Molecular Evidence of the Toxic Effects of Diatom Diets on Gene Expression Patterns in Copepods

Abstract

BackgroundDiatoms are dominant photosynthetic organisms in the world's oceans and are considered essential in the transfer of energy through marine food chains. However, these unicellular plants at times produce secondary metabolites such as polyunsaturated aldehydes and other products deriving from the oxidation of fatty acids that are collectively termed oxylipins. These cytotoxic compounds are responsible for growth inhibition and teratogenic activity, potentially sabotaging future generations of grazers by inducing poor recruitment in marine organisms such as crustacean copepods.Principal FindingsHere we show that two days of feeding on a strong oxylipin-producing diatom (Skeletonema marinoi) is sufficient to inhibit a series of genes involved in aldehyde detoxification, apoptosis, cytoskeleton structure and stress response in the copepod Calanus helgolandicus. Of the 18 transcripts analyzed by RT-qPCR at least 50% were strongly down-regulated (aldehyde dehydrogenase 9, 8 and 6, cellular apoptosis susceptibility and inhibitor of apoptosis IAP proteins, heat shock protein 40, alpha- and beta-tubulins) compared to animals fed on a weak oxylipin-producing diet (Chaetoceros socialis) which showed no changes in gene expression profiles.ConclusionsOur results provide molecular evidence of the toxic effects of strong oxylipin-producing diatoms on grazers, showing that primary defense systems that should be activated to protect copepods against toxic algae can be inhibited. On the other hand other classical detoxification genes (glutathione S-transferase, superoxide dismutase, catalase, cytochrome P450) were not affected possibly due to short exposure times. Given the importance of diatom blooms in nutrient-rich aquatic environments these results offer a plausible explanation for the inefficient use of a potentially valuable food resource, the spring diatom bloom, by some copepod species.

Responses of the estuarine copepod Pseudodiaptomus annandalei to diatom polyunsaturated aldehydes: Reproduction, survival and postembryonic development

“…Such adaptive response to toad venom in relation to time has been reported in many snakes (Odie and Brodie, 1990). Therefore the present study points to a bottleneck stage in copepod development beyond which they are able to survive and reproduce in the Lauritano et al (2011). Besides the ecological relevance of the study, there are aquaculture implications as Pseudodiaptomus annandalei is a preferred live feed for grouper fish larvae.…”

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

“…Several field (Jó nasdó ttir et al, 2011;Poulet et al, 2006;Wichard et al, 2008) and mesocosm investigations (Carsten et al, 2012;Gerecht et al, 2013;Koski et al, 2012;Vidoudez et al, 2011b) have also failed to correlate the quantity of PUAs produced with copepod egg production and/or hatching success. These contradictory results may reflect speciesspecific or strain-to-strain (Gerecht et al, 2011) differences in the production of PUAs, clone variability in production levels during the course of a bloom (Taylor et al, 2009) or in different years (Gerecht et al, 2011), unbalanced physiology due, for example, to nutrient-limited growth (Ribalet et al, 2009) or to the capability of some predators to detoxify these compounds or to activate defense systems against them (Lauritano et al, 2011(Lauritano et al, , 2012.…”

An improved method for achieving high-quality RNA for copepod transcriptomic studies

“…Consequently, the number of RNA-based studies in copepods has increased in recent years (e.g., Aruda et al, 2011;Barreto et al, 2011;Flowers and Burton, 2006;Hansen et al, 2008aHansen et al, , 2008bHansen et al, , 2009Hansen et al, , 2010Ki et al, 2009;Kim et al, 2011;Lauritano et al, 2011aLauritano et al, , 2011bLauritano et al, , 2012aRhee et al, 2009;Seo et al, 2006aSeo et al, , 2006bSeo et al, , 2006cTarrant et al, 2008;Voznesensky et al, 2004). Most of these studies focused on the gene expression of the stress response proteins in the model copepod species Calanus finmarchicus and Tigriopus japonicus.…”