Shore Crab Carcinus Maenas Research Articles

Inhibition of Na + /K + -ATPase and of active ion-transport functions in the gills of the shore crab Carcinus maenas induced by cadmium

Inhibition of Na+/K+-ATPase from gill plasma membranes of the shore crab Carcinus maenas by cadmium was investigated and compared with inhibitory effects by known antagonists (ouabain and Ca2+). For comparative considerations the Cd2+-inhibition of the enzyme from dog kidney was also tested. Na+/K+-ATPase from dog kidney and from crab gill differed greatly in sensitivity against ouabain. The inhibition constant Ki of the dog enzyme amounted to 9.1 × 10−7 mol l−1, i.e. more than 300-fold smaller than the Ki of 2.9 × 10−4 mol l−1 determined for the crab enzyme. Ca2+ inhibited the activity of Na+/K+-ATPase from crab gill plasma membranes with a Ki of 4.3 × 10−4 mol l−1. The Na+/K+-ATPase from crab gill was inhibited by Cd2+ with a Ki of 9.1 × 10−5 mol l−1. Cd2+ inhibited the Na+/K+-ATPase from dog kidney with a Ki (6.4 × 10−5 mol l−1) comparable to that observed in the crab gill enzyme. Under experimental conditions Cd2+-inhibition of Na+/K+-ATPase was irreversible. Repeated washing, centrifugation and homogenization of the plasma membranes (four times) with Cd2+-free buffer did not restore any activity lost in the presence of 1 × 10−3 mol l−1 Cd2+. Since ouabain-insensitive (nonspecific) ATPases in the plasma membrane fraction of crab gills were inhibited by Cd2+ in the same way as Na+/K+-ATPase, the heavy metal is considered as an unspecific ATPase inhibitor. Comparing these results with literature data on Cd2+-binding to electrophoretically separated proteins suggests that Na+/K+-ATPase is a Cd2+-binding enzyme. The results obtained on Na+/K+-ATPase were reflected by Cd2+-inhibition of the branchial ion-transport functions depending on this enzyme. The transepithelial short-circuit current of isolated gill half lamellae, a direct measure of area-specific active ion uptake, and the transepithelial potential difference of isolated, perfused whole gills, also indicative of active ion uptake, were inhibited by the heavy metal in a time- and dose-dependent mode. Remarkably these inhibitions were also irreversible. These findings are ecologically and biomedically significant: even when the actual environmental or tissue concentrations measured are low, biological microstructures such as Na+/K+-ATPase may accumulate the heavy metal by tight binding over prolonged periods until the first inhibitory effects occur.

The kinetics of zinc and cadmium in the haemolymph of the shore crab Carcinus maenas (L.)

The trace metals zinc and cadmium are taken up from solution by the shore crab Carcinus maenas into the haemolymph. Both metals are accumulated in the haemolymph at a rate proportional to the external dissolved metal concentration (and hence the rate of metal uptake into the crab). Newly taken up zinc is added sequentially over time to the substantial content of zinc present in the haemolymph, replacing existing zinc already present, but only at extremely high ambient concentrations (1000 μg Zn 1 −1) did the incoming zinc replace significant amounts of existing haemolymph zinc. However, even after long-term exposure, ca. 55% of the zinc in the haemolymph remained too tightly bound to be replaced by incoming zinc. In the haemolymph, newly taken up cadmium, in contrast to zinc, rapidly reaches an equilibrium concentration when the rate of removal matches the rate of cadmium uptake into the haemolymph. This equilibrium concentration of new cadmium in the haemolymph increases with an increase in the external dissolved cadmium concentration. The rapid removal of cadmium from the haemolymph, therefore, indicates that in most circumstances, the haemolymph acts as a transient store for accumulated cadmium. The rate of zinc accumulation in (and uptake into) the haemolymph was not affected by pre-exposure of crabs to zinc, indicating the lack of induction of a zinc-binding system within the haemolymph or in a tissue able to receive zinc from the haemolymph. Cadmium was unable to replace haemolymph zinc, indicating either that zinc is bound too tightly for replacement by cadmium or that it occupies different binding sites in the haemolymph to cadmium. The long half-life of zinc in the haemolymph ( ca. 21 days) probably reflects the turnover of haemocyanin. In Carcinus maenas the high concentration of zinc in the haemolymph ( ca. 35 μg Zn ml −1) acts as a store for zinc. Haemolymph volume of C.maenas was estimated to be 0.32 ± 0.10 ml per gramme total fresh weight.

