Gustatory apparatus of the oropharyngeal cavity in juvenile rainbow trout <Emphasis Type="Italic">Parassalmo mykiss</Emphasis>

Study of the structural organization of gustatory apparatus in rainbow trout Parasalmo mykiss performed using electron scanning microscopy demonstrated that external taste buds are absent in this species in skin covers of the head and in the circumoral region. In the oropharyngeal cavity (oral and gill cavities and pharynx) of the rainbow trout, a well-developed gustatory receptor apparatus was found. In correspondence with specific features of morphology and anatomy of the skull, taste buds form seven gustatory zones. Morphometric analysis demonstrated differences between gustatory zones in the pattern and density of distribution of taste buds, as well as in average sizes of their sensory field. Zones of similar innervation have many common features in morphology. Morphologically similar zones form three regions in the oropharyngeal cavity: rostral, central, and caudal. A tendency for a decrease in the concentration of taste buds in the rostrocaudal direction common for all sensory zones was revealed. The highest concentration of taste buds was recorded at papillae of rostral regions near big teeth. A typical feature of taste buds in rainbow trout is irregular shape of the taste pore. Analysis of ultrastructural specific features of apical processes of taste cells allows us to distinguish five cell shapes in the composition of taste buds. The numeric ratio of cell shapes varies in buds of different localization. The quantitative distribution of taste buds over sensory zones, specific features of morphology and sizes of their sensory field are discussed in relation to the feeding pattern of the species.     

Structural Organization of the Taste Apparatus in Characins (Characidae,Teleostei)

The morphology and distribution of taste buds in the outer integument of the body and in the oral cavity of two forms (blind cave and sighted terrestrial ones) of the astyanax Astyanax fasciatus and in intact and blinded individuals of the Buenos Aires tetra Hyphessobrycon anisitsi have been studied using electronic scanning and light microscopy. In sighted individuals of both species, the morphometric parameters of the taste apparatus and the distribution of taste receptors are similar; the taste apparatus in the oral cavity is more developed than in the outer covers. Morphologically different taste zones were found in the oral cavity of characins. In blind fish, the taste apparatus of the maxillary zones is distinguished by smaller taste buds and a greater density of their distribution. The sensory field of taste buds in blind and sighted individuals of astyanax and tetra has a similar ultrastructure; it is formed by taste cells of three types. In blind astyanaxes and blinded individuals of tetra, numerous modified epidermal cells were found for the first time in the epithelium of the taste zones and in contact with taste buds, which are regarded as tactile receptors and a constituent element of polysensory taste-tactile complexes localized in blind fish in mainly ventral sensory zones.     

Adaptive variability of the gustatory system receptor part of the carp Cyprinus carpio (Cyprinidae, Teleostei) after chronic anosmia

To confirm the existence in fish of the olfactogustatory interactions of adaptive significance, the study was performed of reactions of the receptor part of the carp gustatory system to the complete olfactory deafferentation with use of the method of scanning electron microscopy. Peculiarities of morphological changes of the taste receptor apparatus of the external and oral localization were revealed, and the dynamic of development of the taste receptor adaptive changes was traced for 1–9 months after production of anosmia. Receptors of the intraoral gustatory system had reactions of low statistical significance which were delayed in time by 5–6 months. The receptor apparatus of the external gustatory system receptors of the intraoral taste system showed pronounced hypertrophic changes that appeared since 2–3 months after the beginning of anosmia. The changes consisted in an increase of the area of the taste bud (TB) sensory field and of their number in the sensory zones of the maxillary and mandibular parts. The taste receptors located in the maxillary barbels and in the mandible gular zone had the most expressed reactions to the olfactory deafferentation. In the fish with anosmia, formation of the additional structures of the “external taste” was detected in the form of epidermal processes under the lower lip, which were covered with taste papillae. Thus, it has been shown that the fish olfactory and gustatory systems are functionally interrelated; under conditions of olfactory deprivation the external gustatory system is able to undergo compensatory morphofunctional changes aimed at vicariation of the lost distant chemical reception.     

