Novel epibiotic thiothrix bacterium on a marine amphipod.
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Comparative analysis of the 16S rRNA gene and fluorescent in situ hybridization (FISH) was used to identify epibiotic filamentous bacteria living on the marine amphipod crustacean Urothoe poseidonis. The epibionts belong to the gamma proteobacteria and represent a novel marine phylotype within the genus Thiothrix. FISH and denaturing gradient gel electrophoresis revealed that the Thiothrix filaments are present on the majority of the amphipods examined. (+info)
Prevalence of parasites in amphipods Diporeia spp. from Lakes Michigan and Huron, USA.
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Amphipods of Diporeia spp. have declined considerably during the last decade in the Great Lakes. We examined the possibility that disease may be affecting these populations. A histological survey assessed the parasites in species of Diporeia within Lakes Huron and Michigan, USA, and the host response to some of them and to unknown factors. Amphipods were found to have an intranuclear inclusion body, and were hosts to a rickettsia-like organism, fungi, a haplosporidian, a microsporidian, epibiotic ciliates, a gregarine, a cestode, acanthocephalans and nodule formations. Epibiotic ciliates were most common (37% prevalence of infection), but a microsporidian (3.8%), a rickettsia-like organism (1.6%), fungi, including a yeast-like organism (1.3%), worms (1.3%), and a haplosporidian (0.7%) are likely associated with mortalities or detrimental effects on the host. The role these agents may have played in the decline of Diporeia spp. in the Great Lakes over the last decade is not clear. Interrelationships with the dynamics of various physical and biological factors such as high sedimentation, diminished food supplies, and virulent parasites could synergistically cause the decline in Diporeia spp. populations in Lakes Michigan and Huron. (+info)
Widespread vertical transmission and associated host sex-ratio distortion within the eukaryotic phylum Microspora.
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Vertical transmission (VT) and associated manipulation of host reproduction are widely reported among prokaryotic endosymbionts. Here, we present evidence for widespread use of VT and associated sex-ratio distortion in a eukaryotic phylum. The Microspora are an unusual and diverse group of eukaryotic parasites that infect all animal phyla. Following our initial description of a microsporidian that feminizes its crustacean host, we survey the diversity and distribution of VT within the Microspora. We find that vertically transmitted microsporidia are ubiquitous in the amphipod hosts sampled and that they are also diverse, with 11 species of microsporidia detected within 16 host species. We found that infections were more common in females than males, suggesting that host sex-ratio distortion occurs in five out of eight parasite species tested. Phylogenetic reconstruction demonstrates that VT occurs in all major lineages of the phylum Microspora and that sex-ratio distorters are found on multiple branches of the phylogenetic tree. We propose that VT is either an ancestral trait or evolves with peculiar frequency in this phylum. If the association observed here between VT and host sex-ratio distortion holds true across other host taxa, these eukaryotic parasites may join the bacterial endosymbionts in their importance as sex-ratio distorters. (+info)
Mitochondrial COI-NC-COII sequences in talitrid amphipods (Crustacea).
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Mitochondrial (mt) sequences from cytochrome oxidase subunit I to the subunit II gene (COI, COII) were analysed in crustacean talitrid amphipods. Species of the genera Orchestia, Talitrus and Talorchestia from the Mediterranean-East Atlantic area were examined. The expected tRNALeu-UUR gene was not revealed between COI and COII. Instead, a short (35-48 bp) noncoding (NC) AT-rich (ca. 90%) region with putative stem loops was found. Here, we discuss briefly the NC region and explore its potential involvement in generating this novel rearrangement. The COI-NC-COII organization, as well as preliminary phylogenetic results, based on both COI-COII nucleotide and amino-acid sequence indicate monophyly of these talitrid taxa. (+info)
Haemolymph [Na+] and [Cl-] loss in Gammarus fossarum exposed in situ to a wide range of acidic streams.
