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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You know nothing, humans! A planarian genome challenges our understanding of how life works

by Piter Kehoma Boll

We finally have a rather complete sequencing of a planarian’s genome, more precisely, of the planarian Schmidtea mediterranea, which is an important model organism for the study of stem cells and regeneration.

In case you don’t know, planarians have a remarkable ability of regeneration, so that even tiny pieces are able to regenerate into a whole organism. They are like a real-life Wolverine, but somewhat cooler! This amazing ability is possible due to the presence of a group of stem cells called neoblasts that can differentiate into any cell type found in the planarian’s body. In fact, all differentiated cell types in planarians are unable to undergo mitosis, so that neoblasts are responsible for constantly replacing cells in every tissue. But we are not here to explain the details of planarian regeneration. We are here to talk about Schmidtea mediterranea‘s genome!

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Look at its little cock eyes saying “I will destroy everything you think you know, humans!” Photo by Alejandro Sánchez Alvarado.*

A rather complete genome of S. mediterranea has been recently published and its analysis reveal some astonishing features.

First of all, 61.7% of S. mediterranea‘s genome is formed by repeated elements. Repeated elements are basically DNA strands that occur in multiple copies throught the genome of an organism. They are thought to come from the DNA of virus that was incorporated to the host’s DNA. In humans, about 46% of the genome is formed by repeated elements. Most repeated elements of S. mediterranea belong to unidentified families of retroelements, thus suggesting that they are new undescribed families. Those repeats are very long, having more than 30 thousand base pairs, which are not known to exist in other animals. The only other group of repeated elements with a similar size is found in plants and known as OGRE (Origin G-Rich Repeated Elements). The long repeat found in Schmidtea was therefore called Burro (Big, unknown repeat rivaling Ogre).

But certainly the most surprising thing about S. mediterranea‘s genome is the lack of many highly conserved genes that are found in most eukaryotes and that were thought to be essential for cells to function properly.

Schmidtea mediterranea lacks genes responsible for repairing double-stranded breaks (DSBs) in DNA, which would make them very likely to suffer a lot of mutations and sensitive to anything that induces DSBs. However, planarians are known to have an extraordinary resistance to gamma radiation that induces DSBs. Do they have other repairing mechanisms or is our current understanding about this process flawed?

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Several “essential” genes and their presence (in green) or absence (in red) in several animals. Schmidtea mediterranea lacks them all. Image extracted from Grohme et al. (2018).**

Another important gene that was not found in S. mediterranea is the Fatty Acid Synthase (FASN) gene, which is essential for an organism to synthesize new fatty acids. Planarians therefore would have to rely on the lipids acquired from the diet. This gene is also absent in parasitic flatworms and was at first thought to be an adaptation to parasitism but since it is absent in free-living species as well, it does not seem to be the case. Could it be a synapomorphy of flatworms, i.e., a character that identifies this clade of animals?

That is not enough for little Schmidtea, though. More than that, this lovely planarian seems to lack the MAD1 and MAD2 genes, which are found in virtually all eukaryotes. Those genes are responsible for the Spindle Assembly Checkpoint (SAC), an important step during cell division that prevents the two copies of a chromosome to separate from each other before they are all connected to the spindle apparatus. This assures that the chromosomes will be evenly distributed in both daughter cells. Errors in this process lead to aneuploidy (the wrong number of chromosomes in each daughter cell), which is the cause of some genetic disorders such as the Down syndrome in humans. Planarians do not have any trouble in distributing their chromosomes properly, so what is going on? Have they developed a new way to prevent cellular chaos or, again, is our current understanding about this process flawed?

Let’s wait for the next chapters.

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Reference:

Grohme, M. A.; Schloissnig, S.; Rozanski, A.; Pippel, M.; Young, G. R.; Winkler, S.; Brandl, H.; Henry, I.; Dahl, A.; Powell, S.; Hiller, M.; Myers, E.; Rink, J. C. (2018). “The genome of Schmidtea mediterranea and the evolution of core cellular mechanisms”. Nature. doi:10.1038/nature25473

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Friday Fellow: Timor Black Bamboo

by Piter Kehoma Boll

If there is one important family of flowering plants that hasn’t been featured here yet is the grass family Poaceae. And what would be a better grass to be the first one than a bamboo? So here we have the Timor black bamboo Bambusa lako.

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The beautiful black culms of the Timor black bamboo. Photo by Cas Liber.

As its common name suggests, this species is native from the island of Timor, one of the lesser Sunda Islands in the Indonesian Archipelago. One of the most striking features of the Timor black bamboo is its black stem. As in all bamboos, the stem of the Timor black bamboo is divided into culms. Those are initially green, but become shiny black when mature and may reach 10 cm in diameter. The whole plant can reach a height of 21 m.

