Pseudochattonella cf. verruculosa - Phytoflagellate

Pseudochattonella cf. verruculosa – Phytoflagellate

Pseudochattonella cf. verruculosa is a phytoflagellate, Dictyochophyceae class that has abundant golden chloroplasts. It has two flagella, one of which, is directed forward, thereby allowing cell movement.

The cell size varies between 12 – 45 microns depending on the stage of its life cycle. Its surface, the cell is covered by specialized structures that resemble papillae or warts, hence the name “verrucous”. These structures are mucocysts through which mucus is discharged.

Gill, severe multifocal lamellar aneurysms, whole mount.
Gill, severe multifocal lamellar aneurysms, whole mount.

It is distributed in water bodies that fluctuate between 10 – 18 oC, salinities between 11-32 ppm and relatively high nitrate concentrations.

It has been reported in Germany, Denmark, Sweden, Norway, Japan and southern Chile. At the beginning of 2016, high and persistent densities of Pseudochattonella cf. verruculosa and A. catenella were detected in the estuarine and marine ecosystems of southern Chile.

The mechanism of toxicity is still unknown, but the most common effects include acute gill irritation and damage, reducing gas exchange efficiency. Osmotic stress can be considered as a determining factor because it would generate the lysis of the cell that accelerates the mortality of salmon.

Pseudochattonella cf. verruculosa.
Pseudochattonella cf. verruculosa.

The toxicity threshold for Pseudochattonella cf. verruculose, is <1 cell / mL, but at 11° C, this threshold increases significantly until reaching the value of 2150 cells / mL.

Affected fish show high mortalities, superficial swimming, lethargy, and they have branchial petechiae. Histopathology shows lamellar aneurysms and diffuse lamellar thrombosis, lamellar epithelial necrosis and branchial hyperplasia. Multifocal hepatic necrosis is also observed, no doubt due to hypoxaemia.




REFERENCES

  • Andersen, Nikolaj & Hansen, Per & Engell-Sørensen, Kirsten & Nørremark, LH & Andersen, Per & Lorenzen, Ellen & Lorenzen, Niels. (2015). Ichthyotoxicity of the microalga Pseudochattonella farcimen under laboratory and field conditions in Danish waters. Diseases of Aquatic Organisms. 116. 10.3354/dao02916.
  • Chang, F & Sutherland, Judith & McVeagh, Margaret & Gall, Mark. (2014). Molecular phylogeny, pigmentcomposition, toxicology and life history of Pseudochattonella cf.verruculosa (Class Dictyochophyceae) from Wellington Harbour, New Zealand. Harmful Algae. 34. 42–55. 10.1016/j.hal.2014.02.002.
  • Eckford-Soper, Lisa & Daugbjerg, Niels. (2016). A quantitative real‐time PCR assay for identification andenumeration of the occasionally co‐occurring ichthyotoxic Pseudochattonella farcimen and P. erruculosa (Dictyochophyceae) and analysis of variation in gene copy numbers during the growth phase of single and mixed cultures. Journal of Phycology. 52. 10.1111/jpy.12389.
  • Hosoi-Tanabe, Shoko & Honda, Daiske & Fukaya, Sachiko & Otake, Isamu & Inagaki, Yuji & Sako, Yoshihiko. (2007). Proposal of Pseudochattonella verruculosa gen. nov., comb. nov. (Dictyochophyceae) for a formar raphidophycean alga Chattonella verruculosa, based on 18S rDNA phylogeny and ultrastructural characteristics. Phycological Research. 55. 185 – 192. 10.1111/j.1440-1835.2007.00461.x.
  • MacKenzie, L.A., Smith, K.F., Rhodes, L.L., Brown, A., Langi, V., Edgar, M., Lovell, G., Preece, M., 2011. Mortalities of sea cage salmon (Oncorhynchus tshawytscha) due to a bloom of Pseudochattonella verruculosa (Dicyochophyceae) in Queen Charlotte Sound, New Zeland, harmful Algae 11, 45-53.
  • Montes, R. M., Rojas, X., Artacho, P., Tello, A., & Quiñones, R. A. (2018). Quantifying harmful algal bloom thresholds for farmed salmon in southern Chile, Volume 77, Pages 55-65.
  • Villanueva, Fabiola & Urrutia, Geysi & Uribe, Claudia & Seguel, Miriam & Aguilera B., Alejandra & Olivares, Bian & Varela, Daniel & Paredes, Javier. (2016). Harmful Algal Bloom of Pseudochattonella verruculosa (Dictyochophyceae, Florenciellales) associated with salmon farm mortalities in the South of Chile.. 10.13140/RG.2.2.19377.38242.

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