The broad objective of our study was to use a histological approach to examine possible tissue-level effects of exposure to elevated CO2 in freshwater young-of-year salmonids.
To study these effects, young-of-year Arctic Char Salvelinus alpinus, Rainbow Trout Oncorhynchus mykiss, and Brook Trout S. fontinalis were exposed to either control levels of CO2 (1400 μatm) or elevated levels of CO2 (5236 μatm) for 15 days. Fish were then sampled for gill, liver, and heart tissues and histologically analyzed.
A species effect was observed for the length of secondary lamellae, as Arctic Char had significantly shorter secondary lamellae than the other species. No notable changes within the gills and livers of Arctic Char, Brook Trout, or Rainbow Trout exposed to elevated CO2 were observed.
Generally, our results indicated that elevated CO2 levels over 15 days do not induce catastrophic tissue damage and it is unlikely that fish health would be seriously impacted. Ongoing research dedicated to examining how elevated CO2 long-term may affect internal tissues of fish will allow for a more comprehensive understanding of how fish may fair with ongoing climate change and in aquaculture facilities.
Cutaneous ulcerative skin lesions in a complex of invasive Gulf of Mexico lionfish (Red Lionfish Pterois volitans, Devil Firefish P. miles, and the hybrid Red Lionfish × Devil Firefish) became epizootic beginning in mid-August 2017. Herein, we provide the first pathological descriptions of these lesions and summarize our analyses to elucidate the etiology of the disease.
We examined ulcerated and normal fish through gross pathology and histopathology, bacterial sampling, and unbiased metagenomic next-generation sequencing. We tracked prevalence of the disease, and we used biological health indicators (condition factor, splenosomatic and hepatosomatic index) to evaluate impacts to health, while considering sex and age as potential risk factors.
Typical ulcerative lesions were deep, exposing skeletal muscle, and were bordered by pale or reddened areas often with some degree of scale loss. Only incidental parasites were found in our examinations. Most fish (86%; n = 50) exhibited wound healing grossly and histologically, confirmed by the presence of granulation tissues. A primary bacterial pathogen was not evident through bacterial culture or histopathology. Metagenomic next-generation sequencing did not reveal a viral pathogen (DNA or RNA) but did provide information about the microbiome of some ulcerated specimens. Compared with clinically healthy fish, ulcerated fish had a significantly lower condition factor and a higher splenosomatic index. Disease prevalence at monitored sites through July 2021 indicated that ulcerated fish were still present but at substantially lower prevalence than observed in 2017.
Although some common findings in a number of specimens suggest a potential role for opportunistic bacteria, collectively our suite of diagnostics and analyses did not reveal an intralesional infectious agent, and we must consider the possibility that there was no communicable pathogen.
Carnobacterium maltaromaticum is considered an emerging pathogen of salmonids in the United States and around the world.
Bacterial cultures obtained from the posterior kidney and skin of moribund Rainbow Trout Oncorhynchus mykiss from a commercial aquaculture facility in Virginia, USA, grew C. maltaromaticum, which was confirmed by additional phenotypic and molecular characterization.
A presumptive diagnosis based on the clinical signs, necropsy observations, histopathology, and bacterial cultures was bacterial septicemia due to C. maltaromaticum.
This represents the first documentation of C. maltaromaticum in Rainbow Trout from Virginia.
With the growing demand for caviar products, sturgeon (family Acipenseridae) have become some of the most popular species in the aquaculture industry. Since sturgeon need more than 10 years to become sexually mature, protection against fatal diseases becomes particularly important in the industry. In March 2018, approximately 10% of Siberian Sturgeon Acipenser baerii fingerlings in a sturgeon hatchery in Jeolla Province, Republic of Korea, exhibited anorexia, abdominal distension, buoyancy loss, and abnormal behavior and eventually showed a 90% fatality rate. Twenty moribund fish were necropsied, and a distended stomach filled with gas was found in every case. A single colony dominated the intestinal lumen smear and was identified as Candida manassasensis by polymerase chain reaction targeting 18S ribosomal RNA. The same microorganism was also detected in the sturgeons' feed. Antifungal resistance was examined using the VITEK 2 system, and the isolate was susceptible to voriconazole, caspofungin, micafungin, and flucytosine. The environmental stress factor for this case was speculated as decreased water temperature. Since similar cases have been observed for many years, further research to optimize precise treatment and prevention methods is required.
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：