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Corbicula fluminea is an aggressive invasive species that has successfully colonized aquatic habitats worldwide, producing changes in natural environments and impacting endemic populations. As disturbed environments may favor the adaptive success of exotic species over native ones, we studied the fitness response of two freshwater bivalves, invasive C. fluminea and native Diplodon delodontus, to the presence of metals in the Parana de la Palmas River. To assess the health status of both species, we analyzed morphological and histological alterations in the digestive gland and their relation to metal concentrations in this organ and in the water. Water and specimens sampling took place in the first section of the delta of the Parana River in June and September. Most metal concentrations increased in the river, although in the digestive gland only iron in D. delodontus and nickel and zinc in C. fluminea increased seasonally. Digestive gland factor and hepatosomatic index indicated higher values in C. fluminea in both periods. Despite histological analysis showing a decrease in atrophic tubules frequency in both species, which was followed by histomorphometric parameters of the epithelium and lumen of the digestive tubules, C. fluminea exhibited a greater physiological capacity for metal metabolism and recovery. These results suggest that the physiological characteristics of the Asian clam C. fluminea, combined with its reproductive efficiency and broad dispersal capacities, could explain its invasive dispersal competence over the D. delodontus in the disturbed environmental conditions observed in the Parana de las Palmas River. [ABSTRACT FROM AUTHOR]

Simple Summary: The invasion of the invasive alien species Pomacea canaliculata is of great concern because of its adverse influences on ecosystems, agriculture, and human health in the Asian region. Metaldehyde-containing molluscicides are often used as an effective method of controlling this species. In view of this, the present study conducted experiments to investigate the lethal concentrations of metaldehyde on Pomacea canaliculata at different exposure times. Moreover, the study also elucidated changes in enzyme activity and provided detailed histopathological evidence that shed light on the mode of action and effects of metaldehyde exposure on Pomacea canaliculata. The findings of this study not only deepen our understanding of the effects of metaldehyde on mollusks, but also provide important insights for developing better control strategies. Pomacea canaliculata, as an invasive exotic species in Asia, can adversely affect crop yields, eco-environment, and human health. Application of molluscicides containing metaldehyde is one effective method for controlling P. canaliculata. In order to investigate the effects of metaldehyde on adult snails, we conducted acute toxicological experiments to investigate the changes in enzyme activities and histopathology after 24 h and 48 h of metaldehyde action. The results showed that the median lethal concentrations (LC) of metaldehyde on P. canaliculata were 3.792, 2.195, 1.833, and 1.706 mg/L at exposure times of 24, 48, 72, and 96 h, respectively. Treatment and time significantly affected acetylcholinesterase (AChE), glutathione S-transferase (GST), and total antioxidant capacity (TAC) activity, with sex significantly affecting AChE, GST, and TAC activity and time significantly affecting carboxylesterase (CarE). In addition, the interaction of treatment and time significantly affected the activity of GST, CarE and TAC. In addition, histopathological changes occurred in the digestive glands, gills and gastropods of apple snail exposed to metaldehyde. Histological examination of the digestive glands included atrophy of the digestive cells, widening of the hemolymph gap, and an increase in basophils. In treated snails, the hemolymph gap in the gills was widely dilated, the columnar cells were disorganized or even necrotic, and the columnar muscle cells in the ventral foot were loosely arranged and the muscle fibers reduced. The findings of this study can provide some references for controlling the toxicity mechanism of invasive species. [ABSTRACT FROM AUTHOR]

Pharmaceutical and personal care products (PPCPs) containing persistent and potentially hazardous substances have garnered attention for their ubiquitous presence in natural environments. This study investigated the impact of polyethylene glycol (PEG), a common PPCP component, on Mytilus galloprovincialis. Mussels were subjected to two PEG concentrations (E1: 0.1 mg/L and E2: 10 mg/L) over 14 days. Oxidative stress markers in both gills and digestive glands were evaluated; cytotoxicity assays were performed on haemolymph and digestive gland cells. Additionally, cell volume regulation (RVD assay) was investigated to assess physiological PEG-induced alterations. In the gills, PEG reduced superoxide dismutase (SOD) activity and increased lipid peroxidation (LPO) at E1. In the digestive gland, only LPO was influenced, while SOD activity and oxidatively modified proteins (OMPs) were unaltered. A significant decrease in cell viability was observed, particularly at E2. Additionally, the RVD assay revealed disruptions in the cells subjected to E2. These findings underscore the effects of PEG exposure on M. galloprovincialis. They are open to further investigations to clarify the environmental implications of PPCPs and the possibility of exploring safer alternatives. [ABSTRACT FROM AUTHOR]

Abstract Human pharmaceuticals represent a major challenge in natural environment. A better knowledge on their mechanisms of action and adverse effects on cellular pathways is fundamental to predict long-term consequences for marine wildlife. The FTIRI Imaging (FTIRI) spectroscopy represents a vibrational technique allowing to map specific areas of non-homogeneous biological samples, providing a unique biochemical and ultrastructural fingerprint of the tissue. In this study, FTIRI technique has been applied, for the first time, to characterize (i) the chemical building blocks of digestive glands of Mytilus galloprovincialis, (ii) alterations and (iii) resilience of macromolecular composition, after a 14-days exposure to 0.5 µg/L of carbamazepine (CBZ), valsartan (VAL) and their mixture, followed by a 14-days recovery period. Spectral features of mussels digestive glands provided insights on composition and topographical distribution of main groups of biological macromolecules, such as proteins, lipids, and glycosylated compounds. Pharmaceuticals caused an increase in the total amount of protein and a significant decrease of lipids levels. Changes in macromolecular features reflected the modulation of specific molecular and biochemical pathways thus supporting our knowledge on mechanisms of action of such emerging pollutants. Overall, the applied approach could represent an added value within integrated strategies for the effects-based evaluation of environmental contaminants.

Human pharmaceuticals represent a major challenge in natural environment. A better knowledge on their mechanisms of action and adverse effects on cellular pathways is fundamental to predict long-term consequences for marine wildlife. The FTIRI Imaging (FTIRI) spectroscopy represents a vibrational technique allowing to map specific areas of non-homogeneous biological samples, providing a unique biochemical and ultrastructural fingerprint of the tissue. In this study, FTIRI technique has been applied, for the first time, to characterize (i) the chemical building blocks of digestive glands of Mytilus galloprovincialis, (ii) alterations and (iii) resilience of macromolecular composition, after a 14-days exposure to 0.5 µg/L of carbamazepine (CBZ), valsartan (VAL) and their mixture, followed by a 14-days recovery period. Spectral features of mussels digestive glands provided insights on composition and topographical distribution of main groups of biological macromolecules, such as proteins, lipids, and glycosylated compounds. Pharmaceuticals caused an increase in the total amount of protein and a significant decrease of lipids levels. Changes in macromolecular features reflected the modulation of specific molecular and biochemical pathways thus supporting our knowledge on mechanisms of action of such emerging pollutants. Overall, the applied approach could represent an added value within integrated strategies for the effects-based evaluation of environmental contaminants. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate and compare the effects on biochemical parameters and organosomatic indices in the freshwater bivalve Diplodon chilensis exposed to a glyphosate-based formulation under direct and dietary exposures (4 mg a.p./L). After 1, 7, and 14 days of exposure, reduced glutathione (GSH) and thiobarbituric acid reactive substances (TBARS) levels and the activities of glutathione-S- transferase (GST), superoxide dismutase (SOD), and catalase (CAT) were evaluated in the gills and digestive gland. The hepatosomatic (HSI) and branchiosomatic (BSI) indices were also analyzed. Direct and dietary glyphosate-based formulation exposure altered the redox homeostasis in the gills and digestive gland throughout the experimental time, inducing the detoxification response (GST), the antioxidant defenses (SOD, CAT, GSH), and causing lipid peroxidation. After 14 days of exposure, the HSI and BSI increased significantly (43% and 157%, respectively) only in the bivalves under direct exposure. Greater changes in the biochemical parameters were induced by the dietary exposure than by the direct exposure. Furthermore, the gills presented an earlier response compared to the digestive gland. These results suggested that direct and dietary exposure to a glyphosate-based formulation induced oxidative stress in the gills and digestive glands of D. chilensis. Thus, the presence of glyphosate-based formulations in aquatic ecosystems could represent a risk for filter-feeding organisms like bivalves. [ABSTRACT FROM AUTHOR]

