The golden cuttlefish (Sepia esculenta) is an important cephalopod species with a lifespan of approximately one year. The species plays a crucial role in marine ecological support services and is commercially valuable in fisheries. In the seas around China, this species has emerged as the main target for cuttlefish fisheries, replacing Sepiella maindroni since the 1990s. Variations in oceanographic conditions associated with global warming could significantly impact the temporal-spatial distribution of the species. In this study, we performed bottom trawling surveys with four cruises during 2018-2019 in the East China Sea region to determine the current resource status and seasonal-spatial variations in S. esculenta. We found that the average individual weight (AIW) values were 4.87 and 519.00 g/ind at stations located at 30.50° N, 124.00° E and 30.50° N, 124.50° E, respectively, with the aggregation of larvae and parent groups in spring. The species was not distributed north of 32.00° N in summer. The catch per unit effort by weight (CPUEw) value decreased in the order of 2772.50→2575.20→503.29→124.36 g/h, corresponding to latitudes of 34.50° N→34.00° N→33.50° N→32.50° N 121.50° E in autumn. The most suitable fishing areas were the south of the East China Sea region in spring; the south of the East China Sea region extending to the center and outer parts of the East China Sea region in summer; the south of the Yellow Sea close to the Haizhou Bay fishing ground and the forbidden fishing line region of the Lusi and Dasha fishing grounds in autumn; and the south and center of the East China Sea region in winter. The most suitable sea bottom temperature (SBT) values from spring to winter were 14.76-20.53 °C, 19.54-22.98 °C, 11.79-17.64 °C, and 16.94-20.36 °C, respectively. The most suitable sea bottom salinity (SBS) values were 31.53-34.80‱ in spring, 32.95-34.68‱ in summer, 31.51-34.77‱ in autumn, and 33.82-34.51‱ in winter. We concluded the following: (1) the southern and northern areas of the East China Sea region are spawning and nursery grounds, respectively, in spring; (2) the central distribution is located at a latitude of 28.00° N in autumn and winter; and (3) the southern area of the Yangtze River to the north is a spawning ground in spring, and the areas located at 29.00-34.50° N, 124.00-124.50° E, and 28.00-30.50° N, 125.50-126.50° E are nursery grounds. The results of this study provide useful guidance for appropriate fisheries management, thereby avoiding a collapse in the S. esculenta population, which has been experienced in other species in this area.

Copper (Cu) and Cadmium (Cd), prevalent heavy metals in marine environments, have known implications in oxidative stress, immune response, and toxicity in marine organisms. Sepia esculenta, a cephalopod of significant economic value along China\'s eastern coastline, experiences alterations in growth, mobility, and reproduction when subjected to these heavy metals. However, the specific mechanisms resulting from heavy metal exposure in S. esculenta remain largely uncharted. In this study, we utilized transcriptome and four oxidative, immunity, and toxicity indicators to assess the toxicological mechanism in S. esculenta larvae exposed to Cu and Cd. The measurements of Superoxide Dismutase (SOD), Malondialdehyde (MDA), Glutathione S-Transferase (GST), and Metallothioneins (MTs) revealed that Cu and Cd trigger substantial oxidative stress, immune response, and metal toxicity. Further, we performed an analysis on the transcriptome data through Weighted Gene Co-expression Network Analysis (WGCNA) and Protein-Protein Interaction (PPI) network analysis. Our findings indicate that exposure methods and duration influence the type and the extent of toxicity and oxidative stress within the S. esculenta larvae. We took an innovative approach in this research by integrating WGCNA and PPI network analysis with four significant physiological indicators to closely examine the toxicity and oxidative stress profiles of S. esculenta upon exposure to Cu and Cd. This investigation is vital in decoding the toxicological, immunological, and oxidative stress mechanisms within S. esculenta when subjected to heavy metals. It provides foundational insights capable of advancing invertebrate environmental toxicology and informs S. esculenta artificial breeding practices.

Sepia esculenta is an economically important mollusk distributed in the coastal waters of China. Juveniles are more susceptible to stimulation by the external environment than mature individuals. The ocean salinity fluctuates due to environmental changes. However, there is a lack of research on the salinity adaptations of S. esculenta. Therefore, in this study, we investigated the differential expression of genes in S. esculenta larvae after stimulation by low salinity. RNA samples were sequenced and 1039 differentially expressed genes (DEGs) were identified. Then, enrichment analysis was performed using the Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) databases. Finally, a protein-protein interaction network (PPI) was constructed, and the functions of key genes in S. esculenta larvae after low-salinity stimulation were explored. We suggest that low salinity leads to an excess proliferation of cells in S. esculenta larvae that, in turn, affects normal physiological activities. The results of this study can aid in the artificial incubation of S. esculenta and reduce the mortality of larvae.

