Chlorodendrales
Chlorodendrales | |
---|---|
Tetraselmis suecica | |
Scientific classification | |
(unranked): | Viridiplantae |
Division: | Chlorophyta |
Class: | Chlorodendrophyceae Massjuk |
Order: | Chlorodendrales Melkonian |
Families | |
Chlorodendrales are an order of green,
Habitat and ecology
Species within Chlorodendrales are found in
Cell morphology
Cell shape and size of Chlorodendrales cells varies depending on the species. The cells range greatly in size from species to species, with an upper limit of ~25 µm in length.[3] Cells can be round, ovoid, elliptical, flattened, or compressed; there is great diversity in Chlorodendrales cells.[3]
Flagellar and cell-body scales
Chlorodendrales scales are unique from other Prasinophyceae lineages because the scales fuse to form a theca, which acts as an exterior protective casing for the cell.[1] All Prasinophyceae lineages produce these external scales within the Golgi apparatus, and secrete the scales via the endomembrane system.[1] Vesicles budding from the trans-Golgi face carry the scales to the cell surface, and upon fusion release the scales to the external cell face.[1] In Chlorodendrales lineages, these scales fuse after secretion to produce the thecal wall, in which individual scales bind by cross-linking to one another.[1]
The flagellar scales and the cell body scales are structurally and functionally different, the main difference being the fusion of cell-body scales.[1] The scales also differ in size, shape, and macromolecular composition.[1] The Golgi apparatus is only capable of producing one scale-type at a time, thus, species with multiple scale-types must have different phases of thecal development separated by time and space.[1] This also means that cell body and flagellar scale production occurs separately.[1]
Scales used for taxonomic purposes and species identification
The thecae of Chlorodendrales species are often unique, and it is an important character for species identification and classification.[1] Thecate features vary greatly from species to species, in which thecae can vary between 1-5 scale layers, in scale shape, in scale size, and in molecular composition/ultrastructure.[1] These thecate features are genetically determined, and thus, they are a consistent and reliable characteristic that will not be influenced by environmental factors.[1]
Genera within Chlorodendrales
There are two genera within the order Chlorodendrales, Tetraselmis and Scherffelia. Both species are green, photoautotrophs, flagellated, and thecate.[4] The difference between the two genera is the presence or absence of pyrenoids; Tetraselmis contains pyrenoids and Scherffelia does not.[4] Flagella within the two genera are distinct in composition and morphology from species to species, which can be used to infer taxonomy and identification.[1] Both genera produce three types of flagellar scales, in scale combination, and scale patterning, is unique between species. Scales differ mainly in composition and ultrastructure, and these are the main features examined from flagellar scales when identifying species.[1] The increase in knowledge about the morphological and ultrastructural features of flagellar scales, and the ability to identify species as a result, has been due to the development of advanced microscopy and staining techniques.[1]
Phylogenetic studies
Researchers have collected and analyzed molecular data from 13 prasinophyte taxa to better construct the
References
- ^ a b c d e f g h i j k l m n o p q r Becker, B., Marin, B. and Melkonian, M. 1994: Structure, composition, and biogenesis of prasinophyte cell coverings. Protoplasma. 181: 233-244. 10.1007/BF01666398
- ^ See the NCBI webpage on Chlorodendrales. Data extracted from the "NCBI taxonomy resources". National Center for Biotechnology Information. Retrieved 2007-03-19.
- ^ a b c Arora, M., Anil, A.C., Leliaert, F., Delany, J. and Mesbahi, E. 2013: Tetraselmis indica (Chlorodendrophyceae, Chlorophyta), a new species isolated from salt pans in Goa, India. European Journal of Phycology. 48: 61-78. 10.1080/09670262.2013.768357
- ^ a b c d Norris, R.E., Hori, T., and Chihara, M. 1980: Revision of the Genus Tetraselmis (Class Prasinophyceae). Bot. Mag. Tokyo. 93: 317-339. 10.1007/BF02488737
- ^ a b c d e Nakayama, T., Marin, B., Kranz, H.D., Surek, B., Huss, V.A., Inouye, I. and Melkonian, M. 1998: The Basal Position of Scaly Green Flagellates among the Green Algae (Chlorophyta) is Revealed by Analyses of Nuclear-Encoded SSU rRNA Sequences. Protistology. 149: 367-380. 10.1016/S1434-4610(98)70043-4