The Experts below are selected from a list of 795 Experts worldwide ranked by ideXlab platform
Craig M Young - One of the best experts on this subject based on the ideXlab platform.
-
salinity and temperature tolerance of the nemertean worm carcinonemertes errans an egg predator of the Dungeness Crab
The Biological Bulletin, 2015Co-Authors: Paul H Dunn, Craig M YoungAbstract:Estuaries can be harsh habitats for the marine animals that enter them, but they may also provide these species with sub-saline refuges from their parasites. The nemertean egg predator Carcinonemertes errans is known to occur less frequently and in smaller numbers on its host, the Dungeness Crab Metacarcinus magister, when the hosts are found within estuaries. We examined the temperature and salinity tolerances of C. errans to determine if this observed distribution represents a true salinity refuge. We monitored the survival of juvenile and larval worms exposed to ecologically relevant salinities (5–30) and temperatures (8–20 °C) over the course of several days under laboratory conditions. Juvenile worms were unaffected by the experimental temperature levels and exhibited robustness to salinity treatments 25 and 30. However, significant mortality was seen at salinity treatments 20 and below. Larvae were less tolerant than juveniles to lowered salinity and were also somewhat more susceptible to the higher...
-
salinity and temperature tolerance of the nemertean worm carcinonemertes errans an egg predator of the Dungeness Crab
The Biological Bulletin, 2015Co-Authors: Paul H Dunn, Craig M YoungAbstract:Estuaries can be harsh habitats for the marine animals that enter them, but they may also provide these species with sub-saline refuges from their parasites. The nemertean egg predator Carcinonemertes errans is known to occur less frequently and in smaller numbers on its host, the Dungeness Crab Metacarcinus magister, when the hosts are found within estuaries. We examined the temperature and salinity tolerances of C. errans to determine if this observed distribution represents a true salinity refuge. We monitored the survival of juvenile and larval worms exposed to ecologically relevant salinities (5-30) and temperatures (8-20 °C) over the course of several days under laboratory conditions. Juvenile worms were unaffected by the experimental temperature levels and exhibited robustness to salinity treatments 25 and 30. However, significant mortality was seen at salinity treatments 20 and below. Larvae were less tolerant than juveniles to lowered salinity and were also somewhat more susceptible to the higher temperatures tested. Given that the Dungeness Crab can tolerate forays into mesohaline (salinity 5-18) waters for several days at a time, our findings suggest that salinity gradients play an important role in creating a parasite refuge for this species within the estuaries of the Pacific Northwest.
-
Larval settlement of the nemertean egg predator Carcinonemertes errans on the Dungeness Crab, Metacarcinus magister
Invertebrate Biology, 2014Co-Authors: Paul H Dunn, Craig M YoungAbstract:Due to their habitat specificity, marine parasites present excellent systems for studying the processes and patterns of larval settlement. Settlement of Carcinonermertes errans, an egg predator of the Dungeness Crab, is described here for the first time. Upon contact with a host individual, competent larvae of C. errans settled on the Crab's exoskeleton and migrated under the abdominal flap within 24 h. When removed from the host, recently settled worms retained their larval characteristics. After 48 h on the host, however, metamorphosis proceeded and larvae became juvenile worms. Additional field studies showed that competent larvae were present in the waters of the Coos Bay Estuary during the months of August through early November, could infect Crab hosts directly from the water column, and exhibited density-dependent gregarious settlement.
-
finding refuge the estuarine distribution of the nemertean egg predator carcinonemertes errans on the Dungeness Crab cancer magister
Estuarine Coastal and Shelf Science, 2013Co-Authors: Paul H Dunn, Craig M YoungAbstract:Abstract Parasites can significantly impact ecosystems by altering the distributions and population sizes of their host organisms. Some hosts are thought to find refuge from parasitism by entering habitats where their parasites cannot survive. The nemertean worm Carcinonemertes errans is an egg predator that infects the Dungeness Crab, Cancer magister, throughout the host's range. To determine if C. magister experiences a refuge from C. errans within estuarine environments, we examined the distribution of C. errans on Dungeness Crabs within Oregon's Coos Bay Estuary. Year-round sampling over a three-year period also allowed us to test for temporal variation in the parasite's distribution. We found that parasite prevalence, mean intensity, and parasite density of C. errans infecting C. magister varied along a clear estuarine gradient, with Crabs nearest the ocean carrying the heaviest parasite loads. Larger Crabs were more heavily infected with worms, and seasonal infection patterns were observed at some sites within the bay. Crabs sampled from coastal waters near the estuary carried significantly more worms than did Crabs from the bay, suggesting that the estuary is acting as a spatiotemporal parasite refuge for this important fishery species.
