Monthly Archives: February 2018

Whose Wednesday: Karl Ernst von Baer

by Piter Kehoma Boll

Hello, folks! So I decided to start one more regular section at our blog. Every Wednesday I’ll bring you a naturalist or other scientist so that you can know a little bit more about those that made biology what it is today. I’ll try to make it about someone whose birthday falls on that day, but I cannot asure that it will work every week, as I (still) don’t know at least one biologist that was born on every day of the year.

But our category will start right now with an Estonian scientist.

Karl Ernst Ritter von Baer, Edler von Huthorn, was born on February 28, 1792, in Piep (or Piibe), Estonia. During his adolescence and early adulthood, he was very unsatisfied with the education he received in his home country and eventually left it to study abroad in Berlin, Vienna and Würzburg. In Würzburg, he met physician Ignaz Döllinger and was introduced by him to the field of embryology, which he embraced gladly.

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Portrait of Karl Ernst von Baer made before 1852. Author unknown.

From 1817 to 1834 he was a professor at Königsberg University (which no longer exists, having been closed in 1946 when the city of Königsberg was transfered to the Soviet Union and renamed Kaliningrad). He dedicated most of his research there to embryology, making remarkable discoveries in the field. He discovered the blastula stage of the embryonic development, as well as the notochord. Together with the embryologist Heinz Christian Pander, he described the germ layer theory of development (i.e., the theory that embryos develop from three (or two) germ layers: ectoderm, mesoderm and endoderm). He also stated that the embryo of “higher” forms do not resemble the adults of “lower” forms, but rather the embryos of those lower forms, which contrasts with the more famous theory of Ernst Haeckel that says that the embryo stages recapitulate the previous forms (“ontogeny recapitulates phylogeny”). For such astounding contributions, von Baer is sometimes called the founding father of embryology.

In 1834, von Baer moved to St. Petersburg and joined the St. Petersburg Academy of Sciences. He then kind of let his interest for embryology aside and concentrated in zoology, geography and so on, doing a lot of field research. In 1845, he helped to found the Russian Geographical Society and, in 1859, the Russian Entomological Society, becoming its first president.

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Karl Ernst von Baer in 1865, aged 73.

Later in life, von Baer become a leading critic of Charles Darwin, rejecting the idea of natural selection, even though he stated many years before that he believed in the transmutation of species.

Von Baer died on November 28, 1876, in his sleep, aged 84.

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Friday Fellow: Giant Salvinia

by Piter Kehoma Boll

We are moving out of the sea this week, but will still remain in the water to bring you a peculiar fern. Commonly known as giant salvinia, kariba weed or giant watermoss, its scientific name is Salvinia molesta and it comes from southeastern Brazil.

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Fronds of Salvinia molesta growing in Hawaii. Photo by Forrest & Kim Starr.*

The water salvinia is an aquatic fern that floats on the surface of the water and has a peculiar anatomy. It lacks roots, and it produces leaves in sets of three. Two of them remain at the surface of the water, side by side, and the third one is submerged, acting like a modified root. The upper side of the surface leaves (which are anatomically their underside) have many small hairs that turn them into a waterproof surface and the underside have very long hairs that look like roots.

Preferring slow-moving waters, the giant salvinia grows very quickly in ideal conditions and has become an invasive species in several parts of the world. It was exported from Brazil to be used in aquaria and garden ponds and ended up in natural environments. While spreading, the giant salvinia can cover the entire surface of water bodies, blocking light for other plants and algae, which decreases photosynthesis and reduces the amount of oxygen in the water. Additionally, it can clog waterways, blocking natural or artificial water flows.

The problem caused by the giant salvinia in areas where it has become invasive led to the development of control methods. One of the simplest methods is simply removing the plants mechanically, but it is difficult in areas with large infestations, as even small remaining populations may quickly recover. Another alternative is the use of biological control using Cyrtobagous salviniae, a tiny weevil that feeds on the giant salvinia in its natural environment.

