Pleurosigma is mainly a
benthic genus of diatoms, whose cells are several times longer than they are wide. They present bright green
chloroplasts observed in the shape of ribbons under a
microscope. The central
nucleus composes the core of the
cytoplasm. During
anaphase, daughter
chromosomes join at the poles of the
spindle apparatus, and then move farther apart. During
telophase, the daughter nuclei are organized.
Cytokinesis starts during anaphase, where a small cleavage slices the cytoplasm into two along the valvar plane.[2] The median part of each chloroplast branches into a large, elongated lobe along the interior of one of the valves, and into two similar lobes on the other valve. Cell division begins by a fissure across the median lobe. After the division, the parts of the chloroplast migrate to the inner side of the old valves.[3]
Species
The following list displays the accepted species belonging to Pleurosigma. Many species of the genus were described by Albert Mann in 1925, but remained unrecorded due to hasty documentation. In 2002, the
type specimens of said species were reviewed in hopes of restoring their taxonomic placement; this revision brought several changes, such as the conversion of some species into
synonyms of others.[4]
^
abcdefghStidolph, Stuart R. (2002). "Observations and remarks on the morphology and taxonomy of the diatom genera Gyrosigma Hassall and Pleurosigma W. Smith V. Pleurosigma types of: a critical re-investigation". Micropaleontology. 48 (3): 273–284.
doi:
10.1661/0026-2803(2002)048[0273:OAROTM]2.0.CO;2.
^Stidolph, Stuart R. (1992). "Observations and remarks on the morphology and taxonomy of the diatom genera Gyrosigma Hassall and Pleurosigma W. Smith III. Gyrosigma sterrenburgii sp. nov., and Pleurosigma amara sp. nov". Diatom Research. 7 (2): 345–366.
doi:
10.1080/0269249X.1992.9705224.
^
abSar, Eugenia A.; Sterrenburg, Frithjof A.S.; Sunesen, Inés (2014). "Pleurosigma hinzianum sp. nov. and P. frenguellianum sp. nov. (Pleurosigmataceae, Bacillariophyta) from Argentinean coastal waters, in comparison with P. amara Stidolph and P. elongatum W. Smith". European Journal of Phycology. 49 (2): 151–164.
doi:
10.1080/09670262.2014.898101.
hdl:11336/101501.