BACKGROUND: Cadmium (Cd) flows into the ocean with industrial and agricultural pollution and significantly affects the growth and development of economic cephalopods such as Sepia esculenta, Amphioctopus fangsiao, and Loligo japonica. As of now, the reasons why Cd affects the growth and development of S. esculenta are not yet clear.
RESULTS: In this study, transcriptome and four oxidation and toxicity indicators are used to analyze the toxicological mechanism of Cd-exposed S. esculenta larvae. Indicator results indicate that Cd induces oxidative stress and metal toxicity. Functional enrichment analysis results suggest that larval ion transport, cell adhesion, and some digestion and absorption processes are inhibited, and the cell function is damaged. Comprehensive analysis of protein-protein interaction network and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis was used to explore S. esculenta larval toxicological mechanisms, and we find that among the 20 identified key genes, 14 genes are associated with neurotoxicity. Most of them are down-regulated and enriched to the neuroactive ligand-receptor interaction signaling pathway, suggesting that larval nervous system might be destroyed, and the growth, development, and movement process are significantly affected after Cd exposure.
CONCLUSIONS: S. esculenta larvae suffered severe oxidative damage after Cd exposure, which may inhibit digestion and absorption functions, and disrupt the stability of the nervous system. Our results lay a function for understanding larval toxicological mechanisms exposed to heavy metals, promoting the development of invertebrate environmental toxicology, and providing theoretical support for S. esculenta artificial culture.

Sepia esculenta is a cephalopod widely distributed in the Western Pacific Ocean, and there has been growing research interest due to its high economic and nutritional value. The limited anti-stress capacity of larvae renders challenges for their adaptation to high ambient temperatures. Exposure to high temperatures produces intense stress responses, thereby affecting survival, metabolism, immunity, and other life activities. Notably, the molecular mechanisms by which larval cuttlefish cope with high temperatures are not well understood. As such, in the present study, transcriptome sequencing of S. esculenta larvae was performed and 1,927 differentially expressed genes (DEGs) were identified. DEGs were subjected to functional enrichment analyses using the Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) databases. The top 20 terms of biological processes in GO and 20 high-temperature stress-related pathways in KEGG functional enrichment analysis were identified. A protein-protein interaction network was constructed to investigate the interaction between temperature stress-related genes. A total of 30 key genes with a high degree of participation in KEGG signaling pathways or protein-protein interactions were identified and subsequently validated using quantitative RT-PCR. Through a comprehensive analysis of the protein-protein interaction network and KEGG signaling pathway, the functions of three hub genes (HSP90AA1, PSMD6, and PSMA5), which belong to the heat shock protein family and proteasome, were explored. The present results can facilitate further understanding of the mechanism of high temperature resistance in invertebrates and provide a reference for the S. esculenta industry in the context of global warming.

As a common and high-concentration heavy metal in the ocean, Cu can induce metal toxicity and significantly affect the metabolic function of marine organisms. Sepia esculenta is an important economic cephalopod found along the east coast of China, the growth, movement, and reproduction of which are all affected by heavy metals. Hitherto, the specific metabolic mechanism of heavy-metal exposure in S. esculenta is still unclear. In this study, we identified 1131 DEGs through transcriptome analysis of larval S. esculenta within 24 h of Cu exposure. GO and KEGG functional enrichment analysis results indicated that Cu exposure may affect purine metabolism, protein digestion and absorption, cholesterol metabolism, and other metabolic processes in S. esculenta larvae. It is worth noting that in this study we explore metabolic mechanism of Cu-exposed S. esculenta larvae through the comprehensive analysis of protein-protein interaction network and KEGG enrichment analysis for the first time and find 20 identified key and hub genes such as CYP7A1, CYP3A11, and ABCA1. Based on their expression, we preliminarily speculate that Cu exposure may inhibit multiple metabolic processes and induce metabolic disorders. Our results lay a foundation for further understanding the metabolic mechanism of S. esculenta against heavy metals and provide theoretical help for S. esculenta artificial breeding.

