Effect of static magnetic field on marine mollusc Elysia leucolegnote

Abstract

Artificial magnetic fields are unavoidable environment for offshore marine organisms. With the substantially increasing submarine cables, the impact of magnetic field generated by cables on marine organisms has gradually attracted people's attention. However, there are few studies on the effect of magnetic field on molluscs. To explore whether magnetic fields could interfere with the physiological functions of offshore molluscs, here we systematically analyzed the change of metabolism and transcriptome of Elysia leucolegnote exposed to either geomagnetic field or 1.1 T static magnetic field. The blood glucose and lipid levels, as well as the activities of antioxidant enzymes in E. leucolegnote were significantly increased upon the exposure to high static magnetic field for 10 days. Meanwhile, the activities of enzymes related to digestive performance and liver functions were decreased. Possible mechanisms were further revealed through comparative transcriptome analysis. A total of 836 differentially expressed genes were identified, 352 of which were up-regulated and 484 of which were down-regulated after exposure to the high static magnetic field. The up-regulated differential genes were mainly concentrated in lysosomal and apoptotic pathways, and down-regulated differential genes were mainly involved in digestive and immune systems including phagocytosis. This pattern was further confirmed by RT-qPCR analysis. In conclusion, prolonged exposure to a 1.1 T static magnetic field increased oxidative stress and blood glucose and lipid levels, and decreased immunity and physiological conditions in E. leucolegnote. The data we presented here provides a comprehensive view of metabolism change and gene expression pattern of E. leucolegnote exposed to static magnetic field. It may expand our knowledge on the magnetic field effects on offshore mollusc at molecular level, and contribute to clarification of the interaction between marine animals and artificial magnetic fields, which is certainly ecologically important.

Keywords: Elysia leucolegnote; apoptosis; digestive; geomagnetic field; oxidative stress; static magnetic field; transcriptomics.

FIGURE 1

A schematic representation of the experimental setup. (A) Illustration of E. leucolegnote exposed to SMF provided by a permanent magnet. (B) Magnetic field distribution on the magnet surface measured by a magnet analyzer. The black rectangle represents the area where E. leucolegnote were placed.

FIGURE 2

The effect of 1.1 T static magnetic field on blood glucose and lipid of E. leucolegnote. Glucose levels (A), Triglyceride levels (B) and Total cholesterol levels (C) of E. leucolegnote were compared between the geomagnetic field group and 1.1 T static magnetic field group by Student’s t-test. *p < 0.05.

FIGURE 3

The 1.1 T static magnetic field caused oxidative stress in E. leucolegnote. Enzyme activities of catalase (A), superoxide dismutase (B), glutathione (C), glutathione peroxidase (D), lysozyme (E), aspartate aminotransferase (F) and alanine transaminase (G) of E. leucolegnote exposed to 1.1 T SMF and GMF group were measured and compared. All comparisons were made between the GMF group and SMF group by Student’s t-test. *p < .05.

FIGURE 4

The effect of 1.1 T static magnetic field on digestive enzyme activity of E. leucolegnote. The enzyme activities of amylase (A), lipase (B) pepsin (C) and trypsin (D) of E. leucolegnote exposed to 1.1 T SMF and GMF were measured and compared. All comparisons were made between the GMF group and SMF group by Student’s t-test. *p < .05.

FIGURE 5

Comparative transcriptomic analysis of E. leucolegnote exposed to 1.1 T static magnetic field and geomagnetic field. (A) The number of up- and down-regulated DEGs were identified in the 1.1 T SMF and GMF treatment. (B–F) GO term annotation analysis (B), GO term enrichment analysis (C, D) and KEGG enrichment analysis (E, F) to mapping the DEGs in response to 1.1 T SMF treatment compared with GMF treatment. Pathway enrichment analysis plots (top 20) of expressed metabolisms according to p < .05.

FIGURE 6

GO annotations and KEGG enrichment analysis of upregulated genes of E. leucolegnote under 1.1 T static magnetic field. GO term annotation analysis (A), GO term enrichment analysis (B, C) and KEGG enrichment analysis (D, E) of upregulated genes in response to 1.1 T SMF and GMF treatment were analyzed and compared. Pathway enrichment analysis plots (top 20) of expressed metabolisms according to p < .05.

FIGURE 7

GO annotations and KEGG enrichment analysis of downregulated genes of E. leucolegnote under 1.1 T static magnetic field. GO term annotation analysis (A), GO term enrichment analysis (B, C) and KEGG enrichment analysis (D, E) of downregulated genes in response to 1.1 T SMF and GMF treatment were analyzed and compared. Pathway enrichment analysis plots (top 20) of expressed metabolisms according to p < .05.

FIGURE 8

Validation of the transcriptome expression pattern RT-qPCR. The expression levels of selected genes (see details in text) were measured and compared between 1.1 T SMF group and GMF group. Each normalized to that of the geomagnetic field group. All comparisons were made by Student’s t-test. *p < .05.