Magnetic resonance imaging shows spinal curvature in Chinook salmon (Oncorhynchus tshawytscha) is associated with chronic inflammation of peri-vertebral soft tissues.

Chinook salmon (Oncorhynchus tshawytscha) farmed in New Zealand are known to develop abnormal spinal curvature late in seawater production. Its cause is presently unknown, but there is evidence to suggest a neuromuscular pathology. Using magnetic resonance imaging (MRI), we evaluated the relationship between soft tissue pathology and spinal curvature in farmed Chinook salmon. Regions of interest (ROIs) presenting as pathologic MRI signal hyper-intensity were identified from scans of 24 harvest-sized individuals: 13 with radiographically-detectable spinal curvature and 11 without. ROIs were excised from individuals using anatomical landmarks as reference points and histologically analysed. Pathologic MRI signal was observed more frequently in individuals with radiographic curvature (92%, n = 12) than those without (18%, n = 2), was localized to the peri-vertebral connective tissues and musculature, and presented as three forms: inflammation, fibrosis, or both. These pathologies are consistent with a chronic inflammatory process, such as that observed during recovery from a soft tissue injury, and suggest spinal curvature in farmed Chinook salmon may be associated with damage to and/or compromised integrity of the peri-vertebral soft tissues. Future research to ascertain the contributing factors is required.

Case definitions for skin lesion syndromes in chinook salmon farmed in Marlborough Sounds, New Zealand.

Skin lesions are commonly reported in farmed salmonids. Chinook salmon (Oncorhynchus tshawytscha), introduced from California USA, is the only salmonid species commercially farmed in New Zealand, although trout are cultured for release by Fish and Game New Zealand. There are several farming areas in New Zealand, including Marlborough Sounds, Canterbury and Stewart Island. While the industry has not been affected by any of the major production diseases seen internationally, skin lesions have been recorded with an increase in prevalence from 2012 onwards in the Marlborough Sounds and were associated with elevated summer mortalities on farms in 2015. Here we are proposing case definitions for different types of skin lesions for future monitoring and research. Based on our current understanding of the above skin conditions, we developed case definitions for spots, spreading spots, ulcerated spreading spots and Regular Outline Flank Ulcers defining a positive case for three study units, including individual fish, pen/unit and farm.

New Zealand rickettsia-like organism (NZ-RLO) and Tenacibaculum maritimum: Distribution and phylogeny in farmed Chinook salmon (Oncorhynchus tshawytscha).

A total of 777 fish from three growing regions of New Zealand Chinook salmon farms comprising of five sites were tested. Quantitative PCR was used to determine the distribution of New Zealand rickettsia-like organism and Tenacibaculum maritimum. Genetic information from these bacteria were then compared with strains reported worldwide. Using this information, suggested associations of pathogens with clinically affected fish were made. NZ-RLO was detected in two of the three regions, and T. maritimum was detected in all regions. Three strains of NZ-RLO were identified during this study. Based on analysis of the ITS rRNA gene, NZ-RLO1 appears to be part of an Australasian grouping sharing high similarity with the Tasmanian RLO, NZ-RLO2 was shown to be the same as an Irish strain, and NZ-RLO3 was shown be closely related to two strains from Chile. Based on multi-locus sequence typing, the New Zealand T. maritimum was the same as Australian strains. NZ-RLOs were detected more frequently in fish with skin ulcers than fish without skin ulcers. While additional research is required to investigate the pathogenicity of these organisms, this is the first time that NZ-RLOs have been associated with the development of clinical infections in farmed Chinook salmon.

Vertebral fusions in farmed Chinook salmon (Oncorhynchus tshawytscha) in New Zealand.