This study aimed to assess microplastics (MPs) in the digestive glands of Mytilus galloprovincialis mussels. Mussels were collected from pristine, aquaculture, and port areas of the northern Adriatic Sea (Slovenia and Croatia coastline). MPs were detected using scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). The characterized MPs were further categorized based on their shape, size, and color. The highest number of 32.85 ± 27.98 MPs per mussel digestive gland was found in the mussels sampled from the ACI marina Rovinj (Croatia). The predominant MPs found in the mussel digestive glands at all investigated locations belonged to the smallest analyzed category (5–10 μm in size) and exhibited spherical and fragment shapes. The most abundant MPs found in mussels by color were white particles. MPs were found in both wild and farmed mussels and, hence, the results point out that the abundance of microplastic pollution is omnipresent along the coastal waters of the northern Adriatic Sea. [ABSTRACT FROM AUTHOR]

To investigate the impact of heavy metals on the physiology of aquatic organisms, previous studies have focused on selected biomarker measurements in samples. However, most studies do not take into account toxicity effects on both males and females. The present paper aims to examine the effect of sex on the detoxification response using metallothioneins (MTs), a biomarker of metallic contamination. MTs were measured in different organs (mantle, digestive gland and gonad) of both males and females of Donax trunculus L. (Mollusca, Bivalvia) exposed to cadmium (Cd). The samples were collected at El Battah beach, far from any source of pollution, and reared in the laboratory for four days. Cd was added to the rearing water at two previously determined sublethal concentrations (LC10 and LC25). Measurements of MTs were made at (0, 48 and 96 h). Cd exposure caused a significant induction (P < 0.05) of MTs in all studied organs in both sexes with a marked effect in females. The digestive gland had the highest MT levels, followed by the gonad and then mantle. Female and male individuals of this species differ in their susceptibility to Cd. This study supports the importance of sex and tissue in ecotoxicological studies. [ABSTRACT FROM AUTHOR]

Pharmaceutical and personal care products (PPCPs) containing persistent and potentially hazardous substances have garnered attention for their ubiquitous presence in natural environments. This study investigated the impact of polyethylene glycol (PEG), a common PPCP component, on Mytilus galloprovincialis. Mussels were subjected to two PEG concentrations (E1: 0.1 mg/L and E2: 10 mg/L) over 14 days. Oxidative stress markers in both gills and digestive glands were evaluated; cytotoxicity assays were performed on haemolymph and digestive gland cells. Additionally, cell volume regulation (RVD assay) was investigated to assess physiological PEG-induced alterations. In the gills, PEG reduced superoxide dismutase (SOD) activity and increased lipid peroxidation (LPO) at E1. In the digestive gland, only LPO was influenced, while SOD activity and oxidatively modified proteins (OMPs) were unaltered. A significant decrease in cell viability was observed, particularly at E2. Additionally, the RVD assay revealed disruptions in the cells subjected to E2. These findings underscore the effects of PEG exposure on M. galloprovincialis. They are open to further investigations to clarify the environmental implications of PPCPs and the possibility of exploring safer alternatives.

Pomacea canaliculata, as an invasive exotic species in Asia, can adversely affect crop yields, eco-environment, and human health. Application of molluscicides containing metaldehyde is one effective method for controlling P. canaliculata. In order to investigate the effects of metaldehyde on adult snails, we conducted acute toxicological experiments to investigate the changes in enzyme activities and histopathology after 24 h and 48 h of metaldehyde action. The results showed that the median lethal concentrations (LC) of metaldehyde on P. canaliculata were 3.792, 2.195, 1.833, and 1.706 mg/L at exposure times of 24, 48, 72, and 96 h, respectively. Treatment and time significantly affected acetylcholinesterase (AChE), glutathione S-transferase (GST), and total antioxidant capacity (TAC) activity, with sex significantly affecting AChE, GST, and TAC activity and time significantly affecting carboxylesterase (CarE). In addition, the interaction of treatment and time significantly affected the activity of GST, CarE and TAC. In addition, histopathological changes occurred in the digestive glands, gills and gastropods of apple snail exposed to metaldehyde. Histological examination of the digestive glands included atrophy of the digestive cells, widening of the hemolymph gap, and an increase in basophils. In treated snails, the hemolymph gap in the gills was widely dilated, the columnar cells were disorganized or even necrotic, and the columnar muscle cells in the ventral foot were loosely arranged and the muscle fibers reduced. The findings of this study can provide some references for controlling the toxicity mechanism of invasive species.

Schistosomiasis is one of the most important tropical diseases. Analogs of nitrogen-based heterocycles hold a unique position in medicinal chemistry as a valuable source of therapeutic agents. This study aims to investigate the effects of different concentrations (0.25 and 1 ppm) of quinoline derivative as 7-chloro 4-amino ethyl amino quinoline hydrochloride salt (CAAQ) on survival, growth rates, mortality, immune response, histological structure and protein patterns of Biomphalaria alexandrina snails with/without S. mansoni infection under the effect. Exposure of snails to 0.25 and 1 ppm significantly (P = 0.001) increased mortality and marginally decreased growth rates. In addition, exposure increased hayalinocytes (17.3 and 17.4 %, respectively) when compared to the control (5 %), decreased the granulocytes "spreading and non-spreading" (48.5 %, 51.6 % and 34.2 %, 31 %, respectively) when compared to the control (56.1 and 38.9 %, respectively). Exposure to both concentrations decreased the phagocytic haemocytes and increased the unphagocytic haemocytes percentages compared to the control snails. The present results indicated that the histological effect of CAAQ exposure on non and/or infected snails caused marked changes in the histological architecture of the ovotestis and digestive gland. The sublethal concentrations of CAAQ caused disturbance in the tissue total protein content of the ovotestis and digestive gland. SDS-PAGE of total protein pattern in ovotestis and digestive gland of exposed-infected snails showed occasional appearance and/or absence of certain protein bands. In conclusion, CAAQ modulated the immune responses of B. alexandrina with/without S. mansoni infection, histological structure and protein expression (SDS-PAGE). Consequently, CAAQ was recommended as a molluscicide of plant origin for the control program of schistosomiasis. [ABSTRACT FROM AUTHOR]

