Trace metal concentrations and contents in the tissues of the shore crab<Emphasis Type="Italic"> Carcinus maenas</Emphasis>: effects of size and tissue hydration

Water content in the tissues, tissue proportions, and content and concentrations of copper, zinc, iron, cadmium, manganese, and cobalt were determined in male shore crabs Carcinus maenas of different sizes. Average wet to dry weight ratios in midgut gland, gills, muscle, exoskeleton, stomach, heart, testes, hypodermis, and haemolymph were 5.3, 9.5, 4.1, 1.5, 4.8, 6.1, 3.8, 4.7, and 13, respectively. The water content in the soft tissues generally increased with increasing size of the crabs (except in testes). Dry midgut gland, gills, muscle, exoskeleton, stomach, heart, testes, hypodermis, and haemolymph constituted 4, 0.9, 20, 68, 0.5, 0.12, 0.5, 0.7 and 5.3%, respectively, of the body dry weight. Dry midgut gland, gills, stomach, hypodermis, and haemolymph constituted a larger proportion of the body weight in small than in large crabs, whereas the opposite was the case for exoskeleton. Protein concentrations in the haemolymph decreased with size whereas haemolymph volume increased. Seventy percent of the copper body burden was located in the haemolymph. The majority of zinc (61%) occurred in muscle, whereas the midgut gland was the major site of cadmium storage (89%). The exoskeleton contained the major part of the body burden of iron (71%) and manganese (95%). Most of the cobalt body burden was located in the exoskeleton (45%) and haemolymph (44%). As tissue hydration and tissue proportions changed with size, tissue metal concentrations did not necessarily vary identically with size when expressed on a dry weight compared to a wet weight basis. Tissue potassium concentrations were negatively correlated with tissue water contents, indicating that water in tissues with a high wet to dry weight ratio was of extracellular origin. However, comparison of tissue and haemolymph copper levels showed that this extracellular water could not be pure haemolymph as tissue copper concentrations would have been higher than the values actually found.     

Automated interpulse duration assessment (AIDA) in the shore crab Carcinus maenas in response to copper exposure

The effects of acute (24 h) and chronic (4␣weeks) copper exposure and subsequent recovery in “clean” conditions on cardiac activity were examined in shore crabs ( Carcinus maenas). Cardiac activity was monitored by automated interpulse duration assessment (AIDA) which permits detection of irregularities in cardiac rhythms in selected invertebrates. Mean interpulse durations, maximum interpulse durations and coefficients of variation were significantly affected by exposure to copper for 24 h and 4 weeks. Mean interpulse durations decreased reflecting an increase in heart rate, whereas maximum interpulse durations and coefficients of variation increased with increasing exposure concentration. Recovery of normal cardiac activity was evident following a 6-week recovery period in “clean” conditions. However, high levels of mortality were seen among crabs exposed to the two highest copper concentrations (0.6 and 0.8 mg l⁻¹ Cu). The extent of recovery was assessed by subjecting the surviving crabs to a physiological challenge. There were no apparent differences in circulatory response to physiological challenge between crabs previously exposed to copper and control crabs. Gill copper concentrations were significantly elevated in crabs that had previously been exposed to copper, despite their return to “clean” sea water for 6 weeks. Midgut gland wet weight/dry weight ratios, haemolymph total protein and midgut gland metallothionein concentrations did not reflect the previous copper exposure. The findings of the present study indicate that AIDA may be a valuable tool for use in toxicity testing. Received: 24 March 1997 / Accepted: 21 October 1997     

Interindividual variability in metal status in the shore crab<Emphasis Type="Italic"> Carcinus maenas</Emphasis>: the role of physiological condition and genetic variation

