Category Archives: Algae

Friday Fellow: Tender Nori

by Piter Kehoma Boll

If you like Japanese food, you have eaten sushi for sure, and thus have ingested the famous alga from Japanese cuisine known as nori that is used to wrap the rice, right? Well, it does not necessarily mean that you have eaten the species I am introducing today and you soon will know why.

Dried nori sheets as used in Japanese cuisine. Photo by Yuichi Kosio.*

During most of the Japan history, the main nori species used as a food was the tender nori, which is scientifically known as Pyropia tenera (formerly known as Porphyra tenera) and known in Japan as 浅草海苔 (asakusa nori). This species is a red alga and is closely related to other edible species used in other parts of the world.

Cultivated tender nori. Extracted from http://godairikibune.blog83.fc2.com/blog-category-7.html

The life cycle of the tender nori includes two different generations as seen in all plants. One generation, the gametophyte, is composed by haploid cells, i.e., with only one copy of each chromosome. This gametophyte stage is the largest and the one commonly used as food. It produces both female and male gametes and uses the water current to guide the male gametes, which are unable to swim, to the female gametes. For a long time, this was the only life stage known for the nori. The gametophytes were harvested in the wild, where they grow on the available substrate, especially wood. Only during the 20th century it became clear that the sporophyte, the other life stage, is smaller and needs the shell of mollusks as a substrate to grow. In fact, the sporophyte was already known, but was mistaken for a different organism classified in a genus named Conchocelis. Thus, the sporophyte is still commonly known as tie Conchocelis stage.

After the complete life-cycle of these algae was known, it did not take too long for people to develop cultivation methods that greatly increased the production of nori. Two nori strains soon became the main cultivars in Japan from around the beginning of the 1960s: Pyropia tenera var. tamatsuensis and Pyropia yezoensis f. narawaensis. The latter, as you can see, belongs to a different species of nori, the Ezo nori, known in Japan as 荒び海苔 (susabi nori).

Although the tender nori was considered of better quality and better taste, it was not as tolerant to the strong waves and winds as the Ezo nori. As a result, the Ezo nori became the favorite cultivar and spread quickly, so that this is the main species used nowadays in the Japanese cuisine. This increased cultivation of the Ezo nori displaced the original tender nori to the point that the tender nori is currently a very rare species, so rare that it is considered an endangered species by the Japanese government since 1997.

The distinction between species of Pyropia in wild populations is usually difficult because there is little morphological variation between them. Recent molecular studies from nori growing across Japan showed that the tender nori is not as rare as previously thought, although it does not makes it imune to extinction. Since the tender nori is considered softer and more tasty than the Ezo nori, there have been some attempts to increase the commercial interest on it, which could prevent it from becoming extinct in the near future.

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References:

Hwang MS, Kim S-O, Ha D-S, Lee JU, Lee S-R (2013) Complete sequence and genetic features of the mitochondrial genome of Pyropia tenera (Rhodophyta). Plant Biotechnology Reports 7(4): 435–443. doi: 10.1007/s11816-013-0281-4

Iwasaki H (1961) The life-cycle of Porphyra tenera in Vitro. Biological Bulletin 121(1): 173–187. doi: 10.2307/1539469

Niwa K, Iida S, Kato A, Kawai H, Kikuchi N, Kobiyama A, Aruga Y (2009) Genetic diversity and ingrogression in two cultivated species (Porphyra yezoensis and Porphyra tenera) and closely related wild species of Porphyra (Bangiales, Rhodophyta). Journal of Phycology 45(2): 493–502. doi: 10.1111/j.1529-8817.2009.00661.x

Niwa K, Kikuchi N, Aruga Y (2005) Morphological and molecular analysis of the endangered species Porphyra tenera (Bangiales, Rhodophyta). Journal of Phycology 41(2): 294–304. doi: 10.1111/j.1529-8817.2005.04039.x

ウィキペディア (Wikipedia in Japanese)。アサクサオリ。Available at <
https://ja.wikipedia.org/wiki/%E3%82%A2%E3%82%B5%E3%82%AF%E3%82%B5%E3%83%8E%E3%83%AA >. Access on 25 March 2019.

