Taste preferences in fishes are known mainly for carnivorous species while herbivorous consumers were rarely used in such studies. The main goal of the present study was to evaluate the taste preferences in the herbivorous African cichlid fish, Nile tilapia Oreochromis niloticus. In laboratory settings, the palatability of widely used taste substances (4 taste substances, that are considered to be sweet, sour, bitter and salty for humans - sucrose, citric acid, calcium chloride and sodium chloride; 21 free L-amino acids; 12 sugars and artificial sweetener Na-saccharin; 0.1-0.0001 M) was evaluated. In each trial, a standard agar pellet flavored with a substance was offered for fish individually. The consumption of pellet, the number of grasps and the retention time before the pellet was finally ingested or rejected were registered. Overall, 21 of 38 substances were palatable, while other substances did not shift pellets consumption in relation to blank pellets. Pellets containing citric acid, L-cysteine, L-norvaline, L-isoleucine, L-valine, Na-saccharin, D-sorbitol were consumed in > 85% of trials. Taste attractiveness of amino acids was highly species-specific and was not associated with the trophic category of 19 the species compared. Also, it did not correlate with dietary quantitative requirements of Nile tilapia (rs = 0.27; p > 0.05). Palatability of sugars for O. niloticus and their sweetness for humans did not correlate as well (rs =0.21; p>0.05), however, Na-saccharin has the most attractive taste for both O. niloticus and humans. The most palatable amino acids lost their effect if the concentration was lowered to 0.01 M for L-cysteine and 0.001 M for L-norvaline (lower than 242.3 μg and 23.4 μg per a pellet, respectively). Single pellet grasp was characteristic of O. niloticus feeding behavior (> 95% of trials) and this pattern may be related to the social life style of this species. Fish spent 4-8 s on average for orosensory evaluation of pellet edibility. The retention time correlated with the palatability of substances and was a significantly longer in trials that ended up with pellet swallowing. It is suggested that prolonged orosensory evaluation of food before swallowing provides a reliable and accurate sensory evaluation, which, in turn, can reduce the probability that inadequate food will be consumed. This article is protected by copyright. All rights reserved.

中文翻译：

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兼性食草鱼尼罗罗非鱼 Oreochromis niloticus 的口味偏好和摄食行为

鱼类的口味偏好主要是肉食性物种，而草食性消费者很少用于此类研究。本研究的主要目标是评估食草性非洲慈鲷鱼尼罗罗非鱼 Oreochromis niloticus 的口味偏好。在实验室环境中，广泛使用的味觉物质的适口性（4 种味觉物质，被认为是人类的甜味、酸味、苦味和咸味 - 蔗糖、柠檬酸、氯化钙和氯化钠；21 种游离 L-氨基酸；12糖和人造甜味剂 Na-糖精；0.1-0.0001 M) 进行了评估。在每次试验中，都为鱼单独提供了一种用某种物质调味的标准琼脂颗粒。记录颗粒的消耗量、抓取次数和颗粒最终被摄入或拒绝之前的保留时间。全面的，38 种物质中有 21 种是可口的，而其他物质相对于空白颗粒没有改变颗粒消耗。超过 85% 的试验消耗了含有柠檬酸、L-半胱氨酸、L-正缬氨酸、L-异亮氨酸、L-缬氨酸、Na-糖精、D-山梨糖醇的颗粒。氨基酸的口味吸引力具有高度的物种特异性，并且与所比较的 19 个物种的营养类别无关。此外，它与尼罗罗非鱼的日粮定量需求无关（rs = 0.27；p > 0.05）。O. niloticus 的糖的适口性与其对人类的甜度也没有相关性（rs = 0.21；p>0.05），但是，糖精钠对 O. niloticus 和人类来说都具有最吸引人的味道。如果 L-半胱氨酸的浓度降低至 0.01 M，而最美味的氨基酸将失去作用。L-正缬氨酸为 001 M（每个颗粒分别低于 242.3 μg 和 23.4 μg）。单颗粒抓握是 O. niloticus 摄食行为的特征（> 95% 的试验），这种模式可能与该物种的社会生活方式有关。鱼平均花费 4-8 秒进行颗粒可食性的感官评估。保留时间与物质的适口性相关，并且在最终吞咽颗粒的试验中明显更长。建议在吞咽前对食物进行长时间的口腔感官评估，提供可靠和准确的感官评估，这反过来又可以减少摄入不足食物的可能性。本文受版权保护。版权所有。尼罗罗非鱼的摄食行为（> 95% 的试验），这种模式可能与该物种的社会生活方式有关。鱼平均花费 4-8 秒进行颗粒可食性的感官评估。保留时间与物质的适口性相关，并且在最终吞咽颗粒的试验中明显更长。建议在吞咽前对食物进行长时间的口腔感官评估，提供可靠和准确的感官评估，这反过来又可以减少摄入不足食物的可能性。本文受版权保护。版权所有。尼罗罗非鱼的摄食行为（> 95% 的试验），这种模式可能与该物种的社会生活方式有关。鱼平均花费 4-8 秒进行颗粒可食性的感官评估。保留时间与物质的适口性相关，并且在最终吞咽颗粒的试验中明显更长。建议在吞咽前对食物进行长时间的口腔感官评估，提供可靠和准确的感官评估，这反过来又可以减少摄入不足食物的可能性。本文受版权保护。版权所有。保留时间与物质的适口性相关，并且在最终吞咽颗粒的试验中明显更长。建议在吞咽前对食物进行长时间的口腔感官评估，提供可靠和准确的感官评估，这反过来又可以减少摄入不足食物的可能性。本文受版权保护。版权所有。保留时间与物质的适口性相关，并且在最终吞咽颗粒的试验中明显更长。建议在吞咽前对食物进行长时间的口腔感官评估，提供可靠和准确的感官评估，这反过来又可以减少摄入不足食物的可能性。本文受版权保护。版权所有。