A. O. Kasumyan

Sounds and sound production in fishes

The main information on the sounds and sound production in fishes is reviewed. The present systems of sound classification and specialized sound production in fishes with different taxonomic positions and ecology are described. The anatomy of sound generating organs is analyzed, and the mechanisms of production of different types of sounds (stridulation, drumming, cavitation, and percussion, as well as hydrodynamic, pneumatic, stringed, and respiratory sounds) are discussed. A brief characterization of the acoustic parameters of different sound types is given. Recent data on the anatomy and morphology of the sonic muscles (including their innervation, physiology, sexual dimorphism, and seasonal changes) are reviewed. The dynamics of the development of sound generating organs are described, and their capacity for sound production in the ontogeny of fishes is followed.

Early development of the olfactory organ in sturgeons of the genus Acipenser: a comparative and electron microscopic study

Formation and morphology of the olfactory organ of vertebrates has been intensely studied in some taxa for more than a century. As a functionally important and complex sensory organ, its ontogenetic development has often been a matter of debate on higher-level craniate evolution. However, sufficient knowledge of structure and development of the olfactory organ in the crucial taxa needed for a serious phylogenetic reasoning is generally not available. This study aims at this essential primary data source, the detailed structure, morphogenesis, and character definition of the olfactory organ in more basal clades of jawed vertebrates (Gnathostomata). Sturgeon fishes (Acipenseriformes) as recent basal actinopterygians are expected to provide insight into archaic characters and character combinations in bony fishes. Thus, the development of the olfactory placodes of the sterlet, Acipenser ruthenus, and the Siberian sturgeon, Acipenser baerii, was followed histologically, by semi-thin serial sections, and by scanning and transmission electron microscopy. Except for the timing, virtually no differences were observed between the two species. The olfactory placodes become two-layered early in embryonic development. Both the superficial epidermal and the subepidermal layer can easily be distinguished and their development followed by ultrastructural properties. There are three different types of receptor cells: ciliated, microvillous, and crypt cells. The development of the ciliated and the less abundant microvillous receptor cells from the subepidermal layer of the placode is demonstrated. The non-sensory cells of the differentiated olfactory epithelium, i.e. ciliated non-sensory cells and supporting cells, exclusively derive from the superficial epidermal layer. In this respect, acipenserids clearly demonstrate close resemblance to the morphogenetic process found in the tetrapod Xenopus (Anura). The only other adequately described mode found in the actinopterygian zebrafish (Danio rerio), is considered a derived character. In this case, all cells of the differentiated olfactory epithelium derive from one placodal cell layer. The mode of formation of the nasal sac and its ventilatory openings found in the acipenserids examined here, represents a widespread and probably a plesiomorphic condition of osteognathostomes. In both species, differentiation of the basic cellular composition of the olfactory epithelium is far advanced at the time of onset of extrinsic feeding.

Acoustic Signaling in Fish

The paper lists basic data on the role of sounds in fish behavior. The involvement of acoustic signaling in the control of reproductive, territorial, agonistic, aggressive, social, and feeding behavior in fish that differ in the systematics and mode of life is considered. Species and population specifics and individual sound variation in fish, diurnal and seasonal cyclicity of sound activity, and behavior that accompany acoustic signaling and the effects upon it of different environmental factors are considered. Evidence on the formation of acoustic signaling in ontogenesis of fish is provided; the range of sound signaling and correspondence between sound spectra and auditory sensitivity are discussed. Possible applied aspects of results of study of fish bioacoustics are analyzed.

