Settlement Of Crassostrea Ariakensis Larvae: Effects Of Substrate, Biofilms, Sediment And Adult Chemical Cues

The Suminoe oyster (Crassostrea ariakensis) is being considered for introduction into the Chesapeake Bay. However, our current understanding of the biology and ecology of C. ariakensis is insufficient to predict whether an introduction will be successful, provide desired benefits, or have adverse impacts. Behavior of native Eastern oyster (C. virginica) pediveligers has been studied for many years and it is well established that they use a variety of habitat characteristics when selecting a site for colonization. Perhaps the most important of these are chemical cues emitted by adult conspecifics, which can lead to gregarious larval settlement and dense, persistent reef communities. Conversely, almost nothing is known about the mechanisms that regulate larval settlement and metamorphosis for C. ariakensis or how pediveligers might respond to conditions found in Chesapeake Bay. In a comparative study with C. virginica, we examined how environmental factors such as substrate type, natural biofilms, sediment and waterborne chemical cues influence larval settlement for two C. ariakensis strains (‘‘south China’’ and ‘‘west coast’’). Our results demonstrate many similarities but also potentially important differences. Both species and strains of larvae greatly prefer natural substrates (e.g., shell) covered with biofilms for colonization but the west coast strain of C. ariakensis exhibited greater attachment onto manmade substrates (e.g., fiberglass) than C. virginica. Waterborne chemical cues emitted by adult oysters were also found to enhance substrate attachment for all larval forms but cues do not appear to be species specific. These results provide critical insight to the ability of C. ariakensis larvae to identify and colonize suitable substrates in the Chesapeake Bay, which will have a large impact on recruitment success and their ability to establish self-sustaining populations

A Comparative Field Study Of Crassostrea ariakensis (Fujita 1913) And Crassostrea virginica (Gmelin 1791) In Relation To Salinity In Virginia

We examined survival, growth, and disease susceptibility of triploid Crassostrea ariakensis (= rivularis) and compared results with that of diploid Crassostrea virginica. Two hundred and fifty oysters (age = 2 yr, mean shell height = 60-64 mm) of each species were deployed at duplicate sites, (Chesapeake Bay, and the Atlantic Coast of Virginia) within low, medium, and high salinity regimes respectively (\u3c 15%, 15-25%, \u3e 25%). Over the course of the study, from June 1998 to September 1999, C. virginica exhibited low survival, modest growth and high disease susceptibility. In contrast, C. ariakensis exhibited high survival, high growth rate, and low disease susceptibility. At low salinity sites, final mean cumulative mortality of C. virginica (81%) was significantly higher than that of C. ariakensis (14%). At medium and high salinity sites, all C. virginica died before the end of the study whereas final mean cumulative mortality in C ariakensis was 13 to 16%. After 1 year of deployment, mean shell height of C. virginica at low, moderate, and high salinity sites was respectively 70, 80 and 73 mm. In comparison, mean shell height of C. ariakensis was respectively 93, 121 and 137 mm. At low salinity sites, mean growth rate of C virginica was not significantly different from that of C ariakensis. At medium and high salinity sites, mean growth rate of C virginica was significantly lower than that of C ariakensis. Prevalence and intensity of Perkinsus marinus infections were significantly higher in C. virginica than in C. arlakensis. During the second summer of disease exposure, prevalence in C. virginica was 100% at all sites whereas in C ariakensis it ranged from 0 to 28%. Heavy intensity of infections were prevalent in C. virginica whereas infections in C. ariakensis were limited to light intensity. Haplosporidium nelsoni (MSX) was present in C. virginica, but absent in C. ariakensis. Mud worms (Polydora spp.) were present in both oyster species, but infestations were low and did not appear to affect condition or growth. In summary, wide salinity tolerance and low disease susceptibility were associated with high survival and growth of C. ariakensis in Chesapeake Bay and the Atlantic Coast of Virginia

A Comparative Field Study of Crassostrea ariakensis and Crassostrea virginica in Relation to Salinity in Virginia