David A. Armstrong - One of the best experts on this subject based on the ideXlab platform.
-
Ocean distribution of Dungeness Crab megalopae and recruitment patterns to estuaries in Southern Washington State
Estuaries, 2003Co-Authors: G. Curtis Roegner, David A. Armstrong, Barbara M Hickey, Alan L. ShanksAbstract:We investigated the distribution of meroplankton and water properties off southern Washington and simultaneously measured time series of larval abundance and water properties in two adjacent estuaries, Grays Harbor and Willapa Bay. The cruise period, in late May 1999, coincided with large variation in the alongshore wind stress that caused dynamic change in the position of the Columbia River plume, coastal upelling and downwelling, and offshore phytoplankton production. In the coastal ocean, meroplankton groups responded differently to this wind event and the associated advection of water masses. Dungeness Crab ( Cancer magister ) megalopae were largely indifferent to the wide salinity variation, and were found throughout the surveyed area in both plume and recently upwelled waters. Megalopae of kelp Crab ( Pugettia producta ) and hermit Crab ( Pagurus spp ). were more abundant in upwelled water and low numbers were caught in the plume water. Barnacle cyprids appeared to track the advective transport suggesting that they may be more passively dispersed. Within the estuaries, hydrography responded rapidly and synchronously to variation in wind stress. Intrusions of both plume and newly upwelled waters were detected at estuarine sites, depending on the type of water present at the coast, indicating a tight link between the estuaries and the coastal ocean in this region. A 90-d record of C. magister megalopae abundance was made at 3 estuarine sites using light traps. The bulk of the C. magister recruitment was limited to a relatively brief period in late May through June. Within this window, megalopae occurred in distinct pulses of 3–5 d interspaced with periods of low or zero abundance. C. magister megalopae recruited to the estuaries over a wide range of wind forcing, and were transported into the estuary within varied water types. There were no periodic patterns indicative of spring-neap tidal variations in the abundance time series. Abundance was only weakly cross-correlated between the adjacent Grays Harbor and Willapa Bay estuaries, which contrasts with the more synchronous estuarine-coastal linkages measured for water properties. These results suggest the interaction of larval aggregation size in the ocean with estuary-ocean exchange processes likely controls patterns of estuarine recruitment.
-
the necessity for intertidal foraging by estuarine populations of subadult Dungeness Crab cancer magister evidence from a bioenergetics model
Estuaries, 2003Co-Authors: Kirstin K Holsman, David A. Armstrong, David A Beauchamp, Jennifer L RuesinkAbstract:Complex intertidal habitats characteristic of northeastern Pacific coastal estuaries provide critical nursery environments for young-of-the-year Dungeness Crab,Cancer magister, yet their role in supporting subsequent year classes remains unclear. SubadultC. magister (40–130 mm; 1+ and >1+ year classes), which reach densities as high as 4,300 Crabs ha−1 in subtidal channels during low tides, migrate during flood tides from subtidal refuges into intertidal habitats to forage. As with other brachyuran species that undertake extensive tidally-driven migrations, intertidal foraging may contribute significantly to the energy budget of subadultC. magister. In order to explore the energetic incentive for intertidal migrations by subadult Crabs, we developed an ontogenetically-based bioenergetics model for Crabs within Willapa Bay, Washington. The model showed that energetic demand varied spatially across the bay, with the highest average energetic demand of a population of subadult Crabs (2.13×106 kJ ha−1) occurring in a habitat stratum termed lower side channel (LSC) and characterized by relatively little subtidal area and extensive intertidal flats. Comparison of model results with subtidal prey production revealed that the latter could not satisfy subadultC. magister energetic demands, especially in LSC where modeled Crab predation depleted subtidal prey biomass within 17 simulation days. We estimate that 1 ha of subtidal Crabs from LSC would minimally require an additional 1.6 ha of intertidal area to satisfy energetic demands without depleting prey biomass. Our model results support the assertion thatC. magister make regular migrations to forage on productive intertidal flats, and suggest that intertidal foraging may contribute significantly to the diet of subadult Crabs in coastal estuaries.