The relations between genetic variation, physiological condition, size and metal status in the shore crab Carcinus maenas (L.) were investigated. Shore crabs were collected at three sites around the island of Funen, Denmark, and carapace width, colour, moulting stage and major ions and protein in the haemolymph were determined. Concentrations of water, cadmium, copper and zinc in midgut glands, muscles and gills were measured, and allozyme variation at 15 loci was studied. Generally, tissue water content and copper, zinc and cadmium concentrations decreased from the moulting stages C₃ over C₄ to D crabs, whereas the opposite was true for copper and zinc concentrations in gills and muscle. However, the water content of the tissues increased with the size of the crabs. Since tissue water contents changed consistently over moulting stages, conclusions on changes in metal concentrations sometimes diverged when expressed on a dry versus wet weight basis. Regarding allozymes, esterase, malate dehydrogenase and phosphoglucomutase were polymorphic. The crabs showed a low level of genetic variability for both polymorphism (0.14) and for heterozygosity (0.07) at the three sites. Allelic frequencies showed very low levels of differentiation among the samples, no evidence of inbreeding and no population subdivision. Multilocus heterozygosity was positively correlated with size. Concentrations of copper and zinc in midgut gland, muscle tissue and gill were not correlated with genotype, whereas a weak correlation between phosphoglucomutase genotypes and concentrations of cadmium in the midgut gland was found.Communicated by M. Kühl, Helsingør     

Cadmium accumulation in the female shore crab Carcinus maenas during the moult cycle and ovarian maturation

 The influence of moulting and ovarian maturation on cadmium accumulation in the tissues of female shore crabs Carcinus maenas exposed to 1 mg Cd l⁻¹ in the water was investigated. Cadmium accumulation in all tissues examined was markedly increased in crabs in the postmoult stages (A and B) compared to crabs in all other moult stages. During the moult cycle, average cadmium accumulation in the midgut gland ranged from 29 μg Cd g⁻¹ dw at premoult stage (D₂) to 589 μg Cd g⁻¹ dw at postmoult stage (A). Average cadmium concentrations in the haemolymph ranged from 0.56 μg Cd ml⁻¹ at intermoult stage (C₄) to 4.6 μg Cd ml⁻¹ at postmoult stage (A), while the gills accumulated from 103 μg Cd g⁻¹ dw in intermoult stage (C₃) to 352 μg Cd g⁻¹ dw in postmoult stage (A). Cadmium concentration in gills and haemolymph was also significantly higher in crabs in late premoult stage (D₃) compared to C₄-crabs, while midgut gland cadmium concentration remained elevated in C₁- and C₃- intermoult stages relative to C₄. During ovarian maturation the cadmium accumulation in midgut gland, gills, ovaries and haemolymph decreased. Average cadmium concentration in the midgut gland decreased from 63 μg g⁻¹ dw in ovarian Stage I to 19 μg g⁻¹ dw in ovarian Stage VI. The same pattern was observed for gills, haemolymph and ovaries. The present study demonstrates that cadmium accumulation in the female shore crab strongly depends on the physiological status of the animal. A possible association between physiological calcium requirements and cadmium accumulation during moulting is discussed. Received: 20 January 2000 / Accepted: 20 July 2000     

Studies on the uptake of cadmium by the crab Carcinus maenas in the laboratory. I. Accumulation from seawater and a food source

The crab Carcinus maenas (L.) was exposed to radioactively labelled cadmium dissolved in seawater at concentrations of 0.1, 1 and 10 ppm, the latter concentration being toxic to the crabs (50% mortality after 12.3 days). Net accumulation of cadmium from solution was proportional to the level and time period of cadmium exposure. Total absorbed cadmium levels reached 0.0043 and 0.0412 mg Cd g^-1 dry weight after 40 days exposure to 0.1 and 1 ppm Cd, respectively, and 0.1115 mg Cd g^-1 dry weight after 12.3 days average exposure to 10 ppm Cd. The highest tissue concentration was found in the midgut gland, reaching 0.786 mg Cd g^-1 dry weight after 12.3 days average exposure to 10 ppm Cd. The midgut gland only contained about 10% of the total cadmium absorbed from solution, while the exoskeleton contained the bulk of obsorbed cadmium (59 to 80%) probably passively adsorbed onto the surface. When cadmium was absorbed by the crabs from a food source, the midgut gland contained 16.9% of the total absorbed cadmium whereas the exoskeleton now contained only 22.2%. Ten percent of the cadmium available in the food source (Artemia salina) was accumulated by the crabs. When placed in cadmium-free seawater, crabs that had accumulated cadmium from solution lost 69% of the absorbed cadmium in 10 days, mostly from the exoskeleton which lost 78% of its original absorbed cadmium concentration.     

