Hemocyanin, an oxygen-transport protein, is widely distributed in the hemolymph of marine arthropods and mollusks, playing an important role in their physiological processes. Recently, hemocyanin has been recognized as a multifunctional glycoprotein involved in the immunological responses of aquatic invertebrates. Consequently, the link between hemocyanin functions and their potential applications has garnered increased attention. This review offers an integrated overview of hemocyanin\'s structure, physicochemical characteristics, and bioactivities to further promote the utilization of hemocyanin derived from marine products. Specifically, we review its implication in two aspects of food and aquaculture industries: quality and health. Hemocyanin\'s inducible phenoloxidase activity is thought to be an inducer of melanosis in crustaceans. New anti-melanosis agents targeted to hemocyanin need to be explored. The red-color change observed in shrimp shells is related to hemocyanin, affecting consumer preferences. Hemocyanin\'s adaptive modification in response to the aquatic environment is available as a biomarker. Additionally, hemocyanin is endowed with bioactivities encompassing anti-microbial, antiviral, and therapeutic activities. Hemocyanin is also a novel allergen and its allergenic features remain incompletely characterized.

Crinoids (Echinodermata) exhibit unique morphological and behavioral characteristics that facilitate a wide range of symbiotic relationships with diverse organisms. Our comprehension of their interactions with microscopic copepod crustaceans is, however, still in a nascent and fragmented state. Here, we review and discuss the 166 literature records to date in which a total of 39 copepod species in 6 families have been reported in association with 33 species of the crinoid order Comatulida. Many of these associations have been reported just once. The respective localities cover 5 of the World Ocean\'s 12 ecoregions, with a notable concentration of both host and symbiont diversity in the Central and Western Indo-Pacific. In contrast, the documentation of copepod-crinoid associations in the Atlantic appears markedly limited. Copepods have been found predominantly in ectosymbiotic relationships with crinoids, with a lower incidence of endosymbiosis. Copepods of the genera Collocheres Canu, 1893 and Pseudanthessius Claus, 1889 are particularly prominent in the list, and the comatulid family Comatulidae displays the most diverse assortment of copepod associations. The current scope of knowledge encompasses a mere 5% of the potential crinoid host diversity, underscoring the need for more extensive research in this area.

As new organic flame retardants, chlorinated organophosphate esters (Cl-OPEs) have high water solubility and structural similarity to organophosphate pesticides, posing risks to aquatic organisms. The potential neurotoxicity of Cl-OPEs has attracted attention, especially in marine invertebrates with a relatively simple nervous system. In this study, a marine rotifer with a cerebral ganglion, Brachionus plicatilis, was exposed to tris (1,3-dichloro-2-propyl) phosphate (TDCPP) (two environmental concentrations and one extreme level), and the changes in feeding and swimming behaviors and internal mechanism were explored. Exposure to 1.05 nM TDCPP did not change the filtration and ingestion rates of rotifers and average linear velocity. But 0.42 and 4.20 μM TDCPP inhibited these three parameters and reduced unsaturated fatty acid content, reproduction and population growth. All TDCPP test concentrations suppressed AChE activity, causing excessive accumulation of acetylcholine within rotifers, thereby disturbing the neural innervation of corona cilia. Molecular docking and molecular dynamics revealed that this inhibition was because TDCPP can bind to the catalytic active site of rotifer AChE through van der Waals forces and electrostatic interactions. TRP420 was the leading amino residue in the binding, and GLY207 contributed to a hydrogen bond. Nontargeted metabolomics using LC-MS and GC-MS identified differentially expressed metabolites in TDCPP treatments, mainly from lipid and lipid-like molecules, especially sphingolipids. TDCPP decreased ganglioside content but stimulated ceramide generation and the expression levels of 3 genes related to ceramide de novo synthesis. The mitochondrial membrane potential (MMP) and ATP content decreased, and the electron respiratory chain complex and TCA cycle were deactivated. An inhibitor of ceramide synthase, fumonisin, alleviated MMP and ATP, implying a critical role of ceramide in mitochondrial dysfunction. Thus, TDCPP exposure caused an energy supply deficit affecting ciliary movement and ultimately inhibiting rotifer behaviors. Overall, this study promotes the understanding of the neurotoxicity of Cl-OPEs in marine invertebrates.