Taste attractiveness of free amino acids for juveniles of Persian sturgeon <Emphasis Type="Italic">Acipenser persicus</Emphasis>

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.     

Atlantic and shortnose sturgeons of the Hudson River: common and divergent life history attributes

The Hudson River estuary supports substantial number of Atlantic sturgeon, Acipenser oxyrinchus, and shortnose sturgeon, Acipenser brevirostrum. Both species have complex life cycles that have been studied sporadically in the past 50 years. The life cycle of the shortnose sturgeon may be divided into four life intervals: non-spawning adults, spawning adults, eggs and larvae, and juveniles. The life cycle of the Atlantic sturgeon is reviewed in six intervals: non-spawning adults, female spawners, male spawners, eggs and larvae, early juveniles, and late juveniles. Both species are long-lived, mature at advanced age, have rapid and similar growth during the first few years of life, feed on generally similar taxa, use deep channel habitats for all life intervals, and have complex migratory patterns with distinct, seasonal, concentration areas. Atlantic and shortnose sturgeons differ, however, in ages and sizes at maturity, maximum size, timing and location of spawning, migratory behaviors, and management. Use of marine habitats and long-distance coastal migrations are restricted to Atlantic sturgeon, but some evidence indicates that large Atlantic sturgeon juveniles reside in riverine habitats along the Atlantic coast during warm months. Movements and habitat use by both sturgeons in the Hudson River estuary contrasts with the spatial segregation of the species reported in other river systems. Juvenile shortnose sturgeon and early juvenile Atlantic sturgeon have almost the same distributions in the Hudson River estuary during all seasons. During this period of co-occurrence, both species are very similar in size, grow at about the same rate, feed on similar foods, and share deep, channel habitats. Adult shortnose sturgeon distribution overlaps with the distribution of juvenile Atlantic sturgeon, and the latter commence river emigration at a size comparable to co-occurring adult shortnose sturgeon. Life history information on the Hudson River sturgeons substantiates the need to carefully conserve these species because of vulnerability to exploitation and habitat disruption.     

Proliferative zones in the brain of the Amur sturgeon fry. Interactions with neuromeres and migration of secondary matrix zones

Neurogenesis in the forebrain region was studied in the Amur sturgeon Acipenser schrenki fry using immunocytochemical marking of the proliferative nuclear antigen. The brain zones with high proliferative activities were located at the brain ventricle surface facing the periventricular cavity. In addition to the periventricular zone of primary proliferation, several secondary proliferative zones were found in the forebrain region of the Amur sturgeon.     

Taste Receptors in the Oral Cavity of Juvenile Common Carp Cyprinus carpio and White Sea Сod Gadus morhua marisalbi

Journal of Ichthyology - A comparative study into morphological features of the intraoral gustatory apparatus in juveniles of the common carp Cyprinus carpio and White Sea cod Gadus morhua...     

Reduction of sensory cells in antennal sensilla correlated with changes in feeding behavior in the beetle Loricera pilicornis (Insecta,Coleoptera, Carabidae)

Summary The structure of the setae on the proximal antennal segments of the beetle Loricera pilicornis is described using electron microscopical methods. These setae are part of a prey-capturing apparatus and are inserted within flexible sockets. They have no central lumen.Four or five sensory cells are connected to each seta. One cell is characterized as a mechanoreceptor due to the presence of a tubular body and the location of its dendritic outer segment. The other sensory cells are of two types. One type shows the usual features of sensillar receptors except that the dendritic outer segments end beneath the seta within the cuticular sheath. In the other type all parts of the cell, including the perikaryon, appear undersized, and no axon was found. In a single case a sixth cell was found which lacks any process, although, due to its location, it belongs to the sensory cell group.The enveloping cells also deviate from the usual pattern. Trichogen and tormogen cells have no membrane folds nor microvilli. From the membrane of the thecogen cell, where it borders on the inner receptor lymph cavity, invaginations have developed which form voluminous membrane whorls. Portasomes are found on these membranes.On the basis of the structural features we hypothesize that the setae represent sensilla undergoing stepwise reduction, losing primordial gustatory units whilst the prey-capturing mechanism is optimized.Dedicated to Professor Dr. Dietrich Schneider on occasion of his 65th birthday     