Predation on postlarvae and juveniles of the shore crab Carcinus maenas:importance of shelter, size and cannibalism

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 166:211-225 (1998) - doi:10.3354/meps166211 Predation on postlarvae and juveniles of the shore crab Carcinus maenas: importance of shelter, size and cannibalism P-O. Moksnes1,*, L. Pihl1, J. van Montfrans2 1Göteborg University, Kristineberg Marine Research Station, S-45034 Fiskebäckskil, Sweden 2Virginia Institute of Marine Science, The College of William and Mary, Gloucester Point, Virginia 23062, USA *E-mail: p.moksnes@kmf.gu.se Settlement and early juvenile stages are considered a bottleneck in the life history of many epibenthic organisms because of high predation mortality. Nursery habitats may play an important role in mitigating settlement and post-settlement mortality by providing refuge from predation. We examined these relationships in postlarvae and early juvenile stages of the shore crab Carcinus maenas L. in laboratory and field tethering experiments. We studied habitat and size related habitat mortality using postlarvae and young juvenile crabs as prey, and various predators, including juvenile conspecifics, in several habitats common in shallow (0 to 1 m) soft bottom nursery areas on the Swedish west coast. Settling mortality was high in open sand (80 to 90%), whereas a significant habitat refuge was obtained in mussel beds, eelgrass and filamentous green algae, the latter yielding the lowest mortality (13 to 14%). Small differences in structural complexity of ephemeral macroalgae dramatically affected predation mortality of first instar crabs, with a significant refuge obtained only in algae of medium complexity. Predation rate on tethered crabs in the field was high (52 to 67%) only on the smallest crabs (<5 mm carapace width, CW), which obtained a significant refuge in the eelgrass habitat compared to open sand. Mortality for larger crabs (5 to 25 mm CW) was low (<10%) and similar in sand and eelgrass habitats. Our results indicate that predation is an important process that can create a bottleneck for juvenile shore crab populations during settlement and early juvenile stages, mediated by the availability of nursery habitats. Postlarvae obtained refuge from predation in several different habitats, suggesting that the recruitment of juvenile shore crabs will be less affected by temporal and spatial variation of any single habitat type. The strong size refuge for crabs larger than 4 mm CW indicates that key predators are small. We suggest that cannibalistic juveniles, which caused predation rates similar to or higher than all other investigated predators, are dominant predators on settling postlarvae and young juvenile crabs in nursery areas. We further propose that habitat- and size-specific predation by small epibenthic predators are an important selective force in habitat selection by postlarvae and ontogenetic shifts in habitat use by juveniles. Bottleneck · Nursery habitats · Size refuge · Habitat complexity · Settlement · Megalopa · Macroalgae · Skagerrak-Kattegat Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 166. Publication date: May 28, 1998 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1998 Inter-Research.

Changes in the tissue concentrations and contents of calcium, copper and zinc in the shore crab Carcinus maenas (L.) (Crustacea: Decapoda) during the moult cycle and following copper exposure during ecdysis

The tissue concentrations and contents of calcium, copper and zinc were determined at different stages in the moult cycle of the shore crab Carcinus maenas. The crabs were dissected into the following tissues: the midgut gland, the gill, the ‘rest tissue’ (the latter defined as the left over tissue, i.e. muscles and exoskeleton), and the haemolymph, and analysed as such. One group of crabs was maintained in clean seawater. In these crabs, calcium was lost from haemolymph during premoult and apparently stored in the midgut gland. At ecdysis approximately 90% of the whole body calcium content was lost with the exuviae while the haemolymph calcium content doubled. During early postmoult calcium stored in the midgut gland was used in combination with calcium absorbed from the surrounding seawater for a rapid calcification of the new exoskeleton. Both the copper and zinc concentrations declined in the ‘rest tissue’ compartment during premoult. At ecdysis the haemolymph copper and zinc contents increased 35 and 86%, respectively, from premoult to the newly moult stage. At the same time, however, the copper and zinc haemolymph concentrations decreased. During postmoult, copper (25%) and zinc (45%) were lost from haemolymph and mainly excreted but a minor fraction (5–10%) was stored in the midgut gland. A second group of crabs was maintained in copper-contaminated seawater (0.1 mgl −1) during ecdysis and postmoult. Following exposure of the animals to raised ambient levels of copper, the calcium and zinc contents of the midgut gland were reduced while the copper contents of the midgut gland and most other tissues were increased in comparison to crabs held in clean seawater.