Arsenic accumulation in the shore crab Carcinus maenas: the influence of nutritional state,sex and exposure concentration

The accumulation of arsenate from seawater by the shore crab Carcinus maenas L. (collected from Odense Fjord, Denmark in 1991 and from Restronguet Creek, UK in 1991) was investigated in a series of laboratory experiments. A field study was also carried out to determine the effects of raised environmental arsenic concentrations on intra-organismal distribution and tissue concentrations. Studies on the influence of nutritional state and sex on accumulation of As(5) from seawater indicated that most of the arsenic taken up from seawater in laboratory experiments was retained in the gills and the midgut gland. Arsenic accumulation exhibited sex-dependent differences which were also evident in correlation analyses carried out between total lipid contents and total arsenic contents of midgut glands of individual crabs. Arsenic concentrations in the gonads of both sexes were strongly influenced by the nutritional state of the crabs. Elevated arsenic concentrations in seawater and food at an arsenic polluted site (Restronguet Creek) significantly influenced arsenic concentrations and distribution among the tissues of C. maenas. Arsenic concentrations and distribution patterns differed markedly from those crabs from an unpolluted site in Odense Fjord. The gills of the crabs from Restronguet Creek contained extremely high arsenic concentrations ranging from 179 to 483 g As g^-1 dry wt. These values were even higher than those measured in the gills of Odense crabs that had been exposed to 3 mgl^-1 As(5) for 2 wk in the laboratory. Arsenic concentrations in the exoskeleton of Odense Fjord crabs were 15 times lower than those measured in exoskeletons of Restronguet Creek crabs. Approximately 69% of the total body burden of arsenic was located in muscle tissue of crabs from Odense Fjord, whereas the major pool of arsenic (46%) in Restronguet Creek crabs was located in the exoskeleton.     

Copper and zinc handling during the moult cycle of male and female shore crabs Carcinus maenas

Tissue concentrations and contents of copper and zinc were determined at 11 different stages of the moult cycle in male and female shore crabs Carcinus maenas. Metal concentrations in haemolymph, gills, midgut gland, muscle, and exoskeleton of males and haemolymph, gills, and midgut gland of females were determined, as were haemocyanin concentrations and haemolymph volumes (using ¹⁴C-inulin) in males. The changes in tissue Cu and Zn concentrations and contents that occur throughout the moult cycle can be attributed to muscle breakdown in late premoult, the period of starvation in late premoult and early postmoult, the resorption from and shedding of the old exoskeleton, and the dilution of the haemolymph caused by water uptake around the time of ecdysis. The present study demonstrates that whole-body Cu and Zn contents remain constant during a large part of the moult cycle of male and female C. maenas. This state of whole-body trace metal homeostasis is maintained in spite of major changes in tissue proportions and tissue Cu and Zn concentrations and contents. Previous studies have not carried out the necessary analysis to move from theoretical estimates to quantitative determination of the changes in tissue metal distribution associated with moulting in crustaceans; the data presented illustrate the necessity of measuring both tissue concentrations and contents of metals to avoid misinterpretation of either.     

