The role of gastropods in African swine fever virus ecology.

The spread of the African swine fever virus (ASF virus) genotype ii in the Eurasian region has been very successful and often inexplicable. The virus spreads rapidly and persists in areas with wild boar populations, but areas without feral pig populations are also affected. The virus has shown the ability to survive for a long time in the environment without a population of susceptible hosts, both pigs and Ornithodoros soft ticks. Published data indicated that ASF viruses persist significantly longer in an environment with some freshwater snails (especially Pomacea bridgesii, Tarebia granifera, Asolene spixii, Melanoides tuberculate, and Physa fontinalis), compared to freshwater without snails. Data obtained in this study suggest that gastropods theoretically can be the hosts of the ASF virus. Also, we have proven the possibility of long-term existence of an infectious virus when infected in vitro.

Panmixia and local endemism: a revision of the Eubranchus rupium species complex with a description of new species.

Species of the genus Eubranchus Forbes, 1838 (Mollusca: Gastropoda: Nudibranchia) are common faunistic elements of boreal benthic ecosystems, associated with hydroid communities. Recent studies have suggested that the widely distributed trans-Arctic E. rupium (Møller, 1842) constitutes a complex of at least three candidate species, but the detailed taxonomy of the complex remains unresolved. The purpose of the present paper is to conduct an integrative taxonomic study including molecular genetic methods (a phylogenetic analysis using COI , 16S rRNA and histone H3 with application of species delimitation methods) and morphological study (light and scanning electron microscopy) of E. rupium and closely related species. The specific aims of this study were to establish the species boundaries, morphological variability, and the phylogeographic structure within this group. The phylogeographic analysis included a TCS -based network analysis, an analysis of molecular variance (AMOVA), divergence time estimations, and ancestral area reconstructions. We demonstrate that specimens initially identified as E. rupium included three distinctive species: the nominal E. rupium with an amphiboreal range, the new species Eubranchus novik sp. nov. from the Sea of Japan, for which a taxonomic description is provided in this paper, and Eubranchus sp. from the northern Kuril Islands, which requires the collection and study of additional material for formal description. Our results confirm the amphiboreal distribution of E. rupium , as no geographic structure was found across Pacific, Arctic and Atlantic populations, and the results of the AMOVA analysis showed no differences between groups of samples from different geographic regions. The divergence of the 'Eubrancus rupium species complex' is estimated from the late Miocene or the Miocene-Pliocene boundary to the late Pliocene. It is hypothesised that the most probable ancestral region for the Eubranchus rupium species complex is the north-western Pacific, and the subsequent speciation likely occurred due to dispersal followed by allopatric speciation. ZooBank: urn:lsid:zoobank.org:pub:228E0C46-0BF7-4DDD-9C00-67B50E298D65.

Morphologic, cytometric, quantitative transcriptomic and functional characterisation provide insights into the haemocyte immune responses of Pacific abalone (Haliotis discus hannai).

In recent years, the abalone aquaculture industry has been threatened by the bacterial pathogens. The immune responses mechanisms underlying the phagocytosis of haemocytes remain unclear in Haliotis discus hannai. It is necessary to investigate the immune mechanism in response to these bacterial pathogens challenges. In this study, the phagocytic activities of haemocytes in H. discus hannai were examined by flow cytometry combined with electron microscopy and transcriptomic analyses. The results of Vibrio parahaemolyticus, Vibrio alginolyticus and Staphylococcus aureu challenge using electron microscopy showed a process during phagosome formation in haemocytes. The phagocytic rate (PP) of S. aureus was higher than the other five foreign particles, which was about 63%. The PP of Vibrio harveyi was about 43%, the PP peak of V. alginolyticus in haemocyte was 63.7% at 1.5 h. After V. parahaemolyticus and V. alginolyticus challenge, acid phosphatase, alkaline phosphatase, total superoxide dismutase, lysozyme, total antioxidant capacity, catalase, nitric oxide synthase and glutathione peroxidase activities in haemocytes were measured at different times, differentially expressed genes (DEGs) were identified by quantitative transcriptomic analysis. The identified DEGs after V. parahaemolyticus challenge included haemagglutinin/amebocyte aggregation factor-like, supervillin-like isoform X4, calmodulin-like and kyphoscoliosis peptidase-like; the identified DEGs after V. alginolyticus challenge included interleukin-6 receptor subunit beta-like, protein turtle homolog B-like, rho GTPase-activating protein 6-like isoform X2, leukocyte surface antigen CD53-like, calponin-1-like, calmodulin-like, troponin C, troponin I-like isoform X4, troponin T-like isoform X18, tumor necrosis factor ligand superfamily member 10-like, rho-related protein racA-like and haemagglutinin/amebocyte aggregation factor-like. Some immune-related KEGG pathways were significantly up-regulated or down-regulated after challenge, including thyroid hormone synthesis, Th17 cell differentiation signalling pathway, focal adhesion, melanogenesis, leukocyte transendothelial migration, inflammatory mediator regulation of TRP channels, ras signalling pathway, rap1 signalling pathway. This study is the first step towards understanding the H. discus hannai immune system by adapting several tools to gastropods and providing a first detailed morpho-functional study of their haemocytes.