Ocean acidification (OA) and trace metal pollutants coexist to exert combined effects on the functions and services of marine ecosystems. Increasing atmospheric carbon dioxide has caused a decrease in the pH of the ocean, affecting the bioavailability and speciation of trace metals and consequently altering metal toxicity in marine organisms. As an important trace metal functioned in hemocyanin, the richness of Copper (Cu) in octopuses is remarkable. Therefore, the biomagnification and bioaccumulation capacities of Cu in octopuses may be a non-negligible risk of contamination. Here, Amphioctopus fangsiao was continuously exposed to acidified seawater (pH 7.8) and copper (50 μg/L) to investigate the combined effect of ocean acidification and Cu exposure on marine mollusks. Our results showed that A. fangsiao could adapt well to ocean acidification after 21 days of the rearing experiment. However, the accumulation of Cu in A. fangsiao intestine increased significantly in acidified seawater under high levels of Cu stress. In addition, Cu exposure can influence the physiological function of A. fangsiao, including growth and feeding. This study also demonstrated that Cu exposure disturbed glucolipid metabolism and induced oxidative damage to intestine tissue, and ocean acidification further exacerbated these toxic effects. The obvious histological damage and microbiota alterations were also caused by Cu stress and its combined effect with ocean acidification. At the transcription level, we found numerous differentially expressed genes (DEGs) and significantly enriched KEGG pathways, involving glycolipid metabolism, transmembrane transport, glucolipid metabolism, oxidative stress, mitochondrial, protein and DNA damage, all revealing the strong toxicological synergetic effect of Cu and OA exposure and the molecular adaptation mechanism of A. fangsiao. Collectively, this study demonstrated that octopuses may withstand future ocean acidification conditions, however, the complex interactions of future OA and trace metal pollution need to be emphasized. OA can influence the toxicity of trace metals, inducing a potential threat to marine organism safety.

The ubiquitous presence of pentachlorophenol (PCP) in ocean environments threatens marine organisms. However, its effects on immunity of marine invertebrates at environmentally realistic levels are still largely unknown. In this study, the immunotoxicity of PCP to a representative bivalve species was evaluated. In addition, its impacts on metabolism, energy supply, detoxification, and oxidative stress status were also analysed by physiological examination as well as comparative transcriptomic and metabolomic analyses to reveal potential mechanisms underpinning. Results illustrated that the immunity of blood clams was evidently hampered upon PCP exposure. Additionally, significant alterations in energy metabolism were detected in PCP-exposed clams. Meanwhile, the expressions of key detoxification genes and the in vivo contents (or activity) of key detoxification enzymes were markedly altered. Exposure to PCP also triggered significant elevations in intracellular ROS and MDA whereas evident suppression of haemocyte viability. The abovementioned findings were further supported by transcriptomic and metabolomic analyses. Our results suggest that PCP may hamper the immunity of the blood clam by (i) constraining the cellular energy supply through disrupting metabolism; and (ii) damaging haemocytes through inducing oxidative stress. Considering the high similarity of immunity among species, many marine invertebrates may be threatened by PCP, which deserves more attention.

Tetrabromobisphenol A (TBBPA) pollution in marine environmental media poses great risks to marine organisms due to its potential endocrine-disrupting effects. However, limited attention of TBBPA\'s endocrine-disrupting effects has been paid on marine invertebrates. In this work, the reproductive endocrine-disrupting effects of TBBPA were evaluated by observing the gametes development, quantifying the gender-specific gene expression, and determining vertebrate sex hormones in mussels Mytilus galloprovincialis treated with TBBPA for 30 days. Additionally, transcriptomic profiling and enzymes activities were conducted to investigate the potential mechanisms of reproductive endocrine-disrupting effects. We found that promotion of gametogenesis and alterations of vertebrate sex hormones occurred in TBBPA-treated mussels of both sexes. Meanwhile, estrogen sulfotransferase (SULT1E1) and steroid sulfatase (STS) were up-regulated at transcript level as a result of TBBPA treatments, suggesting that TBBPA disrupted the steroidogenesis in mussels through promoting steroids sulfonation and hydrolysis of sulfate steroids. The induction of SULTs for TBBPA biotransformation might be responsible for the dysregulation of steroidogenesis and steroids metabolism. Overall, these findings provide a new insight into assessing impact of TBBPA as well as TBBPA biomonitoring in marine environment.

