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Brook trout (Salvelinus fontinalis) is a species of fish native to North-East America. Brook trout are also commercially raised in large numbers for food production. Skin infection and/or parasite outbreaks can have a serious economics effect on aquaculture businesses. For this reason, it has been hybridized with the more resistant Arctic char (Salvelinus alpinus). The aim of this study was an examination of the epidermal structure and dynamic in brook trout and its Arctic char hybrid which is less sensitive to skin infection. The samples of fish (72 brook trout, 72 brook trout x Arctic char hybrid) from fish farm in Pravíkov (49°19'10"N, 15°5'40"E) were collected five times during the year 2011. Absolute and relative epidermal thickness (in relation to body size) and relative proportion of secretory cells in a given volume of epidermis were measured. The epidermis structure of brook trout and brook trout x Arctic char hybrid both display similar seasonal dynamics, with a decrease in absolute and relative epidermal thickness and a reduction in the relative percentage of mucous secretory cells over the summer. On the other hand, the lower absolute (mean 103 urn (range 84-146 urn) in brook trout; 88 urn (range 68-115 urn) in hybrids) and relative epidermal thickness (mean 4.8 (range 3.6-6.8) in brook trout; 4.4 (range 2.9-6.4) in hybrids) and lower volume of secretory cells was observed to the hybrid (mean 28% (range 19-33%) in brook trout; 23% (range 10-30%) in hybrids). It can interrelate with their higher resistance to infection and/or parasite outbreaks. [ABSTRACT FROM AUTHOR]

Despite being genetically very closely related, the marble trout Salmo marmoratus and the brown trout Salmo trutta exhibit marked phenotypic differences, particularly with regard to skin pigmentation. Histological analysis of skin from the head and gill cover of differently aged individuals of the two species was carried out in order to characterize differences in skin structure. The basic structure of skin of the individuals studied corresponded with that described for other salmonids, though the head epidermis was somewhat thicker in S. marmoratus than in S. trutta, thickening with age in both species. Numerous secretory goblet cells and sporadic secretory sacciform cells were observed in the upper and middle part of the epidermis in both species. Melanophores were present in both species only in the dermis, and were bigger in S. marmoratus and present at lower average density than in S. trutta, and more or less constant across all age classes. In adult S. marmoratus with fully established marble pigmentation, light areas at low density with small (i.e. aggregated) melanophores were present, while in S. trutta melanophores were more uniformly distributed. [ABSTRACT FROM AUTHOR]

The article focuses on a study which tested the hypothesis that the appearance of spawning marks in Danubian spined loach Cobitis elongatoides females resulted from grazing by males while attached to the female. The study found that the average thickness of the outer layer of the integument is about 100 µ meter. The dermis of Cobitis elongatoides females contains scales that cause an undulation of the line between epidermis and dermis. Study authors concluded that the appearance of spawning marks in Cobitis elongatoides females is caused by physiological change sin female organism while spawning.