Dietary Clostridium autoethanogenum protein has dose-dependent influence on the gut microbiota, immunity, inflammation and disease resistance of abalone Haliotis discus hannai.

Clostridium autoethanogenum protein (CAP) is an eco-friendly protein source and has great application potential in aquafeeds. The present study aimed to investigate the effects of dietary CAP inclusion on the anti-oxidation, immunity, inflammation, disease resistance and gut microbiota of abalone Haliotis discus hannai after a 110-day feeding trial. Three isonitrogenous and isolipidic diets were formulated by adding 0 % (control), 4.10 % (CAP4.10) and 16.25 % (CAP16.25) of CAP, respectively. A total of 540 abalones with an initial mean body weight of 22.05 ± 0.19 g were randomly distributed in three groups with three replicates per group and 60 abalones per replicate. Results showed that the activities of superoxide dismutase and glutathione peroxidase in the cell-free hemolymph (CFH) were significantly decreased and the content of malondialdehyde in CFH was significantly increased in the CAP16.25 group. The diet with 4.1 % of CAP significantly increased the activities of lysozyme and acid phosphatase in CFH. The expressions of pro-inflammatory genes such as tumor necrosis factor-α (tnf-α), nuclear factor-κb (nf-κb) and toll-like receptor 4 (tlr4) in digestive gland were downregulated, and the expressions of anti-inflammatory genes such as ß-defensin and mytimacin 6 in digestive gland were upregulated in the CAP4.10 group. Dietary CAP inclusion significantly decreased the cumulative mortality of abalone after the challenge test with Vibrio parahaemolyticus for 7 days. Dietary CAP inclusion changed the composition of gut microbiota of abalone. Besides, the balance of the ecological interaction network of bacterial genera in the intestine of abalone was enhanced by dietary CAP. The association analysis showed that two bacterial genera Ruegeria and Bacteroides were closely correlated with the inflammatory genes. In conclusion, the 4.10 % of dietary CAP enhanced the immunity and disease resistance as well as inhibited the inflammation of abalone. The 16.25 % of dietary CAP decreased the anti-oxidative capacity of abalone. The structure of the gut microbiota of abalone changed with dietary CAP levels.

Chemical defences indicate bold colour patterns with reduced variability in aposematic nudibranchs.

The selective factors that shape phenotypic diversity in prey communities with aposematic animals are diverse and coincide with similar diversity in the strength of underlying secondary defences. However, quantitative assessments of colour pattern variation and the strength of chemical defences in assemblages of aposematic species are lacking. We quantified colour pattern diversity using quantitative colour pattern analysis (QCPA) in 13 dorid nudibranch species (Infraorder: Doridoidei) that varied in the strength of their chemical defences. We accounted for the physiological properties of a potential predator's visual system (a triggerfish, Rhinecanthus aculeatus) and modelled the appearance of nudibranchs from multiple viewing distances (2 and 10 cm). We identified distinct colour pattern properties associated with the presence and strength of chemical defences. Specifically, increases in chemical defences indicated increases in colour pattern boldness (i.e. visual contrast elicited via either or potentially coinciding chromatic, achromatic and/or spatial contrast). Colour patterns were also less variable among species with chemical defences when compared to undefended species. Our results indicate correlations between secondary defences and diverse, bold colouration while showing that chemical defences coincide with decreased colour pattern variability among species. Our study suggests that complex spatiochromatic properties of colour patterns perceived by potential predators can be used to make inferences on the presence and strength of chemical defences.

