Density shift, morphological damage, lysosomal fragility and apoptosis of hemocytes of Indian molluscs exposed to pyrethroid pesticides

Immunotoxic effects of exposure to the antifouling copper(I) biocide on target and nontarget bivalve species: a comparative in vitro study between Mytilus galloprovincialis and Ruditapes philippinarum

Edible bivalves constitute an important bioresource from an economic point of view, and studies on their immune responses to environmental pollutants are crucial for both the preservation of biodiversity and economic reasons. The worldwide diffusion of copper(I)-based antifouling paints has increased copper leaching into coastal environments and its potential impact on both target and nontarget organisms. In this study, immunotoxicity assays were carried out with short-term (60 min) cultures of hemocytes from the bivalves Mytilus galloprovincialis-a mussel dominant in the macrofouling community-and Ruditapes philippinarum-a clam dominant in the soft-sediment community-exposed to CuCl to compare the toxic effects on their immune responses. The LC50 values were similar, 40 μM (3.94 mg L-1) for the mussel and 44 μM (4.33 mg L-1) for the clam. In both species, apoptosis occurred after exposure to 1 µM (98.9 μg L-1) CuCl, the concentration able to significantly increase the intracellular Ca2+ content. Biomarkers of cell morphology and motility revealed microfilament disruption, a significant decrease in yeast phagocytosis and lysosome hydrolase (β-glucuronidase) inhibition beginning from 0.5 µM (49.5 μg L-1) CuCl in both the mussel and clam. The same concentration of CuCl affected biomarkers of oxidative stress, as a significant decrease in reduced glutathione content in the cytoplasm and inhibition of mitochondrial cytochrome-c oxidase (COX) were detected in both species. Comparison of the biomarkers showed that clam is more sensitive than the mussel regarding alterations to the lysosomal membrane and reactive oxygen species (ROS) production, which supports the potential harmful effects of antifouling biocides on the survival of nontarget pivotal species in the coastal community.

Hemocytes: A Useful Tool for Assessing the Toxicity of Microplastics, Heavy Metals, and Pesticides on Aquatic Invertebrates

Invertebrates have long been an important tool for assessing water pollution due to their characteristics as intermediate consumers in aquatic ecosystem food chains. Most of the time, the effects of contaminants are measured by their effect on oxidative status or by mortality, although there already exists an easier tool-hemocytes. Hemocytes are circulating cells with a very important role in the immune system of invertebrates, which can be found within the hemolymph, analogous to the blood in vertebrates. The collection of hemolymph samples is easy, fast, minimally invasive, and poses no danger to the life of invertebrates. The purpose of this review was to highlight the advantages of using hemolymph for toxicity assays of various substances, including heavy metals, micro- and nano-plastics, pesticides, hydrocarbons, and oil spills. A literature search was conducted for this purpose using the most common and most often used databases, with a focus on the most recent and relevant studies. Bivalve mollusks, crustaceans, and gastropods were chosen for this investigation. This review found a growing number of studies choosing to use hemolymph as the standard methodology for toxicology assays, confirming their qualities as reliable tools.

Bivalve Haemocyte Subpopulations: A Review

Bivalve molluscs stand out for their ecological success and their key role in the functioning of aquatic ecosystems, while also constituting a very valuable commercial resource. Both ecological success and production of bivalves depend on their effective immune defence function, in which haemocytes play a central role acting as both the undertaker of the cellular immunity and supplier of the humoral immunity. Bivalves have different types of haemocytes, which perform different functions. Hence, identification of cell subpopulations and their functional characterisation in immune responses is essential to fully understand the immune system in bivalves. Nowadays, there is not a unified nomenclature that applies to all bivalves. Characterisation of bivalve haemocyte subpopulations is often combined with 1) other multiple parameter assays to determine differences between cell types in immune-related physiological activities, such as phagocytosis, oxidative stress and apoptosis; and 2) immune response to different stressors such as pathogens, temperature, acidification and pollution. This review summarises the major and most recent findings in classification and functional characterisation of the main haemocyte types of bivalve molluscs.