Tactile reception and behavior of fish

Available fragmentary data on tactile sensie of fish are summed up for the first time. Data are presented on morphology and distribution of tactile receptors (free nerve endings, Merkel cells, Rohon-Beard cells, etc.) and on their innervation. Main tactile organs of fish are considered—barbels and various other cutaneous outgrowths, free rays of fins, rostrum, breeding tubercles, dermal teeth. Information is presented on functional parameters of tactile reception and its significance in orientation and in manifestation by fish of reproductive, defensive, social, exploratory, and food searching behavior. An important role is shown of the intraoral tactile reception in estimation by fish of texture and attractiveness of food objects. Time of formation of tactile sensitivity in fish ontogenesis is indicated and dynamics of its formation is analyzed. A low level of knowledge of structure and function of the tactile system is noted. The majority of the available data are mostly facts indicating the importance of tactile sense in various life manifestations of fish but not disclosing the functional potential of the system.

Behavioural responses of the Persian sturgeon (Acipenser persicus) juveniles to free amino acid solutions

This study analysed the attraction/avoidance responses of the Persian sturgeon (Acipenser persicus) juveniles to 20 free L-amino acid solutions, 0.001 M. We used aquaria with two parallel compartments with a water flow of ≈ 300 mL min−1 in each compartment. During each trial, the flow of clean water in one compartment was replaced for 3 min by a test solution of free amino acids. We counted the number of fish in each compartment every 30 s for 3 min and also used a qualitative assessment to characterise the sturgeons searching behaviour. Daphnia water extracts were used as a positive control. Treatments and positive and negative controls (clean water) were replicated 10 times each. Solutions of alanine and glycine elicited the strongest food searching responses. This was confirmed by comparing the numbers of fish in test and control compartments. Leucine, histidine, cysteine, isoleucine and proline evoked low positive responses, which were confirmed by a quantitative assessment. Aspartic acid, tyrosine and glutamic acid evoked negative responses. The highest negative effects were evoked by glutamic acid. Therefore, alanine and glycine can be considered as attractants and glutamic acid as a repellent for Persian sturgeon juveniles.

Taste attractiveness of free amino acids for juveniles of Persian sturgeon Acipenser persicus

Taste preferences towards 20 free amino acids (L-isomers, 0.1–0.0001 M) were determined in juveniles of Persian sturgeon Acipenser persicus. It was found that most amino acids (16) had a positive effect on extraoral gustatory reception (increased the frequency of catching artificial pellets by fishes). The most efficient amino acids were the following: threonine, histidine, arginine, asparagine, phenylalanine, cysteine, glutamine, and glycine. Fifteen amino acids were efficient for intraoral gustatory receptors: serine, arginine, cysteine, histidine, alanine, and some others. The presence of these amino acids in pellets increased the consumption. Amino acids decreasing the frequency of catching or consumption of pellets were not found. Highly significant positive correlation was found between the amino acid ranges mediated by the extraoral and intraoral gustatory reception. The fishes demonstrated maximum sensitivity to aspartic acid, 0.01 and 0.001 M, respectively, for intraoral and extraoral gustatory systems. The threshold concentrations of arginine and glycine were higher for the intraoral gustatory system (0.01 M) than for the extraoral one (0.1 M). The comparison of Persian sturgeon with sturgeon fishes (Russian sturgeon A. gueldenstaedtii, Siberian sturgeon A, baerii, and starred sturgeon A. stellatus) studied earlier confirmed high species specificity of intraoral taste preferences in representatives of Acipenser genus. Species specificity of extraoral taste ranges was less pronounced.

Chemoreception in chronically anosmiated fish: A phenomenon of compensatory development of the gustatory system

The main results of studying the phenomenon of recovery of sensitivity to food smells after a long olfactory deprivation found in fish are presented. This ability is detected in fish of different taxonomic groups (Chondrostei, Teleostei) having normally external gustatory receptors. At the behavioral level, this effect starts to manifest itself six weeks upon anosmia, and its development apparently ends during the first three to five months in a partial, rather than complete, recovery of sensitivity to food smells. A more prolonged olfactory deprivation (6–14 months) does not cause any further decrease in the threshold concentration of stimulus solutions. The response to other types of chemical signals (alarm pheromone) is not restored. The ability of fish after a prolonged olfactory deprivation to recover sensitivity to food smells is provided by compensatory processes taking place in the external gustatory system. Recovery occurs due to substances that have taste attraction for fish. Species were found in which the food search response in the norm is provided simultaneously by the olfactory and the gustatory systems. The anosmia of such fish leads only to a partial decrease in the efficiency of search behavior. The complementarity of chemosensory systems, their functional interaction, capacity for a compensatory development, and vicariation are considered sensory mechanisms providing the reliability of realization by fish of the most important behavioral patterns, of food, in particular.