Responses at various levels of ecological hierarchy indicate acclimation to sequential sublethal heatwaves in a temperate benthic ecosystem.

Marine heatwaves have caused massive mortality in coastal benthic ecosystems, altering community composition. Here, we aim to understand the effects of single and sequential sublethal heatwaves in a temperate benthic ecosystem, investigating their disturbance on various levels of ecological hierarchy, i.e. individual physiology, trophic groups' biomass and ecosystem carbon fluxes. To do so, we performed a near-natural experiment using outdoor benthic mesocosms along spring/summer, where communities were exposed to different thermal regimes: without heatwaves (0HW), with one heatwave (1HW) and with three heatwaves (3HWs). Gastropods were negatively impacted by one single heatwave treatment, but the exposure to three sequential heatwaves caused no response, indicating ecological stress memory. The magnitude of ecosystem carbon fluxes mostly decreased after 1HW, with a marked negative impact on mesograzers' feeding, while the overall intensity of carbon fluxes increased after 3HWs. Consumers' acclimation after the exposure to sequential heatwaves increased grazing activity, representing a threat for the macroalgae biomass. The evaluation of physiological responses and ecological interactions is crucial to interpret variations in community composition and to detect early signs of stress. Our results reveal the spread of heatwave effects along the ecological hierarchical levels, helping to predict the trajectories of ecosystem development.This article is part of the theme issue 'Connected interactions: enriching food web research by spatial and social interactions'.

Molecular Cloning, Characterization, and Function of Insulin-Related Peptide 1 (IRP1) in the Haliotis discus hanna.

Abalone is a popular mollusk in the marine aquaculture industry of China. However, existing challenges, like slow growth, individual miniaturization, and the absence of abundant abalone, have emerged as significant obstacles impeding its long-term progress in aquaculture. Studies have demonstrated that insulin-related peptide (IRP) is a crucial factor in the growth of marine organisms. However, limited studies have been conducted on IRP in abalone. This study indicated that the hdh-MIRP1 open reading frame (ORF) was composed of 456 base pairs, which encoded 151 amino acids. Based on the gene expression and immunofluorescence analyses, the cerebral ganglion of Haliotis discus hannai (H. discus hannai) was the primary site of hdh-MIRP1 mRNA expression. Moreover, hdh-MIRP1 expression was observed to be higher in the larger group than in the smaller group abalones. Only single nucleotide polymorphism (SNP) was related to their growth characteristics. However, approximately 82 proteins that may interact with hdh-MIRP1 were identified. The functional enrichment analysis of the 82 genes indicated that hdh-MIRP1 may be involved in the regulation of glucose metabolism and the process of growth. This study established a benchwork for further investigating the role of IRP in the growth of abalone.

The Central Paratethys Sea-rise and demise of a Miocene European marine biodiversity hotspot.

The Miocene Climate Optimum (MCO, ~ 17-14 Ma) was a time of extraordinary marine biodiversity in the Circum-Mediterranean Region. This boom is best recorded in the deposits of the vanished Central Paratethys Sea, which covered large parts of central to southeastern Europe. This sea harbored an extraordinary tropical to subtropical biotic diversity. Here, we present a georeferenced dataset of 859 gastropod species and discuss geodynamics and climate as the main drivers to explain the changes in diversity. The tectonic reorganization around the Early/Middle Miocene boundary resulted in the formation of an archipelago-like landscape and favorable conditions of the MCO allowed the establishment of coral reefs. Both factors increased habitat heterogeneity, which boosted species richness. The subsequent cooling during the Middle Miocene Climate Transition (~ 14-13 Ma) caused a drastic decline in biodiversity of about 67%. Among the most severely hit groups were corallivorous gastropods, reflecting the loss of coral reefs. Deep-water faunas experienced a loss by 57% of the species due to changing patterns in circulation. The low sea level led to a biogeographic fragmentation reflected in higher turnover rates. The largest turnover occurred with the onset of the Sarmatian when bottom water dysoxia eradicated the deep-water fauna whilst surface waters-dwelling planktotrophic species underwent a crisis.