Isolation and identification of multiple neuropeptides of the allatostatin superfamily in the shore crab Carcinus maenas.

20 neuropeptides belonging to the allatostatin superfamily were isolated from extracts of cerebral and thoracic ganglia of the shore crab Carcinus maenas. They were purified by HPLC, monitored by radioimmunoassay and identified by mass spectrometry and amino acid sequencing. The allatostatins are characterised by a common C-terminal pentapeptide sequence -YXFGL-NH2. Previously such peptides have only been reported from insects. In insects the variable post-tyrosyl residue is restricted to Ala, Asn, Asp, Gly or Ser. In C. maenas, however, there are only two types; thirteen of the peptides having a post-tyrosyl Ala and the other seven, a post-tyrosyl Ser. The crab peptides include the shortest allatostatins so far identified (YAFGL-NH2 and YSFGL-NH2) as well as the longest, a 27-residue peptide. The total of 20 peptides exceeds the highest number of allatostatins found in any of the insects investigated so far (14 in Periplaneta americana). It is of interest that, despite their clear homology, none of the peptides of C. maenas is identical to any of the more than 50 known insect allatostatins. The crab allatostatins show evidence of gene duplication and mutation that has resulted in several sub-groups with close structural similarities. For example, there are four heptapeptides with the common C-terminus -PYAFGL-NH2 that differ only at the N-terminal residue, which is either Glu, Asp, Asn or Ser. Other motifs, variously extended at the N-terminus, include -GPY(A/S)FGL-NH2 (three peptides), -DMY(A/S)FGL-NH2 (three peptides), and -GQY(A/S)FGL-NH2 (two peptides). Unique among the allatostatin superfamily, one of the crab peptides has a Tyr for Phe substitution at position three from the C-terminus (GGPYSYGL-NH2). Immunocytochemistry has provided clues to the functions of the allatostatins in crustaceans by showing their widespread presence in the central and stomatogastric nervous systems.

Molecular Approaches to Understanding Salinity Adaptation of Estuarine Animals

The molecular processes by which estuarine organisms adjust to salinity change are the central focus of this review, with emphasis on identifying the relevant mechanisms in euryhaline crustaceans using the techniques of molecular biology. This review is not intended to be complete with respect to ecological and physiological aspects but rather is an attempt to outline a molecular approach which other investigators may find useful as they address their own specific questions. Membrane transporters of sodium ions serve as the major focus, beginning with an examination of candidate transport systems in gill epithelial cells. Particular emphasis is placed on the recent identification and sequencing of a putative Na+/H+ antiporter cDNA from gills of the green shore crab Carcinus maenas

Combined effects of water pH and salinity on the bioaccumulation of inorganic mercury and methylmercury in the shore crab Carcinus maenas

Tissue mercury concentrations were analysed in the whole organism and various organs of the euryhaline shore crab Carcinus maenas after 3 and 15 days of exposure to inorganic mercury (Hg(II)) and methylmercury (MeHg) at a nominal concentration of 1 μgHg l −1. Chemical speciation of the metals was varied by using four pH/salinity conditions (combinations between pH 7.0 and 8.5/salinity 560 and 140 mM NaCl). In all conditions, the results showed a particularly important Hg accumulation in gill tissue, smaller levels in the carapace and internal organs, and very low concentrations in circulating haemolymph. For Hg(II), accumulation was generally favoured at low salinity, but the data revealed complex pH/salinity interactions. Positive correlations were found between tissue metal levels and the abundance of some inorganic Hg species: HgCl 2, HgCl − 3, Hg 2+, HgCl +, indicating that chemical speciation may be an important factor governing metal uptake. The balance of evidence favours HgCl 2 and CH 3HgCl as the most bioavailable species for uptake of Hg(II) and MeHg, respectively.