Pathogenic Impacts of Bacillus cereus Strains on Crassostrea gigas

Regarding the economic importance of bivalve farming, a great deal of interest has recently been devoted to studying the pathogenesis of infectious diseases of these mollusks to prepare for public health emergencies. Bacillus cereus is one of these pathogens; it is a ubiquitous soil bacterium responsible for many types of gastrointestinal diseases associated with food. This study was conducted to determine the pathogenic effect of B. cereus on Crassostrea gigas. This effect was studied by assessing hemocytes death using flow cytometry analysis. The results showed that only ∼15% of C. gigas were able to survive after B. cereus artificial infection with 10⁸ CFU (colony-forming unit)/oyster. Evenly, the percentage of nonviable hemocytes gradually increased with the concentration of B. cereus, with a peak value of ∼40% after infection. Indeed, findings showed that this strain is harmful to C. gigas.

Biochemical, physiological (haematological, oxygen-consumption rate) and behavioural effects of mercury exposures on the freshwater snail, Bellamya bengalensis

The widespread occurrence of Mercury (Hg) and its derivatives in the aquatic environment and risks to the health of local populations has necessitated investigations into its toxic effects on sessile species. The toxicity of Mercury was observed sequentially from 96 h acute exposure regime (behavioural endpoints) to chronic durations (haematological and biochemical toxicity endpoints) in Bellamya bengalensis. Time-dependent lethal endpoints for acute toxicity (LC50) of mercury i.e., 24,48,72 and 96 h were estimated as 0.94, 0.88, 0.69 and 0.40 mg/l respectively. Threshold effect values i.e., LOEC (Lowest Observed Effect Concentration), NOEC (No Observed Effect Concentration) and MATC (Maximum Acceptable Toxicant Concentration) at 96 h were found to be 0.10, 0.05, 0.039 mg/l respectively. The study of oxygen consumption rate and behavioural changes during acute toxicity and haematological and biochemical responses during chronic toxicity to sublethal concentrations (10% and 20% of 96 h LC50) of mercury to the snail were also conducted. The organisms showed initial elevation at 24 h but later gradual decrease in oxygen consumption rate with the increase of concentration of mercury and time of exposure. For behavioural studies, variable test concentrations from 0.00 to 1.00 mg/l were used for 24, 48, 72 and 96 h. The crawling activity and clumping tendency decreased with the progress of time at all treatment periods and stopped ultimately at 96 h of exposure from 0.7 mg/l onwards whereas touch reflex was not observed at 96 h exposure at all treatments except at 0.09 mg/l. In haemocyte count, no significant variation was observed among control values between various exposure periods (p > 0.05) though variations were observed in sub-lethal concentrations versus control at all treatment duration (7, 14, 21, 28d, p < 0.05). In biochemical response study, the protein content in hepatopancreas of the snails treated at sublethal concentrations of mercury (10% and 20% of 96 h LC50) reduced significantly versus control after 21d of exposure (p < 0.05). In gonads, the protein content of the treated snails significantly reduced at all treatment concentrations versus control at all exposure times (p < 0.05). Based on the safe levels indicated above, the concentration of 0.01 to 0.04 ppm of mercury can be considered safe for Bellamya bengalensis and any less-hardy aquatic species. These responses elicited by our molluscan model will not only help in biomonitoring of environmental mercury contamination in water bodies but will also provide support to ecological health and risk assessment.