-
the competitive and predatory impacts of the nonindigenous Crab carcinus maenas l on early benthic phase Dungeness Crab cancer magister dana
Journal of Experimental Marine Biology and Ecology, 2001Co-Authors: Sean P Mcdonald, Gregory C Jensen, David A. ArmstrongAbstract:We evaluate the potential competitive and predatory impacts of nonindigenous European green Crab Carcinus maenas on native Dungeness Crab Cancer magister in the northeast Pacific. The coastal estuaries of Washington State, USA, provide appropriate habitat for recently introduced green Crab, yet these areas are important nursery grounds for Dungeness Crab and contribute greatly to the coastal Crab fishery. Juvenile Dungeness Crabs are dependent on limited intertidal epibenthic shell for refuge habitat during early benthic life and experience increased mortality on open sand and mud as a result of predation by fish and birds. Early juveniles throughout the subtidal are similarly at risk due to predation by fish and especially adult conspecifics. Laboratory experiments and infrared video observations revealed that juvenile green Crab displace Dungeness Crab of equal size from shelters during one-on-one competition. Green Crab also consistently win nocturnal foraging trials in which the species compete for fresh, damaged clams. Field and laboratory enclosure experiments show that juvenile Dungeness Crab emigrate from oyster shell habitat as a result of competition and predation by adult green Crab. Depending on the extent to which the two species overlap, interactions with the dominant nonindigenous species could have a negative influence on juvenile Dungeness Crab survival and could conceivably impact recruitment to the fishery. However, current evidence indicates that the distribution of green Crab in Washington State is far removed from nursery areas of Dungeness Crab.
-
structure of the female reproductive tract in the Dungeness Crab cancer magister and implications for the mating system
The Biological Bulletin, 1996Co-Authors: Pamela C Jensen, Jose Maria Orensanz, David A. ArmstrongAbstract:Anatomical and behavioral aspects of repro- duction in female Dungeness Crab, Cancer magister, were investigated. Female Crabs were collected over a two-year period and external indicators of reproductive condition were recorded. A subset of Crabs was retained for mac- roscopic and histological examination of the reproductive tract. In addition, males and females were held in the laboratory for mating observations, thus providing females of known mating history for dissection. The spermatheca is of the "ventral type," i.e., the vagina and the oviduct open into the spermatheca in close proximity to each other. A novel organ that often contains sperm, the bursa, is separate and distinct from the spermatheca in both position and origin and is reported for the first time for a brachyuran Crab. The bursa is located just inside the vulva, distal to the spermatheca, and opens into the va- gina. The sperm plug of C. magister, described here for the first time, is unique in form among cancrids. The sperm plug is placed in the vagina by the first male to mate with a soft-shelled female and prevents subsequent access to the spermatheca. However, the sperm plug does not occlude the vulva nor prevent subsequent copulation; ejaculates from subsequent matings are deposited in the bursa. Hypotheses of the possible function of the bursa are discussed.
-
environmental impact of intertidal juvenile Dungeness Crab habitat enhancement effects on bivalves and Crab foraging rate
Journal of Experimental Marine Biology and Ecology, 1995Co-Authors: Oscar Iribarne, Miriam Fernandez, David A. ArmstrongAbstract:An intertidal oyster shell habitat has been created and used to mitigate the subtidal dredging impact on Dungeness Crab (Cancer magister Dana) population resulting from widening and deepening of the Grays Harbor navigation channel (47 °N, 124'W, USA). This paper addresses the effect of this artificial habitat on soft bottom species, focusing in particular on: (1) growth rate of the suspension feeder bivalve Mya arenaria L.; (2) both settlement and survival of the bivalve Macoma balthica (Linne); and (3) the effects of habitat heterogeneity, clam density, and Crab density on the foraging rate of juvenile Dungeness Crabs preying on Macoma balthica. Epibenthic shells did not affect the growth rate of Mya arenaria transplanted into oyster shell habitat. Recruitment of the bivalve Macoma balthica was not affected by shell either, but mortality rate was higher in areas covered by shell when compared with open mud. Laboratory experiments showed a positive density-dependent (Type III) functional response, indicating that Macoma balthica finds refuge at low clam density. At increased Crab density in shell habitats interaction among juvenile Crabs affects consumption rate of clams. Tethering experiments showed that juvenile Crab mortality was higher in open mud, intermediate at the border of the shell plots, and lower in the center. This pattern of Crab mortality suggests that juvenile Dungeness Crabs only affect local clam populations in shell covered areas. These results indicate that although the artificial shell habitat successfully enhances settlement and survival of juvenile Dungeness Crabs, it affects the ecology of some non-target species, in part through intensified predator-prey dynamics due to the increased local densities of young-of-the-year Crabs.
Paul H Dunn - One of the best experts on this subject based on the ideXlab platform.
