Amyloid associated with neoplasia in two captive tricolour sharkminnows Balantiocheilus melanopterus Bleeker

Molecular changes in skin pigmented lesions of the coral trout Plectropomus leopardus

A high prevalence of skin pigmented lesions of 15% was recently reported in coral trout Plectropomus leopardus, a commercially important marine fish, inhabiting the Great Barrier Reef. Herein, fish were sampled at two offshore sites, characterised by high and low lesion prevalence. A transcriptomic approach using the suppressive subtractive hybridisation (SSH) method was used to analyse the differentially expressed genes between lesion and normal skin samples. Transcriptional changes of 14 genes were observed in lesion samples relative to normal skin samples. These targeted genes encoded for specific proteins which are involved in general cell function but also in different stages disrupted during the tumourigenesis process of other organisms, such as cell cycling, cell proliferation, skeletal organisation and cell migration. The results highlight transcripts that are associated with the lesion occurrence, contributing to a better understanding of the molecular aetiology of this coral trout skin disease.

Epitheliocystis in lake trout Salvelinus namaycush (Walbaum) is associated with a β-proteobacteria

Lake trout Salvelinus namaycush (Walbaum) raised for stocking experienced yearly (2011-13) winter epizootics of epitheliocystis. Affected fish were dispersed on the bottom of the tank, had decreased feed and fright response, and mortality often reached 40%. Peak mortality occurred within 3 weeks of the appearance of clinical signs, and outbreaks typically lasted 6 weeks. Affected fish had no gross lesions but histologically had branchial epithelial necrosis and lamellar hyperplasia, with small to large numbers of scattered epithelial cells containing 10- to 20-μm inclusions. A longitudinal study was undertaken of one annual outbreak, and lamellar hyperplasia was most closely associated with mortality. The number of inclusions was statistically greater (P < 0.05) before and during peak mortality, but inclusions were present in low numbers before clinical signs occurred. Results of histochemical staining, immunohistochemistry and transmission electron microscopy supported the presence of a β-proteobacteria rather than a Chlamydiales bacterium within inclusions. PCR primers to identify Chlamydiales did not give consistent results. However, the use of universal 16S rDNA bacterial primers in conjunction with laser capture microdissection of inclusions demonstrated that a β-proteobacteria was consistently associated with affected gills and is more likely the cause of the disease in lake trout.