S. S. Sidorov

Taste preferences and behavior of testing gustatory qualities of food in stone loach Barbatula barbatula (Balitoridae, Cypriniformes)

Extraoral and intraoral taste preferences of stone loach Barbatula barbatula to 21 free amino acid (L-isomers) and 4 classic taste substances were established. It was found that most amino acids (19), as well as citric acid and calcium chloride are suppressants, i.e., significantly decrease grasping of artificial pellets. Such action is most typical of cysteine, glutamine, asparagine, and citric acids. The number of deterrent stimuli among the used substances is smaller than that of suppressants. Only aquatic chironomid extract has positive gustatory properties. The remaining substances have no pronounced taste properties. Touching of a pellet by barbels is an obligatory element of behavior of testing by fish of pellet properties always preceding grasping. It was found that the subsequent development of feeding behavior of fish proceeds according to one of the possible behavioral stereotypes of testing by fish of taste properties of food items. The revealed behavioral response stereotypes differ in the number of manipulations performed by fish with a food item (rejections and repeated graspings) and in the duration of its retention. Stereotype selection is determined by the extraoral taste attractiveness of the food item for fish.

Taste preferences and feeding behavior of the stone loach Barbatula barbatula (Balitoridae, Cypriniformes) after partial deprivation of circum-mouth external gustatory and tactile receptors

Comparative study of the feeding behavior and gustatory preferences mediated by extraoral and intraoral gustatory reception in the stone loach Barbatula barbatula in the norm and 1–6 months after extirpation of all three pairs of barbels was performed. It was found that partial loss of external gustatory receptors and the sensory deficit caused by it do not lead to any noticeable disturbances of the ability of fish to evaluate taste properties of food objects (artificial agar-agar pellets containing L-isomers of alanine, lysine, cysteine or an water extract of chironomid larvae) and make an adequate decision of their grasping or ignoring and swallowing or refusing. The extirpation of the barbels does not influence feeding behavior related to determination by fish of the taste properties of pellets and completely retains in its ritual an obligatory preliminary examination of the food object using external gustatory reception. It is suggested that external taste buds having different localization are equally capable of providing for fish a preliminary evaluation of the taste properties of the object. After extirpation of the barbels, the efficiency of grasping pellets decreases in fish, which indicates an important role of tactile reception in the determination of the site of location of the food object and in providing of the accuracy of the hunter’s dart in fish with a weak vision development.

Behavior of food objects testing by taste in the carp Cyprinus carpio in the norm and at chronic anosmia

Comparative study of behavior of testing artificial food objects (agar-agar pellets containing L-proline 0.1 M, L-alanine 0.1 M, L-glutamine 0.1 M, or L-glutamic acid 0.01 M and control pellets) by intact and olfactorily deprived (16 months) two-year-olds of the carp Cyprinus carpio (TL 8.5 cm) was performed. It was found that chronic anosmia causes in fish an increase in the latent time of response to food objects (period from pellet falling in water up to the moment of its being grasped by fish); however, the main characteristics of behavior related to sensory testing (intraoral gustatory reception) of suitability of food objects for consumption do not change in fish. Intact and deprived carps retain the pellet in the oral cavity at the first grasp for a maximum time and reduce this time with each subsequent retention, whereas the duration of intervals between the grasps do not obey this regularity. In experiments that terminate with pellet consumption, fish perform considerably less repeated acts of testing and retain the pellet at each grasping several times longer than in experiments terminating with the rejection by fish from its consumption. It is suggested that the sensory properties of the food object are evaluated by fish at the moment of its first grasping and that the results of such assessment are the basis for the subsequent behavior whose development can proceed according to two different stereotypes.

