Persistent exposure to artificial light at night (ALAN) accelerates metamorphosis and colonization in larvae of marine shellfish

The ongoing course of urbanization has led to excessive use of artificial light at night (ALAN), which has rapidly become an important source of pollution in many cities. The Pacific abalone (Haliotis discus hannai) Larvae were kept under a 12/12 h light/dark photoperiod (DD) in order to determine the effects of ALAN on embryonic development. To simulate the street lighting conditions at night, the artificial light was switched on from 18:00 until midnight (AD) or until 06:00 the next day (ND). Moreover, Groups AD and ND had a considerably greater hatching success rate and metamorphosis rate than Group DD (P < 0.05), whereas Group DD had a significantly longer hatching period and course to complete the metamorphosis of the larvae (P < 0.05). Transcriptomic analyses showed that members of Groups AD and DD had considerably higher expression levels of genes involved in ribosome biogenesis, spliceosome function, and the mRNA surveillance pathway. Prostaglandin B2, L-palmitoylcarnitine, stearic acid, palmitic acid, leukotriene C4, and arachidonic acid were screened by non-targeted metabolomics as differential metabolic markers that played a vital role in the response of larvae to different ALAN conditions. Multi-omics correlation analysis suggested that five pathways related to fatty acid synthesis, catabolism, and metabolism, such as biosynthesis of unsaturated fatty acids and arachidonic acid metabolism, were enriched in each comparison. Further quantitative analysis showed that compared to Group DD, 33 out of 50 fatty acids were upregulated in Group AD, and the levels of almost all fatty acids were increased in Group ND, which in turn suggested that fatty acids played a vital role in the physiological response of larvae to illumination changes. The findings of this work were significant for the unbiased and full-scale assessment of the ecological effects of ALAN, as well as the structural stability of the marine benthic community