Are the taste preferences similar in closely related fish of the same trophic category? A case of Nile and Mozambique tilapias

Species specificity of taste preferences supposes the ability of fish to consume food with particular taste and thus minimize feeding competition while sympatry. However, the problem of the extent to which taste preferences can be related to trophic category and phylogeny of fish has not been yet resolved. We evaluated the taste preferences in Mozambique tilapia Oreochromis mossambicus for 37 substances (amino acids, sugars, basic taste substances) that we used earlier in experiments with the Nile tilapia O. niloticus . In O. mossambicus, taste attractive substances are the least numerous (4) and substances with an indifferent taste predominate (25). In O. niloticus , the numbers of taste attractive and indifferent substances are nearly equal (20 and 17), while substances with repulsive taste were not found. The difference between these facultative phytophagous fish is most noticeable for sugars palatability: in O. mossambicus none of the sugars have attractive taste, and 6 of them evoke aversive responses. In opposite, 9 of sugars have attractive taste, while others are indifferent, and none of sugars decrease ingestion of flavoured agar pellets in O. niloticus . Nevertheless, many substances are arranged in a similar order in the rows ranked by palatability for these fish. The patterns of feeding behavior are almost the same in tilapias. The study highlights that the phylogenetic proximity and similarity in the trophic category does not lead to the similarity of fish taste preferences. Most probably, feeding competition in the historical past is the main force that triggers the divergence in fish taste system functionality. Graphical abstract