Not everything about the giant salvinia is bad, actually. Its peculiar leaf anatomy led to the discovery of what was properly called “the salvinia effect”, a phenomen by which an air layer becomes stable over a submerged surface, as in the leaves of species of Salvinia. By developing artificial structures that make use of this phenomenon, it is possible to produce devices that move smoothly in water, such as ships with reduced friction.

A considerably recent study also found out that some compounds extracted from the giant salvinia are effective in the control of human tumor cells.

Our relationship with this peculiar plant is therefore one of love and hate.

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References:

Coetzee, J. A.; Hill, M. P.; Byrne, M. J.; Bownes, A. (2011) A Review of the Biological Control Programmes on Eichhornia crassipes (C.Mart.) Solms (Pontederiaceae), Salvinia molesta D.S.Mitch. (Salviniaceae), Pistia stratiotes L. (Araceae), Myriophyllum aquaticum (Vell.) Verdc. (Haloragaceae) and Azolla filiculoides Lam. (Azollaceae) in South Africa. African Entomology 19: 451-468.

Li, S.; Wang, P.; Deng, G.;  Yuan, W.; Su, Z. (2013)  Cytotoxic compounds from invasive giant salvinia (Salvinia molesta) against human tumor cells. Bioorganic & Medicinal Chemistry Letters 23(24): 6682-6687.

Wikipedia. Salvinia molesta. Available at < https://en.wikipedia.org/wiki/Salvinia_molesta >. Access on February 21, 2018.

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Friday Fellow: Greater Blue-Ringed Octopus

by Piter Kehoma Boll

Tropical waters are always thriving with diversity, therefore it is hard to keep away from them. Today’s Friday Fellow is one more creature from the tropical oceanic waters, more precisely from the Indo-Pacific waters. Being found from Sri Lanka to the Phillipines, Japan and Australia, our fellow is called Hapalochlaena lunulata and popularly known as the greater blue-ringed octopus.

This adorable octopus is very small, measuring only about 10 cm, arms included. It is, however, easy to caught attention because its whitish to dark-yellow body is covered by about 60 rings that show a beautiful electric-blue color with a black outline. As with most octopuses, the color may change according to the animal’s needs in order to make him more or less visible.

A specimen of the greater blue-ringed octopus in Indonesia. Photo by Jens Petersen.*

This adorable color pattern, which may look attractive to us, humans, is nevertheless a warning sign. The grater blue-ringed octopus is a venomous creature and may even kill a human being if threatened. As other octopuses, it is a predator and feeds mainly on crustaceans and bivalves and immobilizes them with a toxin before consumption. This is a mild toxin, though. The real danger is on its defensive behavior.

When threatened, the greater blue-ringed octopus usually begins a warning display by flashing its rings in strong colors. If this is not enough to make the threatening creature retreat, it will atack and bite its harasser. The bite is usually painless but deadly. The venom injected is nothing more nothing less than the infamous tetrodoxin, the same thing that makes a pufferfish a dangerous meal. As you may know, tetrodoxin is a potent neurotoxin that kills within a few minutes to a few hours by blocking the action potential in cells, leading to paralysis and death by asphyxia. In the greater blue-ringed octopus, tetrodotoxin is produced by bacteria that live inside their salivary glands.

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A greater blue-ringed octopus swimming. Photo by Elias Levy.**

A study analyzing the sexual behavior of the greater blue-ringed octopus showed that mating occurs during encounters of both male-female and male-male pairs. The mating ritual of octopuses consists of the male introducing the hectocotylus, a modified arm specialized in delivering sperm, into the female mantle. In male-male pairings, one of the males always put its hectocotylus into the other male’s mantle and there was no attempt from the receptive male to avoid the act. The only difference between males mating with females or with other males was that they only delivered sperm to females and never to males. What can we conclude? Have octopuses found an efficient way to be bisexual creatures by having fun with other males while still able to keep their sperm to give it to females?

The diversity of life always fascinates us!