Pendimethalin-based herbicide impairs cellular immune response and haemocyte morphology in a beneficial ground beetle

Herbicides have become the most commonly applied agrochemicals in agroecosystems. Thus, basic knowledge of their physiological effects on insects is needed, especially for understanding their impact on beneficial insect species. In this study, we evaluated the effect of a pendimethalin-based herbicide (PND) on the cellular immune response of the carabid beetle Harpalus (Pseudoophonus) rufipes (De Geer 1774) (Coleoptera, Carabidae), acting as biocontrol agent in agroecosystems. Total and differential haemocyte counts and phagocytosis assay, performed by injecting in vivo carboxylate-modified polystyrene latex beads, were measured in beetles exposed to a recommended field dose (4L per ha) of PND to evaluate the exposure effects over the time. The pattern of haemocyte subpopulations and the decrease of the phagocytic index after the exposure to PND suggested a lowering of P. rufipes ability to face an infection performing a cell-mediated response. PND was also found to cause cytotoxic effects on the haemocyte ultrastructure. Ultrastructural alterations such as irregular shape, large vacuolization of the cytoplasm, and condensation of marginated chromatin were recorded from 2d of exposure. The loss of RER, Golgi apparatus, mitochondria integrity and the swelling of the outer nuclear membrane found in some haemocytes suggested an interference of PND with the membrane permeability. Results indicated that the exposure to PND impairs the distribution, morphology and physiological functions of haemocytes causing a decrease of P. rufipes immunocompetence. Moreover, the sensitivity to herbicide exposure makes this species a suitable model and a useful bioindicator for monitoring exposure effects on non-target species. This study provides useful information to protect and preserve biodiversity of insects in agroecosystems.

Shift in phagocytosis, lysosomal stability, lysozyme activity, apoptosis and cell cycle profile in the coelomocytes of earthworm of polluted soil near a tannery field of India

Calcutta Leather Complex of the state of West Bengal, India has been designated as an industrially active zone with around 400 active tannery units. This area spanning 4.5 km² is surrounded by human habitation. The soil of this region is contaminated with metal pollutants and exhibited an alteration in selected physicochemical parameters, namely cation exchange capacity, moisture content, pH, total nitrogen, total organic carbon and water holding capacity. Metaphire posthuma, a common variety of endogeic earthworm inhabiting this region is thus continuously exposed to these toxic metals. Coelomocytes, the chief immune effector cells of earthworm presented a shift in phagocytosis, lysosomal membrane stability, lysozyme and phosphatase activity, physiological apoptosis and cell cycle profile of M. posthuma sampled from the soil of tannery industry. Presence of high concentration of toxic metals and change in the physicochemical characteristics of soil led to a state of cellular stress and immunocompromisation in M. posthuma, a common inhabitant of soil of this region. Experimental endpoints bear ecotoxicological significance as biomarkers of physiological stress in earthworm for monitoring the health of soil around this tannery industrial zone.

Physiological and biochemical responses of Mediterranean green crab, Carcinus aestuarii, to different environmental stressors: Evaluation of hemocyte toxicity and its possible effects on immune response

Effects of natural stressors such as copper (Cu²⁺), temperature, hypoxia, chloroform and adrenaline on physiological and biochemical responses were investigated in the Mediterranean green crab Carcinus aestuarii from tidal shallow waters of Narta Lagoon, Albania. For this purpose, hemolymph glucose levels, total and differential hemocyte count, in normal and eye-stalked individuals, exposed to above mentioned stressors like, were assessed. In addition, lysosomal membrane stability was evaluated as biomarker of hemocyte toxicity, with possible implications on crab immune response. Hemolymph glucose levels were significantly increased in all treatment groups with 1.25-to 3.5-fold above baseline levels of 37.8 ± 2.7 mgdL^-1. Response times were being manifested within 30-120 min following exposure and recovery happened within 2 h of restoration of pretreatment conditions. Total hemocyte count (THC) and differential hemocyte count (DCH) showed a significant decrease for all stressors, except for copper, were an increase of semi-granular hemocyte fraction were recorded. Meanwhile, significant reduction of neutral red retention time (NRRT), in both eyestalk-ablated and exposed animals, were recorded, indicated the loss of hemocyte lysosomal membrane integrity. The responsiveness of hemolymph blood levels to all stressors, the decrease in total hemocyte count, as well as the loss of lysosomal membrane integrity demonstrated that exposure to environmentally realistic stressors placed a heavy metabolic load on C. aestuarii, modulating their immune competence and overall physiological wellness. Overall, results suggest that monitoring cellular and biochemical parameters like hemolymph glucose titres, TCH, DHC and NRRT, may be useful and sensitive means of evaluating the crustacean's ability to cope with the wide variety of environmental stressors through modulation of the immune parameters.

