Chemical interactions in diatoms: role of polyunsaturated aldehydes and precursors

Abstract

Summary Chemicals produced by aquatic organisms, and especially micro‐organisms, have received increasing attention in the last decade for their role in shaping interactions and communities. Several cases emphasize the fact that chemical signals or defence may modulate interspecific interactions. Notably, it has been shown that diatoms, unicellular algae and key primary producers in aquatic ecosystems produce a wide range of bioactive metabolites. Among these compounds, polyunsaturated short‐chain aldehydes in vitro strongly impair the reproduction of various potential grazers. In the field, the relationship between aldehyde production and reproductive failure in copepods remains unclear. Recent studies have suggested that these putative defence compounds may also be involved in intercellular communication and in interactions with competitors. Potential effects of the aldehyde precursors on various organisms have also been described. This review presents an overview of various results obtained in the last decade that could help us to understand the role of polyunsaturated aldehydes and their precursors in the ecology of diatoms. It is focused on the dichotomy between freshwater and marine environments. Indeed, most of the results on anti‐proliferative aldehydes concern marine planktonic diatoms, whereas they are also known to be produced by benthic and freshwater species.

The Effect of Polyunsaturated Aldehydes on Skeletonema marinoi (Bacillariophyceae): The Involvement of Reactive Oxygen Species and Nitric Oxide

“…On the other hand, PT does not produce any PUA [2]. We therefore suggest that SM recognizes OCTA and HEPTA as intracellular signaling molecules and uses them as infochemicals, while PT reacts to PUA as external deleterious stimuli (probably allelochemicals) [81]. Tests on other diatom species and/or other taxa are needed before concluding that this is a general rule in diatoms and phytoplankton.…”

Induced defences in marine and freshwater phytoplankton: a review

“…They produce a variety of chemicals that negatively affect reproductive success in copepods. These chemicals include polyunsaturated aldehydes (PUAs) and other oxylipins (reviewed by Leflaive & Ten-Hage, 2009;. Oxylipins have a range of different functions in algae, higher plants, animals and fungi, which complicates evaluations of the question whether they primarily evolved as a defence (see Flynn & Irigoien, 2009 for model-based criticism on this hypothesis for a plankton system).…”

Non-volatile oxylipins can render some diatom blooms more toxic for copepod reproduction

“…However, the beneficial role of diatoms in supporting marine food webs has been challenged by the discovery that they can produce low-molecular-weight volatile oxylipins such as polyunsaturated aldehydes (PUAs) (Miralto et al, 1999) that compromise grazer embryonic and larval development by inhibiting fertilization processes and inducing malformations in predator offspring (reviewed by Caldwell, 2009;Ianora and Miralto, 2010;Ianora et al, 2012;Leflaive and Ten-Hage, 2009;Van Donk et al, 2011).…”