In situ variation in heart rate of the shore crab Carcinus maenas in relation to environmental factors and physiological condition

Heart rate of Carcinus maenas was recorded continuously for two days in situ, together with water temperature, salinity, depth and light intensity. Of each sex, 25 crabs were used and assigned to groups on the basis of size and colour (the carapace changes colour with prolongation of the intermoult phase). Wet weight:dry weight ratios of midgut gland, muscle, gonads and whole body were examined together with midgut gland lipid content and haemolymph protein concentration. Heart rates and wet wt:dry wt ratios for all the tissues examined were higher in early intermoult than in late intermoult stages of the adult C. maenas (P<0.05). Heart rate, lipid content and haemolymph protein concentrations were higher and wet wt:dry wt ratios of midgut gland, gonads and whole body were lower in juvenile crabs than in adults (P<0.05). The relationship between heart rate and wet wt:dry wt of whole body differed among C. maenas in early and late intermoutl. Heart rate was positively correlated with midgut gland lipid content (a Darwinian fitness parameter) in crabs that were in late intermoult. Physico-chemical environmental parameters, sex and colour accounted for 12% of the variation in heart rate of C. maenas recorded in situ. Temperature and prolonged intermoult were the most important factors influencing heart rate. The findings are discussed in relation to laboratory studies of cardiac activity and observed behaviour of C. maenas in the field.     

Influence of cadmium accumulation and dietary status on fatty acid composition in two colour forms of shore crabs, Carcinus maenas

 The effects of cadmium exposure and dietary status on cadmium accumulation, fatty acid (FA) content and profiles were investigated in two colour forms of the shore crab Carcinus maenas. Groups of shore crabs were either starved or fed with blue mussels, Mytilus edulis, during a 40 d exposure period to 2 or 6 μM Cd²⁺ (as CdCl₂). Starved green individuals accumulated more cadmium in haemolymph and hepatopancreas than did red crabs and green crabs fed during the experiments. In the red colour form, no difference in cadmium accumulation was observed between starved and fed individuals. In both colour forms, hepatopancreas contained more FA than gills and muscle. The FAs often present in the largest amounts in the tissues were 16:0, 16:1ω7, 18:1ω7, 18:1ω9, 20:4ω6, 20:5ω3 and 22:6ω3. However, saturated (SAFA) and mono-unsaturated fatty acids (MUFAs) were dominant in hepatopancreas, whereas poly-unsaturated fatty acids (PUFAs) were dominant in gills and muscles. At the beginning of the experiment, the total FA content in the hepatopancreas was 111.6 mg g⁻¹ (dry weight) for red crabs and 78.4 mg g⁻¹ for green shore crabs. During the experiment, however, the FA content decreased in red crabs. This decrease was more pronounced for starved individuals than for fed individuals. Also, the decrease in FA content was more pronounced in crabs exposed to 6 μM cadmium compared to crabs exposed to 2 μM or crabs not exposed to cadmium. No change in FA content was observed in green shore crabs, irrespective of diet and cadmium exposure. For both colour forms, no change in FA content was observed for gills and muscle. In red crabs, a decrease was observed for all FAs in the hepatopancreas. This decrease, however, was more pronounced for SAFAs and MUFAs than for PUFAs, indicating that the metabolism of FAs during starvation and cadmium exposure is selective. The experiments indicate that green colour forms of shore crabs are more tolerant of natural stress such as starvation and anthropogenic stress, e.g. cadmium exposure, than are red colour forms of shore crabs. Received: 23 September 1999 / Accepted: 29 April 2000     

Transbranchial potentials and ion fluxes across isolated,perfused gills of Uca rapax