Staging of post-settlement growth in the nudibranch Hypselodoris festiva.

Sea slugs of the family Chromodorididae (Nudibranchia, Gastropoda, Mollusca) have garnered attention by researchers and hobbyists alike for their bright and variable color patterns. However, the chromodorid life cycle has yet to be fully elucidated as there exist no reports of their rearing in the laboratory. Here, we report the rearing of Hypselodoris festiva from eggs to adults, where we categorized their post-settlement growth patterns from juvenile to adult stages. Body coloration appeared around 36 days, and organogenesis of vital adult organs began within 42 days after hatching. The anus of H. festiva was observed to change from a ventral to dorsal position during juvenile growth. Individuals reached sexual maturity after six months post-hatching, with successful mating and spawning observed ex situ. This study outlines comprehensive rearing methods and life cycle staging that could be applied to other chromodorid species. We propose H. festiva as a model organism for chromodorid research, with this research contributing to the progress of developmental and evolutionary research on sea slugs.

The molecular phylogeny of Caenogastropoda (Mollusca, Gastropoda) based on mitochondrial genomes and nuclear genes.

Comprising about 60 % of gastropod diversity, caenogastropods display almost all kinds of shell forms and include many commercially important marine groups. Although the monophyly of Caenogastropoda has been widely accepted, thier internal phylogenetic relationships remain unclear. In the present study, a total of 27 caenogastropods belonging to eight superfamilies were sequenced and used for phylogenetic reconstruction. All newly sequenced mitogenomes adhered to the consensus gene order of caenogastropods, except for those of Vanikoroidea, Vermetoidea and Cerithioidea, which involved protein-coding genes. The reconstructed mitogenomic phylogeny suggested the monophylies of Architaenioglossa, Sorbeoconcha, Hypsogastropoda and the siphonate clade. The present study also identified a close affinity among Cypraeoidea, Ficoidea, Tonnoidea, and Neogastropoda, supported by the presence of a pleurembolic proboscis. The monophyly of Neogastropoda was not supported, as Cancellariidae was found to be sister to the limpet-shaped group Calyptraeoidea, and (Tonooidea + Ficoidea) were sister to the remaining neogastropods. This study provides important information for better understanding the evolution of caenogastropods, as well as for the protection and utilization of these diverse and economically significant marine resources.

The shell formation mechanism of Turbo argyrostomus based on ultrastructure and transcriptome analysis.

The gold inner shell of Turbo argyrostomus is an important morphological classification characteristic in Gastropoda. However, the gene sets responsible for shell formation in gastropods remain poorly explored. In this study, we investigated the microstructure using scanning electron microscopy (SEM), hematoxylin-eosin (HE) and Alcian blue staining-periodic acid-Schiff (AB-PAS) staining. The SEM results illustrated that the T. argyrostomus shell exhibited a special "sandwich" microstructure. The results of histological observation demonstrated two major cell types: adipocytes and mucin cells. A total of 318 differentially expressed genes were identified between edge mantle and central mantle, among which whey acidic protein, N66, and nacre-like proteins, and Lam G and EGF domains may be related to shell microstructure. 22.39% - 25.20% of the mucin genes had biomineralization related domains, which supported for the relationship between mucins and shell formation. Moreover, this study revealed energy distribution differences between the edge mantle and central mantle. These results provide insights for further understanding of the biomineralization mechanism in Gastropoda.

The Families of Non-LTR Transposable Elements within Neritimorpha and Other Gastropoda.

Repeated sequences, especially transposable elements (TEs), are known to be abundant in some members of the important invertebrate class Gastropoda. TEs that do not have long terminal repeated sequences (non-LTR TEs) are frequently the most abundant type but have not been well characterised in any gastropod. Despite this, sequences in draft gastropod genomes are often described as non-LTR TEs, but without identification to family type. This study was conducted to characterise non-LTR TEs in neritimorph snails, using genomic skimming surveys of three species and the recently published draft genome of Theodoxus fluviatilis. Multiple families of non-LTR TEs from the I, Jockey, L1, R2 and RTE superfamilies were found, although there were notably few representatives of the first of these, which is nevertheless abundant in other Gastropoda. Phylogenetic analyses of amino acid sequences of the reverse transcriptase domain from the elements ORF2 regions found considerable interspersion of representatives of the four neritimorph taxa within non-LTR families and sub-families. In contrast, phylogenetic analyses of sequences from the elements' ORF1 region resolved the representatives from individual species as monophyletic. However, using either region, members of the two species of the Neritidae were closely related, suggesting their potential for investigation of phyletic evolution at the family level.

