Urinary calculi in larvae of striped trumpeter, Latris lineata.

Urinary calculi are observed in some cultured marine fish larvae and may negatively impact larval health and survival. This study assessed urinary calculi in striped trumpeter Latris lineata larvae from hatching to 28 days post-hatching (dph). The prevalence of urinary calculi was variable over time and ranged from 15% to 50%, whereas the average size of calculi increased with larval age. Urinary calculi were semi-translucent, light cream to white colour with irregular morphology and a uniform internal structure. The calculi resulted in pressure atrophy causing a distended epithelium of the urinary bladder of fish with calculi. The calculi were predominantly formed of calcium hydrogen phosphate (CaHPO4 ). Routine assessment of the prevalence of urinary calculi in marine fish larvae is recommended, along with other parameters, to monitor larval quality and inform hatchery management actions.

Triploid Atlantic salmon shows similar performance, fatty acid composition and proteome response to diploids during early freshwater rearing.

There is currently renewed interest in farming triploid Atlantic salmon. Improving farming requires identifying triploid specific phenotypic and physiological traits that are uniquely derived from ploidy per se and developed under optimal growing conditions. This study investigated firstly, the impact of ploidy on growth performance and whole body composition of Atlantic salmon at different early freshwater stages [34dph (days post-hatching) alevin, 109dph fry, and 162dph parr] and secondly, whether phenotypic differences at these stages were reflected in protein samples collected from whole fish, white muscle or liver tissue. Female diploid and triploid Atlantic salmon (n=3) were first fed at 35dph and then maintained by feeding to satiation on commercial feeds. Triploids were significantly lower in weight at the late alevin and fry stages but matched diploid weight at the parr stage. The whole-body lipid content was significantly higher for triploids at the parr stage, while the whole-body lipid class profile was broadly similar and was largely not affected by ploidy. Comparative label-free shotgun proteomic analysis did not detect significant alterations in protein expression between diploids and triploids at any growth stage. The present results indicate that ploidy under optimal growing conditions and during early freshwater stages only result in small phenotypic differences in weight and whole body lipid content that were not reflected at the proteome level. These findings suggest that optimal husbandry conditions for freshwater Atlantic salmon are similar between ploidies, at least for all-female populations.

Multigenic Delineation of Lower Jaw Deformity in Triploid Atlantic Salmon (Salmo salar L.).

Lower jaw deformity (LJD) is a skeletal anomaly affecting farmed triploid Atlantic salmon (Salmo salar L.) which leads to considerable economic losses for industry and has animal welfare implications. The present study employed transcriptome analysis in parallel with real-time qPCR techniques to characterise for the first time the LJD condition in triploid Atlantic salmon juveniles using two independent sample sets: experimentally-sourced salmon (60 g) and commercially produced salmon (100 g). A total of eleven genes, some detected/identified through the transcriptome analysis (fbn2, gal and gphb5) and others previously determined to be related to skeletal physiology (alp, bmp4, col1a1, col2a1, fgf23, igf1, mmp13, ocn), were tested in the two independent sample sets. Gphb5, a recently discovered hormone, was significantly (P < 0.05) down-regulated in LJD affected fish in both sample sets, suggesting a possible hormonal involvement. In-situ hybridization detected gphb5 expression in oral epithelium, teeth and skin of the lower jaw. Col2a1 showed the same consistent significant (P < 0.05) down-regulation in LJD suggesting a possible cartilaginous impairment as a distinctive feature of the condition. Significant (P < 0.05) differential expression of other genes found in either one or the other sample set highlighted the possible effect of stage of development or condition progression on transcription and showed that anomalous bone development, likely driven by cartilage impairment, is more evident at larger fish sizes. The present study improved our understanding of LJD suggesting that a cartilage impairment likely underlies the condition and col2a1 may be a marker. In addition, the involvement of gphb5 urges further investigation of a hormonal role in LJD and skeletal physiology in general.

The first chondracanthid (Copepoda: Cyclopoida) reported from cultured finfish, with a revised key to the species of Chondracanthus.

A new species of the Chondracanthidae (Copepoda: Cyclopoida), Chondracanthus goldsmidi, is described based on material collected from the nasobranchial region of striped trumpeter (Latris lineata [Forster]) cultured at the Tasmanian Aqua-culture and Fisheries Institute, Marine Research Laboratories, Australia. This represents the first report of a chondracanthid copepod infecting cultured finfish and the first metazoan parasite from cultured striped trumpeter. Chondracanthus goldsmidi n. sp. can be distinguished from its female congeners by the absence of lateral processes on the head and the presence of 3 pairs of lateral trunk outgrowths, 3 middorsal body outgrowths (of which the first 2 are rounded), a small and subcylindrical antennule, and unornamented legs 1 and 2. A revised key to the 39 valid species of Chondracanthus is provided.