Transbranchial potentials (TP) and sodium or chloride fluxes were measured in an apparatus designed for the simultaneous perfusion of eight isolated gills of Uca rapax. In anterior gills perfused with U. rapax–saline (US) the TP varied almost linearly from-7.5 to +10 mV inside, and in posterior gills from +2 to-8.5 mV (inside), on exposure to salinities ranging from 8.7 through 52, i.e. 25 to 150% seawater (100%=34.6 S). Sodium influx and efflux in anterior gills exposed to US, 8.7 or 43.3 S (0.7 to 4.0 mmol h^–1 g^–1 dry wt) were always greater than in posterior gills (0.5 mmol h^–1). The chloride fluxes were slightly smaller than sodium fluxes in anterior gills, while in the posterior gills the chloride influx (2.8 to 4.6 mmol h^–1) was always larger than chloride efflux (0.6 to 1.1 mmol h^–1) or the sodium fluxes. At least three ion-transport mechanisms may be present in these gills: (1) an internal ( = basolateral), ouabain-sensitive Na⁺, K⁺ pump, restricted to anterior gills; (2) a furosemide-sensitive Na⁺, K⁺, 2Cl^– (plus water) transporter, apparently restricted to posterior gills, and (3) a Na⁺ exchanger (and possibly other as yet unidentified ion transporters, as suggested by large increases of the chloride influxes caused by amiloride), probably located on the apical membranes of the epithelial cells of both gill types. The differential selectivity of the gills of U. rapax for sodium or chloride may limit the transbranchial movements of either ion, without a reduction of the overall permeability of these crabs.Communicated by N.H. Marcus, Tallahassee     

Effect of copper on ion- and osmoregulation in the shore crab Carcinus maenas

The uptake and effect of dissolved copper on regulation of hemolymph osmolality and Na⁺, K⁺, Cl^-, Ca⁺⁺, and Mg⁺⁺ concentrations in the shore crab Carcinus maenas (L.) were determined at 400 mOsm (=14 S) ambient salinity. One mg Cu l^-1 resulted in 50% mortality in 11 to 22 d; the highest sensitivity was observed around the moulting period. 0.25 and 0.5 mg Cu l^-1 were not lethal after a onemonth exposure. Ten, 1, and 0.5 mg Cu l^-1 altered regulation of osmolality, Na⁺, K⁺, and Cl^- concentrations, while 0.25 mg Cu l^-1 did not. Exposure to 1 mg Cu l^-1 reduced hemolymph osmolality and Na⁺, K⁺, and Cl^- concentrations to 80 to 90% of controls within 4 to 6 d and no further reduction was observed during a 21-d exposure. The effect of various copper concentrations on these four parameters were almost identical and the highest sensitivity was observed around the moulting period. Hemolymph calcium levels increased 20 to 80% in crabs exposed to 1 mg Cu l^-1, while they decreased 20 to 30% in crabs exposed to 0.5 mg Cu l^-1. Prolonged exposure to copper caused 20 to 70% reductions in hemolymph magnesium levels. Crabs exposed to 0.5 mg Cu l^-1 for 29 d accumulated copper in hepatopancreas, gills, carapace, heart, testes, and hypodermis, but not in muscles and hemolymph. Increased copper levels in crabs exposed to 0.25 mg Cu l^-1 were observed in hepatopancreas, gills, and carapace only. The present results suggest that effects of copper on ion regulatory processes in part explain why the toxicity of copper towards euryhaline invertebrates increases at low salinities.     

Biochemical composition of the deep-sea red crab Chaceon quinquedens (Geryonidae): organic reserves of developing embryos and adults

Deep-sea red crabs Chaceon quinquedens (Smith) were collected in traps at depths of 860 and 1043 m in the northern Gulf of Mexico. Ovigerous crabs were maintained in the laboratory and the developing embryos were sampled every 2 wk until hatching. Proximate analysis (lipid, protein, carbohydrate, and ash) of embryos was performed to determine patterns and rates of organic reserve utilization during embryogenesis. Midgut gland, gonads, and clutch (as appropriate) of adult crabs (males, non-ovigerous females and ovigerous females) were analyzed for the same components as the embryos. Red crab embryos exhibited different patterns of yolk deposition and subsequent depletion of yolk components during embryogenesis. There was a range of lipid to protein (L:P) ratios among the different clutches examined, indicating plasticity in the relative proportions of lipid and protein yolk. The energy used for embryogenesis was estimated by converting the amounts of lipid, protein and carbohydrate in the embryos to their caloric equivalents; final values, taken from 9 mo-old embryos whose siblings were hatching as zoeae, were subtracted from the initial values of sibling embryos sampled at the time of collection (2 to 3 mo old). The amount of energy consumed during embryogenesis in the laboratory was relatively constant (0.12 to 0.13 cal egg^-1). There was considerable variability among the concentrations of organic reserves in the midgut gland of adult crabs and in the ovaries of females. Variations in midgut gland L:P ratios and ovaries were related to the reproductive status of the females, but there were no trends related to depth of capture.     

