Elemental composition (C,N, H) and energy in the development of Pagurus bernhardus (Decapoda: Pagurida) megalopa

No differences in development time and mortality were detected between starved and fed laboratory raised megalopa of Pagurus bernhardus. The average time of development in 138 megalopa was determined as 7.3±0.1 (95% CI) days. During megalopa development P. bernhardus loses about 7% in dry weight (DW), 17% in carbon (C), 6% in nitrogen (N) and 17% in hydrogen (H). During development C/N ratio and individual energy content descend about 14 and 22% respectively. Weight specific energy content decreases by 17% in the first 3 d and remains constant at 12.3±0.3 (95% CI) J·(mg DW)^-1 thereafter. About another 25% in individual energy content was lost by molting to crabs. The measured compounds do not follow a steady decrease. The possibility is discussed that a period of low energy cost (about the first half of development) alternates with times of higher energy expenditure mainly based on lipids. A fixed physiological program different from starvation capability is indicated for P. bernhardus megalopae. By comparing megalopae hatched in two different seasons and years reference is given to the variability in growth pattern.     

Respiratory metabolism of Pagurus bernhardus (Decapoda: Paguridae) megalopa

Individual oxygen consumption was determined during the megalopa development of Pagurus bernhardus at 18°C in 1983. The maximum observed range was from 0.101 to 0.343 l O₂ h^-1 ind^-1. Individual respiration rate dropped by about 33% during the first two days and continued to remain at that level throughout the moult cycle. The results are discussed together with data on biomass and the fact that P. bernhardus megalopa do not feed.     

Influence of limited starvation periods on growth and elemental composition (C,N,H) of Carcinus maenas (Decapoda: Portunidae) larvae reared in the laboratory

Zoea-1 larvae of Carcinus maenas L. (Decapoda: Brachyura: Portunidae) were from Helgoland in March 1984 and reared in the laboratory at 18°C through ecdysis. Dry weight (DW) and elemental composition of carbon (C), nitrogen (N), and hydrogen (H) were analyzed in newly hatched zoea-1, after different initial starvation periods, and in newly moulted zoea-2. Continually starved zoea-1 lost biomass and energy steadily, and logarithmic functions show best fit of empirical and predicted data. Biomass and energy equivalents of newly moulted zoea-2 are significantly correlated with starvation periods in the zoea-1, showing lower values with longer initial starvation. After about 25 to 34% individual biomass and energy losses, larvae exceed the point-of-noreturn (PNR), and do not recover or moult to the zoea-2, even if re-fed. When starvation ceases before the PNR, larvae moult to the zoea-2, and develop with lower average growth rates (AGR) after prolonged periods of initial food deprivation. The later larvae were re-fed, the less absolute amounts of DW, C, H, and individual energy, but more DW-related energy equivalents and N accumulated during subsequent feeding towards ecdysis. It is suggested that lipid, rather than protein, is the main source of energy controlling the maintenance of larval moult cycles. After lipid reserves are depleted, zoea-1 larvae live on body protein, and lose the ability to absorb and restore sufficient lipid if re-fed later than the PNR.Contribution to research project An-145/1-1 granted by the Deutsche Forschungsgemeinschaft (DFG)     

Growth and elemental composition (C,N, H) in Inachus dorsettensis (Decapoda: Majidae) larvae reared in the laboratory

Larvae of the spider crab Inachus dorsettensis were reared in the laboratory at constant 12 °C. Development lasted 8 to 10 d in the Zoea I, 10 to 12 d in the Zoea II and 14 to 20 d in the megalopa stage. During this time, larval growth was measured in samples taken every 2 to 4 d as dry wt (W), carbon (C), nitrogen (N), and hydrogen (H); energy content (E) was calculated from C. Biomass and energy (per individual) increased in each larval stage as a parabola-shaped function of age, which could be fitted by a power equation. C, H, and E show a higher percentage gain (relative to the initial values at hatching) than W or N, suggesting that proportionally more lipid than protein is accumulated during larval development. There are cyclical changes in the relative (per unit of W) biomass and energy figures, corresponding to the larval moult cycles: immediately after each ecdysis all these values decrease, presumably due to rapid uptake of water and minerals, then they increase again due to tissue growth and remain high until the next moulting occurs. Cyclical changes in the C/N ratio suggest that proportionally more lipid than protein is accumulated during the initial (postmoult) phase of the moult cycle, followed by a period of balanced or protein-dominated gain during the intermoult and premoult phases. These patterns of growth and elemental composition observed during the complete larval development and in single moult cycles of I. dorsettensis are compared with those described in the literature for other decapod species. This comparison suggests a high degree of similarity in biochemical composition and growth characteristics of larval decapod crustaceans.     