Inheritance of some quantitative morphological characters in reciprocal hybrids of starred sturgeon <Emphasis Type="Italic">Acipenser stellatus</Emphasis>and beluga <Emphasis Type="Italic">A. huso</Emphasis> (Acipenseridae)

Some quantitative characters of three-summer old reciprocal hybrids of beluga Acipenser huso and starred sturgeon A. stellatus,as well as of juveniles of their parental species, are comparatively analyzed. The found maternal and paternal effects in manifestation of some characteristics in hybrids are considered in connection with elucidation of inheritance type of morphological characters in acipenserids. The paternal effect observed by some characters in hybrids beluga × starred sturgeon is explained by prevalence of dominant alleles in the genome of starred sturgeon in comparison with beluga. The maternal effect is elucidated by a few characteristics related to parameters of the head, first of all to the volume of the brain region of skull. Evidently, in this case, the matrocliny depends on the fact that information on the number of segments of embryo and their position is determined by the maternal organism during oogenesis.     

Processes of Proliferation and Apoptosis in the Brain of the Amur Sturgeon

Using techniques of immunoperoxidase staining of proliferating cell nuclear antigen (PCNA) and TUNEL labeling of fragmented DNA, we studied sites of proliferation and apoptosis in the myelencephalon, cerebellum, tectum opticum, thalamus, and hypothalamus of the Amur sturgeon (Acipenser schrenckii). We found that the processes of proliferation and apoptosis are maintained in the brain of 3-year-old sturgeon individuals; the ratio of these processes in different cerebral regions varied significantly. The maximum intensity of proliferative activity was found in the periventricular zone of the myelencephalon (proliferation index, on average, 21.0 ± 1.3%). This fact allows us to consider this cerebral region a most important zone were adult neurogenesis occurs in the sturgeon. In the medial reticular formation, dorsal thalamic nuclei, inner fibrous layer of the tectum, and lateral hypothalamus, the maximum numbers of apoptotic elements were found. Therefore, these zones in the brain of the sturgeon correspond, apparently, to the regions where postmitotic neuroblasts are localized. In sensory centers (tectum and nuclei of the V, VII, and X nerves), significantly varying ratios of intensities of proliferation and apoptosis were found; this is indicative of dissimilar rates of growth and differentiation in visual and chemosensory centers of the sturgeon brain. The high proliferative activity in sensory and motor cerebral centers of the sturgeon allows us to hypothesize that a neotenic pattern is preserved in these CNS regions of adult sturgeons over a long period after the embryogenesis has been completed.     

Proliferative zones in the brain of the Amur sturgeon fry. Interactions with neuromeres and migration of secondary matrix zones

Neurogenesis in the forebrain region was studied in the Amur sturgeon Acipenser schrenki fry using immunocytochemical marking of the proliferative nuclear antigen. The brain zones with high proliferative activities were located at the brain ventricle surface facing the periventricular cavity. In addition to the periventricular zone of primary proliferation, several secondary proliferative zones were found in the forebrain region of the Amur sturgeon Acipenser schrenki.     

Morphometric variation among river sturgeons (Scaphirhynchus spp.) of the Middle and Lower Mississippi River