The synergistic effects of increasing temperature and CO2 levels on activity capacity and acid–base balance in the spider crab, Hyas araneus

With global climate change, ocean warming and acidification occur concomitantly. In this study, we tested the hypothesis that increasing CO₂ levels affect the acid–base balance and reduce the activity capacity of the Arctic spider crab Hyas araneus, especially at the limits of thermal tolerance. Crabs were acclimated to projected oceanic CO₂ levels for 12 days (today: 380, towards the year 2100: 750 and 1,120 and beyond: 3,000 μatm) and at two temperatures (1 and 4 °C). Effects of these treatments on the righting response (RR) were determined (1) at acclimation temperatures followed by (2) righting when exposed to an additional acute (15 min) heat stress at 12 °C. Prior to (resting) and after the consecutive stresses of combined righting activity and heat exposure, acid–base status and lactate contents were measured in the haemolymph. Under resting conditions, CO₂ caused a decrease in haemolymph pH and an increase in oxygen partial pressure. Despite some buffering via an accumulation of bicarbonate, the extracellular acidosis remained uncompensated at 1 °C, a trend exacerbated when animals were acclimated to 4 °C. The additional combined exposure to activity and heat had only a slight effect on blood gas and acid–base status. Righting activity in all crabs incubated at 1 and 4 °C was unaffected by elevated CO₂ levels or acute heat stress but was significantly reduced when both stressors acted synergistically. This impact was much stronger in the group acclimated at 1 °C where some individuals acclimated to high CO₂ levels stopped responding. Lactate only accumulated in the haemolymph after combined righting and heat stress. In the group acclimated to 1 °C, lactate content was highest under normocapnia and lowest at the highest CO₂ level in line with the finding that RR was largely reduced. In crabs acclimated to 4 °C, the RR was less affected by CO₂ such that activity caused lactate to increase with rising CO₂ levels. In line with the concept of oxygen and capacity limited thermal tolerance, all animals exposed to temperature extremes displayed a reduction in scope for performance, a trend exacerbated by increasing CO₂ levels. Additionally, the differences seen between cold- and warm-acclimated H. araneus after heat stress indicate that a small shift to higher acclimation temperatures also alleviates the response to temperature extremes, indicating a shift in the thermal tolerance window which reduces susceptibility to additional CO₂ exposure.     

Effects of copper and cadmium on osmoregulation and oxygen consumption in two species of estuarine crabs

Green crabs (Carcinus maenas) and rock crabs (Cancer irroratus) were exposed to various concentrations of copper as cupric chloride (CuCl₂ · 2 H₂O), and cadmium as cadmium chloride (CdCl₂ · 21/2 H₂O) for 48 h. The exposures were conducted at 5 different salinities. At the end of each exposure period, tests of blood-serum osmolality and gill-tissue oxygen consumption were performed. Copper-exposed crabs exhibited loss of osmoregulatory function with increasing copper concentration until normally hyperosmotic serum became isosmotic with the surrounding medium. Cadmium elevated greencrab serum above its normal hyperosmotic state. Copper had no effect on gill-tissue oxygen consumption; however, cadmium reduced the rate of oxygen consumption in both species tested.     