Physiology and immunity of the invasive giant African snail, Achatina (Lissachatina) fulica, intermediate host of Angiostrongylus cantonensis

As one of the most successful invasive land snail species, Achatina (Lissachatina) fulica Bowdich, 1822 has achieved wide global distribution, particularly in (sub)tropical regions, with further dispersal likely due to climate change. This species of giant African snails (up to 17 cm shell length) is a pest that has extensive negative impact on agriculture and can serve as vector for several parasites, including Angiostrongylus cantonensis, a nematode parasite that causes (human) eosinophilic meningitis, an emergent disease. Investigation showed that A. cantonensis infection negatively impacts the metabolism of A. fulica by depleting polysaccharide stores of the intermediate host, compromising the energy balance of the snail. A review of the literature indicates that A. fulica possesses potent innate type immune defenses to counter infection, including phagocytic hemocytes capable of deploying reactive oxygen species and lectins for non-self recognition, a serine protease-dependent coagulation response (not observed in other taxa of gastropods), as well as antimicrobial proteins including achacin, an antimicrobial protein. A recent chromosome level genome assembly will facilitate progressively detailed characterization of these immune features of A. fulica. We strongly encourage further immunological studies of A. fulica, ranging from organismal level to molecular biology to gain better understanding of the A. fulica internal defense response to nematode pathogens like A. cantonensis and the contribution of immune function to the invasiveness of (snail) species. Characterization of immunity of A. fulica, representing the understudied Stylommatophora (panpulmonate landsnails) will also broaden the comparative immunology of Gastropoda.

Effects of azinphos-methyl on enzymatic activity and cellular immune response in the hemolymph of the freshwater snail Chilina gibbosa

The use of a battery of biomarkers, especially those more closely related to species integrity, is desired for more complete ecotoxicological assessments of the effects of pesticide contamination on aquatic organisms. The phosphorodithioate azinphos-methyl has been intensively used in agriculture worldwide and have been found in the habitat of Chilina gibbosa, a freshwater snail endemic to South America. This snail has been proposed as a good model organism for ecotoxicity bioassays on the basis of studies focused mainly on enzymatic responses in whole tissue homogenates. Our aim was to evaluate the effect of an acute 48 h exposure to an environmental concentration of azinphos-methyl on C. gibbosa hemolymph enzymatic activity and cellular immune response. Our results show that cholinesterase activity was strongly inhibited (94%) in hemolymph of exposed snails. Carboxylesterase activity measured with p-nitrophenyl butyrate and glutathione S-transferase activity were augmented 47% and 89% respectively after exposure. No differences were found for hemolymph carboxylesterase activity measured with p-nitrophenyl acetate. These results differ from those reported for whole tissue homogenates and reveal that tissue-specific responses of enzymatic biomarkers exist in this species. Regarding immune cell response, hemocytes were identified for the first time for C. gibbosa. Their viability and phagocytic activity decreased after azinphos-methyl exposure although total number of circulating cells did not differ between treatments. We conclude that concentrations of azinphos-methyl that can be found in the environment can compromise both hemolymph cholinesterase activity and the immune system of C. gibbosa. Furthermore, we propose that carboxylesterase and glutathione S-transferase activities measured in hemolymph and hemocyte viability and phagocytic activity could be incorporated as sensitive biomarkers to evaluate the effects of pesticide exposure on this and related species.