Vertebral fusions are an established economic concern in farmed Atlantic salmon, but have not been studied in detail in farmed Chinook salmon. Two radiographic studies of vertebral fusions were performed in farmed Chinook salmon. Sixteen of 1,301 (1.2%) smolt and 201 of 2,636 (7.6%) harvest fish had fusions. There were no significant differences in the number of fused vertebrae/fusion in smolt compared with harvest fish. Secondly, tagged fish were repeatedly radiographed to determine the progression of the fusions. Nineteen (4.4%), 23 (5.3%) and 39 (9.0%) fish had fusions as smolt, after 129 days in sea water, and at harvest, respectively. There were no significant differences in the average number of vertebra/fusion between the three time points. Of the fusions that were observed in smolt, additional vertebra did not become fused in 81% of the lesions. Within the rare fusions that did progress due to the involvement of adjacent vertebra, an average of 1.6 vertebrae were added per year. Fish with fusions were significantly lighter than non-affected fish at harvest. Fusions are common in farmed Chinook salmon; however, they are typically stable after development. As fish with fusions were lighter at harvest, reducing fusions may have an economic benefit.

Unilateral perivertebral fibrosis associated with lordosis, kyphosis and scoliosis (LKS) in farmed Chinook salmon in New Zealand.

Vertebral column lordosis, kyphosis and scoliosis (LKS) can result in downgrading of farmed Chinook salmon Oncorhynchus tshawytscha in New Zealand. No cause of LKS has been identified. Radiography and histology were used to quantify LKS and perivertebral fibrosis in 27 fish with LKS visible at harvest and 30 visually normal fish from 3 New Zealand farms. Radiographic LKS was present in all 27 fish with LKS and in 18 of 30 fish without visible LKS. Quantification of the radiographic severity revealed significantly higher radiographic severity scores in fish with visible LKS (mean ± SD = 5.89 ± 2.41) than in fish with no visible, but radiographic LKS (1.44 ± 0.86, p < 0.001). The most frequent histological finding was unilateral perivertebral fibrosis that often extended into the horizontal septum and adjacent myomeres resulting in separation or loss of myocytes. Fibrosis was visible in all fish with LKS and in 12 of 30 fish without visible LKS. Fibrosis scores were higher in fish with visible LKS (3.32 ± 1.71) than in fish without visible LKS (0.35 ± 0.57, p < 0.001). The radiographic LKS severity scores were significantly correlated to the fibrosis scores (R2 = 0.59 p < 0.001) in the fish. Histology of other tissues revealed multifocal inflammation within muscle, peripheral connective tissues and myocardium which were considered most likely incidental in these fish. In this study, LKS was consistently and significantly associated with perivertebral fibrosis, suggesting that perivertebral fibrosis is an important process in the development of LKS. Further research to determine the cause of the fibrosis is required.

Developing Successful Breeding Programs for New Zealand Aquaculture: A Perspective on Progress and Future Genomic Opportunities.

Over the past 40 years New Zealand (NZ) aquaculture has grown into a significant primary industry. Tonnage is small on a global scale, but the industry has built an international reputation for the supply of high quality seafood to many overseas markets. Since the early 1990s the industry has recognized the potential gains from selective breeding and the challenge has been to develop programs that can overcome biological obstacles (such as larval rearing and mortality) and operate cost-effectively on a relatively small scale while still providing significant gains in multiple traits of economic value. This paper provides an overview of the current status, and a perspective on genomic technology implementation, for the family based genetic improvement programs established for the two main species farmed in NZ: Chinook (king) salmon (Oncorhynchus tshawytscha) and GreenshellTM mussel (Perna canaliculus). These programs have provided significant benefit to the industry in which we are now developing genomic resources based on genotyping-by-sequencing to complement the breeding programs, enable evaluation of the genetic diversity and identify the potential benefits of genomic selection. This represents an opportunity to increase genetic gain and more effectively utilize the potential for within family selection.

Temperature sensitive regions of the Chinook salmon vertebral column: Vestiges and meristic variation.