Effects of the organophosphorous pesticide, dimethoate, on cardiac and acetylcholinesterase (AChE) activity in the shore crab Carcinus maenas

The potential use of biochemical and physiological responses as biomarkers of organophosphate exposure and/or effect were assessed in the shore crab ( Carcinus maenas). Male crabs were assigned to one of four dimethoate treatments (0, 0.5, 1.0 or 2.0 mg l −1). Cardiac activity was measured non-invasively before and during dimethoate exposure using automated interpulse duration assessment. Heart rates decreased significantly in a concentration-dependent manner ( p < 0.05). Serial measurements of acetylcholinesterase activity in haemolymph samples taken from crabs before and after exposure indicated that 2 mg l −1 dimethoate also significantly reduced acetylcholinesterase activity ( p < 0.05). The percentage inhibition in acetylcholinesterase activity was correlated with the percentage reduction in heart rate following dimethoate exposure ( r = 0.55, p < 0.01). This suggests that organophosphates may directly effect neuronal control of the heart. The experiments indicate that non-destructive, serial measurements of cardiac activity and acetylcholinesterase activity are valuable biomarkers of organophosphate exposure and adverse effects.

Evaluation of changes in the adaptive physiology of shore crabs ( Carcinus maenas ) as an indicator of pollution in estuarine environments

The major objective of this study was to determine whether there were significant differences in the physiological responses of shore crabs (Carcinus maenas L.) sampled from environments with varying degrees of contamination. Crabs collected from a range of sites were subjected to a standardised, environmentally realistic sequence of physiological challenges in the laboratory to determine if such measures would prove sensitive enough to differentiate among the sites. Heart-rate changes and osmoregulatory ability were measured. The results indicated that changes in osmoregulatory ability were sufficiently sensitive to detect differences in environmental contamination. The utility of physiological measurements in environmental monitoring is discussed.

Endogenous control of timing of metamorphosis in megalopae of the shore crab Carcinus maenas

Batches of hundreds of freshly collected megalopae of the shore crab Carcinus maenas (L.) showed persistent circatidal rhythms of moulting to the juvenile crab stage when maintained in constant laboratory conditions. Peaks of moulting occurred around expected times of high tides, with few megalopae moulting at other times. In larvae collected offshore, the highest tidally-timed peak of metamorphosis occurred during the second to fifth expected times of high tide, and metamorphosis of 50% of each batch took about 22 h or longer. In contrast, in larvae collected at the water's edge, 70% metamorphosed during the first expected episode of high tide, within 6 to 8 h after collection. However, although inshore megalopae moulted before offshore ones, the tidal timing of moulting remained unaltered whether megalopae were collected at neaps or springs, from the water's edge or farther offshore, in the presence or absence of natural substratum, and under various light–dark and salinity regimes. Metamorphosis of C. maenas megalopae around the times of high tides may enhance settlement into the upper intertidal zone. Early juveniles of the crab apparently prefer that zone as they are most abundant there and, unlike adults, do not undertake up-and-down-shore migration with tides. The present finding demonstrates, for the first time, endogenous physiological timing of circatidal periodicity in the metamorphic moult of crab megalopae, suggesting that endogenous factors, as well as exogenous ones should be taken into account in considering the process of settlement by crab megalopae.

Predator‐induced changes in byssal attachment, aggregation and migration in the blue mussel, Mytilus edulis

Blue mussels, Mytilus edulis, were exposed to the water‐borne scent of predators, either to the starfish Asterias rubens, or the shore crab Carcinus maenas, in laboratory experiments. Predator‐exposed mussels developed a stronger byssal attachment compared to that of unexposed mussels, which was significant after about, 24 h, and twice as strong after four days. The byssal attachment response was variable. In the short term (<10h), predator scents could inhibit byssus production in those experimental batches where unexposed mussels had a high rate of byssus production. Predator‐exposed mussels also formed larger aggregates, migrated less, and sought structural refuges more often. Experiments showed that these traits gave significant protection against predation from both crabs and starfish.

Involvement of a 3 β-hydroxysteroid dehydrogenase activity in ecdysteroid biosynthesis

Ecdysteroid biosynthesis was analyzed in vitro using dissociated Y-organ cells from the shore crab Carcinus maenas. 3-Dehydroecdysone (3DE) was detected as a minor secretory product, in addition to the formerly identified end-products 25-deoxyecdysone and ecdysone (E). In conversion studies, 3DE was formed from tritiated 5 β-ketodiol (2,22,25-trideoxyecdysone), 2,22deoxyecdysone and 2-deoxyecdysone but not from E. Further experiments were performed in order to understand the interconversions between 3-oxo and 3 β-OH compounds in the crab Y-organ. The enzyme involved in 3 β-dehydrogenation was not ecdysone oxidase, a soluble enzyme found in peripheral tissues of many arthropods but it presented strong similarities with 3 β-hydroxysteroiddehydrogenase enzymes from vertebrates: it was membrane-bound and NAD +-dependent. Moreover, a NADH-dependent 3 β-reduction of several 3-oxo-ecdysteroids was obtained using the same microsomal fraction (100 000× g pellet) of Y-organs, indicating that the reaction might be reversible. As this activity was specific of molting glands, we hypothesize that there is at least one 3 β-hydroxysteroid dehydrogenase enzyme involved in the biosynthetic pathway of ecdysteroids.