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Friday Fellow: Toothed Micrasterias

by Piter Kehoma Boll

Leia em Português

A new year is beginning with Friday Fellow, and we are going to start small with a lovely tiny alga named Micrasterias denticulata, or the toothed micrasterias as I decided to call it. Found in freshwater habitats, especially peat bogs with acid water, all around the world, this species belongs to the order Desmidiales, which is characterized by its peculiar cell anatomy.

As most desmids, the toothed micrasterias is a single-celled organism and its cell is divided into two halfs, called semi-cells, which are united by a narrow isthmus. Each semi-cell contains a large chloroplast, and the nucleus lies within the isthmus. Due to its symmetrical cell with a well-defined shape, including a series of lobes, the toothed micrasterias and other species of its genus are ideal organisms for the study of cell morphogenesis.

Recently, Micrasterias denticulata has been used to study the effect of several environmental variables, especially pollutants and nutrients, on cell shape. Such studies are important to understand the effects of environmental changes caused by human activities, such as agriculture and waste production, on freshwater ecosystems. Living in an environment that changes constantly regarding pH, salinity and temperature, the toothed micrasterias is a tough organism and has developed mechanisms to avoid intoxication, such as crystalization of heavy metals to make them innactive inside the cell.

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References:

Affenzeller MJ, Darehshouri A, Andosch A, Lütz C, Lütz-Meindl U (2009) Salt stress-induced cell death in the unicellular alga Micrasterias denticulata. Journal of Experimental Botany 60(3): 939–954.
https://doi.org/10.1093/jxb/ern348

Niedermeier M, Gierlinger N, Lütz-Meindl U (2018) Biomineralization of strontium and barium contributes to detoxification in the freshwater alga Micrasterias. Journal of Plant Physiology 230: 80–91.
https://doi.org/10.1016/j.jplph.2018.08.008

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Friday Fellow: Ehux

by Piter Kehoma Boll

We’ll continue among the unicellular marvels of the sea this week. This time our fellow is another member of a poorly known but hugely important group of protists, the coccolithophores.

The coccolithophores are a group of unicellular algae of the marine phytoplankton that is characterized by a series of calcium carbonate plates, called coccoliths, that cover their body, making them look like cells covered by scales.

Today we’ll know the most widespread and abundant species of this group, Emiliania huxleyi, usually simply called Ehux, which I will use here as its common name.

600px-emiliania_huxleyi_coccolithophore_28plos29

Scanning elctron micrograph cell of Emiliania huxleyi covered by coccoliths. Credits to Alison R. Taylor.*

Ehux is found in the oceans all around the world, being absent only close to the poles. According to the fossil record, this species appeared about 270 thousand years ago, but became the dominant coccolithophore only anout 70 thousand years ago. Due to its abundance, Ehux is an important species controling global climate. As a photosynthetic organism, it helps to increase atmospheric oxygen and decrease carbon dioxide. Additionally, the fact that its cell is covered by calcium carbonate plates increases even more its importance in removing CO2 from the atmosphere. By capturing CO2 as calcium carbonate, Ehux send it directly to the ocean floor when it dies and the shell sinks.

The life cycle of Ehux is not yet completely understood, but includes at least two different cell forms. The C form is spherical, nonmotile and covered by coccoliths (hence the name C) and can reproduce asexually by fission. Another form, called S (scaly) lacks coccoliths but is covered by a group of organic scales. This form is motile, swimming using two flagella, and also reproduces asexually by fission. How one form turns into the other is unclear, but there are some evidences that the C form is diploid and the S form is haploid, so C cells could turn into S cells by meiosis and two S cells could act as gametes and fuse to produce a new C cell. A third form, called N (naked) cell is similar to a C cell but is unable to produce the coccoliths. It is assumed that they appear by a mutation of C cells that makes them lose the ability to produce coccoliths, as N cells never change back to the C form.

750px-cwall99_lg

A bloom of Ehux south of Great Britain as seen from a sattelite photo. Credits to NASA.