Seasonal effects of fish, seaweed and abalone cultures on dissolved organic matter and carbon sequestration potential in Sansha Bay, China.

Coastal bays serve as undeniable dissolved organic matter (DOM) reactors and the role of prevalent mariculture in DOM cycling deserves investigation. This study, based on four seasonal field samplings and a laboratory incubation experiment, examined the source and seasonal dynamics of DOM and fluorescent dissolved organic matter (FDOM) in the seawater of fish (Larimichthys crocea, LC), seaweed (Gracilaria lemaneiformis, GL) and abalone (Haliotis sp., HA) culturing zones in Sansha Bay, China. Using three-dimensional fluorescence spectroscopy coupled with parallel factor analysis (EEMs-PARAFAC), three fluorescent components were identified, i.e. protein-like C1, protein-like C2, and humic-like C3. Our results showed that mariculture activities dominated the DOM pool by seasonal generating abundant DOM with lower aromaticity and humification degrees. Accounting for 40-95 % of total fluorescent components, C1 (Ex/Em = 300/340 nm) was regarded the same as D1 (Ex/Em = 300/335 nm) identified in a 180-day degradation experiments of G. lemaneiformis detritus, indicating that the cultured seaweed modulated DOM through the seasonal production of C1. In addition, the incubation experiment revealed that 0.7 % of the total carbon content of seaweed detritus could be preserved as recalcitrant dissolved organic carbon (RDOC). However, fish culture appeared to contribute to liable DOC and protein-like C2, exerting a substantial impact on DOM during winter but making a negligible contribution to carbon sequestration, while abalone culture might promote the potential export and sequestration of seaweed-derived carbon to the ocean. Our results highlight the influences of mariculture activities, especially seaweed culture, in shaping DOM pool in coastal bays. These findings can provide reference for future studies on the carbon accounting of mariculture.

Cellular-resolution gene expression mapping reveals organization in the head ganglia of the gastropod, Berghia stephanieae.

Gastropod molluscs such as Aplysia, Lymnaea, and Tritonia have been important for determining fundamental rules of motor control, learning, and memory because of their large, individually identifiable neurons. Yet only a small number of gastropod neurons have known molecular markers, limiting the ability to establish brain-wide structure-function relations. Here we combine high-throughput, single-cell RNA sequencing with in situ hybridization chain reaction in the nudibranch Berghia stephanieae to identify and visualize the expression of markers for cell types. Broad neuronal classes were characterized by genes associated with neurotransmitters, like acetylcholine, glutamate, serotonin, and GABA, as well as neuropeptides. These classes were subdivided by other genes including transcriptional regulators and unannotated genes. Marker genes expressed by neurons and glia formed discrete, previously unrecognized regions within and between ganglia. This study provides the foundation for understanding the fundamental cellular organization of gastropod nervous systems.

Structural and functional characterization of Hdh-HSBP1 and its involvement in heat stress and early development in Pacific abalone, Haliotis discus hannai.

Heat shock factor binding protein 1 (HSBP1) is known to regulate the activity of heat shock factor 1 (HSF1) and the early development of organisms. To understand the involvement of HSBP1 in the heat shock response and embryonic and larval development of Pacific abalone (Haliotis discus hannai), the Hdh-HSBP1 gene was sequenced from the digestive gland (DG) tissue. The full-length sequence of Hdh-HSBP1 encompassed 738 nucleotides, encoding an 8.42 kDa protein consisting of 75 deduced amino acids. The protein contains an HSBP1 domain and a coiled-coil domain, which are conserved features in the HSBP1 protein family. Protein-protein molecular docking revealed that the coiled-coil region of Hdh-HSBP1 binds to the coiled-coil region of Hdh-HSF1. Tissue expression analysis demonstrated that the highest Hdh-HSBP1 expression occurred in the DG, whereas seasonal expression analysis revealed that this gene was most highly expressed in summer. In heat-stressed abalone, the highest expression of Hdh-HSBP1 occurred at 30 °C. Moreover, time-series analysis revealed that the expression of this gene began to increase significantly at 6 h post-heat stress, with higher expression observed at 12 h and 24 h post-heat stress. Furthermore, Hdh-HSBP1 mRNA expression showed a link to ROS production. Additionally, the expression of Hdh-HSBP1 showed significantly higher expression in the early stages of embryonic development in Pacific abalone. These results suggest that Hdh-HSBP1 plays a crucial role in the stress physiology of Pacific abalone by interacting with Hdh-HSF1, as well as its embryonic development.