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     

Effects of temperature and salinity on larval development ofNecora puber (Brachyura: Portunidae)

Temperature and salinity affected both length of larval development and mortality inNecora puber collected in the Ría de A Coruña during December 1984 and January 1985. Development time decreased considerably with increased temperature. This decrease was sharper when temperature increased from 15° to 20°C than when it increased from 20° to 25°C. At 35S, average development took 48, 32 and 28 d at 15°, 20° and 25°C, respectively. At the three salinities tested (25, 30 and 35), larval development was completed only at 15°C, at 20°C/30 and 35S, and at 25°C/35S. Development times at 15° and 20°C were highly significantly different at both 35 and 30S (P 0.01). However, there were no significant differences between development times at 20° and 25°C (P > 0.05). Within any one specific temperature series, no significant difference was observed between the salinity values tested (P > 0.05). The duration of each of the five zoeal stages was similar within each and the same temperature/salinity combination, whereas the duration of the megalop was twice as long as any of the zoeal stages. The combination of the lowest temperature (15°C) and the highest salinity (35) tested resulted in the greatest larval survival of 28%. Highest mortality occurred at 25°C, at which temperature development was completed only at 35S. A sharp drop in larval survival was observed in the transition period Zoea V — megalop in all combinations of temperature and salinity tested. Within the limits of tolerance to temperature and salinity, the former effected more pronounced differences in the duration of larval development, while salinity appeared to constitute a limiting factor for survival.     

Population dynamics and growth of juveniles of the velvet swimming crab Necora puber (Decapoda: Portunidae)

Recruitment variability plays a critical role in determining local population densities of benthic organisms, but extreme vulnerability at the onset of juvenile life is a trait that is largely responsible for population survivorship trends. The aim of the present study was to determine the role of juvenile recruitment in the population structure of Necora puber. Juveniles of N. puber were collected from the lower intertidal of rocky shores of Plymouth Sound (southwest coast of the UK) and monthly size–frequency distribution were used to determine the dynamics and the growth of the population. The parameters of the von Bertalanffy growth function were estimated (K=0.281 year⁻¹; t ₀=0.043; C=0.103; and t _s=0.268) assuming a L _∞=105 mm. Growth was markedly seasonal and present results indicated a slower juvenile growth rate than described previously for N. puber. The recruitment period was extensive and was two times higher in 2001 than in 2000 at the start of the 1+ year, but levelled off at the end of the 1+ year class on three of the four shores studied. Instantaneous mortality as high as 5.1 year⁻¹(99.4% year⁻¹) was observed during the higher recruitment year. Early juvenile mortality appears to be density dependent and a demographic bottleneck appears to limit the number of juveniles on some shores.     

Chela loss in the shore crab Carcinus maenas (Crustacea: Brachyura) and its effect on mating success

Field and experimental studies were conducted to determine the incidence of chela loss and its effect on mating success in a population of the shore crab Carcinus maenas (Linnaeus, 1758) inhabiting the Menai Straits, North Wales. The study was performed between 1989 and 1993. Male crabs showed a higher degree of chela loss (12.5%) than females (7.9%). In males, frequencies ranged from 10% at sizes 50 mm CW (carapace width) up to 30% in the largest crabs of 70 to 80 mm CW. The percentage of females with missing chelae appears to be unrelated to size. The most common type of chela loss in the population studied was of a missing crusher chela of right-handed crabs. Red crabs, which are assumed to be in prolonged intermoult, had a much higher degree of chela loss (20.5%) than the green, early intermoult crabs (9.7%). The proportion of red crabs with chela losses increased with size, possibly reflecting an increase in intermoult duration with size. In green crabs, there was no such increase. The proportion of male crabs with missing chelae found in mating pairs in the field was much lower than that found in the adult unpaired population, suggesting that the loss of a chela constitutes a handicap to a male crab when trying to mate. Also, by studying the relative frequencies of different categories of chela loss, it is suggested that the loss of a crusher chela exerts a more deleterious effect than the loss of a cutter. Experiments were performed in the laboratory where pairs in pre-copula were confronted with an additional single male in various combinations of sizes and patten of chela loss. These showed that the loss of a chela constitutes a handicap for a male crab when either competing for or defending a paired pre-moult female. This handicap was estimated to be equivalent to a reduction in size of 7 to 8 mm CW relative to the size of the competitor.     

