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In teleosts, the mucosal epithelial barriers represent the first line of defence against environmental challenges such as pathogens and environmental contaminants. Mucous cells (MCs) are specialised cells providing this protection through mucus production. Therefore, a better understanding of various MC quantification methods is critical to interpret MC responses. Here, we compare histological (also called traditional) quantification of MCs with a novel mucosal mapping method to understand the differences between the two methods' assessment of MC responses to parasitic infections and pollution exposure in shorthorn sculpins (Myoxocephalus scorpius). Overall, both methods distinguished between the fish from stations with different levels of pollutants and detected the links between MC responses and parasitic infection. Traditional quantification showed relationship between MC size and body size of the fish whereas mucosal mapping detected a link between MC responses and Pb level in liver. While traditional method gave numerical density, mucosal mapping gave volumetric density of the mucous cells in the mucosa. Both methods differentiated MC population in skin from those in the gills, but only mucosal mapping pointed out the consistent differences between filament and lamellar MC populations within the gills. Given the importance of mucosal barriers in fish, a better understanding of various MC quantification methods and the linkages between MC responses, somatic health and environmental stressors is highly valuable. • Both methods could distinguish between fish from stations with different level of pollution • Both methods detected links between mucous cell responses and parasitic infection • Both methods differentiated between mucous cell population in skin from those in gills • Traditional method gave numerical density, mucosal mapping resulted in volumetric density of mucous cells in mucosa • Mucosal mapping showed consistent differences between filament and lamellar mucous cell populations between gill filaments and gill lamellae [ABSTRACT FROM AUTHOR]

There are limited reports of infectious agents affecting Australian cowtail stingrays. In the present study, a new species of ascaridoid nematode belonging to the genus Mawsonascaris is described. The most distinct characteristic features were observed in females (the presence of a polar spine in the eggs and a flap‐like projection in the vulval area). An identification key for Mawsonascaris spp. is provided. Additionally, internal transcribed spacers (ITS) sequences were obtained for the new species. Alignment of the ITS sequence of the specimens in the present study with those deposited in GenBank showed that there exists no other highly similar sequence. Phylogenetic analyses resulted in a distinct grouping of our specimens supporting morphological distinction from previously described Mawsonascaris spp. Histology was used to investigate the pathology caused by the infection. Necrosis, inflammation and fibrosis were evident at the border of the nodules formed by parasite. A large number of parasites were present in muscularis mucosae and submucosa but not in the muscularis of the stomach. The parasites were associated with an increased inflammatory response, which was also found in the muscularis mucosae and submucosa. Similar pathology has been described in elasmobranchs infected by cestodes, although with more severe lesions. [ABSTRACT FROM AUTHOR]

For many years, the sculpin has been utilized as a sentinel monitoring species for anthropogenic impacts on the marine environment. To further develop its potential as a screening model body burden of several trace elements, including cadmium (Cd), copper (Cu), mercury (Hg), lead (Pb) and selenium (Se), were investigated. In addition, histopathology in shorthorn sculpins (Myoxocephalus scorpius; n = 20) and fourhorn sculpins (Myoxocephalus quadricornis; n = 10) were examined at three sites around the Scoresby Sound settlement in Central East Greenland. Fourhorn sculpins caught at the most distant site from the settlement, contained significantly higher hepatic Cu and Cd concentrations as well as significantly elevated gill Pb levels compared to the shorthorn sculpins collected at two other sites closer to the settlement. Histological examinations showed that fish with significantly higher concentrations of hepatic Cd and Se exhibited greater nuclear alterations, interstitial hyperplasia/hypertrophy, interstitial mononuclear infiltrations and granulomas. Further, fish with higher Cd and Cu gill tissue levels displayed a significantly higher number of cytoplasmic alterations and lamellar epithelium lifting, hypertrophic and hyperplastic epithelium along with mucus cell hyperplasia. While the presence of liver lesions were not species or sex-specific, the presence of gill lesions decreased in the order female fourhorn sculpins > female shorthorn sculpins > male fourhorn sculpins > male shorthorn sculpins. Hepatic Hg concentrations exceeded known lowest observable effect doses (LOED) for fish (0.1–0.5 μg g−1 ww) in 27% of fish, while liver Cd residues in 80% exceeded LOED (0.42–1.8 μg g−1 ww). Based upon these results, data suggest that using the sculpin as a valuable sentinel fish species histopathology may serve as a reliable tool for assessing marine ecosystem exposure to trace metals. However, confounding physiological and ecological factors also need to be considered. [ABSTRACT FROM AUTHOR]

Fourhorn sculpins ( Myoxocephalus quadricornis ) and shorthorn sculpins ( Myoxocephalus scorpius ) have been considered suitable local bioindicators for environmental monitoring studies in the Arctic. Because these species share many characteristics, data from the two species have previously been pooled when assessing marine metal contamination. A chemical and histological study was conducted on fourhorn and shorthorn sculpins collected around a contaminated lead-zinc mine at East Greenland to investigate whether there were any differences in the residues of metals, histopathology and parasites in liver and gills between the two sculpin species. The results demonstrated that concentrations of copper (Cu), zinc (Zn), mercury (Hg) and lead (Pb) were significantly higher in the fourhorn sculpins ( p <0.001) while there were no significant differences for arsenic (As) or cadmium (Cd). Furthermore, density of blood vessel fibrosis ( p =0.028), prevalence and density of chondroplasia ( p =0.002 and p =0.005, respectively), number of mucin-containing mucous cells ( p <0.001) and chloride cells ( p <0.001) and mean intensity of colonial Peritricha ( p <0.001) were significantly higher in fourhorn sculpin. Based on these results we suggest that pooling the two species when conducting environmental assessments is not recommended as it can lead to incorrect conclusions. We propose that a larger study investigating the biological effects of zinc-lead mining in Greenland is needed. [ABSTRACT FROM AUTHOR]

Barramundi (Lates calcarifer), an economically important species for mariculture in the Asia-Pacific region, has been threatened by various infectious diseases. Lates calcarifer herpes virus (LCHV) is a newly emerging virus which was first reported in farmed barramundi in 2015. Up to now, the pathognomonic histopathological lesion of this disease has not yet been described for the purpose of disease diagnosis. This study investigated the histology of five natural LCHV outbreaks throughout a year and consistently detected the presence of a typical type of intra-nuclear inclusion bodies (IIBs) in various organs of infected fish. Experimental infection was conducted by injecting the healthy fish with filtered supernatant of crude extract from the LCHV-positive barramundi from the field. Histological examination of experimentally infected barramundi clearly indicated the presence of the same type of IIBs in multiple organs, including the liver, pancreas, kidney, eyes, gills, and adipose tissue. The presence of IIBs in barramundi infected with LCHV was a pathognomonic feature that can be used for the histological diagnosis and particularly for surveillance of this emerging viral disease in barramundi farming countries. • Intra-nuclear inclusion bodies (IIBs) were found in all natural LCHV-infected barramundi. • IIBs were successfully reproduced in experimental infection. • Natural LCHV-infected barramundi were likely coinfected with other pathogens. [ABSTRACT FROM AUTHOR]