With extensive use of plastic products, microplastics (MPs, < 5 mm) and nanoplastics (NPs, < 1 μm) have become major pollutants in ecosystem, especially in marine environment. In recent years, researches on the impact of NPs on organisms have gradually increased. However, studies on the influence of NPs on cephalopods are still limited. Golden cuttlefish (Sepia esculenta), an important economic cephalopod, is a shallow marine benthic organism. In this study, the effect of acute exposure (4 h) to 50-nm polystyrene nanoplastics (PS-NPs, 100 μg/L) on the immune response of S. esculenta larvae was analyzed via transcriptome data. A total of 1260 DEGs were obtained in the gene expression analysis. The analyses of GO, KEGG signaling pathway enrichment, and protein-protein interaction (PPI) network were then performed to explore the potential molecular mechanisms of the immune response. Finally, 16 key immune-related DEGs were obtained according to the number of KEGG signaling pathways involved and the PPI number. This study not only confirmed that NPs had an impact on cephalopod immune response, but also provided novel insights for further unmasking the toxicological mechanisms of NPs.

As a well-known marine metal element, Cd can significantly affect bivalve mollusk life processes such as growth and development. However, the effects of Cd on the molecular mechanisms of the economically important cephalopod species Sepia esculenta remain unclear. In this study, S. esculenta larval immunity exposed to Cd is explored based on RNA-Seq. The analyses of GO, KEGG, and protein-protein interaction (PPI) network of 1,471 differentially expressed genes (DEGs) reveal that multiple immune processes are affected by exposure such as inflammatory reaction and cell adhesion. Comprehensive analyses of KEGG signaling pathways and the PPI network are first used to explore Cd-exposed S. esculenta larval immunity, revealing the presence of 16 immune-related key and hub genes involved in exposure response. Results of gene and pathway functional analyses increase our understanding of Cd-exposed S. esculenta larval immunity and improve our overall understanding of mollusk immune functions.

Marine organisms are threatened by various environmental contaminants, and nanoplastics (NPs) is one of the most concerned. Studied have shown that NPs has a certain impact on marine organisms, but the specific molecular mechanism is still unclear. At present, researches on the effect of NPs on marine life mostly focus on crustaceans, gastropods, and bivalves. In this study, cephalopod Sepia esculenta larvae were first used to investigate the potential immune response molecular mechanisms caused by PS-NPs (50 nm, 50 mg/L) short-term exposure (4 and 24 h). Through S. esculenta larvae transcriptome profile of gene expression analysis, 548 and 1990 genes showed differential expression at 4 and 24 h after NPs exposure, respectively. GO and KEGG enrichment analysis were performed to find immune related DEGs. Then, the interaction relationship between the immune related DEGs after NPs exposure was known through the constructed protein-protein interaction network. 20 hub genes were found on the base of KEGG pathway numbers involved and protein-protein interaction numbers. This research supply valuable genes for the study of cephalopod immune response caused by NPs, which can help us further uncover the molecular mechanisms of organism against NPs.

Sepia esculenta is a popular economic cephalopod with high yield, delicious meat, and rich nutrition. With the rapid development of heavy industry and medical industry, a large amount of waste has been released into the ocean recklessly in recent years, inducing a significant increase in the content of heavy metals, especially cadmium (Cd) and copper (Cu), in the ocean. This phenomenon significantly affects the growth and development of S. esculenta, causing a serious blow to its artificial breeding. In this study, transcriptome analysis is used to initially explore immune response mechanisms of Cd and Cu co-exposed juvenile S. esculenta. The results show that 1,088 differentially expressed genes (DEGs) are identified. And DEGs functional enrichment analysis results suggests that co-exposure may promote inflammatory and innate immune responses in juvenile S. esculenta. Fifteen key genes that might regulate the immunity of S. esculenta are identified using protein-protein interaction (PPI) network and KEGG enrichment analyses, of which the three genes with the highest number of interactions or involve in more KEGG pathways are identified as hub genes that might significantly affect the immune response processes. Comprehensive analysis of PPI network and KEGG signaling pathway is used for the first time to explore co-exposed S. esculenta juvenile immune response processes. Our results preliminarily reveal immune response mechanisms of cephalopods exposed to heavy metals and provide a valuable resource for further understanding of mollusk immunity.