Parasitism of cephalopods is common, including infection with Aggregata spp., Ichthyobodo spp., dicyemids, cestodes of the orders Tetraphyllidea and Trypanorhynchidea, and various crustaceans. Cestodiasis in octopuses is reported, although a full histologic description of lesions has not been previously described. Cestodiasis was identified in 10 octopuses of 4 different species, which included 4 common octopuses (Octopus vulgaris), 3 Caribbean reef octopuses (Octopus briareus), 2 two-spot octopuses (Octopus bimaculoides), and 1 giant Pacific octopus (Enteroctopus dofleini). Larval cestodes were present in the cecum (n = 5), intestines (n = 4), digestive gland (n = 3), chitinous alimentary tract (n = 2), renal appendage (n = 1), and salivary duct (n = 1). In 5 cases, larval cestodes invaded tissue and were associated with hemocytic inflammation and tracts of necrotic tissue in the intestines (n = 3), digestive gland (n = 3), and/or renal appendage (n = 1). When present in the chitinous alimentary tract (esophagus, stomach) or cecum, larval cestodes were in the central lumen and not associated with lesions. One adult cestode was identified in the mantle cavity and was not associated with lesions. Other common concurrent parasitic infections included enteric Aggregata spp. infection, branchial Rickettsia-like organism infection, enteric nematodiasis, and an arthropod-associated branchitis. [ABSTRACT FROM AUTHOR]

Heavy metal pollution of the environment is especially apparent within or around urban areas and around industrial facilities. This paper deals with the concentration of zinc, copper, manganese and cadmium in the soil, leaves of fodder plants and in the body parts of the Turkish snail (H. lucorum). The study included ten localities, arranged in four groups, situated in and around the city of Skopje. The first group consisted of five urban localities that were in the central city area. The second group included two suburban localities. The third group consisted of two rural sites. The fourth group represented one site that was located away from the metropolitan area (control site). Soils, leaves of four plant species (Cardaria draba, Lamium purpureum, Rumex crispus and Taraxacum officinale) and a sample of 10 adult snails were collected from each locality. Heavy metals content was determined by wet combustion and atomic absorption spectroscopy. Digestive gland was an organ with the highest amount of all heavy metals and with proven bioaccumulation for Zn and Cd; it showed a prominent correlation with soil concentrations for the four heavy metals but not with the examined plant species. The foot and shell of the snails had limited indicator values since they exhibited weak correlation with soil concentrations of Cu and Mn. [ABSTRACT FROM AUTHOR]

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Pyrethroids are among the most widely used insecticides. Permethrin and tetramethrin, which are synthetic pyrethroids, are generally used to control insects in agricultural areas and household applications. Due to broad use areas, they contaminate aquatic ecosystems and cause adverse effects to the non-target aquatic organisms. Even though permethrin and tetramethrin are known to alter the oxidative stress parameters of in vivo aquatic animal model organisms, there are limited studies in vitro. This study aims to determine the adverse effects of permethrin and tetramethrin in the in vitro models of freshwater mussels exposed to 1 mg/L, 10 μg/L, 100 ng/L and 1 ng/L concentrations of chemicals for 24 h. For this purpose, reduced glutathione activities were evaluated as biomarkers of the primary gill and digestive gland cell cultures. In both cell cultures, reduced glutathione values increased in the exposed groups, compared to the control group. Even though the results showed that reduced glutathione activities had not significantly changed concentration-dependently (p > 0.05), significant differences were observed in the reduced glutathione activities of both cell cultures (p < 0.05). This study showed that permethrin and tetramethrin had highly toxic effects in the in vitro models of mussels even at low concentrations. [ABSTRACT FROM AUTHOR]

Background: The invasive gastropod Pomacea canaliculata has received great attention in the last decades as a result of its negative impact on crops agriculture, yet knowledge of their digestive physiology remains incomplete, particularly the enzymatic breakdown of macromolecules such as proteins and lipids. Results: Discovery proteomics revealed aspartic peptidases, cysteine peptidases, serine peptidases, metallopeptidases and threonine peptidases, as well as acid and neutral lipases and phospholipases along the digestive tract of P. canaliculata. Peptides specific to peptidases (139) and lipases (14) were quantified by targeted mass spectrometry. Digestion begins in the mouth via diverse salivary peptidases (nine serine peptidases; seven cysteine peptidases, one aspartic peptidase and 22 metallopeptidases) and then continues in the oesophagus (crop) via three luminal metallopeptidases (Family M12) and six serine peptidases (Family S1). Downstream, the digestive gland provides a battery of enzymes composed of aspartic peptidase (one), cysteine peptidases (nine), serine peptidases (12) and metallopeptidases (24), including aminopeptidases, carboxypeptidases and dipeptidases). The coiled gut has M1 metallopeptidases that complete the digestion of small peptides. Lipid extracellular digestion is completed by triglyceride lipases. Conclusion: From an integrative physiological and anatomical perspective, P. canaliculata shows an unexpected abundance and diversity of peptidases, which participate mainly in extracellular digestion. Moreover, the previously unknown occurrence of luminal lipases from the digestive gland is reported for the first time. Salivary and digestive glands were the main tissues involved in the synthesis and secretion of these enzymes, but plausibly the few luminally exclusive peptidases are secreted by ventrolateral pouches or epithelial unicellular glands. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

This study aimed to assess microplastics (MPs) in the digestive glands of Mytilus galloprovincialis mussels. Mussels were collected from pristine, aquaculture, and port areas of the northern Adriatic Sea (Slovenia and Croatia coastline). MPs were detected using scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). The characterized MPs were further categorized based on their shape, size, and color. The highest number of 32.85 ± 27.98 MPs per mussel digestive gland was found in the mussels sampled from the ACI marina Rovinj (Croatia). The predominant MPs found in the mussel digestive glands at all investigated locations belonged to the smallest analyzed category (5–10 μm in size) and exhibited spherical and fragment shapes. The most abundant MPs found in mussels by color were white particles. MPs were found in both wild and farmed mussels and, hence, the results point out that the abundance of microplastic pollution is omnipresent along the coastal waters of the northern Adriatic Sea.

Bivalve farming plays a dominant role in mariculture in China. Paralytic shellfish toxins (PSTs) can be accumulated in bivalves and cause poisoning the consumers. A sensitive detection of PSTs can provide early warning to decrease poisoning events in bivalve consuming. PSTs are traditionally examined using the whole soft-tissues. However, PSTs accumulation varies dramatically in different tissues of bivalves. Some tough tissues/organs (such as mantle), which account for a large proportion of the total soft body, exhibit a lower accumulation of PSTs and make the toxin extraction time- and reagent-consuming, potentially decreasing the accuracy and sensitivity of PSTs monitoring in bivalves. To develop a sensitive and cost-effective approach for PSTs examination in massively farmed bivalves, we fed three commercially important bivalves, Yesso scallop Patinopecten yessoensis, Pacific oyster Crassostrea gigas, and blue mussel Mytilus edulis with PSTs-producing dinoflagellate Alexandrium catenella, and detected PSTs concentration in different tissues. For all three bivalve species, the digestive gland accumulated much more PSTs than other tissues, and the digestive gland's toxicity was significantly correlated with the PSTs toxicity of the whole soft-tissues, with r2 = 0.94, 0.92, and 0.94 for Yesso scallop, Pacific oyster, and blue mussel, respectively. When the toxicity of the whole soft-tissues reached 80 µg STXeq(100g)−1, the regulatory limit for commercial shellfish, the digestive gland's toxicity reached 571.48, 498.90, and 859.20 µg STXeq(100g)−1 in Yesso scallop, Pacific oyster, and blue mussel, respectively. Our results indicate that digestive gland can be used for the sensitive and cost-effective monitoring of PSTs in bivalves. [ABSTRACT FROM AUTHOR]