During some special conditions, such as high irradiance, ideal temperatures and nitrogen-rich waters, Ehux populations can cause blooms which extend over large portions of the ocean. This species is known as a producer of Dimethyl Sulphide (DMS), a flammable liquid that boils at 37°C and has a characteristic smell usually called “sea smell” or “cabbage smell”. The release of DMS in the atmosphere interferes in cloud formation, so that this is one more way by which Ehux influences global climate.

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References:

Paasche E (2002) Paasche, E. (2001). A review of the coccolithophorid Emiliania huxleyi (Prymnesiophyceae), with particular reference to growth, coccolith formation, and calcification-photosynthesis interactions. Phycologia 40(6), 503–529. doi:10.2216/i0031-8884-40-6-503.1

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Friday Fellow: Handsome Asterisk-Diatom

by Piter Kehoma Boll

It’s time for the next diatom to be featured here. Differently from the previous ones, today’s diatom is a freshwater species commonly found in lakes of North America and Eurasia. It has also been reported for South America and Africa, but it is likely that these individuals actually belong to another, closely related species.

asterionella_formosa

Asterionella formosa from a lake of the Rocky Mountain National Park, United States

Named Asterionella formosa, this diatom has small rod-shaped cells that are 60 to 85 µm long and only 2 to 4 µm wide. The individuals usually organize themselves in colonies linked by one of the ends in a star fashion. Most colonies include eight organisms and look somewhat like an asterisk, hence I chose to give the common name asterisk-diatom to the genus, this species then being called the “handsome asterisk-diatom”, from the translation of the specific epithet formosa. However, some colonies may have up to 20 individuals and organize in a more spiral fashion.

30848_orig

A spiral-shaped colony from a small lake in Spain. Credits to Proyecto Agua.*

Originally found and described from water supplies used in London, the handsome asterisk-diatom has a preference for cold waters, occurring commonly in temperate lakes under temperatures between 0 and 15 °C. During summer, when temperatures get too high and the light intensity also increases, its photosynthesis is inhibited by these two factors as well as by the increase in oxygen caused by the metabolism of the species itself as well of other algae from the phytoplanktonic community.

Sexual reproduction is not well known in the handsome asterisk-diatom, but must certainly occur, as asexual reproduction alone leads to a continuous decrease in cell size in all diatoms. Studies on genetic diversity show that this species is very genetically diverse, which proves that sexual reproduction indeed occurs and in a apparently high rate, contributing for the dominance of this species in many of the ecosystems of which it takes part.

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References:

AlgaeBase. Asterionella formosa Hassall. Available at < http://www.algaebase.org/search/species/detail/?species_id=31441 >. Access on May 25, 2018.

Belay, A.; Fogg, G. E. (1978) Photoinhibition of photosynthesis in Asterionella formosa (Bacillariophyceae). Journal of Phycology14(3): 341–347. https://doi.org/10.1111/j.1529-8817.1978.tb00310.x

De Bruin, A.; Ibelings, B. W.; Rijkeboer, M.; Brehm, M.; Van Donk, E. (2004) Genetic variation in Asterionella formosa (Bacillariophyceae): is it linked to frequent epidemics of host-specific parasitic fungi? Journal of Phycology40(5): 823–830. https://doi.org/10.1111/j.1529-8817.2004.04006.x

EOL – Enclyclopedia of Life. Asterionella formosa. Available at < http://eol.org/pages/917771/details >. Access on May 25, 2018.

Lund, J. W. G. (1950) Studies on Asterionella formosa Hass: II. Nutrient depletion and the spring maximum. Journal of Ecology38(1): 15–35.

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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.

20118_orig

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: Sea Sparkle

by Piter Kehoma Boll

If you live near the sea or visit it often, you may sometimes have seen the waves glowing while breaking on the shore at night. This beautiful phenomenon is caused by the presence of bioluminescent microorganisms, the most famous of which is our newest Friday Fellow. Scientifically known as Noctiluca scintillans, it is populary known as the sea sparkle.