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References:

Cheng, M. W.; Caldwell, R. L. (2000) Sex identification and mating in the blue-ringed octopus, Hapalochlaena lunulataAnimal Behavior 60: 27-33. DOI: 10.1006/anbe.2000.1447

Mäthger, L. M.; Bell, G. R. R.; Kuzirian, A. M.; Allen, J. J.; Hanlon, R. T. (2012) How does the blue-ringed octopus (Hapalochlaena lunulata) flash its blue rings? Journal of Experimental Biology 215: 3752-3757. DOI: 10.1242/jeb.076869

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Friday Fellow: Dead Man’s Rope

by Piter Kehoma Boll

Widespread in northern temperate waters of the Atlantic and Pacific oceans, today’s Friday Fellow is a brown alga whose scientific name, Chorda filum, meaning “rope thread” is a good way to describe its appearance. Its fronds are long and unbranched, measuring about 5 mm in diameter and reaching up to 8 m in length, so that it actually looks like a long rope, which led to common names such as dead man’s rope, sea lace, cat’s gut, bootlace weed, mermaid’s tresses and mermaid’s fishing line.

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A group of dead man’s ropes growing together. Credits to Biopix: JC Schou.

This alga is usually found in sheltered areas, such as lagoons, inlets, small bays, fjords and even river estuaries, being very tolerant to waters with low salinity, but avoiding open, exposed beaches. It grows attached to the substrate by a small disc, being usually attached to a very unstable substrate, such as loose pebbles or over other algae, being rarely found on stable rocks. As a result, during events in which the water becomes agitated, such as during storms, it can be easily transported to other localities.

Several species live on the fronds of the dead man’s rope, including many algae and sea snails. Other invertebrates, such as amphipods, does not seem to like it very much.

Studies have shown that the dead man’s rope is rich in antioxidants, compounds that help in reducing the aging process and decrease the risk of diseases such as cancer. Although edible, the dead mean’s rope is not widely used as a food source. Perhaps we could change that, providing it is done in a sustainable way.

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References:

Pereira, L. (2016) Edible Seaweeds of the World, CRC Press, London, 463 pp.

South, G. R.; Burrows, E. M. (1967) Studies on marine algae of the British Isles. 5. Chorda filum (L.) StackhBritish Phycological Bulletin3(2): 379-402.

Yan, X.; Nagata, T.; Fan, X. (1998) Antioxidative activities in some common seaweedsPlant Foods for Human Nutrition 52: 253-262.

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Friday Fellow: Bobbit Worm

by Piter Kehoma Boll

Today’s Friday Fellow probably looks like a creature coming directly from hell to the poor sea animals that are its prey. Well, it looks quite scary even for humans! Its name is Eunice aphroditois, a beautiful name. Popularly it is known as the Bobbit worm and looks like a colorful nightmare.

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Anterior portion of a bobbit worm coming out of the sand. Photo by Jenny Huang.*

The Bobbit worm is a polychate worm and is one of the largest known annelids, with several records of individuals reaching up to 1 m in length, and even one record of a specimen that was almost 3 m long. It is found in warm waters all around the world, in the Atlantic, the Indian and the Pacific oceans.

Being an ambush predator, the Bobbit worm buries itself into the ocean floor, among the sediments, and waits for a delicious meal to swim over it. Once a prey is detected, the Bobbit worm projects itself forward and captures it with its sharp teeth.

The name “Bobbit worm” was coined in 1996 and refers to Lorena Bobbitt, who became publicly known in 1993 after cutting off her husband’s penis with a knife while he was asleep. The name seems to be inspired in the worm’s scissor-like jaws and has nothing to do with the female cutting off the male’s penis. In fact, those worms release the gametes in the water, so that there isn’t even a sexual intercourse.

Despite its popularity, being even raised as a “pet” sometimes, little is known about the Bobbit worm’s ecology. If you happen to have one in your fishtank, make some research and publish it!

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References:

Uchida, H.; Tanase, H.; Kubota, S. (2009) An extraordinarily large specimen of the polychaete worm Eunice aphroditois (Pallas) (Order Eunicea) from Shirahama, Wakayama, central Japan. Kuroshio Biosphere 5: 9-5.

Wikipedia. Eunice aphroditois. Available at < https://en.wikipedia.org/wiki/Eunice_aphroditois >. Access on January 31, 2017.

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