The anaerobic endproduct lactate has a behavioural and metabolic signalling function in the shore crab

This study presents the first evidence that, in invertebrates, the anaerobic endproduct lactate has an alarm signal function and induces metabolic and behavioural responses as in the anuran Bufo marinus. In support of this function, behavioural hypothermia was demonstrated in the shore crab Carcinus maenas. The animals moved to a cooler environment when exposed to hypoxic conditions. A decrease in preferred temperature of the same magnitude was also found when normoxic animals were injected with an iso-osmotic lactate solution resulting in a haemolymph concentration of approximately 12 mmol l-1. Under normoxic (PO2=>18 kPa) and moderately hypoxic conditions (PO2=12 kPa), injection of this lactate solution also caused a significant increase in the rate of oxygen consumption (100 and 50 % respectively). The increase in the rate of oxygen consumption was smaller and delayed, but lasted longer, under hypoxic conditions compared with normoxic conditions. Low but significant correlations between levels of lactate and levels of adrenaline, octopamine and tryptophan suggest the involvement of biogenic amines in the mediation of the signal.

Maintenance of motor pattern phase relationships in the ventilatory system of the crab

The central pattern generator responsible for the gill ventilation rhythm in the shore crab Carcinus maenas can produce a functional motor pattern over a large (eightfold) range of cycle frequencies. One way to continue to generate a functional motor pattern over such a large frequency range would be to maintain the relative timing (phase) of the motor pattern as cycle frequency changes. This hypothesis was tested by measuring the phase of eight events in the motor pattern from extracellular recordings at different rhythm frequencies. The motor pattern was found to maintain relatively constant phase relationships among the various motor bursts in this rhythm over a large (sevenfold) range of cycle frequencies, although two phase-maintaining subgroups could be distinguished. Underlying this phase maintenance is a corresponding change in the time delay between events in the motor pattern ranging from 470 to 1800 ms over a sevenfold (300&shy;2100 ms) change in cycle period. Intracellular recordings from ventilatory neurons indicate that there is very little change in the membrane potential oscillation in the motor neurons with changes in cycle frequency. However, recordings from nonspiking interneurons in the ventilatory central pattern generator reveal that the rate of change of the membrane potential oscillation of these neurons varies in proportion to changes in cycle frequency. The strict biomechanical requirements for efficient pumping by the gill bailer, and the fact that work is performed in all phases of the motor pattern, may require that this motor pattern maintain phase at all rhythm frequencies.

Sodium/proton antiporter in the euryhaline crab Carcinus maenas: molecular cloning, expression and tissue distribution.

Gill epithelial cells of euryhaline crustaceans demonstrate net inward transport of sodium ions, possibly via apical Na+/H+ antiporters, Na+/K+/2Cl- cotransporters or Na+ channels working in series with the basolateral Na(+) + K(+)-ATPase. We have identified and sequenced the cDNA coding for a crustacean Na+/H+ antiporter, starting with mRNA isolated from gills of the euryhaline green shore crab Carcinus maenas. The complete 2595-base-pair cDNA includes an open reading frame coding for a 673-amino-acid protein. A search of GenBank revealed more than 20 high-scoring matches, all Na+/H+ antiporter sequences from mammalian, amphibian, teleost and nematode species. Injection of Xenopus laevis oocytes with cRNA transcribed from the cloned crab sequence substantially enhanced Na(+)-dependent H+ efflux from the oocytes. Analysis of crab tissue antiporter mRNA levels by semi-quantitative reverse transcription-polymerase chain reaction revealed that posterior and anterior gills of Carcinus maenas expressed this antiporter the most strongly, followed in decreasing order by skeletal muscle, hepatopancreas, hypodermis and heart. Hydropathy and transmembrane alpha-helix analysis suggested a 10-helix membrane-spanning topology of the antiporter protein. It is clear from this study that Carcinus maenas gills vigorously transcribe a gene coding for a Na+/H+ antiporter. Whether these gills also express a gene coding for an epithelial Na+ channel or Na+/K+/2Cl- cotransporter remains to be demonstrated.

