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At least 19 recordsLinked to original sources

Sonic/vocal motor pathways in catfishes: comparisons with other teleosts.

Among teleost fishes, representatives of several distantly related groups have sound-producing (sonic/vocal) muscles associated with the swimbladder or pectoral girdle/fin. Here, the diversity of vocal organs and central motor pathways in four families of catfish, order Siluriformes, is compared to that in families from two distantly related orders, the Scorpaeniformes and Batrachoidiformes. Several catfish families have two sonic mechanisms--a swimbladder vibration established by 'drumming muscles' that differ in origin and insertion between families, and a pectoral spine stridulatory apparatus. In ariids, mochokids and doradids, sonic swimbladder muscles originate at various cranial or postcranial elements and insert onto an 'elastic spring' that vibrates the swimbladder, while in pimelodids the muscles insert ventrally at the swimbladder. Sonic motoneurons are located along the midline, ventral to the fourth ventricle/central canal in doradids and mochokids but lateral to the medial longitudinal fasciculus in ariids; pimelodids have motoneurons in both locations. The axonal trajectory for the lateral motoneurons in pimelodids and ariids implies that they are a migrated, midline population of sonic motoneurons. Pectoral spine-associated motoneurons are located in the ventral motor column. Unlike catfishes, a diversity of sonic mechanisms in Scorpaeniformes is not associated with different positions for sonic motoneurons. Cottids (sculpin) lack a swimbladder but have sonic muscles that originate at the occipital cranium and insert at the pectoral girdle; sonic motoneurons are located within the ventral motor column. Some triglids have intrinsic swimbladder muscles, although ontogenetic data indicate a transient association with the pectoral girdle; sonic motoneurons are in the same location as in cottids. Among Batrachoidiformes, all known representatives have intrinsic swimbladder muscles that are never associated with the pectoral girdle and are innervated by midline sonic motoneurons. The results suggest two patterns of organization for sound-producing systems in teleost fishes: pectoral fin/girdle-associated muscles are innervated by sonic motoneurons positioned within the ventral motor column, adjacent to the ventral fasciculus; non-pectoral associated muscles are innervated by sonic motoneurons located on or close to the midline, adjacent to the medial longitudinal fasciculus.

Air Sacs↗

Major patterns of higher teleostean phylogenies: a new perspective based on 100 complete mitochondrial DNA sequences.

A recent preliminary study using complete mitochondrial DNA sequences from 48 species of teleosts has suggested that higher teleostean phylogenies should be reinvestigated on the basis of more intensive taxonomic sampling. As a second step towards the resolution of higher teleostean phylogenies, which have been described as the "(unresolved) bush at the top of the tree," we reanalyzed their relationships using mitogenomic data from 100 purposefully chosen species that fully represented all of the higher teleostean orders, except for the Batrachoidiformes. Unweighted and weighted maximum parsimony analyses were conducted with the data set that comprised concatenated nucleotide sequences from 12 protein-coding genes (excluding 3rd codon positions) and 21 transfer RNA (tRNA) genes (stem regions only) from each species. The resultant trees were well resolved and largely congruent, with most internal branches being supported by high statistical values. All major, comprehensive groups above ordinal level as currently defined in higher teleosts (with the exception of the Neoteleostei and several monotypic groups), such as the Eurypterygii, Ctenosquamata, Acanthomorpha, Paracanthopterygii, Acanthopterygii, and Percomorpha, appeared to be nonmonophyletic in the present tree. Such incongruities largely resulted from differences in the placement and/or limits of the orders Ateleopodiformes, Lampridiformes, Polymixiiformes, Ophidiiformes, Lophiiformes, Beryciformes, Stephanoberyciformes, and Zeiformes, long-standing problematic taxa in systematic ichthyology. Of these, the resulting phylogenetic positions of the Ophidiiformes and Lophiiformes were totally unexpected, because, although they have consistently been considered relatively primitive groups within higher teleosts (Paracanthopterygii), they were confidently placed within a crown group of teleosts, herein called the Percomorpha. It should be noted that many unexpected, but highly supported relationships were found within the Percomorpha, being highly promising for the next investigative step towards resolution of this remarkably diversified group of teleosts.