The Manila clam (Ruditapes philippinarum) is the second most exploited bivalve in the world but remains threatened by diseases and global changes. Their associated microbiota play a key role in their fitness and acclimation capacities. This study aimed at better understanding the behavior of clam digestive glands and extrapallial fluids microbiota at small, but contrasting spatial and temporal scales. Results showed that environmental variations impacted clam microbiota differently according to the considered tissue. Each clam tissue presented its own microbiota and showed different dynamics according to the intertidal position and sampling period. Extrapallial fluids microbiota was modified more rapidly than digestive glands microbiota, for clams placed on the upper and lower intertidal position, respectively. Clam tissues could be considered as different microhabitats for bacteria as they presented different responses to small-scale temporal and spatial variabilities in natural conditions. These differences underlined a more stringent environmental filter capacity of the digestive glands. [ABSTRACT FROM AUTHOR]

Freshwater grazers are suitable organisms to investigate the fate of environmental pollutants, such as weathered multi-walled carbon nanotubes (wMWCNTs). One key process is the uptake of ingested materials into digestive or absorptive cells. To address this, we investigated the localization of wMWCNTs in the intestinal tracts of the mud snail Lymnaea stagnalis (L. stagnalis) and the mayfly Rhithrogena semicolorata (R. semicolorata). In L. stagnalis, bundles of wMWCNTs could be detected in the midgut lumen, whereas only single wMWCNTs could be detected in the lumina of the digestive gland. Intracellular uptake of wMWCNTs was detected by transmission electron microscopy (TEM) but was restricted to the cells of the digestive gland. In larvae of R. semicolorata, irritations of the microvilli and damages in the apical parts of the epithelial gut cells were detected after feeding with 1 to 10 mg/L wMWCNTs. In both models, we detected fibrillar structures in close association with the epithelial cells that formed peritrophic membranes (PMs). The PM may cause a reduced transmission of wMWCNT bundles into the epithelium by forming a filter barrier and potentially protecting the cells from the wMWCNTs. As a result, the uptake of wMWCNTs into cells is rare in mud snails and may not occur at all in mayfly larvae. In addition, we monitor physiological markers such as levels of glycogen or triglycerides and the RNA/DNA ratio. This ratio was significantly affected in L. stagnalis after 24 days with 10 mg/L wMWCNTs, but not in R. semicolorata after 28 days and 10 mg/L wMWCNTs. However, significant effects on the energy status of R. semicolorata were analysed after 28 days of exposure to 1 mg/L wMWCNTs. Furthermore, we observed a significant reduction of phagosomes per enterocyte cell in mayfly larvae at a concentration of 10 mg/L wMWCNTs (p < 0.01). [ABSTRACT FROM AUTHOR]

Microplastics (MPs) constitute the predominant plastic type in marine environments. Since they occupy the same size fraction of sediment particles and planktonic organisms they are potentially bioavailable to a broad scope of organisms, such as filter feeders, which are particularly vulnerable to MP ingestion. To understand the potential impact of MPs in filter feeders it is essential to clarify the uptake, accumulation patterns and elimination rates with time of MPs. The aim of this study was to determine the depuration dynamics and accumulation in tissues of mussels Mytilus galloprovincialis exposed during 24 h to different size polystyrene MPs (1 μm and 10 μm), and depurated for a maximum of 7 days (T = 24 h, T = 48 h and T = 7 d). Mussels were chemically digested with KOH 10% and filtered to quantify the number of MP ingested, and they were cryostat sliced for MP localization in tissues. Both MP sizes were quantified in all depuration times, but mussels accumulated significantly higher quantities of 10 μm MP throughout depuration compared to 1 μm MP. A significant decrease was observed after 7 d depuration in mussels exposed to 10 μm. Mussels removed the same amount of 1 and 10 μm MP after 7 days depuration. However, the depuration dynamics differed for each size-MPs and showed to be size-dependent. Most of both size MPs were eliminated in the first 24 h, but 1 μm MP showed to pass faster through the digestive tract than 10 μm MP. MPs of 1 μm and 10 μm were localized mainly in the lumen and a few in the epithelium of the digestive tract (stomach, intestine and digestive gland) during the depuration and in the gills after the exposure; as confirmed by Raman spectroscopy. The usage of chemical digestion and histological analysis as complementary techniques show to be suitable to infer the depuration dynamics of MPs in mussels. [Display omitted] • Accumulation and depuration dynamics in mussels showed to be MP size-dependant. • 1 and 10 μm MP remained in mussels tissues after 7 days depuration. • Both size-MPs were localized in the lumen and epithelia of digestive tract. • MP isolation and histology allowed to track accurately MP dynamics in mussels. [ABSTRACT FROM AUTHOR]

Simple Summary: The Pacific abalone, Haliotis discus hannai, is a gastropod mollusk in high demand, which is extensively cultured in many Asian countries. The growth and development of Pacific abalone depend on the activation of growth factors and other growth-regulating proteins. Growth factors are secreted, biologically active molecules that stimulate cell growth through signal transduction pathways. The mollusk-like growth factor (MLGF) is a mollusk specific growth factor in the adenosine deaminase related growth factor subfamily having a conserved adenosine deaminase (ADA) domain. Molecular functions of this growth factor include adenosine deaminase activity, growth factor activity, and zinc binding activity. For this growth factor activity, enzymatic activity (ADA activity) that converts adenosine to inosine to stimulate cell growth is essential. As abalone aquaculture completely depends on hatchery-produced seed, proper embryonic and larval development is essential, and MLGF is one of the main growth factors that can regulate this activity. In Pacific abalone, higher expression of Hdh-MLGF mRNA in the embryonic and larval development stages is an indication of higher production of adenosine and increases the growth factor activity that stimulates embryonic and larval cell growth through signal transduction pathways. Growth factors are mostly secreted proteins that play key roles in an organism's biophysical processes through binding to specific receptors on the cell surface. The mollusk-like growth factor (MLGF) is a novel cell signaling protein in the adenosine deaminase-related growth factor (ADGF) subfamily. In this study, the MLGF gene was cloned and characterized from the digestive gland tissue of Pacific abalone and designated as Hdh-MLGF. The transcribed full-length sequence of Hdh-MLGF was 1829 bp long with a 1566 bp open reading frame (ORF) encoding 521 amino acids. The deduced amino acid sequence contained a putative signal peptide and two conserved adenosine deaminase domains responsible for regulating molecular function. Fluorescence in situ hybridization localized Hdh-MLGF in the submucosa layer of digestive tubules in the digestive gland. The mRNA expression analysis indicated that Hdh-MLGF expression was restricted to the digestive gland in the adult Pacific abalone. However, Hdh-MLGF mRNA expressions were observed in all stages of embryonic and larval development, suggesting Hdh-MLGF might be involved in the Pacific abalone embryonic and larval development. This is the first study describing Hdh-MLGF and its involvement in the Pacific abalone embryonic and larval development. [ABSTRACT FROM AUTHOR]

Current understanding of cephalopod digestive tract physiology is based on relatively “old” literature and a “mosaic of data” from multiple species. To provide a background to the discussion of methodologies for investigating physiology we first review the anatomy of the cephalopod digestive tract with a focus on Octopus vulgaris, highlighting structure-function relationships and species differences with potential functional consequences (e.g., absence of a crop in cuttlefish and squid; presence of a caecal sac in squid). We caution about extrapolation of data on the digestive system physiology from one cephalopod species to another because of the anatomical differences. The contribution of anatomical and histological techniques (e.g., digestive enzyme histochemistry and neurotransmitter immunohistochemistry) to understanding physiological processes is discussed. For each major digestive tract function we briefly review current knowledge, and then discuss techniques and their limitations for the following parameters: 1) Measuring motility in vitro (e.g., spatiotemporal mapping, tension and pressure), in vivo (labelled food, high resolution ultrasound) and aspects of pharmacology; 2) Measuring food ingestion and the time course of digestion with an emphasis on understanding enzyme function in each gut region with respect to time; 3) Assessing transepithelial transport of nutrients; 4) Measuring the energetic cost of food processing, impact of environmental temperature and metabolic rate (flow-through/ intermittent respirometry); 4) Investigating neural (brain, gastric ganglion, enteric) and endocrine control processes with an emphasis on application of molecular techniques to identify receptors and their ligands. A number of major knowledge lacunae are identified where available techniques need to be applied to cephalopods, these include: 1) What is the physiological function of the caecal leaflets and intestinal typhlosoles in octopus? 2) What role does the transepithelial transport in the caecum and intestine play in ion, water and nutrient transport? 3) What information is signalled from the digestive tract to the brain regarding the food ingested and the progress of digestion? It is hoped that by combining discussion of the physiology of the cephalopod digestive system with an overview of techniques and identification of key knowledge gaps that this will encourage a more systematic approach to research in this area. [ABSTRACT FROM AUTHOR]