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The interplay between historical and contemporary processes can produce complex patterns of genetic differentiation in the marine realm. Recent mitochondrial and nuclear sequence analyses revealed cryptic speciation in the Japanese mantis shrimp Oratosquilla oratoria. Herein, we applied nuclear microsatellite markers to examine patterns and causes of genetic differentiation in this morphotaxon. Population structure analyses revealed two genetically divergent and geographically structured clades in O. oratoria, one dominating the temperate zone of the Northwestern (NW) Pacific and the other occurring in the subtropical and tropical waters where are influenced by the Kuroshio Current. Two sympatric zones, one around the Changjiang Estuary in China coast and the other in the northern Japan Sea, were demonstrated to be hybrid zones where introgressive hybridization occurred asymmetrically. The interaction between historical climate shifts and contemporary factors (e.g., freshwater discharge, temperature gradient and isolation by distance) may contribute to the present-day genetic architecture in the Japanese mantis shrimp. Range shift induced by climate changes and oceanographic factors may promote hybridization and gene flow between the O. oratoria complex. Our results provide insights into the interacting mechanisms that give rise to diversification and speciation of coastal species in the NW Pacific.

Organisms respond to severe environmental changes by entering into hypometabolic states, minimizing their metabolic rates, suspending development and reproduction, and surviving critical ecological changes. They come back to an active lifestyle once the environmental conditions are conducive. Marine invertebrates live in the aquatic environment and adapt to environmental changes in their whole life. Sea cucumbers and sponges are only two recently known types of marine organisms that aestivate in response to temperature change. Sea cucumber has become an excellent model organism for studies of environmentally-induced aestivation by marine invertebrates. DNA methylation, the most widely considered epigenetic marks, has been reported to contribute to phenotypic plasticity in response to environmental stress in aquatic organisms. Most of methylation-related enzymes, including DNA methyltransferases, Methyl-CpG binding domain proteins, and DNA demethylases, were up-regulated during aestivation. We conducted high-resolution whole-genome bisulfite sequencing of the intestine from sea cucumber at non-aestivation and deep-aestivation stages. Further DNA methylation profile analysis was also conducted across the distinct genomic features and entire transcriptional units. A different elevation in methylation level at internal exons was observed with clear demarcation of intron/exon boundaries during transcriptional unit scanning. The lowest methylation level occurs in the first exons, followed by the last exons and the internal exons. A significant increase in non-CpG methylation (CHG and CHH) was observed within the intron and mRNA regions in aestivation groups. A total of 1393 genes were annotated within hypermethylated DMRs (differentially methylated regions), and 749 genes were annotated within hypomethylated DMRs. Differentially methylated genes were enriched in the mRNA surveillance pathway, metabolic pathway, and RNA transport. Then, 24 hypermethylated genes and 15 hypomethylated genes were Retrovirus-related Pol polyprotein from transposon (RPPT) genes. This study provides further understanding of epigenetic control on environmental induced hypometabolism in aquatic organisms.

The rapid pace of increasing oceanic acidity poses a major threat to the fitness of the marine ecosystem, as well as the buffering capacity of the oceans. Disruption in chemical equilibrium in the ocean leads to decreased carbonate ion precipitation, resulting in calcium carbonate saturation. If these trends continue, calcifying invertebrates will experience difficultly maintaining their calcium carbonate exoskeleton and shells. Because malfunction of exoskeleton formation by calcifiers in response to ocean acidification (OA) will have non-canonical biological cascading results in the marine ecosystem, many studies have investigated the direct and indirect consequences of OA on ecosystem- and physiology-related traits of marine invertebrates. Considering that evolutionary adaptation to OA depends on the duration of OA effects, long-term exposure to OA stress over multi-generations may result in adaptive mechanisms that increase the potential fitness of marine invertebrates in response to OA. Transgenerational studies have the potential to elucidate the roles of acclimation, carryover effects, and evolutionary adaptation within and over generations in response to OA. In particular, understanding mechanisms of transgenerational responses (e.g., antioxidant responses, metabolic changes, epigenetic reprogramming) to changes in OA will enhance our understanding of marine invertebrate in response to rapid climate change.