Project description:Abalone amyotrophia is a viral disease that causes mass mortality of juvenile Haliotis discus and H. madaka. Although the cause of this disease has yet to be identified, we had previously postulated a novel virus with partial genome sequence similarity to that of African swine fever virus is the causative agent and proposed abalone asfa-like virus (AbALV) as a provisional name. In this study, three species of juvenile abalone (H. gigantea, H. discus discus, and H. diversicolor) and four species of adult abalone (the above three species plus H. discus hannai) were experimentally infected, and their susceptibility to AbALV was investigated by recording mortality, quantitatively determining viral load by PCR, and conducting immunohistological studies. In the infection test using 7-month-old animals, H. gigantea, which was previously reported to be insusceptible to the disease, showed multiplication of the virus to the same extent as in H. discus discus, resulting in mass mortality. H. discus discus at 7 months old showed abnormal cell masses, notches in the edge of the shell and brown pigmentation inside of the shell, which are histopathological and external features of this disease, while H. gigantea did not show any of these characteristics despite suffering high mortality. Adult abalones had low mortality and viral replication in all species; however, all three species, except H. diversicolor, became carriers of the virus. In immunohistological observations, cells positive for viral antigens were detected predominantly in the gills of juvenile H. discus discus and H. gigantea, and mass mortality was observed in these species. In H. diversicolor, neither juvenile nor adult mortality from infection occurred, and the AbALV genome was not increased by experimental infection through cohabitation or injection. Our results suggest that H. gigantea, H. discus discus and H. discus hannai are susceptible to AbALV, while H. diversicolor is not. These results confirmed that AbALV is the etiological agent of abalone amyotrophia.

Project description:Background: The shells of various Haliotis species have served as models of invertebrate biomineralization and physical shell properties for more than 20 years. A focus of this research has been the nacreous inner layer of the shell with its conspicuous arrangement of aragonite platelets, resembling in cross-section a brick-and-mortar wall. In comparison, the outer, less stable, calcitic prismatic layer has received much less attention. One of the first molluscan shell proteins to be characterized at the molecular level was Lustrin A, a component of the nacreous organic matrix of Haliotis rufescens. This was soon followed by the C-type lectin perlucin and the growth factor-binding perlustrin, both isolated from H. laevigata nacre, and the crystal growth-modulating AP7 and AP24, isolated from H. rufescens nacre. Mass spectrometry-based proteomics was subsequently applied to to Haliotis biomineralization research with the analysis of the H. asinina shell matrix and yielded 14 different shell-associated proteins. That study was the most comprehensive for a Haliotis species to date. Methods: The shell proteomes of nacre and prismatic layer of the marine gastropod Haliotis laevigata were analyzed combining mass spectrometry-based proteomics and next generation sequencing. Results: We identified 297 proteins from the nacreous shell layer and 350 proteins from the prismatic shell layer from the green lip abalone H. laevigata. Considering the overlap between the two sets we identified a total of 448 proteins. Fifty-one nacre proteins and 43 prismatic layer proteins were defined as major proteins based on their abundance at more than 0.2% of the total. The remaining proteins occurred at low abundance and may not play any significant role in shell fabrication. The overlap of major proteins between the two shell layers was 17, amounting to a total of 77 major proteins. Conclusions: The H. laevigata shell proteome shares moderate sequence similarity at the protein level with other gastropod, bivalve and more distantly related invertebrate biomineralising proteomes. Features conserved in H. laevigata and other molluscan shell proteomes include short repetitive sequences of low complexity predicted to lack intrinsic three-dimensional structure, and domains such as tyrosinase, chitin-binding, and carbonic anhydrase. This catalogue of H. laevigata shell proteins represents the most comprehensive for a haliotid and should support future efforts to elucidate the molecular mechanisms of shell assembly.

Project description:Larval settlement and metamorphosis is a vital transition period for marine invertebrates and can have far-reaching effects on the ecology and evolution of a species. To explore the molecular mechanisms of this critical process in a non-model organism, the tropical abalone Haliotis asinina, we employed cDNA microarray methods. By comparing gene expression profiles through mid to late larval development and metamorphosis, we identified 144 genes as likely candidates for a role in competence and/or metamorphosis. Gene characterization showed that ~60% of these were significantly similar to previously described genes from other taxa, while ~40% had no significant similarities to any known genes. A high 49.3% of genes were gastropod- or abalone-specific, but none appear to be Lophotrochozoan-specific, despite the fact that metamorphosis is thought to have had a separate origin in this group. Based on temporal expression profiles, the differentially expressed larval and postlarval genes can be clustered into 5 categories that reveal there are strikingly different transcriptional patterns occurring during this phase of development. Some classes of gene activation are contingent upon exogenous cues and correlate with the initiation of settlement and metamorphosis. Importantly, there is also extensive gene activity associated with the endogenous attainment of competence, which occurs prior to, and independent of, the exogenous induction of settlement. Our results show that as the haliotid veliger larva matures, it requires the coordinated regulation of temporally different batteries of genes involved in a wide range of physiological and developmental processes associated with colonisation of the benthos. Although the signalling pathways operating at metamorphosis may be conserved across the animal kingdom, it appears they are regulating the expression of novel genes specific to abalone, gastropods and molluscs during H. asinina metamorphosis. Keywords: timecourse; metamorphosis; marine ecology

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Nanopore sequencing of the black lip abalone (Haliotis rubra)

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