Genetic diversity and population structure of Physella acuta (Gastropoda: Physidae) in Thailand using mitochondrial gene markers: COI and 16S rDNA.

Physella acuta is a freshwater snail native to North America. Understanding the phylogeography and genetic structure of P. acuta will help elucidate its evolution. In this study, we used mitochondrial (COI and 16S rDNA) and nuclear (ITS1) markers to identify the species and examine its genetic diversity, population structure, and demographic history of P. acuta in Thailand. Phylogenetic and network analyses of P. acuta in Thailand pertained to clade A, which exhibits a global distribution. Analysis of the genetic structure of the population revealed that the majority of pairwise comparisons showed no genetic dissimilarity. An isolation-by-distance test indicates no significant correlation between genetic and geographical distances among P. acuta populations, suggesting that gene flow is not restricted by distance. Demographic history and haplotype network analyses suggest a population expansion of P. acuta, as evidenced by the star-like structure detected in the median-joining network. Based on these results, we concluded that P. acuta in Thailand showed gene flow and recent population expansion. Our findings provide fundamental insights into the genetic variation of P. acuta in Thailand.

The impact of aragonite saturation variability on shelled pteropods: An attribution study in the California Current System.

Observations from the California Current System (CalCS) indicate that the long-term trend in ocean acidification (OA) and the naturally occurring corrosive conditions for the CaCO3 mineral aragonite (saturation state Ω < 1) have a damaging effect on shelled pteropods, a keystone group of calcifying organisms in the CalCS. Concern is heightened by recent findings suggesting that shell formation and developmental progress are already impacted when Ω falls below 1.5. Here, we quantify the impact of low Ω conditions on pteropods using an individual-based model (IBM) with life-stage-specific mortality, growth, and behavior in a high-resolution regional hindcast simulation of the CalCS between 1984 and 2019. Special attention is paid to attributing this impact to different processes that lead to such low Ω conditions, namely natural variability, long-term trend, and extreme events. We find that much of the observed damage in the CalCS, and specifically >70% of the shell CaCO3 loss, is due to the pteropods' exposure to naturally occurring low Ω conditions as a result of their diel vertical migration (DVM). Over the hindcast period, their exposure to damaging waters (Ω < 1.5) increases from 9% to 49%, doubling their shell CaCO3 loss, and increasing their mortality by ~40%. Most of this increased exposure is due to the shoaling of low Ω waters driven by the long-term trend in OA. Extreme OA events amplify this increase by ~40%. Our approach can quantify the health of pteropod populations under shifting environmental conditions, and attribute changes in fitness or population structure to changes in the stressor landscape across hierarchical time scales.

The small GTPase Cdc42 regulates shell field morphogenesis in a gastropod mollusk.

