Whole brain transcriptomics of intermittently fed individuals of the marine teleost Sparus aurata.

A major challenge in fish physiology is to understand the mechanisms underlying the transcriptomic responses of fish brain to food deprivation. Differential gene expression analysis identified in total 2240 transcripts that presented >2-fold change (adjusted p < 0.01) between each treatment and the control group (C). The identity of the transcripts was obtained with annotation against multiple public databases and they were grouped according to their expression patterns. The gene ontology terms that were substantially affected were identified by functional annotation analysis. Genes related to ion transport, cell cycle and cell adhesion were mainly regulated during fasting and refeeding. These findings contribute to identify key indicators for the molecular basis of brain functions during periods of starvation in gilthead seabream.

Identification of the abiotic stress-related transcription in little Neptune grass Cymodocea nodosa with RNA-seq.

Seagrasses exhibit vital ecological roles in the marine environment. Nevertheless, the genomic resources available for seagrasses are still scarce. In the present study, the transcriptome of Cymodocea nodosa was sequenced with a view to study the molecular mechanisms underlying abiotic stress responses. The sequenced transcriptome for the species was near-complete and a high percentage of the transcripts was computationally annotated. An experimental simulation of marine plant exposure to extreme temperature (34°C), salinity (50psu) and their combination was conducted. A dynamic transcriptome 24h response (short-term) from stress initialization was recorded. The most noteworthy alteration in gene expression was observed in heat-stressed plants. Transcripts associated with development, photosynthesis, osmotic balance and stress-response were differentially expressed, under the set experimental conditions. Results indicate a potential negative interaction of heat and osmotic stress on seagrasses transcriptome.

Biochemical composition, growth, and survival of the guppy, poecilia reticulata, during chronic sublethal exposure to cadmium

The survival, growth, and biochemical composition (protein, total lipid, total carbohydrate, free reducing sugars, RNA, DNA) of the guppy, Poecilia reticulata, exposed to low sublethal concentrations of cadmium throughout its life cycle (beginning with 5-day-old juveniles) was studied. The purpose was to get some insight on the cause of metal toxic effects and evaluate the utility of monitoring levels of biomolecules as bioindicators of chronic toxicant effects on fish. The LC50 (48 h) of cadmium for 5-day-old Poecilia was 56.77 mg/L. The median lethal times (LT50) of Poecilia exposed to low cadmium concentrations (0.5-5 mg/L) ranged from 7.65 to 72.51 days, and could be accurately predicted by the mortality observed after 20 days of exposure. The whole-body dry weight increase of cadmium-exposed guppies presented a decline from that of the controls. These declines were statistically significant after 20 days of exposure to concentrations higher than 1 mg/L and after 30 days to concentrations higher than 0.5 mg/L. The percentage content in RNA was the only variable from the studied macrobiomolecules that significantly decreased when guppies were exposed to Cd concentrations higher than 0.5 mg/L for 30 days. The same trend was apparent in the ratio RNA/DNA. However, the ratio protein/RNA/DNA significantly increased after 10 days of growth to 1.5 mg/L and after 20 days to concentrations higher than 0.5 mg/L, thus having a predictive value for early-life history stages of Poecilia exposed to Cd.