Differential response between histological and biochemical biomarkers in the apple snail Pomacea canaliculata (Gasteropoda: Amullariidae) exposed to cypermethrin

To develop effective programs to monitor water quality is necessary to identify sensitive biomarkers in indicator species. The aim of this study was to evaluate different biomarkers in the apple snail Pomacea canaliculata exposed to the insecticide Cypermethrin (CYP). Adult male and female snails were exposed to sublethal CYP concentrations (10, 25 and 100μgl^-1) for 1, 4, 7 and 14days. The recovery of the exposed snails was also studied by a post-exposure assay. The activities of the enzymes superoxide dismutase (SOD), catalase (CAT) and glutathione-S-transferase (GST), the levels of lipid peroxidation (LPO) and protein oxidation (PC) in digestive gland and gills were studied as biomarkers of exposure. Histopathological changes in target tissues were also evaluated. In digestive gland, CYP caused a significant increase in SOD, CAT and GST activities compared to control (p<0.05) as well as in LPO and PC levels (p<0.05). However, such biochemical effects were neither concentration nor time dependent. Histopatological changes were observed in the exposed groups, such as an increase in the number of basophilic cells, hemocytic infiltration and epithelia atrophy. Additionally, a positive correlation between the surface occupied by pigmented corpuscles and CYP concentrations was observed at all exposure periods. Gills showed greater sensitivity to oxidative damage than digestive gland. CYP caused an acute toxic effect in LPO levels in this respiratory organ. The gill filament of exposed snails, exhibited a reduction or loss of cilia, vacuolization of the columnar cells and an increase in haemocyte content irrespective of the concentration. High concentrations of CYP caused disruptions in the columnar muscle fibers. In general, snails did not show an improvement in their basal state during post-exposure treatment. Apparently, males and females do not have differential sensitivity to the pesticide. The results of this study suggest that histopathological changes are the most sensitive time- and dose-dependent biomarkers of toxicity induced by CYP in P. canaliculata.

Studies on acute and chronic toxicity of cadmium to freshwater snail Lymnaea acuminata (Lamarck) with special reference to behavioral and hematological changes

Molluscs have long been regarded as promising bioindicator and biomonitoring subjects for heavy metals as molluscs are highly tolerant to heavy metals and exhibit high accumulation in their body. In spite of several previous studies about the impact of cadmium on molluscs, little information exists in literatures concerning the toxic effects of cadmium on Lymnaea acuminata, especially pertaining to behavioral and hematological changes as these are considered effective bioindicators and biomonitoring variables for detecting heavy metals in polluted water bodies. In the present study, the median lethal concentrations of cadmium chloride to snail, Lymnaea acuminata, were estimated to be 9.66, 7.69, 6.26, and 5.54 mg/L at 24, 48, 72, and 96 h, respectively. For behavioral studies, variable test concentrations of cadmium from 0.00 to 10 mg/L were used. The clumping tendency, crawling activity, and touch reflex in the exposed snails were gradually decreased with higher concentrations at 72 and 96 h. For measuring the hemocyte numbers in the circulating hemolymph of snail during chronic cadmium exposure, two sublethal doses of cadmium (10 and 20% 96-h LC₅₀-0.55 and 1.11 mg/L, respectively) were used. A significant variation (p < 0.05) from the control at all exposure times (7, 14, 21, and 28 days) was recorded at 1.11 mg/L concentration. The total count of circulating hemocytes was significantly reduced (p < 0.05) compared to the controls at both concentrations of cadmium exposure at all time periods except 14 and 21 days exposure at 0.55 mg/L where values were non-significantly increased. In comparison between two sublethal doses, blood cells were significantly (p < 0.05) lowered at 1.11 mg/L cadmium treatment. Considering the behavioral and hematological data, it seems possible to forecast the physiological state of snails in cadmium-contaminated water bodies and these findings can be used in determining the safe disposal level of cadmium in aquatic ecosystem.