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A young and still green branch of the Timor black bamboo. Photo by Mitchell Adams.*

Although still classified in the genus Bambusa, it is known since 2000 that the Timor Black Bamboo is closely related to the genus Gigantochloa, which includes other black bamboos, such as the common black bamboo Gigantochloa atroviolacea.

Currently, the Timor black bamboo is found in many places worldwide and widely used for decoration and landscaping purposes due to its peculiar color.

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References:

Loh, J. P.; Kiew, R.; Set, O.; Gan, L. H.; Gan, Y.-Y. (2000) A Study of Genetic Variation and Relationships within the Bamboo Subtribe Bambusinae using Amplified Fragment Length Polymorphism. Annals of Botany 85: 607–612. https://doi.org/10.1006/anbo.2000.1109

Wikipedia. Bambusa lako. Available at < https://en.wikipedia.org/wiki/Bambusa_lako >. Access on January 22, 2017.

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Xenoturbella, a growing group of weirdoes

by Piter Kehoma Boll

You may never have heard of Xenoturbella, and I wouldn’t blame you. Despite being a fascinating feature of evolution, little is known about it and its magic has been hidden from most of us.

The first Xenoturbella was described in 1949 and named Xenoturbella bocki. At the time, it was considered a strange flatworm, hence its name, from Greek xenos, strange + turbella, from Turbellaria, free-living flatworms. Xenoturbella bocki is a marine animal measuring up to 3 cm in length and looking like a flat worm… a flatworm! Well, actually more like a folded worm, because its body has a series of folds running londitudinally that make it have a W shape in cross section.

Found in the cold waters around northern Europe, its body lacks a centralized nervous system, having only a net of neurons inside the epidermis. There are also no reproductive organs, neither anything similar to a kidney or any other organ beside a mouth and a gut and some structures on its surface.

For decades, X. bocki was the only species of Xenoturbella known to us. A second species was described in 1999 as X. westbladi, but molecular analyses revealed that it was the same species as X. bocki, so we continued having only one species. Thanks to molecular studies, we also figured out that Xenoturbella is not a flatworm at all, but belongs to a group of very primitive bilaterian animals, being closely related to another group of former flatworms, the acoelomorphs. Together, Xenoturbella and the acoelomorphs (a good name for a rock band, right?) form the group called Xenacoelomorpha.

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Xenoturbella churro, “head” to the right. Photo by Greg Rouse.*

Forming its own phylum (or perhaps class if it is grouped in a single phylum with the acoelomorphs) named Xenoturbellida, X. bocki recently discovered that it is not alone in the world. In 2016, four new species were described from the waters of the Pacific Ocean near the coasts of Mexico and the USA, being named Xenoturbella monstrosa, X. churro, X. profunda and X. hollandorum. Considering the small size of X. bocki, some of them were monsters, especially X. monstrosa, which reaches 20 cm in length!

Four new species was quite a finding. The phylum suddenly was five times bigger than before. As someone particularly interested in obscure animal groups, especially those that once were members of the lovely phylum Plathyelminthes, I was very excited by this discovery, but I wasn’t expecting at all what happened after that.

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Photo of the only known specimen of Xenoturbella japonica until now. “Head” to the left. Credits to Nakano et al. (2017).*

In December 2017, one more species was found, this time on the other side of the Pacific, near Japan. Named Xenoturbella japonica, the fifth member of the Xenoturbella genus is very welcome. The new species was based on two specimens, an adult “female” specimen (are they hermaphrodites? I don’t think we can be sure about it yet…) and a juvenile specimen. One more exciting thing is that the juvenile may actually be yet another species! But we need more material to be sure.

You can read the article describing Xenoturbella japonica here.

See also: Acoelomorpha, a phylogenetic headache

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References:

Nakano, H.; MIyazawa, H.; Maeno, A.; Shiroishi, T.; Kakui, K.; Koyanagi, R.; Kanda, M.; Satoh, N.; Omori, A.; Kohtsuka, H. (2017) A new species of Xenoturbella from the western Pacific Ocean and the evolution of XenoturbellaBMC Evolutionary Biology17: 245. https://doi.org/10.1186/s12862-017-1080-2

Rouse, G.W.; Wilson N.G.; Carvajal, J.I.; Vrijenhoek, R.C. (2016) New deep-sea species of Xenoturbella and the position of Xenacoelomorpha. Nature, 530:94–7. doi:10.1038/nature16545.

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