Transcriptomic responses of the calanoid copepod Calanus finmarchicus to the saxitoxin producing dinoflagellate Alexandrium fundyense

Abstract

In the Gulf of Maine, the copepod Calanus finmarchicus co-occurs with the neurotoxin-producing dinoflagellate, Alexandrium fundyense. The copepod is resistant to this toxic alga, but little is known about other effects. Gene expression profiles were used to investigate the physiological response of females feeding for two and five days on a control diet or a diet containing either a low or a high dose of A. fundyense. The physiological responses to the two experimental diets were similar, but changed between the time points. At 5-days the response was characterized by down-regulated genes involved in energy metabolism. Detoxification was not a major component of the response. Instead, genes involved in digestion were consistently regulated, suggesting that food assimilation may have been affected. Thus, predicted increases in the frequency of blooms of A. fundyense could affect C. finmarchicus populations by changing the individuals’ energy budget and reducing their ability to build lipid reserves.

Trophic interactions, toxicokinetics, and detoxification processes in a domoic acid‐producing diatom and two copepod species

“…Genes belonging to categories important for the transfer and processing of information transcription, signal transduction, post‐transcriptional, and post‐translational processes provide the basis for organisms to respond to their environment. Similarly, the downregulation of genes that control lipid and carbohydrate metabolisms were observed in C. finmarchicus after grazing on toxic Alexandrium for 5 d (Roncalli et al ). Furthermore, genes involved in energy metabolism were downregulated in both studies, suggesting that algal toxins, or some other unmeasured biochemical difference between species, affected the energy budget and the ability to build lipid reserves, both factors that are essential for copepod survival.…”

“…The long exposure time in our study may explain why we found only one potential stress‐related gene among the most upregulated genes and no genes involved in detoxification. Roncalli et al () found that several stress‐related genes were differently regulated after a short (2 d) exposure to toxic Alexandrium, but not after 5 d. The copepod C. helgolandicus exposed to the oxylipin‐producing diatom, Skeletonema marioni , showed differently regulated stress genes after feeding for 2 d (Lauritano et al ) and when fed a dinoflagellate ( Karenia brevis ) strain without brevetoxins but with other potentially toxic metabolites, the copepod genes showed regulation after 5 d and 8 d, but not within 3 d (Lauritano et al ).…”

“…Hierarchically clustering based on sequence similarity (% identity) was performed with the software “CD HIT suite” in a total of four steps (95% identity, 80% identity, 60% identity, 30% identity) (Li and Godzik ). The annotations were further screened for key stress‐related genes that are differently regulated in copepods after grazing on harmful algae: heat‐shock proteins, catalase, glutathione S‐transferase, and aldehyde dehydrogenase (Lauritano et al , ; Carotenuto et al ; Roncalli et al ).…”

“…Two species of Calanus have been tested for reduction in egg production and hatching success after feeding on toxic Pseudo‐nitzschia with no signs of reduction in egg production or hatching success (Miesner et al ). Another method to detect stress is measuring cellular stress, like detecting changes in gene‐expression after feeding on harmful algae (Roncalli et al ).…”

Population Genomics of Marine Zooplankton

“…There are a number of such studies of marine zooplankton, including target-gene and whole-transcriptome analyses of differential gene expression patterns associated with stress responses and environmental variability (Lauritano et al 2012;Schoville et al 2012;De Pittà et al 2013;Smolina et al 2015Smolina et al , 2016Roncalli et al 2016;Batta-Lona et al 2017). The genetic and genomic bases of such gene expression differences have received considerable attention (see review by Romero et al 2014).…”