-
salinity and temperature tolerance of the nemertean worm carcinonemertes errans an egg predator of the Dungeness Crab
The Biological Bulletin, 2015Co-Authors: Paul H Dunn, Craig M YoungAbstract:Estuaries can be harsh habitats for the marine animals that enter them, but they may also provide these species with sub-saline refuges from their parasites. The nemertean egg predator Carcinonemertes errans is known to occur less frequently and in smaller numbers on its host, the Dungeness Crab Metacarcinus magister, when the hosts are found within estuaries. We examined the temperature and salinity tolerances of C. errans to determine if this observed distribution represents a true salinity refuge. We monitored the survival of juvenile and larval worms exposed to ecologically relevant salinities (5–30) and temperatures (8–20 °C) over the course of several days under laboratory conditions. Juvenile worms were unaffected by the experimental temperature levels and exhibited robustness to salinity treatments 25 and 30. However, significant mortality was seen at salinity treatments 20 and below. Larvae were less tolerant than juveniles to lowered salinity and were also somewhat more susceptible to the higher...
-
salinity and temperature tolerance of the nemertean worm carcinonemertes errans an egg predator of the Dungeness Crab
The Biological Bulletin, 2015Co-Authors: Paul H Dunn, Craig M YoungAbstract:Estuaries can be harsh habitats for the marine animals that enter them, but they may also provide these species with sub-saline refuges from their parasites. The nemertean egg predator Carcinonemertes errans is known to occur less frequently and in smaller numbers on its host, the Dungeness Crab Metacarcinus magister, when the hosts are found within estuaries. We examined the temperature and salinity tolerances of C. errans to determine if this observed distribution represents a true salinity refuge. We monitored the survival of juvenile and larval worms exposed to ecologically relevant salinities (5-30) and temperatures (8-20 °C) over the course of several days under laboratory conditions. Juvenile worms were unaffected by the experimental temperature levels and exhibited robustness to salinity treatments 25 and 30. However, significant mortality was seen at salinity treatments 20 and below. Larvae were less tolerant than juveniles to lowered salinity and were also somewhat more susceptible to the higher temperatures tested. Given that the Dungeness Crab can tolerate forays into mesohaline (salinity 5-18) waters for several days at a time, our findings suggest that salinity gradients play an important role in creating a parasite refuge for this species within the estuaries of the Pacific Northwest.
-
Larval settlement of the nemertean egg predator Carcinonemertes errans on the Dungeness Crab, Metacarcinus magister
Invertebrate Biology, 2014Co-Authors: Paul H Dunn, Craig M YoungAbstract:Due to their habitat specificity, marine parasites present excellent systems for studying the processes and patterns of larval settlement. Settlement of Carcinonermertes errans, an egg predator of the Dungeness Crab, is described here for the first time. Upon contact with a host individual, competent larvae of C. errans settled on the Crab's exoskeleton and migrated under the abdominal flap within 24 h. When removed from the host, recently settled worms retained their larval characteristics. After 48 h on the host, however, metamorphosis proceeded and larvae became juvenile worms. Additional field studies showed that competent larvae were present in the waters of the Coos Bay Estuary during the months of August through early November, could infect Crab hosts directly from the water column, and exhibited density-dependent gregarious settlement.
-
finding refuge the estuarine distribution of the nemertean egg predator carcinonemertes errans on the Dungeness Crab cancer magister
Estuarine Coastal and Shelf Science, 2013Co-Authors: Paul H Dunn, Craig M YoungAbstract:Abstract Parasites can significantly impact ecosystems by altering the distributions and population sizes of their host organisms. Some hosts are thought to find refuge from parasitism by entering habitats where their parasites cannot survive. The nemertean worm Carcinonemertes errans is an egg predator that infects the Dungeness Crab, Cancer magister, throughout the host's range. To determine if C. magister experiences a refuge from C. errans within estuarine environments, we examined the distribution of C. errans on Dungeness Crabs within Oregon's Coos Bay Estuary. Year-round sampling over a three-year period also allowed us to test for temporal variation in the parasite's distribution. We found that parasite prevalence, mean intensity, and parasite density of C. errans infecting C. magister varied along a clear estuarine gradient, with Crabs nearest the ocean carrying the heaviest parasite loads. Larger Crabs were more heavily infected with worms, and seasonal infection patterns were observed at some sites within the bay. Crabs sampled from coastal waters near the estuary carried significantly more worms than did Crabs from the bay, suggesting that the estuary is acting as a spatiotemporal parasite refuge for this important fishery species.
Walter J Cretney - One of the best experts on this subject based on the ideXlab platform.