Silver nanoparticles (AgNPs) have been reported as stressors for the bivalves' immune system at different regulatory levels, impacting the detection step and receptors, and other mediators, as well as effector molecules. However, studies on how AgNPs impact the transmission of signals from receptors and whether they have an effect on mediators and transcription factors are still scarce. This study aims to investigate the effect of 12 hours of in vivo exposure to 100 µg/L of AgNPs on the gene expression of the cytosolic adaptor Myeloid, the differentiation protein 88 (MgMyD88-b), and the interferon regulatory factor (Me4-IRF) in the gills and digestive gland of Mytilus galloprovincialis, before and after blocking two major uptake pathways of nanoparticles (clathrin- and caveolae-mediated endocytosis). The results illustrate a tissue-specific gene expression of the MgMyD88-b and the Me4-IRF in the gills and digestive gland of M. galloprovincialis. In the gills, AgNPs did not significantly impact the expression of the two genes. However, blocking the caveolae-mediated endocytosis decreased the expression of Me4-IRF. However, inhibition of clathrin-mediated endocytosis in the digestive gland recorded a significant decrease in the expression of MgMyD88-b. Overall, the inhibition of the AgNPs' uptake routes have highlighted their potential interference with the immune response through the studied mediators' genes, which need to be studied further in future investigations. [ABSTRACT FROM AUTHOR]

As the demand for Octopus maya grows, sustainable farming practices become essential to prevent overexploitation, so that farming can be developed as a sustainable alternative to traditional fishing. Understanding the digestive dynamics of the octopus is essential for devising optimal dietary formulations in aquaculture. Despite the progress in understanding cephalopod digestion, little is known about the specific functioning of the digestive enzymes responsible for breaking down protein substrates. This knowledge gap underscores the need for further research to support sustainable O. maya population management. In this paper, dietary formulations are identified for cephalopods by characterizing O. maya digestive enzymes present in the digestive gland and gastric juice. The investigation revealed that acidic proteases showed a peak activity at higher temperatures than alkaline proteases. Inhibitors confirmed the presence of H, L, and D cathepsins. The lower activation energy of alkaline enzymes compared to acidic ones observed highlights an intriguing aspect of O. maya's digestive physiology. This research provides valuable insights into O. maya digestive enzyme functions, representing a significant advancement in formulating diets crucial for successful octopus farming that may help to fully understand its physiology., Competing Interests: Competing interests The authors declare no competing or financial interests., (© 2024. Published by The Company of Biologists Ltd.)

Ocean acidification (OA) can have widespread implications for marine bivalves. While our current understanding of OA effects on the physiological performance is increasing, very little is known about the physiology of digestive gland of marine bivalves in response to OA. Here, we examined how the digestive system of razor clams (Sinonovacula constricta) responded to OA. Following 35-day exposure to CO2-driven seawater acidification, no significant decreases in phenotypic traits, such as dry body weight gain, specific growth rate, condition index and survival rate, as well physiological functions, such as activities of antioxidant and digestive enzymes, were observed, demonstrating the resistance of razor clams under acidified conditions. Histological results showed that some direct damages on the structure of digestive gland was observed, including degradation of digestive tubular, atrophy of epithelial cells, loose cell arrangement, even diffuse. This study provides insights into the digestive performance of marine bivalves in a rapidly acidifying ocean.

Current understanding of cephalopod digestive tract physiology is based on relatively “old” literature and a “mosaic of data” from multiple species. To provide a background to the discussion of methodologies for investigating physiology we first review the anatomy of the cephalopod digestive tract with a focus on Octopus vulgaris, highlighting structure-function relationships and species differences with potential functional consequences (e.g., absence of a crop in cuttlefish and squid; presence of a caecal sac in squid). We caution about extrapolation of data on the digestive system physiology from one cephalopod species to another because of the anatomical differences. The contribution of anatomical and histological techniques (e.g., digestive enzyme histochemistry and neurotransmitter immunohistochemistry) to understanding physiological processes is discussed. For each major digestive tract function we briefly review current knowledge, and then discuss techniques and their limitations for the following parameters: 1) Measuring motility in vitro (e.g., spatiotemporal mapping, tension and pressure), in vivo (labelled food, high resolution ultrasound) and aspects of pharmacology; 2) Measuring food ingestion and the time course of digestion with an emphasis on understanding enzyme function in each gut region with respect to time; 3) Assessing transepithelial transport of nutrients; 4) Measuring the energetic cost of food processing, impact of environmental temperature and metabolic rate (flow-through/intermittent respirometry); 4) Investigating neural (brain, gastric ganglion, enteric) and endocrine control processes with an emphasis on application of molecular techniques to identify receptors and their ligands. A number of major knowledge lacunae are identified where available techniques need to be applied to cephalopods, these include: 1) What is the physiological function of the caecal leaflets and intestinal typhlosoles in octopus? 2) What role does the transepithelial transport in the caecum and intestine play in ion, water and nutrient transport? 3) What information is signalled from the digestive tract to the brain regarding the food ingested and the progress of digestion? It is hoped that by combining discussion of the physiology of the cephalopod digestive system with an overview of techniques and identification of key knowledge gaps that this will encourage a more systematic approach to research in this area.

Searching for molluscicidal agents of biological origin is mandatory to avoid the drawbacks of using chemical molluscicides. Algae are good candidates as sources of compounds with molluscicidal properties, especially if they are combined with modern techniques such as nanotechnology. This study aimed to evaluate the molluscicidal activity of two algal extracts and their biosynthesized zinc oxide nanoparticles (ZnONPs) on Biomphalaria alexandrina snails. The results indicated that the lowest LC50 was that of Spirulina platensis extract followed by Scenedesmus obliquus extract. Subchronic experiments were conducted for 2 weeks to indicate the effect of LCo of S. obliquus and S. platensis extracts, and 1/4 LCo of ZnONPs synthesized by S. obliquus and that synthesized by S. platensis. Histopathological alterations were observed in the digestive and hermaphrodite glands of treated snails. Also, random amplified polymorphic DNA‐polymerase chain reaction indicated genotoxic effects in the DNA of treated snails, as 1/4 LCo of ZnONPs synthesized by S. obliquus was the most effective treatment. The toxicity assay using Artemia salina indicated that the effective concentrations on B. alexandrina snails were safe on other non‐target organisms. [ABSTRACT FROM AUTHOR]