Feeding ecology of Liocarcinus depurator (Decapoda: Portunidae) in the Ria de Arousa (Galicia,north-west Spain): effects of habitat,season and life history

The diet of the portunid crab Liocarcinus depurator (L.) in soft-bottom areas of the Ría de Arousa (Galicia, north-west Spain) was studied by analysis of stomach contents, and by comparison of habitats of contrasting abundance, composition and diversity of prey communities. Monthly samples were taken from July 1989 to June 1990 (N=3747) in mussel (Mytilus galloprovincialis) raft-culture areas and central channel zones. Ninety-two food items were identified: crustaceans, molluscs, polychaetes, ophiuroids and fishes were the dominant prey. The raft epifauna and the mussels constituted the dominant group of prey in the raft areas and inner channel station (the epifaunal crab Pisidia longicornis comprised 30 to 52% of the diet), whereas the benthic macroinfauna was the dominant food component in the mid-outer channel (polychaetes constituted 32% of the diet). In the epifaunal community, diet selection for P. longicornis was positive and for amphipods was negative, whereas within the infauna diet selection for bivalves and ophiuroids was positive and for polychaetes negative or neutral. The seasonal importance of P. longicornis and M. galloprovincialis varied in the diet of L. depurator parallel to seasonal activities connected with mussel culture (seeding, thinning, harvesting) that determine the availability of prey from the rafts. Major changes in the composition of the diet related to the life history of L. depurator occurred during ontogeny. In the raft zones, consumption of mussels and fishes increased with increasing body size, while the consumption of Natantia, non-decapod crustaceans, gastropods, polychaetes Pectinariidae and plants decreased with increasing crab size. Maximum consumption of P. longicornis was by L. depurator individuals of intermediate size (15 to 44 mm carapace width). Stomach fullness (measured as dry weight of food) increased with increasing body size, but with negative allometry. During the late pre-moult and early post-moult periods L. depurator did not consume any food; maximum stomach fullness was recorded for the late post-moult and intermoult stages. Female food consumption decreased during egg incubation. Food consumption was greater in autumn and winter than at other seasons; this appears to be related to seasonal changes in reproduction and moulting.     

Ontogenetic variation in metabolism, biochemical composition and energy content during the early life stages of Farfantepenaeus paulensis (Crustacea: Decapoda: Penaeidae)

Dry weight (DW), oxygen consumption, ammonia-N excretion, proximate biochemical composition (total protein, carbohydrate, lipid, water and ash), and energy content (estimated from biochemical composition and by wet combustion) were determined in early developmental stages of cultured Farfantepenaeus paulensis. Pooled samples from embryonic, larval and postlarval stages (at 26 ± 1 °C and 34 ± 1‰) were used for measurements. The study focused on physiological and biochemical processes during transitional periods of ontogeny, such as hatching, lecithotrophic and planktotrophic stages, metamorphosis, and the attainment of a benthic existence in postlarva. DW showed higher increment between protozoea I (PZ I) and mysis I (M I) than in the next mysid and postlarval stages. Individual rates of oxygen consumption and ammonia-N excretion increased, while weight-specific rates presented significant reduction throughout development. Higher weight-specific oxygen consumption was registered in nauplius III (N III) and PZ I, following a decrease in subsequent stages. Postlarval stages PL V–VI and PL X–XII exhibited the lowest values among the stages studied. Weight-specific excretion was high in N III and protozoeal stages, with maximum values in PZ II, while the following stages were marked by lower rates. O:N ratios indicated higher protein catabolism in the stages between egg and M I and a shift to more lipid utilization close to metamorphosis. Water content was higher in the protozoeal stages and decreased afterwards. Higher percentages of protein, lipid and carbohydrate (%DW) were observed in egg and nauplius stages. Protein and lipid decreased from the egg through the naupliar and protozoeal stages, rising again in mysis stages. Lipid content (%DW) decreased in PL V–VI and PL X–XII. Lipid:protein ratios showed an increase of the importance of lipid between PZ III and M II. Carbohydrates represented a minor fraction of body composition, and ash percentages increased from egg to a maximum in PZ II, decreasing in subsequent stages. Energy content determined by wet combustion or calculated by energy equivalents presented the same trend throughout development, varying similarly to protein. Protein was the main energy contributor to body energy in all stages, while the importance of lipid was higher in egg and early naupliar stages. Trends observed in metabolic rates and body composition may be associated to morphological and behavioral changes during the early stages of penaeid development, such as the transition from herbivory to omnivory, and the adoption of a benthic existence. Different ontogenetic energy strategies contribute to succeed through such diverse type of development. Received: 4 July 2000 / Accepted: 6 December 2000     