Bioluminescent_sea

Waves glowing blue at Atami, Japan. Photo by Kanon Serizawa.*

The sea sparkle is a dinoflagellate and is common worlwide. It is an heterotrophic flagellate and feeds on many other small organisms, such as bacteria, diatoms, other dinoflagellates and even eggs of copepods and fish. Having only a small tentacle and a rudimentar flagellum, the sea sparkle is unable to swim, making it a very unusual predator. Studies have suggested that it preys by bumping into the prey during water flow or by ascending or descending in the water column due to density differences. It can also produce a string of mucus attached to the tentacle that entagles prey and brings them to their horrible end.

noctiluca_scintillans_unica

A single Noctiluca scintillans. Photo by Maria Antónia Sampayo, Instituto de Oceanografia, Faculdade Ciências da Universidade de Lisboa.**

In temperate waters, the sea sparkle is an exclusive predator, but in tropical water it may maintain some of the ingested algae alive and use them in a symbiotic association to receive nutrients from photosynthesis. Diatoms of the genus Thalassiosira appear to be one of its favorites.

The most striking feature of the sea sparkle, however, is its bioluminescence, from which it receives its names. The light that it emits is produced by a chemical reaction between a compound called luciferin and an enzyme, called luciferase, that oxidizes it, causing it to emit light. The phenomenon is clearly visible on the sea during blooms of the dinoflagellate, which usually happen right after a bloom of its food.

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References:

Kiørbe, T.; Titelman, J. (1998) Feeding, prey selection and prey encounter mechanisms in the heterotrophic dinoflagellate Noctiluca scintillansJournal of Plankton Research 20(8): 1615–1636.

Quevedo, M.; Gonzalez-Quiros, R.; Anadon, R. (1999) Evidence of heavy predation by Noctiluca scintillans on Acartia clausi (Copepoda) eggs of the central Cantabrian coast (NW Spain). Oceanologica Acta 22(1): 127–131.

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Friday Fellow: Lyre ship diatom

by Piter Kehoma Boll

It’s time for the next diatom, and just as with the radiolarian from the last week, it’s a hard task to find good pictures and good information of any species to present here.

Today I’m introducing a species of the most diverse (I guess, or at least one of the most diverse) genus of diatoms, Navicula, a name that means “little ship” in Latin due to the shape of the cells. There are more than 1200 species in this genus, and one of them is called Navicula lyra, which I decided to call the lyre ship diatom. I have also seen it with the name Lyrella lyra, being the type-species of a genus Lyrella (little lyre) that was split from Navicula. I don’t know which one is the official form today, but it seems that Lyrella is sometimes something like a subgenus of Navicula, although sometimes both genera are not even in the same family!

Navicula_lyra

Navicula lyra, a lyre little ship. Photo by Patrice Duros.*

Anyway, the lyre ship diatom is a planktonic species that is found in all the oceans of the world, being present in species lists everywhere. It measures about 100 µm or less, a typical size for a diatom.

As with other diatoms in the genera Navicula and Lyrella, the lyre ship diatom has different varieties, which may eventually be revealed to be separate species, I guess. See, for example, the variety constricta shown below. It looks considerably different from the picture above, which appears to be from the type variety.

Navicula_lyra

Lyrella lyra var. constricta. Extracted from Siqueiros-Beltrones et al. (2017)

Despite being a widespread species, little seems to be known about the natural history of the lyre ship diatom. Aren’t you interested in studying the ecology of these tiny little glass ships?

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References:

Nevrova, E.; Witkowski, A.; Kulikovskiy, M.; Lange-Bertalot, H.; Kociolek, J. P. (2013) A revision of the diatom genus Lyrella Karayeva (Bacillariophyta: Lyrellaceae) from the Black Sea, with descriptions of five new species. Phytotaxa 83(1): 1–38.

Siqueiros-Beltrones, D. A.; Argumedo-Hernández, U.; López-Fuerte, F. O. (2017) New records and combinations of Lyrella (Bacillariophyceae: Lyrellales) from a protected coastal lagoon of the northwestern Mexican Pacific. Revista Mexicana de Biodiversidad 88(1): 1–20.

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