| The marine environment is subject to a wide range of anthropogenic noise impacts,with the main sources of noise being seismic surveys for oil and gas exploration,commercial shipping,sonar and pile driving.Over the past century,increasing levels of anthropogenic noise have been introduced into the marine environment,particularly from ships,which has led to increasing concern about the potential effects of ship noise on aquatic animals.This mainly includes potential effects on animal behavior through masking of auditory sounds,actual physical damage to various tissues,or the generation of neuroendocrine mediated stress.The degree of damage to aquatic animals from noise exposure depends mainly on the characteristics of the sound,including frequency,intensity and duration.The Yangtze River is an important "golden waterway" in China,and with the economic development,the demand for shipping is increasing,but at the same time brings more frequent underwater noise from ships.The mechanism of the role of traps in hearing is still unclear,and the response mechanism of hybrid sturgeon under the exposure to underwater noise from ships is unknown.Therefore,simulating the underwater noise environment,using tissue sectioning,transcriptome,metabolome and other means to study the specific mechanism of trap tissue action in hearing and the response mechanism of ship noise hybrid sturgeon,can provide important basic information for the study of noise impact on fish,and also provide basic data support for the evaluation of ship noise impact on rare fish in Yangtze River.1.Fish skin sensory organs can generally be divided into four types of sensory buds,traps,lateral lines and Loren’s apparatus,these skin sensory organs have mechanical sensation,temperature sensation and electrical sensation and other functions.The more complex structure of the skin sensory organ is in the shape of a concave mound,called the pit organ,also known as the hillock.The ultrastructural observation of the traps of hybrid sturgeon and Chinese sturgeon(Acipenser sinensis)showed that the traps of hybrid sturgeon and Chinese sturgeon were structurally similar,but the traps of Chinese sturgeon were distributed in different locations with different densities,different colors,and asymmetric distribution.Scanning electron microscopy revealed that the traps in the same cluster were distributed in different angles in three dimensions.Combined with previous studies,we found that the increased electroreceptive capacity of sturgeon with individual development was not only due to more electroreceptive organs,but also might be related to the increase of trap width.Nissler staining revealed more peripheral nerves under the receptor cells and supporting cells of the trap tissue,which can conduct electrical signals to the central nerve,which may be a key step in the electrical signal transmission of the trap.Unlike the sound transmission in the inner ear,the special electrical signal transmission mechanism of the trap may play an important role in fish hearing.2.Ship noise has a significant impact on the auditory and physiological aspects of fish,and a multi-omics approach was used to investigate the adaptation mechanisms of hybrid sturgeon to ship noise,with a control group and a noise group(simulated ship noise: 12 h),and liver tissue extracted for high-throughput transcriptome and metabolome sequencing.The analysis of simulated underwater noise showed that the energy of underwater noise in the noise group was concentrated in the frequency: 300 Hz ～ 800 Hz,peak 380 Hz,sound pressure level SPL: 155 d B re 1 u Pa.It is known that the most sensitive hearing range of sturgeon is 100 Hz ～ 500 Hz,and there is an overlapping frequency band between the noise spectrum of the ship and its auditory threshold sensitive area,which meets the requirements of the experimental design.The metabolome data showed that there were 58 differential metabolites.The differential metabolites were mainly concentrated in carbohydrates,amino acids,lipids,steroids,nucleotides and other substances.Glucose metabolism and its downstream amino acid metabolism were upregulated in the liver tissue of hybrid sturgeon after noise exposure,and metabolic pathways related to nucleotide metabolism(pyrimidine metabolism and purine metabolism)were inhibited under ship noise exposure.Thus,underwater noise exposure inhibited DNA replication,RNA transcription and translation,and protein synthesis in hybrid sturgeon.Also riboflavin,vitamin D3 and flavin adenine dinucleotide(FAD)metabolic pathways were down-regulated,indicating that noise exposure affected normal energy conversion in hybrid sturgeon.Finally,arachidonic acid metabolism,cytochrome P450 metabolism and lipid metabolism were inhibited,suggesting that noise exposure has potential effects on glycolipid metabolism in the liver of hybrid sturgeon.3.Transcriptome results showed that a total of 588 differentially expressed genes(DEGs)were detected.The results showed that the expression of genes related to immune-related factors,cell growth,death and motility were upregulated in the noise group.Genes related to carbohydrates,amino acids,and membrane structured organelles(proteasome,lysosome and phagosome)were upregulated in the noise group.Meanwhile,genes related to nucleotide and vitamin D3 metabolism appeared mainly down-regulated in the noise group.The combined transcriptome and metabolome analysis showed that under noise stress,hybrid sturgeon cells showed enhanced apoptosis and cell motility,inhibition of DNA replication,RNA transcription and translation,and protein synthesis,as well as inhibition of lipid metabolism,nucleotide metabolism,and vitamin D3 metabolic pathways.Fortunately,the initiation of the immune response ensured normal immune competence of the hybrid sturgeon.In addition,the material and energy requirements of hybrid sturgeon under noise stress were ensured by the upregulation of carbohydrate and amino acid metabolic pathways. |
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