Pallid sturgeon (Scaphirhynchus albus) captured in the Middle and Lower Mississippi River (i.e. below St. Louis, MO, USA) are morphologically very similar to shovelnose sturgeon (Scaphirhynchus platorynchus). Available empirical data are limited to a few studies based on low sample sizes from disjointed populations. Geneticists are currently searching for markers that will differentiate the two species, but the need for unequivocal species‐specific field characters remains. Continuation of commercial fishing for shovelnose sturgeon in some states necessitates an immediate means for accurate field identifications. Previous studies of lower basin river sturgeon classified individuals with simple morphometric character indices and interpreted intermediacy as interspecific hybridization. In this study, morphometric variation among Scaphirhynchus specimens from the Middle and Lower Mississippi River is examined for evidence of hybridization. Data are compared for large (>250‐mm standard length) hatchery‐reared and wild pallid specimens and wild shovelnose specimens. Specimens are compared using two morphometric character indices, two morphometric/meristic character indices and principal components analysis. Results indicate substantial morphological variation among pallid sturgeon below the mouth of the Missouri River. The amount of variation appears to decrease downstream in the Mississippi River. Sheared principal components analysis of morphometric data shows complete separation of shovelnose and pallid sturgeon specimens, whereas character indices indicate overlap. Both character indices and sheared principal components analysis demonstrate that pallid sturgeon in the Lower Mississippi River are morphologically more similar to shovelnose sturgeon than are pallids from the Upper Missouri River. This similarity, explained in previous studies as hybridization, may be the result of latitudinal morphometric variation and length‐at‐age differences between populations of the upper and lower extremes of the range.     

Surface ultrastructure of the tegument of Clonorchis sinensis newly excysted juveniles and adult worms.

The tegumental structures of newly excysted juveniles and adult worms of Clonorchis sinensis were studied using scanning and transmission electron microscopy. After excystation the juvenile's tegumental surface is characterized by knoblike protuberances and is armed almost entirely with numerous rows of small spines encircling the body. These spines are double- or triple-pointed on the anterior portion of the body and become single-pointed posteriorly. Four types of presumed sensory structures were observed as follow: A) ciliated knoblike papillae and B) nonciliated platelike papillae, both of which are arranged in rougly a bilaterally symmetrical pattern dorsally, ventrally, and laterally; C) rounded swellings of nonciliated papillae on the lips of the ventral and oral suckers, which are characterized in the transmission electron microscope by a rounded dense body in the apical bulb; and D) a sensory receptor with a bulbous projection having the appearance of a modified cilium, which was not found with SEM likely owing to its being enclosed by an extension of the tegument. In full-grown adult worms, the tegumental surface is knobbed or lobulated in various forms without surface spines. The tegumental structures in the adults appear to be clearly differentiated from those in the juveniles. Upraised, buttonlike papillae, each topped by a short cilium, which are similar to the Type A papillae in the juveniles, are distributed thickly around the oral and ventral suckers, and are rather randomly scattered over the remainder of the body. Some nonciliated swollen papillae were found on the lip of the ventral sucker.     

Comparison of turnover in the olfactory organ of early juvenile stage and adult Caribbean spiny lobsters

Proliferation and turnover of neurons occurs in the olfactory systems of many animals. In this study, we examined developmental changes in turnover in the olfactory organ of the Caribbean spiny lobster Panulirus argus by examining two life-history stages—early juveniles and young adults. Turnover was compared using external morphology of the olfactory organ before and after molting to determine addition and loss of aesthetascs and other chemosensilla, and BrdU labeling to identify newly proliferated cells. The number of olfactory receptor neurons (ORNs) innervating each aesthetasc increased only slightly over development, but there was a net increase of olfactory sensory units (i.e. aesthetascs and their ORNs) at each molt. This increase was similar in early juveniles and young adults when expressed as absolute number of ORNs neurons but greater in early juveniles when expressed as a proportion of existing ORNs. The net increase in olfactory sensory units in early juveniles is due solely to addition, since virtually no aesthetascs are lost. In contrast, the net increase in olfactory sensory units in adults reflects addition of new units accompanied by considerable loss of old units. These developmental changes result in expansive enlargement of the olfactory organ without turnover in early juveniles, and a more modest growth combined with continuous turnover and replenishment of ORNs in adults.     