Variation of vertebral centra numbers is common in vertebrates. Likewise, the number of associated elements such as ribs and neural and haemal arches can vary and affect all regions of the vertebral column. In mammals, only the number of cervical vertebrae is invariable. Variation of total vertebral centra numbers is well documented in teleost fish, often related to temperature. Less information is available about which part of the vertebral column and which associated elements are liable to variation. Here, variation in number of vertebral centra and associated elements is studied in Chinook salmon in six distinct anatomical regions. Animals are raised at 8 and 12°C to ask whether the vertebral centrum numbers, the pattern, and the frequency of variation in particular regions are temperature dependent. No significant difference concerning the total number of vertebrae was found, but regional differences occurred between the 8 and 12°C groups. Twelve specimens out of 60 of the 12°C group had three postcranial vertebrae compared to only one specimen in the 8°C group. The number of transitional vertebrae is significantly different in 8 and 12°C specimens. Fewer transitional vertebrae occur in more anterior positions in 8°C specimens. Most specimens of both temperature groups had two ural centra; however 17 specimens out of 60 of the 12°C group had up to five ural centra. Specimens of the 12°C group show more variation in the presence of the vestigial ribs associated with transitional vertebrae. Clearly, the postcranial, transitional, and ural regions are temperature sensitive. This study shows that nonsignificant differences in the total number of vertebrae can mask significant regional variation. Variation of vertebral numbers could be the consequence of loss or gain of vertebral centra and/or a change in the identity of the associated element on the vertebral centrum.

Mapping of the cerebral response to acetazolamide using graded asymmetric spin echo EPI.

Cerebral vascular reactivity in different regions of the rat brain was quantitatively characterized by spatial and temporal measurements of blood oxygenation level-dependent (BOLD)-fMRI signals following intravenous administration of the carbonic anhydrase inhibitor acetazolamide: this causes cerebral vasodilatation through a cerebral extracellular acidosis that spares neuronal metabolism and vascular smooth muscle function, thus separating vascular and cerebral metabolic events. An asymmetric spin echo-echo planar imaging (ASE-EPI) pulse sequence sensitised images selectively to oxygenation changes in the microvasculature; use of a surface coil receiver enhanced image signal-to-noise ratios (SNRs). Image SNRs and hardware integrity were verified by incorporating quality assurance procedures; cardiorespiratory stability in the physiological preparations were monitored and maintained through the duration of the experiments. These conditions made it possible to apply BOLD contrast fMRI to map regional changes in cerebral perfusion in response to acetazolamide administration. Thus, fMRI findings demonstrated cerebral responses to acetazolamide that directly paralleled the known physiological actions of acetazolamide and whose time courses were similar through all regions of interest, consistent with acetazolamide's initial distribution in brain plasma, where it affects cerebral haemodynamics by acting at cerebral capillary endothelial cells. However, marked variations in the magnitude of the responses suggested relative perfusion deficits in the hippocampus and white matter regions correlating well with their relatively low vascularity and the known vulnerability of the hippocampus to ischaemic damage.

Region-specific effects of a tyrosine-free amino acid mixture on amphetamine-induced changes in BOLD fMRI signal in the rat brain.

BACKGROUND: Acute depletion of tyrosine using a tyrosine-free amino acid mixture offers a novel dietary approach to inhibit activated dopamine pathways in the brain. This study investigated the potential of in vivo functional magnetic resonance imaging (fMRI) methods as a noninvasive means to detect effects of tyrosine depletion on dopamine function. METHODS: Changes in blood-oxgenation level dependent (BOLD) contrast induced by administration of the dopamine-releasing agent, amphetamine (3 mg/kg i.v.), were measured in halothane-anaesthetised rats. RESULTS: Amphetamine evoked changes in BOLD signal intensity with the greatest effects observed in the nucleus accumbens (-7.7%), prefrontal cortex (-13.6%), and motor cortex (+12.5%). Pretreatment with a tyrosine-free amino acid mixture attenuated the response to amphetamine in some regions (nucleus accumbens and prefrontal cortex), but not others (motor cortex). Amphetamine itself had no effect in thalamus and hippocampus but, surprisingly, increased the BOLD signal after the amino acid mixture. CONCLUSION: These experiments demonstrate that amphetamine evokes region-specific changes in the BOLD signal in rats, and that this effect is attenuated in some but not all regions by tyrosine depletion. The data support the application of fMRI techniques for studying the effects of tyrosine depletion on dopamine function in animals and also humans.