Introduction,dispersal and potential impacts of the green crab Carcinus maenas in San Francisco Bay,California

The North Atlantic portunid crab Carcinus maenas (Linnaeus, 1758) has invaded the North Pacific Ocean following more than two centuries of global dispersal due to human activities. C. maenas was first collected in San Francisco Bay, California, in 1989–1990, where its distribution and prey selectivity were investigated in 1992–1994. It has become abundant in shallow, warm lagoons (which as favorable and retentive microhabitats may have served as invasion incubators) and spread throughout the north, central and south bays. It may have arrived in ballast water, on fouled ships, amongst algae with imported live bait or lobsters, or by intentional release; genetic comparisons of the Bay population with possible source populations may aid in defining the transport mechanism. C. maenas' eurytopic nature, its high breeding potential, and its diet and feeding behavior suggest the potential for extensive ecosystem alterations through predator-prey interactions, competition, disturbance, and indirect effects. Although both negative economic impacts through reduction or disruption of fisheries and positive impacts of providing bait and human-food fisheries have been documented in a few regions, the potential economic impacts in San Francisco Bay remain largely unknown.     

Elemental and biochemical composition of salps (Tunicata: Thaliacea)

Carbon and nitrogen content have been measured in the solitary and aggregate generations of 11 species of salps. Regression equations for each species and generation permit estimation of carbon or nitrogen content as a function of length of live individuals. Different species of the same length may have nearly tenfold differences in carbon content. Fractionation and biochemical analysis of some samples revealed that the organic content of salps is approximately 80% protein. Ash-free dry weights average 27% of dry weights; mean carbon content is 29% of ash-free dry weight. Excess ash-free dry weight not accountable as organic material is thought to be water of hydration.     

Spread and potential impact of the recently introduced European green crab,Carcinus maenas,in central California

Our study examines the potential impact of the European green crab Carcinus maenas on communities of coastal embayments of western North America. We document the current distribution and range expansion of this species beyond San Francisco Bay, where C. maenas first became established along this coast in 1989–1990, and we test the effect of C. maenas predation on different species and sizes of infaunal invertebrates in field and laboratory experiments. In our samples from eight coastal locations in central California collected between June 1993 and May 1994, we found no green crabs at the two closest embayments south of San Francisco Bay and found the crabs in all four embayments sampled within 120 km north of San Francisco Bay, up to and including Bodega Harbor. C. maenas was not present in samples from sites farther north. This northward range expansion is apparently the result of larval recruitment by a single cohort, corresponding to the predominant northern transport of surface waters and the approximate distance water moves during larval green crab development. At Bodega Harbor, the current northern range limit, the C. maenas population is now well established and reproducing. Females and males became sexually mature within their first year at 40 mm carapace width, molting approximately monthly from summer through fall, and females were ovigerous in late fall of their first year at 50 mm. We expect larvae from this population to recruit locally and to the north, promoting episodic range extensions as new populations are established and reproduce. Enclosure experiments conducted during the summer of 1993 at the intertidal sandflats of Bodega Harbor showed that C. maenas significantly reduced densities of the most abundant taxa, including the bivalves Transennella confusa and T. tantilla, the cumacean Cumella vulgaris, and the amphipod Corophium sp. Furthermore, Carcinus maenas selectively removed larger (>3 mm) rather than smaller (<1 mm) Transennella spp. in both field and laboratory experiments. Based on the available data from this and other studies of green crabs, and our 10 yr study of community dynamics at Bodega Harbor, we predict C. maenas will significantly alter community structure, ecological interactions, and evolutionary processes in embayments of western North America.     