Influence of physiological condition on cadmium transport from haemolymph to hepatopancreas inCarcinus maenas

Accumulation and binding of cadmium in the tissues of the shore crabCarcinus maenas (L.) were investigated in a series of laboratory experiments. The relation between the physiological condition of individual crabs and their ability to transport cadmium from haemolymph to hepatopancreas was specifically addressed. Cadmium was removed from the haemolymph with a half-life of approximately 10 h, and half of the cadmium removed from the haemolymph was taken up in the hepatopancreas. The efficiency with which individual crabs transported cadmium from the haemolymph to the hepatopancreas was strongly related to physiological parameters, such as concentrations of calcium and magnesium in the hepatopancreas and haemolymph volume and haemolymph protein concentration. The transport of cadmium from the haemolymph to the hepatopancreas was saturated in crabs exposed to more than 2 to 4 mg Cd l^–1 in the sea water. In the hepatopancreas of unexposed crabs, cadmium was bound mainly in the insoluble tissue fraction (40%) and in the protein fraction with a molecular weight of approximately 6000 D (50%). Exposure to 0.25 to 1.5 mg Cd l^–1 for 2 w led to dose-dependent increases of the amounts of cadmium bound in the high-molecular weight protein fraction and in the insoluble tissue fraction. Modes of internal cadmium transport and accumulation in tissues and variability in physiological parameters are discussed.     

Calanoid copepod eggs in sea-bottom muds. IV. Effects of some environmental factors on the hatching of resting eggs

During cadmium uptake by the shore crab Carcinus maenas (L.), cadmium appears in both haemolymph and urine within 1 h, and comes into equilibrium with the haemolymp after some 60 h. The equilibrium concentration for haemolymph cadmium is always considerably less than that of the external medium, whether the latter is close to background level or at the artificially high concentration of 2.2 mg l^-1. Despite earlier evidence that cadmium entering the haemolymph is mainly bound to protein, current results show most of this to be freely labile and quickly displaced by cadmium taken up subsequently. There is some evidence to suggest that cadmium is passed on from the haemolymph to the hepatopancreas. A large proportion of whole-body cadmium is adsorbed onto the exoskeleton and gills. The comparatively rapid efflux of ¹⁰⁹Cd from loaded crabs over a period of 1 week is mainly due to desorption of this cadmium from the outer body surface.     

Ultrastructural changes in the gill epithelium of the crab Chasmagnathus granulatus (Decapoda: Grapsidae) in diluted and concentrated seawater

Chasmagnathus granulatus Dana, 1851 is an intertidal estuarine crab that experiences acute salinity changes ranging from <1‰ to full-strength seawater and even hypersaline waters in tide pools concentrated by evaporation. Ultrastructural changes induced by salinity in the posterior gills were examined in crabs collected from the Rio de la Plata estuary Argentina during March 1999. The posterior gills of C. granulatus are involved both in ion uptake and ion secretion depending on the acclimation medium. These organs are mostly lined with a thick tissue, which presents the characteristics of a typical salt-transporting epithelium. Electron microscopy analysis of gill tissue from crabs acclimated to dilute, full, and concentrated seawater (12‰, 34‰, and 45‰ salinity) showed significant development of basolateral membrane interdigitations, with numerous mitochondria and conspicuous apical membrane infoldings. Morphometrical analysis indicated that the subcuticular space delimited by the infolding of the apical membrane was significantly increased in the gills of high-salinity acclimated crabs. Septate junctions, which are thought to define the paracellular permeability, were significantly shorter in high-salinity acclimated crabs, suggesting a possible role of the paracellular pathway in salt secretion.     

Linear alkylbenzene sulphonates (LAS) and bioaccumulation of heavy metals (Cu and Pb) in Ruditapes philippinarum

The effect of linear alkylbenzene sulphonate (LAS) on copper and lead bioaccumulation in Ruditapes philippinarum was studied. The in vitro and in vivo effect of LAS on acid and alkaline phosphatase activities was also examined. For lead, significant differences (P<0.01) were observed between organisms exposed to lead and to the mixture of LAS and lead. In the case of copper, these differences were only significant in the digestive gland (P<0.05). In vitro acid phosphatase was inhibited by LAS and the mixture of LAS with copper showed the effect of decreasing the enzymatic activity. Nevertheless, in vivo no significant differences in the digestive gland and gills (P < 0.05) were observed.     