Functional characterization of hemocytes from Chinese mitten crab Eriocheir sinensis by flow cytometry

Hemocytes comprise a diversity of cell types with functional and structural heterogeneity, and they play key roles in the host defense of invertebrates. In the present study, the hemocytes from Chinese mitten crab Eriocheir sinensis were directly separated into two groups by flow cytometry. The hemocytes in P1 group were full of round and abundant granules with deeply staining cytoplasm, while P2 hemocytes were more diverse with a wide range of sizes and less granularity. Both P1 and P2 hemocytes exhibited phagocytic ability, but the phagocytic rate of P1 hemocytes increased which was significantly higher than that of P2 hemocytes after LPS stimulations. The levels of ROS production and intracellular Calcium as well as lysosome content were higher in P1 hemocytes than that in P2 hemocytes under both normal and immune-activated situations. The genes involved in phagocytosis, antimicrobial and antioxidant activities were mainly expressed in P1 hemocytes, while the genes involved in proPO activation system were highly expressed in P2 hemocytes. These results collectively suggested that P1 hemocytes were the main immunocompetent hemocytes in Chinese mitten crab and P2 hemocytes mainly participated in proPO activation system.

Histopathological effects of cypermethrin and Bacillus thuringiensis var. israelensis on midgut of Chironomus calligraphus larvae (Diptera: Chironomidae)

Pesticides are extensively used for the control of agricultural pests and disease vectors, but they also affect non-target organisms. Cypermethrin (CYP) is a synthetic pyrethroid used worldwide. Otherwise, bioinsecticides like Bacillus thuringiensis var. israelensis (Bti) have received great attention as an environmentally benign and desirable alternative. In order to evaluate the toxicity of those pesticides, Chironomus calligraphus was selected due to its high sensitivity to some toxicants. Third and fourth instars larvae were exposed to serial dilutions of CYP and Bti to determine LC₅₀ values. In order to evaluate the potentially histopathological alterations as biomarkers, after 96-h of exposure, live larvae were fixed for histological analysis of the mid region of digestive tract. The 96-h LC₅₀ values were 0.52 and 1.506μg/L for CYP and Bti, respectively. Midgut histological structure of the control group showed a single layer of cubical cells with microvilli in their apical surface and a big central nucleus. The midgut epithelium of larvae exposed to a low concentration of CYP (0.037μg/L) showed secretion activity and vacuolization while at high concentration (0.3μg/L) cells showed a greater disorganization and a more developed fat body. On the other hand, Bti caused progressive histological damage in this tissue. Chironomus calligraphus is sensitive to Bti and CYP toxicity like other Chironomus species. The histopathological alterations could be a valuable tool to assess toxicity mechanism of different pesticides.

Glucomannan's protective effect on the virulence of Vibrio splendidus in pacific oyster

We examine the effect of Glucomannan, extracted from Candida utilis yeast, on immune parameters and resistance to Vibrio splendidus of Crassostreagigas. Our results showed that Glucomannan was a successful anti-adhesive molecule; it exhibited a stronger inhibitory effect on adhesion of Vibrio splendidus in infected Crassostreagigas. Vibrio splendidus viable cells number declined after incubation with Glucomannan. Furthermore, the Glucomannan diet showed higher activity to trigger the immune response against bacteria. Glucomannan applications, in biological control of seafood associated pathogens can be an alternative solution, providing consumer with a product of good quality owing to the use of 40 non-toxic compounds. Based on our results, Glucomannan could be used as a bio-protective culture in oyster's depuration to prevent Vibrio splendidus growth.

Morphological alteration, lysosomal membrane fragility and apoptosis of the cells of Indian freshwater sponge exposed to washing soda (sodium carbonate)

Washing soda is chemically known as sodium carbonate and is a component of laundry detergent. Domestic effluent, drain water and various anthropogenic activities have been identified as major routes of sodium carbonate contamination of the freshwater ecosystem. The freshwater sponge, Eunapius carteri, bears ecological and evolutionary significance and is considered as a bioresource in aquatic ecosystems. The present study involves estimation of morphological damage, lysosomal membrane integrity, activity of phosphatases and apoptosis in the cells of E. carteri under the environmentally realistic concentrations of washing soda. Exposure to washing soda resulted in severe morphological alterations and damages in cells of E. carteri. Fragility and destabilization of lysosomal membranes of E. carteri under the sublethal exposure was indicative to toxin induced physiological stress in sponge. Prolonged exposure to sodium carbonate resulted a reduction in the activity of acid and alkaline phosphatases in the cells of E. carteri. Experimental concentration of 8 mg/l of washing soda for 192 h yielded an increase in the physiological level of cellular apoptosis among the semigranulocytes and granulocytes of E. carteri, which was suggestive to possible shift in apoptosis mediated immunoprotection. The results were indicative of an undesirable shift in the immune status of sponge. Contamination of the freshwater aquifers by washing soda thus poses an alarming ecotoxicological threat to sponges.