In accordance with the Rational Plan for Testing Application of Non-Native Oyster Species (VIMS 1996) we conducted a field experiment to examine survival, growth and disease susceptibility of Crassostrea ariakensis (=rivularis) in relation to salinity in Virginia. The performance of triploid C. ariakensis in comparison with that of diploid C. virginica, (n = 250, age = 2 years, mean shell height = 60- 64 mm) was evaluated at replicate sites within low, medium, and high salinity regimes (respectively, \u3c 15‰, 15-25‰, \u3e 25‰) in Chesapeake Bay and the Atlantic Coast. During the course of this study, from June 1998 to September 1999, there was a severe oyster disease epizootic prevailing in Chesapeake Bay. At the end of the study C. ariakensis exhibited lower disease prevalence and intensity and superior survival and growth than C. virginica. At low salinity sites cumulative mortality in C. ariakensis (14%) was significantly lower than that in C. virginica (81%). At medium and high salinity sites, cumulative mortality in C. ariakensis was less than 16% whereas all C. virginica were dead by the end of the experiment. After one year of deployment, mean shell height of C. ariakensis at low, moderate, and high salinity sites, was respectively 96 mm, 125 mm, and 140 mm. In comparison, mean shell height of C. virginica was respectively 72 mm, 85 mm, and 75 mm. Prevalence and intensity of Perkinsus marinus infections were significantly lower in C. ariakensis than in C. virginica. During the second summer of disease exposure, prevalence in C. ariakensis ranged form 0-28% whereas prevalence in C. virginica was 100% at all sites. Only light infections were present in C. ariakensis whereas heavy infections were found in C. virginica. MSX was absent in C. ariakensis and present in C. virginica. Mud worms were present in both oyster species but infestations were low and did not appear to affect condition or growth. In summary, wide salinity tolerance and low disease susceptibility were associated with high survival and growth of C. ariakensis in Chesapeake Bay and the Atlantic Coast of Virginia

Survival And Growth Of Triploid Crassostrea Virginica (Gmelin, 1791) And C-Ariakensis (Fujita, 1913) In Bottom Environments Of Chesapeake Bay: Implications For An Introduction

Survival and growth of triploid Crassostrea virginica and triploid C. ariakensis were investigated at four sites Surrounding Chesapeake Bay, United States, that varied tried in salinity, tidal regime, water depth, predation intensity and disease pressure. Four experimental treatments were established at each site: C. virginica; C. ariakensis; 50:50 of C. virginica: C. ariakensis: and shell only. Oysters were deployed at mean shell heights of 12.80 min and 13.85 mm (C. virginica and C. ariakensis, respectively), at an overall density of 347.5 oysters m(-2). Oyster survival and growth varied significantly, with site and species. Survival was significantly higher in C. virginica than C. ariakensis at the intertidal site, and significantly higher in C. ariakensis than C. virginica at the highest salinity, subtidal site. Survival did not differ significantly between species at the mid and low salinity, subticial sites. For both Species. survival differed significantly between sites, with lowest survival in both species Occurring Lit the intertidal site. Among the subtidal sites. C. virginica survival varied inversely with salinity, whereas C. ariakensis had the lowest Survival at the mid salinity site. Eight months after deployment C. ariakensis were significantly, larger than C. virginica at all sites. This difference generally persisted throughout the experiment, though the size differences between oyster species at the lowest salinity site were small (\u3c 10%). Shell heights within single-species treatments differed significantly between sites; highest growth rates were observed at the high salinity, subtidal site, whereas lowest growth rates were observed at the high salinity, intertidal site. At low and mid salinity subtidal sites, C. ariakensis shell heights were significantly greater in the single-species treatment compared with the mixed-species treatment. Perkinsus marinus infections occurred in both species at all sites, with prevalences varying between sites. In C. virginica, moderate and high intensity infections were only common at the two higher salinity sites, whereas infections in C. ariakensis were generally low, to rare. Haplosporidium nelsoni infections in C. virginica were only observed at the two higher salinity sites and prevalences were generally low. Two out of 53 C. ariakensis tested at the high salinity, subtidal site had rare H. nelsoni infections. Bonamia spp. infections were never observed. Our study supports previous laboratory findings and observations from its native range that C. ariakensis Survives poorly in intertidal habitats. In subtidal habitats, however, C. ariakensis displayed broad environmental tolerances, often exceeding native oyster Survival and growth rates. Post-introduction C. ariakensis Populations would be shaped by the survival and growth patterns described here, but also by their reproductive success, larval Survival, predator-prey interactions and prevailing disease dynamics