In aquatic environments the concurrent exposure of molluscs to microplastics (MPs) and estrogens is common, as these pollutants are frequently released by wastewater treatment plants into estuaries. Therefore, this study aimed to evaluate the independent and co-exposure impacts of polyethylene microplastics (PE-MPs) and estrogenic endocrine-disrupting chemicals (EEDCs) at environmentally relevant concentrations on polar metabolites and morphological parameters of the Sydney rock oyster. A seven-day acute exposure revealed no discernible differences in morphology; however, significant variations in polar metabolites were observed across oyster tissues. The altered metabolites were mostly amino acids, carbohydrates and intermediates of the Kreb's cycle. The perturbation of metabolites were tissue and sex-specific. All treatments generally showed an increase of metabolites relative to controls – a possible stimulatory and/or a potential hormetic response. The presence of MPs impeded the exposure of adsorbed and free EEDCs potentially due to the selective feeding behaviour of oysters to microplastics, favouring algae over similar-sized PE-MPs, and the formation of an eco/bio-corona involving faeces, pseudo-faeces, natural organic matter, and algae. [Display omitted] • Effects of microplastics and estrogens are sex and tissue specific. • Single and mixed exposure similarly affect overall metabolic status. • At environmentally realistic concentrations, contaminants exerted a stimulatory effect. • Exposure to low concentrations of both contaminants may present a hormetic response. [ABSTRACT FROM AUTHOR]

In the marine environment, nanoparticles play a role in adsorbing and catalytically degrading organic pollutants, thereby mitigating their toxic effects on aquatic organisms. This study aimed to investigate the impact of nano titanium dioxide (nTiO 2) and tris (2-chloropropyl) phosphate (TCPP) on the hemolymph and digestive function of the thick-shell mussel Mytilus coruscus. Mussels were divided into a control group, a group exposed to TCPP alone, a group exposed to a combination of TCPP and 0.5 mg/L nTiO 2 , and a group exposed to a combination of TCPP and 1 mg/L nTiO 2. After 14 days of exposure, oxidative stress responses, including superoxide dismutase (SOD) activity and malondialdehyde (MDA) content, immune defense responses, including acid phosphatase (ACP) and alkaline phosphatase (AKP) activities, and gene expression, including HSP70 expression, were measured in the hemolymph and digestive glands of the mussels. Compared to the control group, mussels solely exposed to 100 μg/L TCPP exhibited a significant reduction in SOD activity in the hemolymph. When TCPP was co-exposed with 0.5 mg/L nTiO 2 , there were significant increases in MDA content and AKP activity in both the digestive gland and hemolymph compared to the control group. Upon co-exposure of TCPP with 1 mg/L nTiO 2 , MDA content and AKP activity in the digestive gland significantly decreased, while SOD, ACP, and AKP activity in the hemolymph significantly increased and MDA content significantly decreased, returning to the control group levels. Furthermore, in the combined exposure, HSP70 gene expression significantly decreased as the nTiO 2 concentration increased from 0.5 mg/L to 1 mg/L. In summary, TCPP impacted the hemolymph and digestive function of mussels, whereas a concentration of 1 mg/L nTiO 2 effectively alleviated the toxic effects of TCPP. This study is crucial for assessing the ecological risks of nanoparticles and emerging organic pollutants in marine environments, and provides new insights into the interaction between nTiO 2 and TCPP, as well as the influence of nTiO 2 concentration on mitigating TCPP toxicity. [Display omitted] • Low concentration of nTiO 2 enhances the toxic effects of TCPP on mussels. • High concentration of nTiO 2 reduces the toxic effects of TCPP on mussels. • Mussels exhibit tissue-specific responses under combined low-concentration nTiO 2 and TCPP stress. [ABSTRACT FROM AUTHOR]

Classified as marine debris, man made materials are polluting the world's oceans. Recently, glass reinforced plastic (GRP) has been shown to degrade and contaminate the coasts. In this pioneering study, fibreglass particles have been detected in the soft parts of oysters and mussels collected from natural populations, in front of an active boatyard. The presence of particulate glass, with concentrations up to 11,220 particles/kg ww in Ostrea edulis and 2740 particles/kg ww in Mytilus edulis, was confirmed by micro Raman spectroscopy. The results showed higher accumulation during the winter months, when boat maintenance activities are peaking and, through repair work, the release of glass fibres in the environment is more likely. Bivalves are considered high risk species due to their sessile nature and extensive filter feeding behaviour. The microparticle inclusion may contribute to adverse impacts on physiological processes and eventually to a decline in the overall health and subsequent death of the animal. The high costs involved in the proper GRP disposal and the lack of recycling facilities worldwide lead to boat abandonement and further contamination of the coasts. For the first time this study presents the extensive fibreglass contamination of natural bivalve populations, in a popular South England sailing harbour, designated a biological and geological site of specific scientific interest (SSRI). [Display omitted] • Potential threat of glass reinforced plastic (GRP) boats to marine environment. • GRP debris found in oysters & mussels near boatyard on south England coast. • Filter-feeding bivalves at risk due to particle accumulation. • Higher levels in winter when boat maintenance increases. • First study of widespread GRP contamination in bivalves. [ABSTRACT FROM AUTHOR]

The decommissioning and normal functioning of nuclear facilities can result in the production and release of airborne particles in the environment. Aquatic biota are expected to be exposed to these particles considering that nuclear facilities are often located near water bodies. Aerosols, such as cement dust, can interact with radionuclides as well as with heavy metals, and therefore elicit not only radiological impacts but also chemical toxicity. In the present study, we aimed to determine the effects of hydrogenated cement particles (HCPs) as a first step before evaluating any radiotoxicity of tritiated cement particles in the marine mussels, Mytilus galloprovincialis. Responses at different levels of biological organisation were assessed, including clearance rate (CR), tissue specific accumulation, DNA damage and transcriptional expression of key stress related genes. Acute (5 h) and medium-term, chronic (11 d) exposures to 1000 μg L−1 HCPs showed that bioaccumulation, assessed using Cu as a proxy and determined by inductively coupled plasma mass spectrometry, was time and tissue dependent. The highest levels of Cu were found in the digestive gland (DG) after 11 d. HCP exposure caused changes in the expression of oxidative and other stress-related genes, including mt20 in DG and gst and sod in the gill after 5 h exposure, while an overexpression of hsp70 in the gill was observed after 11 d. Genotoxic effects in haemocytes were observed after 11 d of HCP exposure. Multivariate analysis indicated that oxidative stress is the most probable factor contributing to overall physiological dysfunction. Our results provide a baseline to perform further studies employing tritiated cement particles. Specifically, future work should focus on the DG since only this tissue showed significant bioaccumulation when compared to the negative control. [Display omitted] • Hydrogenated cement particle (HCP) accumulation is time- and tissue-specific. • HCP induced changes in gene expression of digestive gland and gill. • Genotoxic effects in mussel haemocytes observed after 11 d exposure to HCPs. • No effect on clearance rate detected after 11 d exposure to HCPs. [ABSTRACT FROM AUTHOR]

The aim of the present study was to investigate the combined effects of seasonality and anthropogenic pressure on a battery of oxidative stress, lipid peroxidation, protein oxidation, DNA damage and histological alterations in the native clam Ruditapes decussatus collected from a less contaminated area (LCA), Ghar El Melh, a moderately contaminated area (MCA), the North Lake, and a highly contaminated area (HCA), the South Lake, all located in the southern Mediterranean Sea. The accumulation of cadmium, lead, copper, iron and zinc was higher in the digestive glandsof clams collected from the MCA and the HCAthan in those from the LCA, particularly during the warm season. Our results reveal that metallothionein, lipid peroxidation, protein oxidation levels and antioxidant defence systems were higher, while acetylcholinesterase activity was lower, in clams from the MCAand HCAthan in those from the LCA. The results also indicate that clams from the MCA and the HCAare characterized by histological alterations and DNA damage. In conclusion, the evident changes of antioxidant defence systems and macromolecules between the studied lagoons reveal the perturbation of the physiological states of clams from polluted sites thatcope with seasonal changes and trace element accumulations.