Developmental time course of peripheral cross‐modal sensory interaction of the trigeminal and gustatory systems

Few sensory modalities appear to engage in cross‐modal interactions within the peripheral nervous system, making the integrated relationship between the peripheral gustatory and trigeminal systems an ideal model for investigating cross‐sensory support. The present study examined taste system anatomy following unilateral transection of the trigeminal lingual nerve (LX) while leaving the gustatory chorda tympani intact. At 10, 25, or 65 days of age, rats underwent LX with outcomes assessed following various survival times. Fungiform papillae were classified by morphological feature using surface analysis. Taste bud volumes were calculated from histological sections of the anterior tongue. Differences in papillae morphology were evident by 2 days post‐transection of P10 rats and by 8 days post in P25 rats. When transected at P65, animals never exhibited statistically significant morphological changes. After LX at P10, fewer taste buds were present on the transected side following 16 and 24 days survival time and remaining taste buds were smaller than on the intact side. In P25 and P65 animals, taste bud volumes were reduced on the denervated side by 8 and 16 days postsurgery, respectively. By 50 days post‐transection, taste buds of P10 animals had not recovered in size; however, all observed changes in papillae morphology and taste buds subsided in P25 and P65 rats. Results indicate that LX impacts taste receptor cells and alters epithelial morphology of fungiform papillae, particularly during early development. These findings highlight dual roles for the lingual nerve in the maintenance of both gustatory and non‐gustatory tissues on the anterior tongue. © 2015 Wiley Periodicals, Inc. Develop Neurobiol 76: 626–641, 2016     

Gustatory organs of Drosophila melanogaster: fine structure and expression of the putative odorant-binding protein PBPRP2

In Drosophila, as in most insects, gustation is mediated by sensory hairs located on the external and internal parts of the proboscis and on the legs and wings. We describe in detail the organization and ultrastructure of the gustatory sensilla on the labellum and legs and the distribution of PBPRP2, a putative odorant-binding protein, in the gustatory organs of Drosophila. The labellum carries two kinds of sensilla: taste bristles and taste pegs. The former have the typical morphology of gustatory sensilla and can be further subdivided into three morphological subtypes, each with a stereotyped distribution and innervation. Taste pegs have a unique morphology and are innervated by two receptor cells: one mechanoreceptor and the other a putative chemoreceptor cell. PBPRP2 is abundantly expressed in all adult gustatory organs on labellum, legs, and wings and in the internal taste organs on the proboscis. In contrast to olfactory organs, where PBPRP2 is expressed in the epidermis, this protein is absent from the epidermis of labial palps and legs. In the taste bristles of the labellum and legs, PBPRP2 is localized in the crescent-shaped lumen of the sensilla, and not in the lumen where the dendrites of the gustatory neurons are found, making a function in stimulus transport unlikely in these sensilla. In contrast, PBPRP2 in peg sensilla is expressed in the inner sensillum-lymph cavity and is in contact with the dendrites. Thus, PBPRP2 could be involved as a carrier for hydrophobic ligands, e.g., bitter tastants, in these sensilla.     

The Morphology of the Lorenzinian Ampullae of the Sturgeon Acipenser ruthenus (Pisces: Chondrostei)

Jørgensen, J. M. 1980. The morphology of the Lorenzinian ampullae of the sturgeon Acipenser ruthenus (Pisces: Chondrostei). (Zoological Laboratory, University of Aarhus, Denmark.) — Acta zool. (Stockh.) 61 (2): 87–92. The snout of a sturgeon, Acipenser ruthenus (Chondrostei, Osteichthyes) is provided with sensory pores. Light and electron microscopical examination of these reveals that the ampullary organs have a sensory epithelium very similar to what has been found in the Lorenzinian ampullae, which are electroreceptors previously examined at a fine structural level in elasmobranchs and the paddle-fish, Polyodon spathula. The sensory cells are pear-shaped with a very small apical part, in the centre of which there is a short cilium. Basally, the sensory cells make several contacts with button-shaped nerve-endings. The presumed synaptic area in the sensory cell is characterized by a presynaptic sheet surrounded by vesicles. Only one type of nerve ending, an afferent type, has been observed.     