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The acid-sensitive amphipod Gammarus fossarum was exposed in situ for 24, 96 and 168 h to 18 streams (9 draining from granite and 9 draining from sandstone bedrock), selected in order to provide a wide range of acidification. After 24 h, exposure to slightly acidic (6.00 < or = pH < or = 5.50) and strongly acidic water (pH < 5.50) led to a severe and significant depletion in haemolymph [Na+] and [Cl-] compared to organisms exposed in circumneutral water. Highly significant linear correlations between stream mean pH value and haemolymph [Na+] and [Cl-] were observed for each exposure time on each bedrock. Organisms exposed to slightly acid streams draining granite bedrock (pH = 5.71, pH = 5.81) showed a physiological adaptation after 96 h of exposure, while animals in acidic sandstone streams did not. Results of this study indicate that haemolymph [Na+] and [Cl-] in G. fossarum could be an effective ecophysiological marker for monitoring freshwater ecosystem acidification. (+info)
The fate of isolated blastomeres with respect to germ cell formation in the amphipod crustacean Parhyale hawaiensis.
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Germ cells may be specified through the localization of germ line determinants to specific cells in early embryogenesis, or by inductive signals from neighboring cells to germ cell precursors in later embryogenesis. Such determinants can be produced and localized during or after oogenesis, either autonomously by oocytes or by associated nutritive cells. In Drosophila, each oocyte is connected to nurse cells by cytoplasmic bridges, and determinants synthesized in nurse cells are transported through these bridges to the oocyte. However, the Drosophila model may not be applicable to all arthropods, since in many species of all four extant arthropod classes, gametogenesis functions without nurse cells. In this paper, I use immunodetection of Vasa protein to study germ cell development in the amphipod crustacean Parhyale hawaiensis, a species whose ovaries lack nurse cells and whose eggs lack obvious polarity. Previous cell lineage analyses have shown that all three germ layers and the germ line are exclusively specified by third cleavage. In the present study, I use a molecular marker to follow germ cell development during P. hawaiensis embryogenesis. I determine the capacity of individual blastomeres to form germ cells by isolating blastomeres at early cleavage stages and provide experimental evidence for localized germ cell determinants at the two-cell stage in P. hawaiensis. These experiments indicate that many aspects of early amphipod development, including timing and symmetry of cell division, the transition from holoblastic to superficial cleavage, and possibly some gastrulation movements, are cell autonomous following first cleavage. (+info)
Establishing genetic transformation for comparative developmental studies in the crustacean Parhyale hawaiensis.
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The amphipod crustacean Parhyale hawaiensis has been put forward as an attractive organism for evolutionary developmental comparisons, and considerable effort is being invested in isolating developmental genes and studying their expression patterns in this species. The scope of these studies could be significantly expanded by establishing means for genetic manipulation that would enable direct studies of gene functions to be carried out in this species. Here, we report the use of the Minos transposable element for the genetic transformation of P. hawaiensis. Transformed amphipods can be obtained from approximately 30% of surviving individuals injected with both a Minos element carrying the 3xP3-DsRed fluorescent marker and with mRNA encoding the Minos transposase. Integral copies of the transposon are inserted into the host genome and are stably inherited through successive generations. We have used reporter constructs to identify a muscle-specific regulatory element from Parhyale, demonstrating that this transformation vector can be used to test the activity of cis-regulatory elements in this species. The relatively high efficiency of this transgenic methodology opens new opportunities for the direct study of cis-regulatory elements and gene functions in Parhyale, allowing functional studies to be carried out beyond previously established model systems in insects. (+info)
Influence of container adsorption upon observed pyrethroid toxicity to Ceriodaphnia dubia and Hyalella azteca.
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Pyrethroid insecticides are known for their potential toxicity to aquatic invertebrates and many fish species. A significant problem in the study of pyrethroid toxicity is their extreme hydrophobicity. They can adsorb to test container surfaces and many studies, therefore, report pyrethroid levels as nominal water concentrations. In this study, pyrethroid adsorption to sampling and test containers was measured and several container treatments were examined for their ability to decrease pyrethroid adsorption. None of the chemical treatments were successful at preventing pyrethroid loss from aqueous samples, but vortexing of containers served to resuspend pyrethroids. The effects of the observed adsorption on Ceriodaphnia dubia and Hyalella azteca permethrin toxicity were examined. Species-specific results showed a time-dependent decrease in toxicity following pyrethroid adsorption to test containers for C. dubia, but not for H. azteca. These results demonstrate that pyrethroid adsorption to containers can significantly affect the observed outcome in toxicity-testing and serves as a caution for researchers and testing laboratories. (+info)