Category Archives: Algae

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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Friday Fellow: Operculate Acrochaete

by Piter Kehoma Boll

Last week I introduced a red alga, the Irish moss. Today I’m bringing another alga, this time a green one, but this is not an ordinary green alga, but a parasite of the Irish moss! So let’s talk about Acrochaete operculata, or the operculate acrochaete as I decided to call it in English, since obviously there would be no common name for an alga parasite of another alga.

Discovered and named in 1988, the operculate acrochaete is an exclusive parasite of Chondrus crispus. The infection occurs when flagellate zoospores of the parasite settle on the outer cell wall of the Irish Moss, where they start their development and digest the cell wall, penetrating the tissues of the host. In sporophytes of the Irish moss, the operculate acrochaete digests the intercellular matrix and spreads through the frond, while in gametophytes the infections remains localized, forming papules. The damages caused by the green alga lead to secondary infections by other organisms, especially bacteria, and the infected fronds end up falling apart, completely degradated.

ccrispus

A frond of the host (Chondrus crispus) to the left and the parasitic Acrochaete operculata that infects its tissues to the right. Photo extracted from chemgeo.uni-jena.de

As mentioned last week, the sporophytes and gametophytes of the Irish Moss have different forms of the polysaccharide carrageenan and this seems to be the reason why the parasite infects both forms differently. The sporophytes have lambda-carrageenan, which seems to increase the virulence of the parasite, while the kappa-carrageenan of the gametophyte seems to limit the green alga’s spread.

Since its discovery, the operculate acrochaete and its interaction with the Irish moss has been studied as a way to both reduce its damage on cultivated crops of the red alga and as a model to understand the relationship of plants and their pathogens.

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References:

Bouarab, K.; Potin, P.; Weinberger, F.; Correa, J.; Kloareg, B. (2001) The Chondrus crispus-Acrochaete operculata host-pathogen association, a novel model in glycobiology and applied phycopathology. Journal of Applied Phycology 13(2): 185-193.

Correa, J. A.; McLachlan, J. L. (1993) Endophytic algae of Chondrus crispus (Rhodophyta). V. Fine structure of the infection by Acrochaete operculata (Chlorophyta). European Journal of Phycology 29(1): 33–47. http://dx.doi.org/10.1080/09670269400650461

Correa, J. A.; Nielsen, R.; Grund, D. W. (1988) Endophytic algae of Chondrus crispus (Rhodophyta). II. Acrochaete heteroclada sp. nov., A. operculata sp. nov., and Phaeophila dendroides (Chlorophyta). Journal of Phycology 24: 528–539. http://dx.doi.org/10.1111/j.1529-8817.1988.tb04258.x

 

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Friday Fellow: Irish Moss

by Piter Kehoma Boll

Growing abundantly along the North Atlantic coasts, our newest Friday Fellow is a cartilaginous red alga commonly known as Irish moss or scientifically as Chondrus crispus, which means something like “curly cartilage”.

chondrus_crispus

The Irish moss usually appears as a mass of curly cartilaginous and soft seaweed with a red or purple tinge. Photo by Wikimedia user Kontos.*

Reaching about 20 cm in length, the Irish moss is attached to the substrate by a discoid base and its thallus branches dichotomously four or five times. The width of the branches may vary from about 2 to 15 mm and the color is even more variable, ranging from green or yellowish to dark red, purple, brown or even white. As with all plants, the Irish moss has a gametophyte (haploid) and a sporophyte (diploid) form. The gametophytes have a blue iridescence (as seen in the photo above), while the sporophytes show a dotted pattern (seen above as well).

The Irish moss is edible and relatively well known among the communities living where it grows. In Ireland and Scotland, it is boiled in milk and sweetened to produce a jelly-like product. The cartilaginous or jelly-like appearance of this alga and its derivatives are due to the presence of high amounts of carrageenan, a polysaccharide that is widely used in food industry as a thickening and stabilizing agent and as a vegan alternative to gelatin.

Due to its economic importance, the Irish moss is cultivated in tanks for the extraction of carrageenan and other products. Both gametophytes and sporophytes produce carrageenans of different types that can be used for different purposes.

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References:

Chen, L. C.-M.; McLachlan, J. (1972) The life history of Chondrus crispus in culture. Canadian Journal of Botany 50(5): 1055–1060. http://doi.org/10.1139/b72-129

McCandless, E. L.; Craigie, J. S.; Walter, J. A. (1973) Carrageenans in the gametophytic and sporophytic stages of Chondrus crispus. Planta 112(3): 201–212.

Wikipedia. Chondrus crispus. Available at < https://en.wikipedia.org/wiki/Chondrus_crispus >. Access on August 1, 2017.

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Friday Fellow: Crawling Spider Alga

by Piter Kehoma Boll

The world of unicelular creatures includes fascinating species, some of which were already presented here. And today one more is coming, the marine phytoplanctonic amoeboid protist Chlorarachnion reptans, which again is a species without a common name, so I created one: crawling spider alga.

chlorarachnion_reptans

A plasmodium of the crawling spider alga Chlorarachnion reptans. Photo by Wikimedia user NEON.*

The crawling spider alga was dicovered in the Canary Islands in 1930. It is an amoeboid alga that forms plasmodia (multinucleated networks) of cells connected by thin strips of cytoplasm (reticulopodia). The reticulopodia are also used to capture prey (bacteria and smaller protists, especially algae) working kind of like a spider web. Additionally, the crawling spider alga has chloroplasts, so being able to conduct photosynthesis. It is, therefore, a mixotrophic organism, having more than one way of feeding.

The chloroplasts of the crawling spider alga, as well of other species in its group, called Chlorarachniophyceae, have four membrane layers and appears to have evolved from a green alga that was ingested and became an endosymbiont. As a result, the chloroplast of the crawling spider alga has two sets of DNA, one from the original chloroplast that came from an endosymbiotic cyanobacteria (located inside the inner membrane) and one of the green algae (between the two inner and the two outer membranes).

Although traditionally seen as a group of algae, the chlorarachniophytes are not closely related to the more “typical” algae, such as red, green, brown and golden algae or diatoms. They are actually relatives of other protists with thin net- or thread- like pseudopods, such as radiolarians and foraminifers, forming with them the group Rhizaria.

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ResearchBlogging.orgReferences:

AlgaeBase. Chlorarachnion reptans Geitler. Available at <http://www.algaebase.org/search/species/detail/?species_id=59340&gt;. Access on March 5, 2017.

EOL – Encyclopedia of Life. Chlorarachnion reptans. Available at <http://eol.org/pages/897235/overview&gt;. Access on March 5, 2017.

Hibberd, D., & Norris, R. (1984). Cytology and ultrastructure of Chlorarachnion reptans (Chlorarachniophyta divisio nova, Chlorarachniophyceae classis nova) Journal of Phycology, 20 (2), 310-330 DOI: 10.1111/j.0022-3646.1984.00310.x

Ludwig, M., & Gibbs, S. (1989). Evidence that the nucleomorphs of Chlorarachnion reptans (Chloraracnhiophyceae) are vestigial nuclei: morphology, division and DNA-DAPI fluorescence Journal of Phycology, 25 (2), 385-394 DOI: 10.1111/j.1529-8817.1989.tb00135.x

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