Can juvenile Baltic sturgeon (Acipenser oxyrinchus) smell the enemy?

Atlantic sturgeon (Acipenser oxyrinchus), also known as Baltic sturgeon, is considered extinct in German waters. Fish‐rearing for conservation purposes largely relies on classical hatchery technology focusing on traits like survival and growth in captivity but rarely focusing on subsequent life in the wild, lacking skills such as foraging or anti‐predation behavior. Predation is hence a major factor for mortality in newly stocked individuals. The aim of this study was to evaluate if naïve Baltic sturgeon juveniles were able to recognize a common predator—zander (Sander lucioperca)—by olfactory cues and adapt accordingly. Over a period of 30 days, Baltic sturgeons were supplied with effluent water from a rearing tank with zander (zander unit) and, as a control, carp (carp unit), three tanks each. Distribution within the tank, morphology of the dorsal scutes, stress (glucose, lactate and cortisol) and gene expression of brain plasticity and cognition were studied in comparison to the control group (carp unit). No significant differences between the zander and the carp unit were observed in any of the parameters measured. Thus, we conclude that naïve Baltic sturgeon is not able to innately recognize potential predators by olfaction alone. Therefore, future studies should focus on applying predator odor together with chemical alarm substances.     

Cellular automaton simulation of tumour growth -- equivocal relationships between simulation parameters and morphologic pattern features.

OBJECTIVE: To develop an interpretation procedure which estimates simulation parameters (tumour cell motility, tumour cell adhesion, autocrine and paracrine growth control, stroma destruction) of simulated patterns solely based on morphometric features of the morphologic pattern. METHODS: A cellular automaton computer simulation program was developed which produces morphologic patterns by growth of a seed of tumour cells. At the beginning of each simulation run certain simulation parameters are assigned to the tumour cells. After the run has been completed, the resulting pattern is evaluated by a set of morphometric features. Simulation parameters and resulting morphometric features of 27,800 simulations were stored in a database and were used for the evaluation of potential relationships. RESULTS: Correlation analysis showed highly significant correlations between morphometric features on the one hand and the preset simulation parameters (tumour cell motility, tumour cell adhesion, autocrine and paracrine growth control, stroma destruction) on the other. Correlation coefficients, however, varied from 0.72 to 0.99. When only one simulation parameter varied while all others were kept constant, morphometric features yielded a highly reliable estimate of the particular simulation parameter. When variability was extended to 4 simulation parameters, morphometric features were less effective in estimating the setting of the parameters. Though in all patterns tested several possible simulation parameter constellations could be ruled out, morphometric features were usually compatible with more than one set of simulation parameters thus preventing a straightforward interpretation. CONCLUSIONS: Though simulation parameters significantly and reproducibly influence the resulting morphologic pattern as characterized by morphometric features, estimates of the simulation parameters based on morphometric features yield equivocal results.     

Population viability analysis of Lower Missouri River shovelnose sturgeon with initial application to the pallid sturgeon

Demographic models for the shovelnose (Scaphirhynchus platorynchus) and pallid (S. albus) sturgeons in the Lower Missouri River were developed to conduct sensitivity analyses for both populations. Potential effects of increased fishing mortality on the shovelnose sturgeon were also evaluated. Populations of shovelnose and pallid sturgeon were most sensitive to age‐0 mortality rates as well as mortality rates of juveniles and young adults. Overall, fecundity was a less sensitive parameter. However, increased fecundity effectively balanced higher mortality among sensitive age classes in both populations. Management that increases population‐level fecundity and improves survival of age‐0, juveniles, and young adults should most effectively benefit both populations. Evaluation of reproductive values indicated that populations of pallid sturgeon dominated by ages ≥35 could rapidly lose their potential for growth, particularly if recruitment remains low. Under the initial parameter values portraying current conditions the population of shovelnose sturgeon was predicted to decline by 1.65% annually, causing the commercial yield to also decline. Modeling indicated that the commercial yield could increase substantially if exploitation of females in ages ≤12 was highly restricted.