Scaling Ecosystem Services to Reef Development : Effects of oyster density on nitrogen removal and reef community structure

Eighteen native oyster experimental reefs (16-m2 each) were restored using six oyster densities (0, 10, 25, 50, 100 and 250 adult oysters m-2) with three replicates of each density at each of two sites: one subtidal site in Onancock Creek, Virginia and one intertidal site in Hillcrest Oyster Sanctuary within The Nature Conservancy’s Virginia Coast Reserve. A science-based monitoring program explored quantitative relationships between structural and functional characteristics of these restored reefs. Structural parameters examined included oyster abundance, oyster size/biomass, surface shell volume, reef topographic complexity and sediment characteristics. Functional parameters included denitrification rates and macrofaunal abundance and biomass. Data were collected from the intertidal site during six sampling periods between April 2012 and July 2013 and from the subtidal site in April and June 2012. Relationships between reef structural parameters and functional parameters were complex and variable. As of July 2014, the intertidal reefs continue to serve as a platform for continued studies of the relationships between reef structural and functional characteristics

Defining Global Gene Expression Changes of the Hypothalamic-Pituitary-Gonadal Axis in Female sGnRH-Antisense Transgenic Common Carp (Cyprinus carpio)

BACKGROUND: The hypothalamic-pituitary-gonadal (HPG) axis is critical in the development and regulation of reproduction in fish. The inhibition of neuropeptide gonadotropin-releasing hormone (GnRH) expression may diminish or severely hamper gonadal development due to it being the key regulator of the axis, and then provide a model for the comprehensive study of the expression patterns of genes with respect to the fish reproductive system. METHODOLOGY/PRINCIPAL FINDINGS: In a previous study we injected 342 fertilized eggs from the common carp (Cyprinus carpio) with a gene construct that expressed antisense sGnRH. Four years later, we found a total of 38 transgenic fish with abnormal or missing gonads. From this group we selected the 12 sterile females with abnormal ovaries in which we combined suppression subtractive hybridization (SSH) and cDNA microarray analysis to define changes in gene expression of the HPG axis in the present study. As a result, nine, 28, and 212 genes were separately identified as being differentially expressed in hypothalamus, pituitary, and ovary, of which 87 genes were novel. The number of down- and up-regulated genes was five and four (hypothalamus), 16 and 12 (pituitary), 119 and 93 (ovary), respectively. Functional analyses showed that these genes involved in several biological processes, such as biosynthesis, organogenesis, metabolism pathways, immune systems, transport links, and apoptosis. Within these categories, significant genes for neuropeptides, gonadotropins, metabolic, oogenesis and inflammatory factors were identified. CONCLUSIONS/SIGNIFICANCE: This study indicated the progressive scaling-up effect of hypothalamic sGnRH antisense on the pituitary and ovary receptors of female carp and provided comprehensive data with respect to global changes in gene expression throughout the HPG signaling pathway, contributing towards improving our understanding of the molecular mechanisms and regulative pathways in the reproductive system of teleost fish

Molecular characterization and expression analysis of five different elongation factor 1 alpha genes in the flatfish Senegalese sole (Solea senegalensis Kaup): Differential gene expression and thyroid hormones dependence during metamorphosis