Animals↗

Evolution of homologous vocal control traits.

Evolutionary neurobiologists want to know how neuronal properties (or traits) have been modified to subserve adaptive changes in behavioral phenotypes. Homology can provide a conceptual framework to distinguish the separate contributions of phylogenetic factors and current adaptive modifications to extant traits and behaviors. In this essay, a suite of nine vocal/sonic motor traits are compared in two orders of teleost fishes, the Batrachoidiformes and Scorpaeniformes. Only three of the traits are modified among Scorpaeniformes, the more advanced group. The large number of conserved characters among the study species suggests their sonic motor systems are homologs. This conclusion is consistent with the known phylogeny of teleosts and further implies that homologous sonic motor traits are more extensively modified among more recently evolved members (in this case the Scorpaeniformes) of the teleostean lineage. Since homology implies a common ontogenetic history for any trait, modifications thereof can potentially be linked to changes in identifiable developmental events, which themselves are homologs. Several hypotheses are proposed to account for the origins of modified sonic traits. The further demonstration that modified traits of the sonic motor system are in fact adaptations sets the stage for behavioral ecological studies that attempt to understand why the modified traits underlie behavioral changes that increase an individual's fitness.

Animal Communication↗

Preliminary findings on the nucleus of large neurons in Lophius piscatorius L. (Osteichthyes, Lophiiformes).

Some Teleosts belonging to the orders Batrachoidiformes, Lophiiformes, Perciformes and Tetraodontiformes show a cluster of large neurons dorsally located at the boundary between the spinal cord and medulla oblongata. These elements have traditionally been grouped with the supramedullary neurons aligned in the dorso-medial region of the spinal cord of other teleosts (see Marini and Benedetti, in press). However, recent morphological and immunohistochemical studies have suggested that the neurons grouped in a cluster on the spinal cord of Lophius piscatorius may not be of the same nature as the supramedullary neurons aligned within the dorsal gray matter of the spinal cord (Benedetti and Mola, 1988; Mola, 1990). Over the course of these previous investigations, it seemed that the nucleus of the neurons in the cluster showed more abundant chromatin than other neurons in the dorsal spinal cord. This prompted a series of investigations on the nucleus of these neurons.

Animals↗

Vocal-acoustic circuitry and descending vocal pathways in teleost fish: convergence with terrestrial vertebrates reveals conserved traits.

Vocal behavior is multifaceted and requires that vocal-motor patterning be integrated at multiple brain levels with auditory, neuroendocrine, and other social behavior processes (e.g., courtship and aggression). We now provide anatomical evidence for an extensive vocal network in teleost fishes (Batrachoididae: Porichthys notatus; Opsanus beta) that is strongly integrated with neuroendocrine and auditory pathways and that exhibits striking similarities to the vocal-acoustic circuitry known for mammals. Biotin compound injections into neurophysiologically identified vocal regions of the forebrain (preoptic area and anterior hypothalamus) and of the midbrain (periaqueductal gray and paralemniscal tegmentum) reveal extensive connectivity within and between these regions, as well as reciprocal relationships with the auditory thalamus and/or auditory midbrain (torus semicircularis). Thus, specific components of the basal forebrain and midbrain are here designated as the forebrain vocal-acoustic complex (fVAC) and midbrain vocal-acoustic complex (mVAC), respectively. Biotin injections into the mVAC and a previously identified hindbrain vocal pattern generator likewise provide anatomical evidence for a distributed network of descending projections to the vocal pacemaker-motoneuron circuitry. Together, the present experiments establish a vocal-auditory-neuroendocrine network in teleost fish that links the forebrain and midbrain to the hindbrain vocal pattern generator (i.e., fVAC --> mVAC --> pattern generator) and provides an anatomical framework for the previously identified neuropeptide modulation of vocal activity elicited from the forebrain and midbrain, which contributes to the expression of sex- and male morph-specific behavior. We conclude with a broad comparison of these findings with those for other vertebrate taxa and suggest that the present findings provide novel insights into the structure of conserved behavioral regulatory circuits that have led to evolutionary convergence in vocal-acoustic systems.

