Effects Of Large Predators On The Field Culture Of The Hard Clam, Mercenaria mercenaria

Individuals in the clam industry h ave used fences to keep the cownose ray, Rhirioptera bonasus, out of planted areas (Lewis 2 ; Burton3 ). Tiller et al. ( 1952) indicated losses due to skates in planted holding areas and stated that One man reported the loss of 600 bushels of small clams in two nights during 1948 .... Merriner and Smith4 stated that cownose ray predation is a serious problem on oyster and clam grounds in Chesapeake Bay. From these observations it is clear that such large predators could be a significant deterrent to the culture of clams from Delaware Bay southward along the Atlantic coast. The present study continues a program designed tv evaluate methods of protecting areas seeded with young Mercenaria mercenari

Effects Of Clam Aquaculture On Nektonic And Benthic Assemblages In Two Shallow-Water Estuaries

Aquaculture of the northern quahog (=hard clam) Mercenaria mercenaria (Linnaeus, 1758) is widespread in shallow waters of the United States from Cape Cod to the eastern Gulf of Mexico. Grow-out practices generally involve bottom planting and the use of predator exclusion mesh. Both the extent and scale of clam farms have increased in recent decades resulting in concerns regarding the impacts of these practices on estuarine fauna. Seasonal distribution, abundance, biomass, species richness, and community composition of nektonic, demersal, epibenthic, and infaunal organisms were examined in cultivated and uncultivated shallow-water habitats in Virginia and New Jersey. The results reveal that clam aquaculture, as practiced in both Virginia and New Jersey, has remarkably few quantifiable impacts on estuarine fauna. Seasonal variations were observed in the biota, but of the 39 population and community metrics tested, mean values associated with 26 did not differ between cultivated and uncultivated areas, 5 had decreases and 8 had increases. For recently harvested areas, 32 of 39 variables were not different from uncultivated areas, 6 decreased in at least one season, and 1, blue crab biomass, had a marginal increase. Decreases were observed in the abundance and biomass of infauna (exclusive of the cultured clams) on clam farms, including in harvested areas, relative to natural uncultivated areas. This was accompanied, however, by substantial increases in epibenthic macroalgae, which in some cases supported increased epifaunal species richness and abundance relative to uncultivated areas. Habitat use by finfish, crustaceans, and terrapins was largely unaffected by the presence of clam farms

Climate change, precipitation and impacts on an estuarine refuge from disease

© The Author(s), 2011. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in PLoS One 6 (2011): e18849, doi:10.1371/journal.pone.0018849.Oysters play important roles in estuarine ecosystems but have suffered recently due to overfishing, pollution, and habitat loss. A tradeoff between growth rate and disease prevalence as a function of salinity makes the estuarine salinity transition of special concern for oyster survival and restoration. Estuarine salinity varies with discharge, so increases or decreases in precipitation with climate change may shift regions of low salinity and disease refuge away from optimal oyster bottom habitat, negatively impacting reproduction and survival. Temperature is an additional factor for oyster survival, and recent temperature increases have increased vulnerability to disease in higher salinity regions. We examined growth, reproduction, and survival of oysters in the New York Harbor-Hudson River region, focusing on a low-salinity refuge in the estuary. Observations were during two years when rainfall was above average and comparable to projected future increases in precipitation in the region and a past period of about 15 years with high precipitation. We found a clear tradeoff between oyster growth and vulnerability to disease. Oysters survived well when exposed to intermediate salinities during two summers (2008, 2010) with moderate discharge conditions. However, increased precipitation and discharge in 2009 reduced salinities in the region with suitable benthic habitat, greatly increasing oyster mortality. To evaluate the estuarine conditions over longer periods, we applied a numerical model of the Hudson to simulate salinities over the past century. Model results suggest that much of the region with suitable benthic habitat that historically had been a low salinity refuge region may be vulnerable to higher mortality under projected increases in precipitation and discharge. Predicted increases in precipitation in the northeastern United States due to climate change may lower salinities past important thresholds for oyster survival in estuarine regions with appropriate substrate, potentially disrupting metapopulation dynamics and impeding oyster restoration efforts, especially in the Hudson estuary where a large basin constitutes an excellent refuge from disease.Funding was provided by the Hudson River Foundation, grant number 00607A, and the New York State Department of Environmental Conservation (MOU 2008)

P2RX7 inhibitor suppresses exosome secretion and disease phenotype in P301S tau transgenic mice

Background: Neuronal accumulation of misfolded microtubule-associated protein tau is a hallmark of neuropathology in Alzheimer’s disease, frontotemporal dementia, and other tauopathies, and has been a therapeutic target. Microglia can spread tau pathology by secreting tau-containing exosomes, although the specific molecular target is yet to be identified for the therapeutic intervention. P2X purinoceptor 7 (P2RX7) is an ATP-gated cation channel, enriched in microglia and triggers exosome secretion. The purpose of the study is to examine the therapeutic effect of an orally applicable, CNS-penetrant P2RX7 specific inhibitor on the early disease stage of a tauopathy mouse model. Methods: Three-months-old P301S tau mice were treated with P2RX7-specific inhibitor GSK1482160 or vehicle for 30 days, followed by behavioral, biochemical and immunohistochemical assessment. GSK1482160 was also tested for exosome secretion from primary cultured murine astrocytes, neurons and microglia in vitro. Results: Oral administration of GSK1482160 significantly reduced accumulation of MC1+ and Alz50+ misfolded tau in hippocampal regions, which was accompanied with reduced accumulation of Tsg101, an exosome marker, in hippocampal neurons. Proximity ligation assay demonstrated complex formation of Alz50+ tau and Tsg101 in hippocampal neurons, which was reduced by GSK1482160. On the other hand, GSK1482160 had no effect on microglial ramification or CD68 expression, which was significantly enhanced in P301S mice, or pro/anti-inflammatory cytokine gene expression. Strikingly, GSK1482160-treated P301S mice show significantly improved working and contextual memory as determined by Y-maze and fear conditioning tests. GSK1482160 also significantly increased accumulation of Tsg101 and CD81 in microglia in vivo, suggesting its suppression of P2RX7-induced exosome secretion from microglia. This effect was confirmed in vitro, as ATP-induced secretion of tau-containing exosome was significantly suppressed by GSK1482160 treatment from primary murine microglia, but not from neurons or astrocytes. Discussion: The oral administration of P2RX7 inhibition mitigates disease phenotypes in P301S mice, likely by suppressing release of microglial exosomes. P2RX7 could be a novel therapeutic target for the early stage tauopathy development