Abstract
Simple SummaryNatural environment monitoring and identification of river or lake water pollution plays an important role for human comfort and safety. Some fish, as water-living animals, are especially sensitive to any water quality changes. Fish skin forms a natural border between the water and internal organs of the animal’s body; therefore, the skin must be able to provide defense and resistance against any factors dangerous for the fish. Some seasonal changes can influence the skin morphology and physiology (mucus composition), blurring the assessment of the skin’s reaction to any contamination.Fish frequently serve as bioindicators of aquatic environments during their ecological evaluation. Carpathian barbel (Barbus carpathicus, Cyprinidae) is a species common to rivers and lakes of Eurasia and Africa. Seasons of the year can influence its skin morphology and mucus composition. The clinical status of the animal depends on the above-mentioned factors. The aim of this study was a histological, histometrical and electrophoretical analysis of periodical changes in barbel common integument. The accessible material was investigated in histological, cytological and electrophoretic analysis using hematoxylin-eosin staining, histometric morphometry, gel electrophoresis and cytological methods. The results demonstrated significant differences in the investigated parameters for spring–summer and autumn–winter periods. Both skin epithelium morphology (epithelium thickness, number of cell layers, melanophores and mucous cell existence) and mucus composition (proteins, immune system cells, keratinocytes and mucocytes) showed significant differences between investigated seasons. These morphological and physiological changes were more pronounced in the dorsal than ventral regions of common integument. The differences in the physical characteristics of mucus and the histological structure of the skin cannot only serve as a source of useful information about an evaluated ecosystem, but can be also related to additional factors, e.g., microbiological and chemical water contamination.
Highlights
One of the features of living organisms is their ability to adapt to variable environmental conditions.Any organism’s existence is limited by two extreme values of a specific factor, i.e., its minimum and maximum
The ability of living organisms to adapt to changing environmental conditions is called tolerance, and its range may by narrow in stenobionts or widen in eurybionts
The barbel is a genus of carp-like freshwater fish belonging to the family of Cyprinidae, comprising a large number of species
Summary
One of the features of living organisms is their ability to adapt to variable environmental conditions.Any organism’s existence is limited by two extreme values of a specific factor, i.e., its minimum and maximum. One of the features of living organisms is their ability to adapt to variable environmental conditions. The ability of living organisms to adapt to changing environmental conditions is called tolerance, and its range may by narrow in stenobionts or widen in eurybionts. Species with narrow tolerance ranges to specific environmental conditions serve as indicator species, or bioindicators [1,2]. The numerous plant and animal species used as pollution bioindicators include algae (cyanobacteria and green algae in eutrophicated waters of poly- and alphamesosaprobic zones), Animals 2020, 10, 645; doi:10.3390/ani10040645 www.mdpi.com/journal/animals. The barbel is a genus of carp-like freshwater fish belonging to the family of Cyprinidae, comprising a large number of species. Since 2008, Carpathian barbel has been present on the Red List of Threatened Species (IUCN)
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