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Near future pH conditions severely impact calcification, metabolism and nervous system in the pteropods Heliconoides inflatus

ABSTRACT: Shelled pteropods play key roles in the global carbon cycle and foodwebs of various ecosystems. Their thin external shell is extremely sensitive to changes in pH and shell dissolution has already been observed in areas where aragonite saturation state is ~ 1. A decline in pteropod abundance has the potential to disrupt trophic networks and directly impact commercial fisheries. Therefore it is crucial to understand how pteropods will be affected by global environmental change, particularly ocean acidification. In the present study, physiological and molecular approaches were used to investigate the response of the Mediterranean pteropod, Heliconoides inflatus, to pH values projected for 2100 under a moderate emissions trajectory (RCP6.0). Pteropods were subjected to pHT 7.9 for 3d and gene expression levels, calcification and respiration rates measured relative to pHT 8.1 controls. Gross calcification decreased markedly under low pH conditions, while genes potentially involved in calcification were up-regulated, reflecting the inability of pteropods to maintain calcification rates. Gene expression data imply that under low pH conditions both metabolic processes and protein synthesis may be compromised, while genes involved in acid-base regulation were up-regulated. A large number of genes related to nervous system structure and function were also up-regulated in the low pH treatment, including a GABAA receptor subunit. This is particularly interesting because GABAA receptor disturbances, leading to altered behaviour, have been documented in several other marine animals after exposure to elevated CO2. The up-regulation of many genes involved in nervous system function suggests that, in addition to its impacts on other aspects of biology, exposure to low pH could have major effects on pteropod behavior. This study not only illustrates the utility of combining physiological and molecular approaches, but also highlights the desirability of including behavioural analyses in studies aimed at understanding the impacts of low pH on marine animals.

ORGANISM(S): Heliconoides inflatus

PROVIDER: GSE77934 | GEO | 2017/01/04

SECONDARY ACCESSION(S): PRJNA312154

REPOSITORIES: GEO

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Project description:Bivalves are well known sentinel organism in the detection of environmental pollutants. Bioaccumulation of these contaminants in bivalves often manifests as specific alterations of their biological processes, which are used as biomarkers for environmental pollution. Tributyltin (TBT) is one such pollutant previously used as a biocide in marine antifouling paints, it now causes a number deleterious effects in bivalves leaching out of sediments in marine ecosystems. One effect extensively documented is shell abnormalities, including shell thickening and chambering. Changes in amino acid compositions of the shell matrix are associated with these deformations suggesting that TBT mode of action influences the biological control of shell biomineralization. This environmental toxicants effect on shell biomineralization was analyzed in this investigation at a transcriptional level in order to elucidate the normal shell biomineralization process. P. maxima animals were exposed to TBT in laboratory conditions and a concentration range for chronic and acute toxicity has been established. Animals exposed to chronic concentrations were analyzed for differential gene expression using PmaxArray 1.0 microarray platform and compared against control animals. Genes indentified as differentially expressed in association with TBT exposure included up-regulation of immunity and detoxification related genes and down-regulation of several shell matrix genes. A number of novel transcripts were additionally identified. The potential actions of these genes are discussed with reference to TBT toxicity and shell biomineralization. This investigation has used a microarray to determine transcriptional effects of TBT on P. maxima and proposed the involvement of novel components in shell formation, aiding the elucidation of the process. Keywords: Expression profiling by array, stress response In order to determine to differential expression profiles for transcripts relevant to TBT exposure, 9 animals treated with TBT 50 ng1-1 were compared to 9 control animals untreated on a dual channel (Cy3 and Cy5) cDNA microarrays. The RNA for the 9 control animals was pooled together for a common reference while the RNA from the 9 treated animals was separated into 3 pooled replicates, each containing RNA from 3 individual animals. Each of the pooled treatment replicates were labeled (Cy3 or Cy5) as was the controls (opposing treatment label) and hybridized to a separate microarray chip, totaling 3 chips. Each chip had duplicate spot grids printed on the left and right of the chip providing technical replication. In total 6 microarrays were challenged and analyzed comprising 3 biological replicates each with 2 technical replicates.

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Near future pH conditions severely impact calcification, metabolism and nervous system in the pteropods Heliconoides inflatus

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