3): 215–221. doi: 10.1007/s10211-017-0264-5

Segalerba A, Toscano-Gadea CA (2016) Description of the Defensive Behaviour of Four Neotropical Harvestmen (Laniatores: Gonyleptidae) Against a Synchronic and Sympatric Wolf Spider (Araneae: Lycosidae). Arachnology 17(1): 52–58. doi:10.13156/arac.2006.17.1.52 

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

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