The taste system in fishes and the effects of environmental variables

Abstract

The adaptability of the taste system in fish has led to a large variety in taste bud morphology, abundance and distribution, as well as in taste physiology characteristics in closely related species with different modes of life and feeding ecology. However, the modifications evoked in the sense of taste, or gustation, particularly during ontogeny when fishes are subject to different environmental variables, remain poorly studied. This review paper focusses on current knowledge to show how plastic and resistant the taste system in fishes is to various external factors, linked to other sensory inputs and shifts in physiological state of individuals. Ambient water temperature is fundamental to many aspects of fish biology and taste preferences are stable to many substances, however, the taste‐cell turnover rate strongly depends on water temperature. Taste preferences are stable within water salinity, which gives rise to the possibility that the taste system in anadromous and catadromous fishes will only change minimally after their migration to a new environment. Food‐taste selectivity is linked to fish diet and to individual feeding experience as well as the motivation to feed evoked by attractive (water extracts of food) and repellent (alarm pheromone) odours. In contrast, starvation leads to loss of aversion to many deterrent substances, which explains the consumption by starving fishes of new objects, previously refused or just occasionally consumed. Food hardness can significantly modify the final feeding decision to swallow or to reject a grasped and highly palatable food item. Heavy metals, detergents, aromatic hydrocarbons and other water contaminants have the strongest and quickest negative effects on structure and function of taste system in fish and depress taste perception and ability of fishes to respond adequately to taste stimuli after short exposures. Owing to phenotypic plasticity, the taste system can proliferate and partially restore the ability of fishes to respond to food odour after a complete loss of olfaction. In general, the taste system, especially its functionality, is regarded as stable over the life of a fish despite any alteration in their environment and such resistance is vital for maintaining physiological homeostasis.

Anatomy and evolution of the pectoral filaments of threadfins (Polynemidae)

“…He also pointed out that the main branches of the RLA carry only gustatory/taste fibers. As described above, the polynemid RLA-OP + SV2 branches run along the entire length of each pectoral filament, and small protuberances with an external opening that clearly correspond to terminal buds [56][57][58] were visible through scanning electron microscopy on the latero-dorsal surface region of the filament of some examined species (Fig. 9).…”

Morphology of the Atlantic salmon (Salmo salar)tongue

“…The relationships among environment, the feeding habits and the morphology and the consequent functions of the oral cavity and especially of the tongue are well known. Recent studies demonstrated the effects of environment on the taste system adaptability in fishes with special regard to the effects of pollution and contaminants (Kasumyan, 2019). The Atlantic salmon is one of the most farmed fish in the world by aquaculture, and in the last years, the world salmon farmers produce 2.5 million tonnes of salmon annually.…”

Anatomical, histological and immunohistochemical study of the tongue in the rainbow trout (Oncorhynchus mykiss)

“…An important role by different hormones in feeding, related to the morphological characteristics, has been recently demonstrated in the digestive system in teleosts (Audira et al., 2018; Carnovali, Luzi, Terruzzi, Banfi, & Mariotti, 2018; Mania et al., 2017; Montalbano et al., 2016, 2018). The most of the functional processes inside the oral cavity are carried out by the tongue, whose presence and description have been showed in different species of fish, demonstrating the variation in the presence of anatomical structures like taste buds, mucous cells and teeth in teleosts, also of commercial interest (Abbate et al., 2006,2017,2020a,2020b; Abbate, Guerrera, Montalbano, Ciriaco, et al., 2012; Abbate, Guerrera, Montalbano, De Carlos, et al., 2012; Alsafy, Bassuoni, & Hanafy, 2018; Amato et al., 2012; Dos Santos, Arantes, Santiago, & Dos Santos, 2015; El Bakary, 2014; Elgendy, Alsafy, & Tanekhy, 2016; Germanà et al., 2009; Guerrera et al., 2015; Ikpegbu, Ibe, & Nlebedum, 2019; Kasumyan, 2019; Kettratad, Senarat, Boonyoung, & Jiraungkoorsku, 2017; Levanti et al., 2017; Mahmoud, Essa, & Sayed, 2016; Sadeghinezhad, Rahmati‐holasoo, Fayyaz, & Zargar, 2015; Sayed, Mahmoud, & Essa, 2019; Yu et al., 2019). Several significant papers, important as comparative data, are present in the literature in upper vertebrates like birds, reptiles and mammals (Abbate et al, 2008, 2009, 2010, 2020b; Abumandour & Kandyel, 2020; Barbosa et al., 2020; Bels et al., 2020; Cizek, Hamouzova, Goździewska‐Harłajczuk, Klećkowska‐Nawrot, & Kvapil, 2020; Cizek, Hamouzova, Kvapil, & Kyllar, 2019; Emura, 2016a,2016b,2016c,2017,2018a,2018b,2018c,2018d,2019; Erdoğan & Alan, 2012; Erdoğan & Iwasaki, 2014…”