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. Received: 2 July 1997 / Accepted: 10 July 1997     

Natural diet of larval Penaeus merguiensis (Decapoda: Penaeidae) and its effect on survival

The relationship between Penaeus merguiensis protozoea larvae and their phytoplankton diet was examined using seasonal plankton surveys and in situ rearing experiments. Larval abundance, phytoplankton community structure, and chlorophyll a concentration in Albatross Bay, Gulf of Carpentaria, were monitored monthly for 2 yr. Larval abundance peaked in November (spring) and March (autumn), at which times diatoms were the most abundant group in net samples of phytoplankton and in the guts of larvae. During November 1989 and March 1990, larvae were reared in nylon mesh enclosures positioned throughout the water column at three depths: 0 to 3 m, 3 to 6 m and 6 to 9 m. Overall, larval survival and gut fullness were both higher in November than in March. In both months, larval survival was lower at the surface than at other depths. This correlated with lower chlorophyll a concentrations, but lower total cell densities were not detected. During the in situ experiments, diatoms were the most abundant phytoplankton group in the water column and in the guts of larvae and, therefore, appeared to be the principal diet of larvae. Pigment analysis demonstrated that while gut contents generally reflected the composition of the phytoplankton community, the larvae were not feeding exclusively on diatoms. They also ingested green algae and possibly seagrass detritus. The in situ experiments demonstrated that the predominantly diatom flora in Albatross Bay can provide a nutritionally adequate environment for prawn larvae even at seasonally low levels. It is unlikely, therefore, that starvation is a major cause of mortality of P. merguiensis larvae during either of the biannual peaks in their abundance in Albatross Bay, Gulf of Carpentaria.     

Weapon size versus body size as a predictor of winning in fights between shore crabs, Carcinus maenas (L.)

Relative body size (carapace width) and weapon size (chela length) were used as indicators of resource holding potential (RHP) in the agonistic behaviour of male shore crabs, Carcinus maenas (L.). Weapon size was found to be a more reliable predictor of the outcome of pairwise fights than body size. Crabs with longer chelae than their opponents were more likely to win fights than crabs with relatively larger bodies. Body size had less influence on the outcome of fights. Relative body and weapon size did not influence initiation of contests but did affect the likelihood of winning; however, this was significant only for weapon size. Winning crabs had heavier claws with greater surface area than losing crabs. There was no relationship between relative size and fight duration. The frequency of cheliped display increased with chela length and win- ners performed significantly more displays than losers. Received: 5 February 1997 / Accepted after revision: 20 May 1997     

Settlement cues in successive developmental stages of the ghost shrimps Callichirus major and C. islagrande (Crustacea: Decapoda: Thalassinidea)

Larvae of Callichirus major (Say) and C. islagrande (Schmitt) were given unconditioned water with sand, water conditioned by previous exposure to adults (AW) without sand, or the combination of both AW and sand to determine if these factors served as settlement cues. Shrimp were first given stimuli upon reaching the last zoeal stage (ZIV), the decapodid stage (D), or the first juvenile stage (J1). Once initiated, exposure of shrimp to stimuli was maintained until termination of␣the experiment. Stage duration, burrowing activity of decapodids and early juveniles and location of exuviae were observed daily. Exposure to sand and AW did not decrease duration of the decapodid stage in either species. However duration of ZIV in C. major appeared to decrease when these stimuli were offered at this stage; this suggests that molting to Stage D may be delayed without such cues. When stimuli were examined separately, AW was found to have a significant effect on the duration of ZIV, while the effect of sand with unconditioned water and effects of simultaneously offered stimuli were not significant. Shrimp that received stimuli at ZIV subsequently burrowed more at D and J1 than individuals that did not receive stimuli at ZIV. Location of exuviae was recorded as on top of sand (not burrowed during molt) or within sand (burrowed during molt) for each shrimp's molt from Stages D to J1 (D molt), and from J1 to J2 (J1 molt). In C. major, the percentage of D exuviae and J1 exuviae found within sand as opposed to on top of sand was significantly higher in individuals which received stimuli at ZIV than for those that first received them at D or J1. When stimuli were examined separately in C. major, the effect of sand on burrowing activity was highly significant, while AW and the stimuli in combination had weaker effects. For C. major, AW appeared to accelerate development to D, while sand triggered settlement. Neither stimulus altered stage duration or burrowing activity of C. islagrande. Received: 7 December 1997 / Accepted: 24 July 1998     

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.