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The
euglenoids (or euglenids) include a diversity of nutrition types from fully
autotrophic to auxotrophic (requiring specific metabolites), to colorless -
either osmotrophic (absorbing organic energy sources), or fully heterotrophic
(phagotrophic - taking in particles through their cytoplasmic membrane). PhycoKey
is based primarily on morphological traits.
Since the 1980s molecular investigations have repeatedly revised
evolutionary relationships among genomes, and this has led to a large
increase in Operational Taxonomic Units (OTUs) far more advanced than just
morphological and ecological defiitions.
A summary is De Mecudo and Menezes (2016). Reproduction
is apparently asexual throughout the class, as there are no published
observations of reduction division (meiosis) or fusion of nuclei.. The
periplast, composed of proteinaceous strips, is unique to the group:
Diagram
of periplast indicating arrangement of protein strips (gray and green),
microtubules (red) and endoplasmic reticulum (light brown). Modified by Tree of Life from Leander et
al. (2007) and posted online. The
strips of protein can be separated by applying pressure (Leedale 1967):
Two of
the strips bear ‘warts’ (thickenings on wall easily seen in intact
cells). Dark bodies are chloroplasts. |
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References: |
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De
Bicudo, C. and M. Menezes (2016). Phylogeny
and Classification of Euglenophyceae: A Brief Review. Frontiers
in Ecological Evolution 4:1-13.
Leander, B.S., H.J. Esson and S.A. Greglia 2007. Macroevolution of complex cytoskeletal systems in euglenids. BioEssays 29:987-1000. Leedale, G.F. 1967. Euglenoid flagellates. Prentice-Hall Biological Science Series. (242 pp).
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