The synurids (order Synurales) are a small group of heterokont algae, found mostly in freshwater environments, characterized by cells covered in silica scales.

Characteristics

They are covered in silicate scales and spines. In Synura, these are formed on the surface of the chloroplasts, two of which are usually present, but sometimes only one divided into two lobes is seen. The cells have two heterokont flagella, inserted parallel to one another at the anterior, whose ultrastructure is a distinguishing characteristic of the group. Both asexual and isogamous sexual reproduction occur.

Morphology

[[File:2023 Synurophyte.svg|center|thumb|upright=2|Representation of a Synurophyte1. Flagellum with mastigonemes 2. Residual flagellum with swelling 3. Surface scale 4. Golgi apparatus; modifies proteins and sends them out of the cell 5. Plastid membranes (4, secondary red) 6. Thylakoid, site of the light-dependent reactions of photosynthesis 7. Nucleus 8. Endoplasmic reticulum, the transport network for molecules going to specific parts of the cell 9. Mitochondrion, creates ATP (energy) for the cell, tubular cristae 10. Lysosome, holds enzymes 11. Phagocytic vacuole with prey 12. Bristle 13. Dome 14. V-rib 15. Shield 16. Hood 17. Flange 18. ]]|undefined

Classification

Synurales are divided into three families, each with one genus:

History

The genus Synura was proposed in 1834 by the German microscopist Christian Gottfried Ehrenberg (1795–1876). The synurids were originally included among the golden algae in the order Ochromonadales as the family Mallomonadaceae or as the family Synuraceae . They were formally defined as a separate group by Andersen in 1987, who placed them in their own class Synurophyceae, based on an earlier approach of more narrowly defining major lineages of chrysophyte algae by British phycologist David Hibberd. The Chrysophyceae and Synurophyceae are currently recognized as closely related taxa within the Stramenopiles. Present classifications include the synurids as an order (Synurales) within Chrysophyceae.