Comparison of a Chilean strain of the ichthyotoxic phytoflagellate <i>Heterosigma akashiwo</i> (Raphidophyceae) with strains from France, Spain and New Zealand

Gómez, Patricia; Inostroza, Ingrid; Castro-Varela, Pablo; Silva, Jeannette; Clément, Alejandro; Rojas, Gabriel; Belmonte, Alejandra Aguilera

doi:10.1080/00318884.2021.1991685

Cited by 4 publications

(10 citation statements)

References 47 publications

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“…Our data show that the most abundant secondary pigments in the CREAN_HA03 strain were fucoxanthin and violaxanthin. Other authors also found fucoxanthin to be the most abundant carotenoid in H. akashiwo strains from other coastal areas [2] and among others Chilean strains [17]. Under high irradiance conditions, microalgal cells increase photoprotective carotenoids, such as fucoxanthin, violaxanthin, and antheraxanthin, to prevent photo-oxidative damage [25,26].…”

Section: Discussionmentioning

confidence: 89%

“…To our knowledge, this is the first formal genetic identification of H. akashiwo in Chilean waters. Previous studies carried out in Chile only identified this raphidophyte on the basis of morphological characteristics [3,12,13,17]. In terms of genetic variability, the Chilean 28S rDNA sequence showed low intraspecific genetic variability against worldwide distributed H. akashiwo genetic sequences [20].…”

Section: Discussionmentioning

confidence: 89%

“…In contrast, recent studies have reported higher growth rate values and enormous cell abundances from other Chilean H. akashiwo strains (1,000,000 cells mL −1 ) that did not relate with natural field cell densities reported from bloom events that occurred in southern Chile (max. 100,000 cells mL −1 ) [13,17]. Despite differing results being able to respond to the intraspecific variation of the strains, attention on cell count methods used in these studies must be taken.…”

Section: Discussionmentioning

confidence: 99%

“…These metabolites, along with the production of reactive oxygen species (ROS) such as hydrogen peroxide, hydroxyl radicals, and superoxide can produce severe injuries to fish gill tissues such as cell necrosis, epithelial lifting, and the alteration of chloride cells [16]. These injuries produce excessive mucus secretion that can cover the fish gills and cause asphyxiation [17]. However, ROS on their own may not be the main cause of ichthyotoxicity in this species [16].…”

Section: Introductionmentioning

confidence: 99%

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Heterosigma akashiwo in Patagonian Fjords: Genetics, Growth, Pigment Signature and Role of PUFA and ROS in Ichthyotoxicity

Flores-Leñero

Vargas-Torres

Paredes-Mella

et al. 2022

Toxins

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Heterosigma akashiwo is the only raphidophyte described for Chilean waters. A recent 2021 fish-killing bloom event of this raphidophyte ignited scientific research, but the ichthyotoxic mechanism and environmental conditions that promote its growth are still unclear. This is the first study confirming the occurrence of H. akashiwo in Chilean waters on the basis of the region D1/D2 of the 28S ribosomal gene. The pigment signature of the CREAN_HA03 strain revealed chlorophyll-a, fucoxanthin, and violaxanthin as the most abundant pigments, but profiles were variable depending on culture and field conditions. A factorial temperature–salinity growth experiment showed a maximal growth rate of 0.48 d−1 at 17 °C and 35 in salinity, but reached a maximal cell abundance of ~50,000 cells mL−1 at 12 °C and 25 in salinity. The fatty acid profile included high levels of saturated (16:0) and polyunsaturated (18:4 ω3; 20:5 ω3) fatty acids, but superoxide production in this strain was low (~0.3 pmol O2– cell−1 h−1). The RTgill-W1 bioassay showed that the H. akashiwo strain was cytotoxic only at high cell concentrations (>47,000 cells mL−1) and after cell rupture. In conclusion, salmon mortality during H. akashiwo bloom events in Patagonian fjords is likely explained by the high production of long-chain PUFAs at high cell densities, but only in the presence of high ROS production.

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Section: Discussionmentioning

confidence: 89%

Section: Discussionmentioning

confidence: 89%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Heterosigma akashiwo in Patagonian Fjords: Genetics, Growth, Pigment Signature and Role of PUFA and ROS in Ichthyotoxicity

Flores-Leñero

Vargas-Torres

Paredes-Mella

et al. 2022

Toxins

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“…The ITS-rDNA region is widely used as a DNA barcode or genetic marker in the taxonomy and phylogeny of marine raphidophyte species because the barcode sequence is easy to amplify and it has a high nucleotide dissimilarity even between closely related species (Connell 2002, Gómez et al 2022, Lum et al 2022. In this study, we observed the specificity of specific primer sets, which amplified the gDNA of the target species without amplifying off-target and non-target amplicons (Fig.…”

Section: Discussionmentioning

confidence: 99%

Quantification of the ichthyotoxic raphidophyte <italic>Chattonella marina</italic> complex by applying a droplet digital PCR

Min¹,

Kim²

2022

Algae

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Quantifying the abundance of Chattonella species is necessary to effectively manage the threats from ichthyotoxic raphidophytes, which can cause large-scale mortality of aquacultured fish in temperate waters. The identification and cell counting of Chattonella species have been conducted primarily on living cells without fixation by light microscopy because routine fixatives do not retain their morphological features. Species belonging to the Chattonella marina complex, including C. marina and C. marina var. ovata, had high genetic similarities and the lack of clear morphological delimitations between the species. To estimate the abundance of C. marina complex in marine plankton samples, we developed a protocol based on the droplet digital polymerase chain reaction (ddPCR) assay, with C. marina complex-specific primers targeting the internal transcribed spacer (ITS) region of the rDNA. Cell abundance of the C. marina complex can be determined using the ITS copy number per cell, ranging from 25 ± 1 for C. marina to 112 ± 7 for C. marina var. ovata. There were no significant differences in ITS copies estimated by the ddPCR assay between environmental DNA samples from various localities spiked with the same number of cells of culture strains. This approach can be employed to improve the monitoring efficiency of various marine protists and to support the implementation of management for harmful algal blooms, which are difficult to analyze using microscopy alone.

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Harmful Algal Blooms Negatively Impact Mugil cephalus Abundance in a Temperate Eutrophic Estuary

Bornman

Lemley

Adams

et al. 2022

Estuaries and Coasts

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Comparison of a Chilean strain of the ichthyotoxic phytoflagellate Heterosigma akashiwo (Raphidophyceae) with strains from France, Spain and New Zealand

Cited by 4 publications

References 47 publications

Heterosigma akashiwo in Patagonian Fjords: Genetics, Growth, Pigment Signature and Role of PUFA and ROS in Ichthyotoxicity

Heterosigma akashiwo in Patagonian Fjords: Genetics, Growth, Pigment Signature and Role of PUFA and ROS in Ichthyotoxicity

Quantification of the ichthyotoxic raphidophyte <italic>Chattonella marina</italic> complex by applying a droplet digital PCR

Harmful Algal Blooms Negatively Impact Mugil cephalus Abundance in a Temperate Eutrophic Estuary

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