-
bioavailability of chlorinated dibenzo p dioxins and dibenzofurans to Dungeness Crab cancer magister at marine pulp mill sites in british columbia canada
Environmental Toxicology and Chemistry, 2000Co-Authors: Mark B Yunker, Walter J CretneyAbstract:Synchronous samples of sediment and Dungeness Crab (Cancer magister) hepatopancreas, which were obtained for monitoring and assessment purposes at British Columbia, Canada, marine pulp mill sites between 1990 and 1995, were used to calculate biota-sediment accumulation factors (BSAFs) for individual chlorinated dibenzo-p -dioxin and dibenzofuran congeners (PCDD/Fs). The BSAFs for individual pairs of samples were highly variable, and no systematic trends were apparent in the observed accumulation factors over time, with Crab size, with Crab lipid concentration, with sediment percent organic carbon, or among mill sites or depositional environments. Composition and source differences in sedimentary PCDD/Fs, which are apparent as principal components analysis class separations in the sediment data set, also did not correlate with differences in BSAFs. This independence from environmental factors provides a valuable endorsement of the BASF concept for the formulation of aquatic effects-based sediment-quality criteria and human risk-assessment guidelines. However, BSAF values did exhibit a significant, nonlinear decrease with increasing log Kow and with sediment and Crab PCDD/F concentrations. The correlation between BSAFs and sediment concentrations accounts for between 14 and 81% of the variability in the BSAF values. The PCDD/F congeners that are present in low concentrations and/or have reduced bioavailability are the congeners that have the strongest correlations between the BSAFs and the sediment PCDD/F concentrations. Congeners that are bioavailable to Dungeness Crab exhibit poorer correlations between the BSAFs and sediment concentrations.
-
concentration dependency of biota sediment accumulation factors for chlorinated dibenzo p dioxins and dibenzofurans in Dungeness Crab cancer magister at marine pulp mill sites in british columbia canada
Environmental Toxicology and Chemistry, 2000Co-Authors: Walter J Cretney, Mark B YunkerAbstract:Biota-sediment accumulation factors (BSAFs) for some chlorinated dibenzo- p -dioxin and dibenzofuran congeners (PCDD/Fs) in Dungeness Crab (Cancer magister) hepatopancreas and associated sediments are concentration independent as required by equilibrium partition models. In particular 2, 3, 7, 8-tetrachlorodibenzo-p -dioxin (2, 3, 7, 8-TCDD), 2, 3, 7, 8-tetrachlorodibenzofuran, the 2, 3, 7, 8-substituted pentachlorodibenzofurans, and the non-2, 3, 7, 8-hexachlorodibenzofurans (HxCDFs) seem to fall into this group. The BSAFs for other isomers exhibit significant, nonlinear variations with sediment or Crab PCDD/F concentrations. For some of these other isomers (e.g., the non-2, 3, 7, 8 TCDDs and possibility the 2, 3, 7, 8-substituted HxCDFs), association of a variable fraction of the total present with soot carbon may provide a satisfactory explanation for the concentration behavior. For the HxCDDs we propose that the nonlinear concentration behavior may arise from the thermodynamic properties of fluids confined in hydrophobic voids within particulate and colloidal material produced by the pulp mills. The nonlinear relationship between BSAFs and PCDD/F concentrations greatly complicates prediction of the potential for dioxin and furan bioaccumulation in Crabs and the formulation of sediment quality criteria. We provide a nonlinear equation relating toxic equivalency and sediment concentrations.
Phillip S. Levin - One of the best experts on this subject based on the ideXlab platform.
-
Movement Patterns and Distributional Shifts of Dungeness Crab (Metacarcinus magister) and English Sole (Parophrys vetulus) During Seasonal Hypoxia
Estuaries and Coasts, 2013Co-Authors: Halley E. Froehlich, Timothy E. Essington, Anne H. Beaudreau, Phillip S. LevinAbstract:Hypoxia (dissolved oxygen < 2 mg L–1) has emerged as a worldwide threat to coastal and estuarine ecosystems. Beyond direct mortality, secondary ecological impacts caused by hypoxia-driven distributional shifts may be equally important. From July–November 2009 and June–September 2010, we quantified the movement patterns of Dungeness Crab (Metacarcinus magister) and English sole (Parophrys vetulus) in Hood Canal, Washington USA, a seasonally hypoxic estuary. Although highly mobile (mean cumulative distance ± SD = 11.0 ± 25.6 km, N = 60), there was little evidence of either species exhibiting large-scale directional movement out of the hypoxic region. However, Dungeness Crab showed significant shifts towards shallower waters and elevation in activity in the hypoxic region, potentially increasing their vulnerability to Crabbing and other indirect ecological consequences. Our findings suggest hypoxia could have a more localized impact on the mobile fauna in Hood Canal. However, more detailed information concerning the local-scale oxygen dynamics and responses of these species, such as English sole vertical movement, is essential for grasping the population and community level effects of hypoxia.
