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Open AccessArticle

Hepatic Steatosis in a Bullhead (Cottus gobio) Population from a High-Mountain Lake (Carnic Alps): Adaptation to an Extreme Ecosystem?

1
Department of Life Sciences, University of Trieste, via Giorgieri 10, 34127 Trieste, Italy
2
Istituto Zooprofilattico Sperimentale del Piemonte, Liguria e Valle d’Aosta, Via Bologna 148, 10154 Torino, Italy
*
Author to whom correspondence should be addressed.
Water 2019, 11(12), 2570; https://doi.org/10.3390/w11122570
Received: 4 November 2019 / Revised: 2 December 2019 / Accepted: 4 December 2019 / Published: 5 December 2019
(This article belongs to the Special Issue Ecology and Conservation of Freshwater Fishes Biodiversity)
The aim of this study was to describe liver alterations observed in a bullhead (Cottus gobio) population from a high-mountain lake (Dimon Lake; 1857 m a.s.l.) located in Carnic Alps (Northeast Italy). Two fish sampling campaigns (summer and autumn) were performed in 2017 to explore the possible causes of this phenomenon. In addition, to investigate the typical liver features of C. gobio, control specimens were captured from Degano Creek in the same seasons. Total length, weight, and liver weight were recorded in fish from both sampling sites. In addition, Fulton’s condition factor (K) and hepatosomatic index (HSI) were calculated. Stomach contents were also analyzed. Liver from each specimen was sampled, and histological examination was carried out. Liver steatosis (L) (nuclear displacement and cytoplasm vacuolization) were histologically evaluated by assigning a semiquantitative severity score. A significant difference in L was found between Dimon Lake and Degano Creek in both summer (Mann–Whitney test; p = 0.0001) and autumn (Mann–Whitney test; p < 0.0001). Regarding HSI, a significant difference was also recorded between Dimon Lake and Degano Creek in summer (Mann–Whitney test; p < 0.0001) and also in autumn (Mann–Whitney test; p < 0.0001), but no seasonal change in K values was recorded between the two sites in both summer (Mann–Whitney test; p = 0.8589) and autumn (Mann–Whitney test; p = 0.6415). A significant positive correlation between HSI and L was found (ρS 0.573). The causes of this abnormality might be related to adaptation by the fish to the high-altitude environment, accumulating lipids in the liver to tackle the adverse season, which lasts for 6 months of the year. Nonetheless, our study does not preclude steatosis induced by a nearly exclusive chironomids diet in bullhead from Dimon Lake. View Full-Text
Keywords: adaptation; alpine lakes; Cottus gobio; hepatic steatosis adaptation; alpine lakes; Cottus gobio; hepatic steatosis
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Pastorino, P.; Prearo, M.; Pizzul, E.; Bertoli, M.; Francese, D.R.; Menconi, V.; Mugetti, D.; Bozzetta, E.; Varello, K. Hepatic Steatosis in a Bullhead (Cottus gobio) Population from a High-Mountain Lake (Carnic Alps): Adaptation to an Extreme Ecosystem? Water 2019, 11, 2570.

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