Carapace Colour, Inter-moult Duration and the Behavioural and Physiological Ecology of the Shore CrabCarcinus maenas

Adult maleCarcinus maenasoccur on the shore with carapace colours ranging from green to deep red. In the past, this was believed to be indicative of moult state; green crabs having recently moulted and red ones being in late inter-moult. A series of different studies carried out in recent years has shown that this is not the full story. Green males have been shown to be more tolerant of salinity fluctuations and aerial exposure than red males. Conversely, red males compete more successfully for mates and food. It is hypothesized that some crabs remain in inter-moult longer than others, developing stronger and thicker carapaces and chelae, and are thus more likely to win mating conflicts. This advantage is gained at the cost of reduced tolerance to the conditions of intertidal life. The change in colouration is believed to be due to photo-denaturation of pigments in the carapace over a long inter-moult. This paper is a synthesis of studies which have led to these conclusions, and their importance is discussed in relation to the behavioural and physiological ecology of other intertidal Crustacea.

Spatial variability in the population structure of the shore crab Carcinus maenas (Crustacea:Brachyura) in a shallow-water, weakly tidal fjord

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 147:97-103 (1997) - doi:10.3354/meps147097 Spatial variability in the population structure of the shore crab Carcinus maenas (Crustacea: Brachyura) in a shallow-water, weakly tidal fjord Abelló P, Aagaard A, Warman CG, Depledge MH The spatial variability in population structure of the shore crab Carcinus maenas was studied in a shallow-water fjord in the island of Fyn, Denmark. The fjord comprises an enclosed area which is geomorphologically divided into a shallow cove (mean depth 2 m), known as Kertinge Nor, and a deeper narrow area, closer to the open sea, known as Kerteminde Fjord. Tidal range is small (ca 20 cm). Sex-ratio favoured males at most of the sites sampled with the exception of the inland slope between the shallow Kertinge Nor and the deeper Kerteminde Fjord, which apparently was a spawning site. Crab densities were much higher in Kerteminde Fjord than in the shallower Kertinge Nor. Ventral carapace colour varied between green and orange-red, with the proportion of the green morphotype increasing with increasing distance from the open sea. Analysis of the population size structure identified 3 differentiated areas for both male and female crabs. Sites closer to the mouth of the fjord were characterized by a numerical dominance of small crabs, whereas crabs in Kertinge Nor were clearly of a much larger size. Sites in Kerteminde Fjord were characterized by a wider range of sizes. Some crabs in Kerteminde Fjord carried epibionts on the carapace, but those were absent in crabs from Kertinge Nor; moreover, a few crabs in Kertinge Nor carried Mytilus edulis byssus threads indicating that epibionts had fallen from the carapaces. Thus, population structure characteristics, such as colour morphotype proportions, size structure and occurrence of epibionts, are in accordance with the occurrence of a high degree of environmental variability in the area decreasing towards the mouth of the fjord and the open sea. Carcinus maenas · Population structure · Crabs · Brachyura Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 147. Publication date: February 27, 1997 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1997 Inter-Research.

Apparent water permeability as a physiological parameter in crustaceans

This article reviews the use of apparent water permeability (AWP) calculated from measurements of isotope-labelled water flux as a physiological estimate of whole-body water permeability in aquatic invertebrates. The rationale and practices of AWP calculations are described in an Appendix. AWP calculations have provided a wealth of information. However, the validity of the method and therefore also of the information obtained have been questioned. Consequently, the use of AWP data in discussions of osmotic and fluid homeostatic questions in aquatic invertebrates is limited. This article reviews three decades of published experiments in which measurements of isotope-labelled water fluxes were used to estimate water permeability in aquatic invertebrates. Data on 24 species of arthropod, most of them decapod crustaceans, are presented. The combined data indicate that the results obtained by different investigators on the same species show good agreement, even though different tracers and experimental methods have been applied. When available, results from other kinds of studies were used to evaluate the results obtained using the AWP measurements. The various results demonstrate that AWP is influenced not only by natural environmental factors, such as salinity and temperature, and by anthropogenic factors, such as potentially toxic trace metals, but that it is also regulated by intrinsic factors, such as ecdysis and life cycle stage. The results obtained can often be explained as effects of components of the habitat of the animal. Accordingly, studies on variations in AWP contribute to our understanding of the different physiological strategies used by species living in a changing environment. We conclude that calculations of AWP offer reliable, relevant physiological data in a range of crustacean species, as long as methodological limitations and uncertainties are kept in mind. In addition, we propose some possible new ways of applying AWP calculations to marine invertebrates other than crustaceans. A major part of this review describes results already obtained for the shore crab Carcinus maenas as this species is probably the animal on which most work has been carried out. We suggest topics for future work on this species and review the possibility of using AWP in C. maenas as a biomarker of metal exposure.

