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.
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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AlgaeBase. Chlorarachnion reptans Geitler. Available at <http://www.algaebase.org/search/species/detail/?species_id=59340>. Access on March 5, 2017.
EOL – Encyclopedia of Life. Chlorarachnion reptans. Available at <http://eol.org/pages/897235/overview>. 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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