Antioxidative and immunological responses in the haemolymph of wolf spider Xerolycosa nemoralis (Lycosidae) exposed to starvation and dimethoate

The aim of this study was to assess the intensity of enzymatic antioxidative parameters [catalase (CAT), glutathione peroxidase (GSTPx), glutathione reductase (GR), total antioxidant capacity (TAC)] and percentage of high granularity cells as well as low to medium granularity cells in haemolymph of wolf spiders Xerolycosa nemoralis exposed to starvation and dimethoate under laboratory conditions. Only in starved males, haemolymph included a lower percentage of high granularity cells, accompanied by high activity of CAT and GSTPx, than in the control. Exposure of males to dimethoate increased CAT activity, after single application, and significantly enhanced GR activity, after five-time application. In females, five-time contact with dimethoate elevated the percentage of high granularity cells. As in comparison to females, male X. nemoralis were more sensitive to the applied stressing factors, it may be concluded that in natural conditions both food deficiency and chemical stress may diminish the immune response of their organisms.

Identifying species at extinction risk using global models of anthropogenic impact

The International Union for Conservation of Nature Red List of Endangered Species employs a robust, standardized approach to assess extinction threat focussed on taxa approaching an end-point in population decline. Used alone, we argue this enforces a reactive approach to conservation. Species not assessed as threatened but which occur predominantly in areas with high levels of anthropogenic impact may require proactive conservation management to prevent loss. We matched distribution and bathymetric range data from the global Red List assessment of 632 species of marine cone snails with human impacts and projected ocean thermal stress and aragonite saturation (a proxy for ocean acidification). Our results show 67 species categorized as 'Least Concern' have 70% or more of their occupancy in places subject to high and very high levels of human impact with 18 highly restricted species (range <100 km(2)) living exclusively in such places. Using a range-rarity scoring method we identified where clusters of endemic species are subject to all three stressors: high human impact, declining aragonite saturation levels and elevated thermal stress. Our approach reinforces Red List threatened status, highlights candidate species for reassessment, contributes important evidential data to minimize data deficiency and identifies regions and species for proactive conservation.

Adult somatic progenitor cells and hematopoiesis in oysters

Long-lived animals show a non-observable age-related decline in immune defense, which is provided by blood cells that derive from self-renewing stem cells. The oldest living animals are bivalves. Yet, the origin of hemocytes, the cells involved in innate immunity, is unknown in bivalves and current knowledge about mollusk adult somatic stem cells is scarce. Here we identify a population of adult somatic precursor cells and show their differentiation into hemocytes. Oyster gill contains an as yet unreported irregularly folded structure (IFS) with stem-like cells bathing into the hemolymph. BrdU labeling revealed that the stem-like cells in the gill epithelium and in the nearby hemolymph replicate DNA. Proliferation of this cell population was further evidenced by phosphorylated-histone H3 mitotic staining. Finally, these small cells, most abundant in the IFS epithelium, were found to be positive for the stemness marker Sox2. We provide evidence for hematopoiesis by showing that co-expression of Sox2 and Cu/Zn superoxide dismutase, a hemocyte-specific enzyme, does not occur in the gill epithelial cells but rather in the underlying tissues and vessels. We further confirm the hematopoietic features of these cells by the detection of Filamin, a protein specific for a sub-population of hemocytes, in large BrdU-labeled cells bathing into gill vessels. Altogether, our data show that progenitor cells differentiate into hemocytes in the gill, which suggests that hematopoiesis occurs in oyster gills.