Animals↗

Putative isotocin distributions in sonic fish: relation to vasotocin and vocal-acoustic circuitry.

Recent neurophysiological evidence in the plainfin midshipman fish (Porichthys notatus) demonstrated that isotocin (IT) and arginine vasotocin (AVT) modulate fictive vocalizations divergently between three reproductive morphs. To provide an anatomical framework for the modulation of vocalization by IT and to foster comparisons with the distributions of the IT homologues mesotocin (MT) and oxytocin (OT) in other vertebrate groups, we describe putative IT distributions in the midshipman and the closely related gulf toadfish, Opsanus beta. Double-label fluorescent histochemistry was used for IT and AVT (by using antibodies for MT, OT, and the mammalian AVT homologue, arginine vasopressin [AVP]). MT/OT-like immunoreactive (MT/OT-lir) cell groups were found in the anterior parvocellular, posterior parvocellular, and magnocellular preoptic nuclei. MT/OT-lir fibers and putative terminals densely innervated the ventral telencephalon and numerous areas in the hypothalamus and brainstem. These distributions included all sites of vocal-acoustic integration recently identified for the forebrain and midbrain and diencephalic components of the ascending auditory pathway. Results were qualitatively comparable across morphs, species, and seasons. In contrast to the widespread distribution of MT/OT-lir, AVP-lir somata, fibers, and putative terminals were almost completely restricted to vocal-acoustic regions. These data parallel previous descriptions of AVT immunoreactivity in these species, although the present methods showed a previously undescribed, seasonally variable AVP-lir cell group in the anterior tuberal hypothalamus, a vocally active site and a component of the ascending auditory pathway. These findings provided anatomic support for the role of IT and AVT in the modulation of vocal behavior at multiple levels of the central vocal-acoustic circuitry.

Animals↗

Gamma-aminobutyric acid is present in a spatially discrete subpopulation of hair cells in the crista ampullaris of the toadfish Opsanus tau.

Although gamma-aminobutyric acid (GABA) and glutamate are known to be present in the vestibular sensory epithelia of a variety of species, the functional relationship between these two transmitters is not clear. The present study addresses the three-dimensional spatial distribution of GABA and glutamate immunoreactivity in the vestibular labyrinth of the oyster toadfish by using whole end organs labeled by immunofluorescence with monoclonal anti-GABA and/or antiglutamate antibodies and visualized as whole mounts by multiphoton confocal microscopy. We find glutamate-immunoreactive hair cells present throughout the sensory epithelium. In contrast, prominent GABA immunoreactivity is restricted to a small population of hair cells located in the central region of the crista. Double immunofluorescence reveals two distinct staining patterns in GABA-labeled hair cells. Most ( approximately 80%) GABA-labeled cells show trace levels of glutamate, appropriate for the metabolic/synthetic role of cytoplasmic glutamate. The remainder of the GABA-stained cells contain substantial levels of both GABA and glutamate, suggesting transmitter colocalization. In the toadfish utricle, glutamatergic hair cells are present throughout the macula. GABA-immunoreactive hair cells follow the arc of the striola, and most GABA-labeled receptor cells coexpress glutamate. The localization of GABA was explored in other species as well. In the pigeon, GABAergic hair cells are present throughout the crista ampullaris. Our findings demonstrate that multiple, neurochemically distinct types of hair cells are present in vestibular sensory epithelia. These observations, together with the excitatory activity generally associated with 8th nerve afferent fibers, strongly suggest that GABA serves an important, specific, and complex role in determining primary afferent response dynamics.