Chemoorientation in the feeding behavior of the blind Mexican cavefish Astyanax fasciatus (Characidae, Teleostei)

It was shown for the first time that the perception of the blind Mexican cavefish Astyanax fasciatus of the odour of food and targeted food search in response to it is completely controlled by olfaction. Blockage of olfactory reception deprives the fish of this ability. The odour concentration threshold (water extract of chironomid larvae) is 10–5 g/L. It is suggested that degeneration of visual organs does not intensify olfaction in troglobiont cavefish, but can cause its insignificant correction. Chronic anosmia (4 months) leads to weak recovery of chemoorientation, which supports the possession of external taste reception in blind cavefish.

Circumpolar phylogeography of the northern pike (Esox lucius) and its relationship to the Amur pike (E. reichertii)

BackgroundFreshwater fishes of the genus Esox are found throughout the Holarctic region. The northern pike (E. lucius) has a circumpolar distribution whereas the assumed sister species the Amur pike (E. reichertii) is only found in the Amur region. The genetic structure and post-glacial dispersal of these species are not well known. Here, we use sequence variation at two mitochondrial DNA regions (cytb and D-loop) to investigate the phylogeography, infer location of glacial refugia and investigate the time of divergence and potential demographic expansion of the various clades detected.ResultsThe two species did not share haplotypes implying long-term isolation with no gene flow, and divergence of the taxa were estimated at 4.55 Myr. The northern pike mtDNA haplotypes revealed three main lineages. One of the northern pike mtDNA lineages was found throughout the entire Holarctic region suggesting transcontinental dispersal from a single refugium. The three lineages exhibited a star phylogeny, indicating population expansion following isolation in separate glacial refugia. Estimated time of divergence of these lineages was 0.18 - 0.26 Myr.ConclusionsThe precise location of the glacial refugia is uncertain, but our data suggests an Asian origin. The expansion of the circumpolar lineage is estimated to be around the end of the second glacial, implying that the current distribution is due to a recent recolonization from an east-Asian refugium. All three northern pike mtDNA lineages occurred sympatrically in Europe, possibly due to secondary contact. Two of the lineages probably originated from different European refugia, one in the Danube-region and one in Western Europe, the latter seems to be the primary source for recolonization of northern Europe.

Comparison of taste preferences in the three-spined Gasterosteus aculeatus and nine-spined Pungitius pungitius sticklebacks from the White Sea Basin

Similarity between the taste preferences of classical taste substances and free L-amino acids in adult three-spined stickleback Gasterosteus aculeatus (forma leiurus) and nine-spined stickleback Pungitius pungitius (forma laevis) was found. The strongest and the most significant responses in both species were evoked by citric acid and cysteine, asparatic, and glutamic acids. Sodium chloride, calcium chloride, sucrose, and the remaining 18 amino acids do not elicit a statistically significant effect on the consumption of agar-agar pellets by the fish or have weak taste attractiveness. Similarity of taste preferences in the three-spined and nine-spined sticklebacks are supported by correlation analysis. Absolute values of the consumption of pellets of the same types are also similar in the two species. There were, however, differences in the behavioral taste response, repeated snaps, and the duration of processing of the pellets. The taste response of the nine-spined stickleback is more similar to taste responses in fish of the limnophilic complex than to the response in the three-spined stickleback. It is hypothesized that taste spectra may be very similar in fish with similar ecology and feeding patterns not only in sticklebacks, but also in other related species.