<p>Abstract</p> <p>Background</p> <p>Eukaryotic elongation factor 1 alpha (eEF1A) is one of the four subunits composing eukaryotic translation elongation factor 1. It catalyzes the binding of aminoacyl-tRNA to the A-site of the ribosome in a GTP-dependent manner during protein synthesis, although it also seems to play a role in other non-translational processes. Currently, little information is still available about its expression profile and regulation during flatfish metamorphosis. With regard to this, Senegalese sole (<it>Solea senegalensis</it>) is a commercially important flatfish in which <it>eEF1A </it>gene remains to be characterized.</p> <p>Results</p> <p>The development of large-scale genomics of Senegalese sole has facilitated the identification of five different <it>eEF1A </it>genes, referred to as <it>SseEF1A1</it>, <it>SseEF1A2</it>, <it>SseEF1A3</it>, <it>SseEF1A4</it>, and <it>Sse42Sp50</it>. Main characteristics and sequence identities with other fish and mammalian eEF1As are described. Phylogenetic and tissue expression analyses allowed for the identification of <it>SseEF1A1 </it>and <it>SseEF1A2 </it>as the Senegalese sole counterparts of mammalian <it>eEF1A1 </it>and <it>eEF1A2</it>, respectively, and of <it>Sse42Sp50 </it>as the ortholog of <it>Xenopus laevis </it>and teleost <it>42Sp50 </it>gene. The other two elongation factors, <it>SseEF1A3 </it>and <it>SseEF1A4</it>, represent novel genes that are mainly expressed in gills and skin. The expression profile of the five genes was also studied during larval development, revealing different behaviours. To study the possible regulation of <it>SseEF1A </it>gene expressions by thyroid hormones (THs), larvae were exposed to the goitrogen thiourea (TU). TU-treated larvae exhibited lower <it>SseEF1A4 </it>mRNA levels than untreated controls at both 11 and 15 days after treatment, whereas transcripts of the other four genes remained relatively unchanged. Moreover, addition of exogenous T4 hormone to TU-treated larvae increased significantly the steady-state levels of <it>SseEF1A4 </it>with respect to untreated controls, demonstrating that its expression is up-regulated by THs.</p> <p>Conclusion</p> <p>We have identified five different <it>eEF1A </it>genes in the Senegalese sole, referred to as <it>SseEF1A1</it>, <it>SseEF1A2</it>, <it>SseEF1A3</it>, <it>SseEF1A4</it>, and <it>Sse42Sp50</it>. The five genes exhibit different expression patterns in tissues and during larval development. TU and T4 treatments demonstrate that <it>SseEF1A4 </it>is up-regulated by THs, suggesting a role in the translational regulation of the factors involved in the dramatic changes that occurs during Senegalese sole metamorphosis.</p

A survey of the ATP-binding cassette (ABC) gene superfamily in the salmon louse (Lepeophtheirus salmonis)

Salmon lice,Lepeophtheirus salmonis(Kr&oslash;yer, 1837), are fish ectoparasites causing significant economic damage in the mariculture of Atlantic salmon,Salmo salarLinnaeus, 1758. The control ofL.salmonisat fish farms relies to a large extent on treatment with anti-parasitic drugs. A problem related to chemical control is the potential for development of resistance, which inL.salmonisis documented for a number of drug classes including organophosphates, pyrethroids and avermectins. The ATP-binding cassette (ABC) gene superfamily is found in all biota and includes a range of drug efflux transporters that can confer drug resistance to cancers and pathogens. Furthermore, some ABC transporters are recognised to be involved in conferral of insecticide resistance. While a number of studies have investigated ABC transporters inL.salmonis, no systematic analysis of the ABC gene family exists for this species. This study presents a genome-wide survey of ABC genes inL.salmonisfor which, ABC superfamily members were identified through homology searching of theL.salmonisgenome. In addition, ABC proteins were identified in a reference transcriptome of the parasite generated by high-throughput RNA sequencing (RNA-seq) of a multi-stage RNA library. Searches of both genome and transcriptome allowed the identification of a total of 33 genes / transcripts coding for ABC proteins, of which 3 were represented only in the genome and 4 only in the transcriptome. Eighteen sequences were assigned to ABC subfamilies known to contain drug transporters,i.e. subfamilies B (4 sequences), C (11) and G (2). The results suggest that the ABC gene family ofL.salmonispossesses fewer members than recorded for other arthropods. The present survey of theL.salmonisABC gene superfamily will provide the basis for further research into potential roles of ABC transporters in the toxicity of salmon delousing agents and as potential mechanisms of drug resistance