The aim of this study is to elucidate the toxicity induced by PbCl2, administered in graded doses (1; 2.5; 5 mg/L), in the redox state, in the fatty acid composition and in the histological structure of Mactra corallina digestive glands. Our findings showed a progressive accumulation of Pb in the M. corallina digestive glands in all treated groups. After 5 days of treatment with PbCl2, an increase in H2O2, MDA, PCO, GSH, NPSH and MT levels was observed in the digestive glands of treated groups. Moreover, activities of antioxidant enzymes, such as GPx and CAT, increased while SOD activity decreased in all treated groups, indicating a failure of the antioxidant defense system. Furthermore, the cholinergic function was evaluated by assessing the acetylcholinesterase activity, which was inhibited in all the treated digestive glands compared to the control group. In our experiment, the levels of n-3 (Omega-3) and n-6 (Omega-6) polyunsaturated fatty acids were greatly altered in the groups treated with 5 mg/L of PbCl2 (p < 0.001). Indeed, DHA and EPA decreased significantly in the digestive glands treated with 2.5 and 5 mg/L of PbCl2, respectively. On the other hand, under exposure to the medium and high doses (2.5 and 5 mg/L), arachidonic acid (ARA) and linoleic acid (LA) significantly increased (p < 0.001). These changes in PUFA were confirmed by significant modifications in the polyene and peroxidation indices. The histological findings confirmed the biochemical results. Integrated parameters were used to explore the toxic effect of PbCl2 graded doses in Mactra corallina digestive gland. Metals accumulation in digestive glands of M. corallina was greatly dependent to dose of PbCl2. Metabolic and macromolecules damaging of clams digestive glands were more sensitive at higher PbCl2 doses. Fatty acids composition especially polyunsaturated fatty acids (PUFA) and essentials fatty acids such as docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) in clams digestive glands were intensively altered at higher PbCl2 doses. Inflammation responses revealed in studied tissue. [ABSTRACT FROM AUTHOR]

Histological and histochemical techniques were used to study specifics of parenchyma and stroma in digestive gland of Cornu aspersum. The parenchyma had 28.8 digestive ducts/mm2 on average (CV = 11.2 %) round-to-oval, with average cross-section of 27700.9 µm2 (CV = 28.1 %). The duct area (79.8 % of parenchyma) and the area of inter-duct connective tissue (20.2 % of parenchyma) were in ratio 4 : 1. The gland completely lacked elastic fibers. The muscle elements between the ducts were of different shape and arrangement, on average 59.7 µm long (CV = 42.3 %) and 1.41 µm wide (CV = 63.2 %). The gland’s capsule was formed by three layers: epithelial, muscular, and the layer of collagen fibers. More than 60 % of the capsule’s thickness belonged to the muscular layer. The proportion of calcium cells in the digestive duct wall was 15.5 % (CV = 23.5 %). Cells of digestive ducts contained a lot of vacuoles with brown granules (336.8 per 1 mm2, CV = 36.1 %). The vacuole area was 2.2 % of all area of digestive gland (CV = 15.8 %). The uneven location of muscle elements and brown granules in the glandular parenchyma indicated the functional features of the individual parts of the digestive gland.

Growth factors are mostly secreted proteins that play key roles in an organism’s biophysical processes through binding to specific receptors on the cell surface. The mollusk-like growth factor (MLGF) is a novel cell signaling protein in the adenosine deaminase-related growth factor (ADGF) subfamily. In this study, the MLGF gene was cloned and characterized from the digestive gland tissue of Pacific abalone and designated as Hdh-MLGF. The transcribed full-length sequence of Hdh-MLGF was 1829 bp long with a 1566 bp open reading frame (ORF) encoding 521 amino acids. The deduced amino acid sequence contained a putative signal peptide and two conserved adenosine deaminase domains responsible for regulating molecular function. Fluorescence in situ hybridization localized Hdh-MLGF in the submucosa layer of digestive tubules in the digestive gland. The mRNA expression analysis indicated that Hdh-MLGF expression was restricted to the digestive gland in the adult Pacific abalone. However, Hdh-MLGF mRNA expressions were observed in all stages of embryonic and larval development, suggesting Hdh-MLGF might be involved in the Pacific abalone embryonic and larval development. This is the first study describing Hdh-MLGF and its involvement in the Pacific abalone embryonic and larval development.

Land snails are often used to monitor soil pollution. The present study aimed to investigate the effects of Weatfert R complex mineral nitrogen, phosphorus, and potassium (N: P: K) fertilizer with high phosphorous content (NPK: 8/36/15 + SO3:13) on Eobania (syn. Helix) vermiculata used as a bioindicator species. Moreover, the histological and biochemical changes in the digestive gland were examined and biomarkers of environmental stress (glutathione peroxidase and lactate dehydrogenase activity) measured. Results showed that the fertilizer tested has a negative impact on the growth rate of juvenile snails. They also revealed alterations in the structure of the digestive gland and changes in biomarker response values in the field, accompanied by significant correlations with bioconcentration. Meanwhile, the biochemical parameters showed varying results representing an increase in the protein rate and a decrease in lipid and carbohydrate rates after treatment with weatfertin. Overall, our study showed that the fertilizer tested could have potential hazards on E. vermiculata and this snail was a suitable sentinel organism and the selected biomarkers are efficient for soil assessment. [ABSTRACT FROM AUTHOR]

Abstract Background Monacha obstructa is one of the most abundant gastropod of Egyptian farms. It is a destructive land snail as they cause great damage to vegetables and crops. The present study aimed to control snails by ultraviolet radiation. Materials and methods Snails under study were subjected to the same dose of UV-A radiation for two different periods. The source of radiation was UV-fluorescent lamps, UV-A 366 nm. Small pieces of mantle edge, foot, digestive gland, and intestine of treated and untreated snails were taken and prepared for histological examination by light microscope. While small pieces of mantle edge and foot only were prepared for scanning electron microscopic examination. Results Histopathological changes in the mantle, foot, digestive gland, and intestine of treated snails were studied. The changes included destruction and disorganization of many cell types. UV-A radiation affected the fitness of the snails; they became less active. The changes in different organs will lead to alteration in their functions. Conclusions UV-A has a destructive effect on different organs of the snails under study. This effect will lead to the control of this snail (Monacha obstructa).

Although some studies have evaluated the use of Siphonaria lessonii as a bioindicator of pollution, no study has identified the effects of human activities on the digestive gland, which is the main centre of detoxification of xenobiotics and a target organ in contamination studies. Thus, the present work aims to evaluate the use of this species as a suitable sentinel of contamination by analysing the digestive gland and shell alterations. The study was carried out in three populations exposed to different degrees of anthropogenic impact in the coast of Buenos Aires: a reference site (VG), a mid-impacted site (MPL) and a highly-impacted site (MPP). A histological analysis of the digestive gland was performed, as well as an assessment of the geometric morphometry, thickness, density and microstructure of the shell. Our results indicated that the individuals from the impacted sites present several histological alterations in the tubules of the digestive gland. These included hypertrophy and hyperplasia of different cell types (MPP), alterations of the digestive tube morphology (MPL and MPP), the presence of lipofuscin-like substances (MPL) and a high inflammatory response (MPP). In the shells, neither microstructural malformations nor changes in the elemental composition were found. However, shell morphometric variations and a decrease in shell hardness (thickness and density) were observed in the impacted sites. In conclusion, our results indicate that S. lessonii is a well-suited sentinel of contamination since the effects of anthropogenic impact may be reflected in both soft and hard structures. Although further investigations are necessary to identify the relationship between these effects and their potential causing agents, these simple and low-cost methodological approaches could be used to diagnose disturbance in the ecosystem health status where this species inhabits.