Effects of lead exposure on redox status,DNA and histological structures in Venus verrucosa gills and digestive gland

ABSTRACT

Lead (Pb) is one of the most toxic heavy metals that affect the physiological status of aquatic organisms. The present investigation evaluated the possible toxic effect of lead chloride (PbCl₂) on biomarkers responses, DNA damage and histological alterations in Venus verrucosa gills and digestive gland. Three concentrations of PbCl₂ (D1:1µgL^?1, D2: 10µgL^?1 and D3: 100µgL^?1) were chosen for V. verrucosa exposure during six days. At the end of the trial, it was found that Pb tended to accumulate in both gills and digestive gland in a dose-dependent manner. However, gill tissues exhibited the highest metal burden. Our results showed an increase of malondialdehyde, protein carbonyls and advanced oxidation protein product levels in both organs following PbCl₂exposure. The induction of both non-enzymatic and enzymatic antioxidant systems; as well as the decrease of the acetylcholinesterase activity and degradation of DNA structure was recorded in the gills and digestive gland. The histopathological alterations observed in gills (disruption of lamellas and cilia filaments?…) and digestive gland (lumens occlusion, necrosis and fibrosis) confirmed the aforementioned results. Our data highlighted the short-term toxicity effects of PbCl₂ on V. verrucosa and pointed out a high sensitivity of gills towards this metal.     

虾夷扇贝毒素(yessotoxin)诱导的栉孔扇贝(Chlamys farreri)体内P糖蛋白转运活性及其分布研究

大量研究表明P-糖蛋白(P-glycoprotein,P-gp)介导的多型异源物质抗性机制(multi-xentiobiotic resistance,MXR)在贝类耐受或抵抗污染水域中有毒有害物质的毒害中具有重要作用,但是该机制在贝类抵抗或耐受食源性毒素方面作用的研究却很少。本研究以栉孔扇贝(Chlamys farreri)为实验动物,向其投喂产虾夷扇贝毒素(yessotoxins,YTXs)的网状原角藻(Protoceratium reticulatum),通过检测栉孔扇贝鳃和消化腺组织中YTX毒素含量随时间的变化情况,结合2种组织中P-gp介导的MXR活性变化及P-gp在组织中的表达和分布,探讨P-gp在扇贝耐受YTX毒素中可能的作用。研究结果表明,随着毒藻暴露时间的延长,栉孔扇贝鳃和消化腺中YTX含量逐渐增加,且具有明显的时间依赖关系。YTX的大量累积虽未导致扇贝死亡,但是仍然对扇贝组织产生不同程度的毒性。苏木精-伊红(hematoxylin-eosin,HE)染色发现,染毒12 h后,栉孔扇贝鳃组织前端出现明显黑化,消化腺组织导管上皮细胞部分脱落入管腔中,腺管内细胞界限模糊,部分腺管崩解。罗丹明B(rhodamine B,Rho B)外排实验表明YTX毒素暴露能显著增强栉孔扇贝鳃和消化腺组织中P-gp的转运活性,暴露12 h后鳃和消化腺Rho B的排出速率就已分别达到对照组的3.8倍和1.4倍,随着暴露时间的延长,P-gp活性略有增强,72 h后开始下降;P-gp的功能性抑制剂维拉帕米(verapamil,VRP)在实验设定的浓度下没有抑制反而增强了Rho B的外排;免疫定位显示,毒素暴露后栉孔扇贝鳃丝前端纤毛柱状细胞及消化腺导管上皮柱状细胞和腺管消化细胞P-gp免疫阳性信号增强,说明YTX毒素暴露提高了P-gp的表达量。综上推断,YTX毒素可能是P-gp的底物,它能够诱导P-gp转运活性增强,并增加P-gp的表达量来参与扇贝对YTX毒素的耐受或抗性;设定浓度的VRP不能抑制P-gp的活性,这可能是由于种属差异造成的,关于VRP对栉孔扇贝Pgp的作用还有待进一步的研究。