In most mollusks (conchiferans), the early tissue responsible for shell development, namely, the shell field, shows a common process of invagination during morphogenesis. Moreover, lines of evidence indicated that shell field invagination is not an independent event, but an integrated output reflecting the overall state of shell field morphogenesis. Nevertheless, the underlying mechanisms of this conserved process remain largely unknown. We previously found that actomyosin networks (regularly organized filamentous actin (F-actin) and myosin) may play essential roles in this process by revealing the evident aggregation of F-actin in the invaginated region and demonstrating that nonmuscle myosin II (NM II) is required for invagination in the gastropod Lottia peitaihoensis (= Lottia goshimai). Here, we investigated the roles of the Rho family of small GTPases (RhoA, Rac1, and Cdc42) to explore the upstream regulators of actomyosin networks. Functional assays using small molecule inhibitors suggested that Cdc42 modulates key events of shell field morphogenesis, including invagination and cell rearrangements, while the roles of RhoA and Rac1 may be nonspecific or negligible. Further investigations revealed that the Cdc42 protein was concentrated on the apical side of shell field cells and colocalized with F-actin aggregation. The aggregation of these two molecules could be prevented by treatment with Cdc42 inhibitors. These findings suggest a possible regulatory cascade of shell field morphogenesis in which Cdc42 recruits F-actin (actomyosin networks) on the apical side of shell field cells, which then generates resultant mechanical forces that mediate correct shell field morphogenesis (cell shape changes, invagination and cell rearrangement). Our results emphasize the roles of the cytoskeleton in early shell development and provide new insights into molluscan shell evolution.

Effects of red-light irradiation and melatonininjection on the antioxidant capacity and occurrence of apoptosis in abalones (Haliotis discus hannai) subjected to thermal stress.

High ocean temperatures caused by global warming induce oxidative stress in aquatic organisms. Melatonin treatment and irradiation using red light-emitting diodes (LEDs) have been reported to reduce oxidative stress in a few aquatic organisms. However, the effects of red LED irradiation and melatonin injection on the antioxidant capacity and degree of apoptosis in abalones, which are nocturnal organisms, have not yet been reported. In this study, we compared the expression levels of antioxidant enzymes, total antioxidant capacity, and the degree of apoptosis in abalones subjected to red LED irradiation and melatonin treatment. The results revealed that at high water temperatures (25 °C), the mRNA expression levels of the superoxide dismutase (SOD) and glutathione peroxidase (GPx) genes and the antioxidant activity of SOD decreased in abalones in the red-LED irradiated and melatonin-treated groups compared with those in abalones in the control group. Although high water temperatures induced DNA damage in the abalone samples, the degree of apoptosis was lower in the red-LED irradiated and melatonin-treated groups than in the control group. Overall, the abalones in the melatonin-treated and red-LED irradiated groups showed reduced oxidative stress and increased antioxidant enzyme levels under thermal stress compared with those in the control group. Therefore, red LED irradiation is a promising alternative to melatonin treatment, which is difficult to administer continuously for a long time, for protecting abalones from oxidative stress.

Pathological and ultrastructural changes of Bellamya bengalensis under chronic carboxylic acid exposure at environmentally relevant levels: Inferences from general unified threshold model for survival (GUTS) predictions and hepatopancreatic integrity assessment.

This study aimed to understand the effects of freshwater acidification, driven by industrial runoff, agricultural activities, and atmospheric deposition, on the freshwater mollusk Bellamya bengalensis. By systematically investigating the impact of two common carboxylic acids, acetic acid (AA) and benzoic acid (BA), this research employed diverse toxicological, pathological, and ecological assessments. We explored survival predictions through the generic unified threshold model of survival (GUTS-SD), examined oxidative stress responses, and investigated hepatopancreatic alterations. In the experimental design, Bellamya bengalensis were subjected to environmentally relevant sublethal concentrations (10%, 20% LC50) of AA (39.77 and 79.54 mg/l) and BA (31.41 and 62.82 mg/l) over 28 days. Acute toxicity tests revealed increased LC50 values, indicating heightened toxicity with prolonged exposure, particularly due to the greater potency of benzoic acid compared to acetic acid. The GUTS-SD model provided accurate predictions of time-specific effects on populations, presenting long-term exposure (100 days) LC50 values for AA (263.7 mg/l) and BA (330.9 mg/l). Sequentially, the integrated biomarker response (IBR) analysis across study intervals highlighted the 28-day interval as the most sensitive, with GST emerging as the most responsive enzyme to oxidative stress induced by AA and BA. Histopathological and ultrastructural assessments of the hepatopancreas showed severe alterations, including necrosis, vacuolation and disrupted micro-villi, which were especially pronounced in higher BA exposure concentrations. These findings highlight the health and survival impacts of carboxylic acid toxicity on Bellamya bengalensis, emphasizing the need for proactive measures to mitigate acidification in aquatic ecosystems. The broader ecological implications underscore the importance of effective management and conservation strategies to address ongoing environmental challenges.