Abstract INTRODUCTION: Biomphalaria snails may display varying levels of susceptibility to Schistosoma mansoni infection. We have been developing an in vitro model to study the interaction between the snail and the parasite, using tissue-derived cell cultures from Biomphalaria. METHODS: The digestive gland- and kidney-derived cells from primary cultures of resistant (B. tenagophila Taim) and susceptible (B. tenagophila HM and B. glabrata BH) strains of Biomphalaria were exposed to S. mansoni sporocysts. RESULTS: S. mansoni sporocysts were surrounded and encapsulated exclusively by cells derived from the digestive gland (DG) of B. tenagophila Taim. The process was followed by a marked decrease in the number of free sporocysts in the culture medium. The morphological characteristics of DG-derived cells in culture have been described. CONCLUSIONS: Cells derived from DG (but not SK) primary cultures of B. tenagophila Taim may participate in S. mansoni sporocyst control.

Digestive microbiota provide a wide range of beneficial effects on host physiology and are therefore likely to play a key role in marine intertidal bivalve ability to acclimatize to the intertidal zone. This study investigated the effect of intertidal levels on the digestive bacterial microbiota of oysters (Crassostrea gigas) and clams (Ruditapes philippinarum), two bivalves with different ecological niches. Based on 16S rRNA region sequencing, digestive glands, seawater and sediments harbored specific bacterial communities, dominated by operational taxonomic units assigned to the Mycoplasmatales , Desulfobacterales and Rhodobacterales orders, respectively. Field implantation modified digestive bacterial microbiota of both bivalve species according to their intertidal position. Rhodospirillales and Legionellales abundances increased in oysters and clams from the low intertidal level, respectively. After a 14-day depuration process, these effects were still observed, especially for clams, while digestive bacterial microbiota of oysters were subjected to more short-term environmental changes. Nevertheless, 3.5 months stay on an intertidal zone was enough to leave an environmental footprint on the digestive bacterial microbiota, suggesting the existence of autochthonous bivalve bacteria. When comparing clams from the three intertidal levels, 20% of the bacterial assemblage was shared among the levels and it was dominated by an operational taxonomic unit affiliated to the Mycoplasmataceae and Spirochaetaceae families. [ABSTRACT FROM AUTHOR]

The determination of in vitro digestibility of acid proteases in the digestive gland (DG) of adult O. vulgaris (> 1.2 kg) was performed, using the flesh of four different prey species (mackerel, Scomber scombrus; green crab, Carcinus maenas; swimming crab, Necora puber; Shortfin squid, Illex coindetii). For each, four processing treatments were applied: (1) frozen, (2) boiled at 100 °C for 1 min, (3) lyophilized, and (4) oven dried at 70 °C. A pH-Stat method was used to determine in vitro digestibility at pH 3. Results showed that digestibility was higher for lyophilized and frozen flesh, compared to the other treatments involving heating (boiled and oven dried), regardless of the species tested. Also, differences were found between species, within each treatment, with higher digestibility for crab (N. puber) and squid (I. coindetii). Regarding "in vitro" acid proteases digestibility, which is the most important for O. vulgaris, results indicate that heat treatments close and/or higher than 70 °C promoted changes in the flesh that prevented or reduced their assimilation by the DG of O. vulgaris. [ABSTRACT FROM AUTHOR]

Mixed pollution of the freshwaters is a worldwide problem; and the scientific evidence showed its impacts on the bivalves` biological processes. In the present study, the freshwater clam, Caelatura nilotica was collected from two water habitats with different degrees of pollution. Examination of gills and digestive gland using routine histology, scanning (SEM), and transmission (TEM) electron microscopy was done. In SEM investigations of the gills, deformation and erosion of cilia, clogging of gills by mucous and ghost gills were observed in the clams collected from a more polluted site. Histological structure of gills proved the appearance of ciliates between the gill filaments. Also, inflammatory reactions appeared and the epithelia lost their integrity and desquamated. The digestive gland showed haemocytes infiltrations, necrosis in some digestive tubules, and granulocytomas was observed. A full description of the digestive gland was done using TEM. In addition, more abnormalities were recorded in different types of the haemocytes, digestive and basophilic cells, flagella, microvilli, lysosomes, residual bodies, mitochondria, nucleus and chromatin with blebbing in most of them. In conclusion, mixed pollution compromised the functions of the gills and digestive gland of the clam, C. nilotica, under the effect of synergistic and/ or antagonistic actions of inorganic and organic contaminants with reference to the more severe effects of the non-point source than the point-source pollution in water pollution impacts. [ABSTRACT FROM AUTHOR]

1,3-β-glucanase enzyme has been proved as antibiofilm by hydrolyzing the main component of extracellular matrix of C. albicans polymicrobial biofilm, to prevent resistancy during the use of antibiotics. The aim of this study is to construct a metagenomic expression library from Achatina fulica’s digestive gland and to screen for a novel 1,3-β-glucanase genes by using its specific substrate of laminarin. A cDNA expression library was constructed using the λTriplEx2 vector in the E. coli strain XL1-Blue. Cre-recombinase circularization was used to convert λTriplEx2 to pTriplEx2 in the E. coli strain BM 25.8;then IPTG induction was used to express 1,3-β-glucanase. High-efficiency cDNA library of A. fulica’s digestive gland was constructed, from where we obtained seventeen halo positive plaques, among them is a novel 1,3-β-glucanase gene designated MkafGlu1. Its nucleotide sequence has similarities to the endo-1,3-β-glucanase from Gossypium hirsutum, as well as the β-glucanases from Paenibacillus mucilaginosus, Verticillium alfalfa, and Cryptopygus antarcticus of 45%, 40%, 38% and 37%, respectively. An open reading frame of 717 bp encoded a protein of 239 amino acids. A novel 1,3-β-glucanase gene called MkafGlu1 was successfully expressed in E.coli BM 25.8 with activity of 1.07 U mL-1. [ABSTRACT FROM AUTHOR]

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The vulnerability of aquatic ecosystems due to the entry of cadmium (Cd) is a concern of public and environmental health. This work explores the ability of tissues and symbiotic corpuscles of Pomacea canaliculata to concentrate and depurate Cd. From hatching to adulthood (4 months), snails were cultured in reconstituted water, which was a saline solution in ASTM Type I water. Then, adult snails were exposed for 8 weeks (exposure phase) to Cd (5 μg/L) and then returned to reconstituted water for other 8 weeks (depuration phase). Cadmium concentration in the digestive gland, kidney, head/foot and viscera (remaining of the snail body), symbiotic corpuscles, and particulate excreta was determined by electrothermal atomic absorption spectrometry. After exposure, the digestive gland showed the highest concentration of Cd (BCF = 5335). Symbiotic corpuscles bioaccumulated Cd at a concentration higher than that present in the water (BCF = 231 for C symbiotic corpuscles, BCF = 8 for K symbiotic corpuscles). No tissues or symbiotic corpuscles showed a significant change in the Cd levels at different time points of the depuration phase (weeks 8, 9, 10, 12, and 16). The symbiotic depuration through particulate excreta was faster between weeks 8 and 10, and then slower after on. Our findings show that epithelial cells of the digestive gland of P. canaliculata and their symbiotic C corpuscles are sensitive places for the bioindication of Cd in freshwater bodies. [ABSTRACT FROM AUTHOR]