The Effect of Food Odor Background on Gustatory Preferences and Gustatory Behavior of Carp Cyprinus carpio and Cod Gadus morhua

It was shown that stimulation by food odor (aquatic extract of food organisms, 10−2 and 10−3 g/l) does not cause shifts in gustatory preferences in carp Cyprinus carpio and cod Gadus morhua but modifies gustatory behavior. The level of consumption by carp of control granules and granules with attractive, by taste, L-proline (0.1 M) or deterrent L-lysine (0.1 M) (item by item presentation of granules) and by cod of control granules and granules with indifferent, to it, L-asparagine (0.1 M) (presentation of 10 granules simultaneously) is similar prior to and during olfactory stimulation. In the presence of food odor, the duration of taste testing for most types of granules, as well as the number of repeated graspings of granules with an attractive taste do not change in fish. At the same time, granules with indifferent or repulsive gustatory properties are rejected and repeatedly grasped by fish against the background of food odor more frequently than in water without odor. Olfactory stimulation leads to a considerable increase in the average number of graspings per one grasped granule with an indifferent or repulsive taste. Such behavior manifested by fish in the presence of food odor in response to granules with unattractive gustatory properties is apparently caused by the contradiction between the information coming via different chemosensory canals—olfactory and gustatory. The obtained results indicate that food stimulation caused by food odor in nature can lead to an increase in the actual consumption of only those accessible food items that have an attractive taste for fish.

Effects of the long-term anosmia combined with vision deprivation on the taste sensitivity and feeding behavior of the rainbow trout Parasalmo (= Oncorhynchus ) mykiss

We compared taste preferences, taste sensitivity, and behavior in testing food objects in the group of intact and two groups of sensory deprived rainbow trout Oncorhynchus mykiss yearlings. We demonstrated that long-term anosmia (for 9 months), as well as anosmia (for 9 months) combined with enucleation (object vision deprivation for 4 months), does not change the taste preference of fish for the agar pellets containing amino acids (L-alanine, L-proline, L-histidine, or glycine; 0.1 M). For all groups of fish, the threshold L-alanine concentration in pellets that caused a significant increase in consumption is 0.01 M. We showed that sensory deprived fish change their behavior of gustatory testing, namely, the rate of repeated snaps decreases as well as the pellet retention time in the mouth cavity. These results demonstrate that long-term anosmia combined with a partial vision deprivation does not significantly change the taste preferences and sensitivity in the fish that have no external taste buds. However, the observed reduction in the testing time of food objects and other changes in fish feeding behavior may suggest some functional alterations in the intraoral sensory systems (gustatory and/or tactile).

The Effect of Starvation on Taste Preferences and Testing Behavior of Food Items in the Carp Cyprinus carpio

The present study is aimed at recording changes in taste preferences and behavior related to testing of artificial agar-agar (2%) pellets with free amino acids (21 amino acids, L-isomers, 0.1–0.001 M) in the carp Cyprinus carpio at increasing duration of starvation (2, 12, 18, 24, 72, and 144 h). Two hours after the end of feeding until satiation, the fish manifest a low foraging activity and, in most cases, they do not grasp the offered pellet. Later on, the feeding motivation in fish increases rapidly and up to 24 h of starvation each of the offered pellets is grasped. In the first hours of starvation the fish refuse from consumption of the grasped pellets even with highly attractive taste stimuli (extract of chironomids, cysteine). Up to 24 h of starvation, the fish restore the differentiated attitude to taste properties of amino acids. Of the latter, four amino acids increase, six decrease, and the other 11 do not render significant influence on consumption of pellets. Up to 72 h of starvation, at the background of continuing increase in the absolute level of consumption of pellets of all types, the taste preferences change but weakly. However, up to 144 h of starvation the number of deterrent amino acids was reduced to one (phenylalanine). At increasing duration of starvation, the number of repeated grasping of pellets changes weakly while duration of testing by fish of pellets of most types increases, especially abruptly in the first 24 h. It is assumed that the decrease or complete loss in fish of the negative reaction to substances, initially having aversive taste properties may be considered as the main mechanism providing expansion of the feeding spectrum and/or transfer of fish onto consumption of new items, initially consumed just occasionally or fully avoided.