Active absorption of Na+ and Cl- across the gill epithelium of the shore crab Carcinus maenas: voltage-clamp and ion-flux studies

Mechanisms of active NaCl uptake across the posterior gills of the shore crab Carcinus maenas were examined using radiochemical and electrophysiological techniques. In order to measure short-circuit current (Isc), transepithelial conductance (Gte) and area-related unidirectional fluxes of Na+ and Cl-, single split gill lamellae (epithelium plus cuticle) of hyperregulating shore crabs were mounted in a modified Ussing chamber. The negative short-circuit current measured with haemolymph-like NaCl saline on both sides of the epithelium could be inhibited by application of basolateral ouabain (ouabain inhibitor constant KOua=56&plusmn;10 &micro;mol l-1), 5-nitro-2-(3-phenylpropylamino)-benzoic acid (NPPB; KNPPB=7.5&plusmn;2.5 mmol l-1) or Cs+ (10 mmol l-1). From the apical side, Isc was nearly completely blocked by Cs+ (10 mmol l-1) or Ba2+ (15 &micro;mol l-1), whereas apical addition of furosemide (1 mmol l-1) resulted in only a small current decrease. Cl- influxes were linearly related to negative Isc. The ratio between net influxes of Cl- and Na+ was found to be approximately 2:1. With a single membrane preparation, achieved by permeabilizing the basolateral membrane with amphotericin B, Cl- influxes which were driven by a concentration gradient were shown to depend on the presence of apical Na+ and K+. On the basis of these observations, we propose that active and electrogenic absorption of NaCl across the gill epithelium of hyperregulating shore crabs proceeds as in the thick ascending limb of Henle's loop in the mammalian nephron. Accordingly, branchial NaCl transport is mediated by apical K+ channels in cooperation with apical Na+/K+/2Cl- cotransporters and by the basolateral Na+/K+-ATPase and basolateral Cl- channels.

Effects of vanadium on population growth and Na-K-ATPase activity of the brackish water hydroid Cordylophora caspia.

Vanadium, a relatively abundant heavy metal, enters the environment naturally through rock weathering. A large fraction of vanadium input is of human origin. The combustion of petroleum- and coal-products, which contain relatively high concentrations of vanadium, is one of the most important sources of the enrichment of vanadium in the environment. As it is used as an alloy, and vanadium rich iron-ores of various origin are used in steel production, the residual slag-stones of the steel industry can contain considerable vanadium concentrations. Wherever slag-stones serve as a cheap and convenient material in riverbank reinforcement, vanadium can leach into the aquatic environment. Vanadium is regarded as an essential trace element for higher animals. Cantley et al. indicated a regulatory function of vanadate in vivo. Although considerable information is available on the toxic effects of vanadium on humans, very little is known about the toxicity of vanadium towards aquatic organisms, especially invertebrates. Bell and Sargent have shown an inhibition of Na-K-ATPase activity in gills of the eel Anguilla anguilla. Holleland and Towle have demonstrated the inhibition of Na-K-ATPase activity in the gills of the shore crab Carcinus maenas. The aim of this study was to determine the toxicity of vanadium towards themore » brackish water hydroid Cordylophora caspia. Hydroids are known to be particularly sensitive to heavy metals and their asexual reproduction can be used in a well-established population growth test. Furthermore, the effects of vanadium on Na-K-ATPase activity in hydroids were studied in in vivo experiments, wherein the animals were exposed to sublethal concentrations of vanadium. In addition, the inhibition of Na-K-ATPase was measured in vitro, by adding vanadium to a microsomal preparation. 16 refs., 4 figs.« less