Many phytoplankton species produce toxic substances, but their functional role is unclear. Specifically, it remains uncertain whether these compounds have a toxic or deterrent effect on grazers; only, the latter is consistent with toxins as defensive tools. Here, we show that 10 of 12 species or strains of toxic dinoflagellates were consumed at lower rates than a similarly sized nontoxic dinoflagellate by a copepod. Through video observations of individual prey-grazer interactions, we further demonstrate that the dominating mechanism is through capture, examination, and subsequent rejection of vital cells, that is, a true deterrent effect that offers a straightforward explanation to its evolution. We argue that the diversity of grazer responses to toxic phytoplankton reported in the literature, including toxic effects, and the high diversity of toxin profiles between strains of the same phytoplankton species reflect different stages of an ever-ongoing evolutionary arms race, facilitated by rapid adaptation of grazers to toxic substances. We further argue that defensive toxicity requires a chemical signal exterior to the cell that informs the grazer about the toxicity of the cell. The signal can be the toxin itself or just an aposematic signal of toxicity. In the former case, allelochemical effects may emerge at high cell concentrations as a nonadaptive side effect of a predator defenses.
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http://dx.doi.org/10.1002/ecy.2479 | DOI Listing |
J Hazard Mater
December 2024
Center for Marine Studies, Federal University of Paraná, Pontal do Paraná, Brazil.
Microplastics (MP) are suitable substrates for the colonization of harmful microalgal cells and the adsorption of their lipophilic compounds including phycotoxins. Moreover, such interactions likely change as physical-chemical characteristics of the MP surface are gradually modified during plastic degradation in aquatic environments. Using a combination of innovative laboratory experiments, this study systematically investigated, for the first time, the influence of various MP characteristics (polymeric composition, shape, size, and/or surface roughness) on its capacity to carry both living harmful algal cells and dissolved phycotoxins.
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January 2025
MOE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences (Qingdao 266003), and Key Laboratory of Tropical Aquatic Germplasm of Hainan Province, Sanya Oceanographic Institution (Sanya 572024), Ocean University of China, China. Electronic address:
Heat shock proteins (Hsps) are highly conserved molecular chaperones with essential roles against biotic and abiotic stressors. A large set of co-chaperons comprising J-domain proteins (DnaJs) regulate the ATPase cycle of Hsp70s with Hsp90s, together constituting a dynamic and functionally versatile network for protein folding/unfolding and regulation. Marine bivalves could accumulate and tolerate paralytic shellfish toxins (PSTs), the well-noted neurotoxins generated during harmful algal blooms.
View Article and Find Full Text PDFSci Rep
January 2025
Department of Landscape Architecture, Poznań University of Life Sciences, 159 Dąbrowskiego Street, Poznań, 60-594, Poland.
As a result of human activities, surface waters worldwide are experiencing increasing levels of eutrophication, leading to more frequent occurrences of microalgae, including harmful algal blooms. We aimed to investigate the impact of decomposing camelina straw on mixed phytoplankton communities from eutrophic water bodies, comparing it to the effects of barley straw. The research was carried out in 15 aquaria (five of each type - containing no straw, camelina straw, and barley straw).
View Article and Find Full Text PDFJ Aquat Anim Health
December 2024
Virginia Institute of Marine Science, William & Mary, Gloucester Point, Virginia, USA.
Objective: The dinoflagellate Alexandrium monilatum forms blooms during summer in tributaries of the lower Chesapeake Bay. Questions persist about the potential for A. monilatum to negatively affect aquatic organisms.
View Article and Find Full Text PDFToxins (Basel)
December 2024
Ifremer, PHYTOX Research Unit, F-44000 Nantes, France.
Harmful algal blooms (HABs) formed by toxic microalgae have seriously threatened marine ecosystems and food safety and security in recent years. Among them, has attracted the attention of scientists and society due to its acute and rapid neurotoxicity in mice. Herein, the growth and gymnodimine A (GYM-A) production of were investigated in diverse culture systems with different surface-to-volume (S/V) ratios and nitrogen/phosphorus concentrations.
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