Animals↗

Distribution of estrogen receptor alpha mRNA in the brain and inner ear of a vocal fish with comparisons to sites of aromatase expression.

Among vertebrates, teleost fish have the greatest capacity for estrogen production in the brain. Previously, we characterized the distribution of the estrogen-synthesizing enzyme aromatase in the brain of the midshipman fish. Here, we investigated the distribution of estrogen receptor alpha (ERalpha). A partial cDNA of ERalpha was cloned and used to generate midshipman-specific primers for RT and real-time PCR which identified transcripts in liver and ovary, the CNS, and the sensory epithelium of the main auditory endorgan (sacculus). In situ hybridization revealed abundant expression throughout the preoptic area, a vocal-acoustic site in the hypothalamus, amygdala homologs of the dorsal pallium, the pineal organ, the inner ear, the pituitary, and the ovary. Weaker expression was found in the midbrain's nucleus of the medial longitudinal fasciculus and in the dimorphic vocal motor nucleus. ERalpha expression in the pineal, gonad, and pituitary axis may function to time seasonal abiotic cues to reproductive state, while expression in the vocal motor and auditory systems support neurophysiological evidence for estrogen as a modulator of vocal motor and auditory encoding mechanisms in midshipman fish. While ERalpha is restricted to specific nuclei, aromatase expression is abundant in glial cells throughout the entire forebrain, and high in midbrain and hindbrain - spinal vocal regions. The only site of aromatase-containing neurons is in the peripheral auditory system, where it is localized to ganglion cells in the auditory nerve. Estrogen production proximal to ERalpha-positive neurons may provide for focal sites of estrogen effects on reproductive-, vocal-, and auditory-related neurons.

Amino Acid Sequence↗

Transport physiology of the urinary bladder in teleosts: a suitable model for renal urea handling?

The transport physiology of the urinary bladder of both the freshwater rainbow trout (Oncorhychus mykiss) and the marine gulf toadfish (Opsanus beta) was characterized with respect to urea, and the suitability of the urinary bladder as a model for renal urea handling was investigated. Through the use of the in vitro urinary bladder sac preparation urea handling was characterized under control conditions and in the presence of pharmacological agents traditionally used to characterize urea transport such as urea analogues (thiourea, acetamide), urea transport blockers (phloretin, amiloride), and hormonal stimulation (arginine vasotocin; AVT). Na(+)-dependence and temperature sensitivity were also investigated. Under control conditions, the in vitro trout bladder behaved as in vivo, demonstrating significant net reabsorption of Na(+), Cl(-), water, glucose, and urea. Bladder urea reabsorption was not affected by pharmacological agents and, in contrast to renal urea reabsorption, was not correlated to Na(+). However, the trout bladder showed a threefold greater urea permeability compared to artificial lipid bilayers, a prolonged phase transition with a lowered E(a) between 5 degrees C and 14 degrees C, and differential handling of urea and analogues, all suggesting the presence of a urea transport mechanism. The in vitro toadfish bladder did not behave as in vivo, showing significant net reabsorption of Na(+) but not of Cl(-), urea, or water. As in the trout bladder, pharmacological agents were ineffective. The toadfish bladder showed no differential transport of urea and analogues, consistent with a low permeability storage organ and intermittent urination. Our results, therefore, suggest the possibility of a urea transport mechanism in the urinary bladder of the rainbow trout but not the gulf toadfish. While the bladders may not be suitable models for renal urea handling, the habit of intermittent urination by ureotelic tetrapods and toadfish seems to have selected for a low permeability storage function in the urinary bladder.

Animals↗

Does exaggerated morphology preclude plasticity to cuckoldry in the midshipman fish ( Porichthys notatus)?

In species with more than one male reproductive morph, there typically exists a larger morph with exaggerated secondary sexual characters, and a smaller morph with reduced secondary sexual characters. These "exaggerated" and "reduced" morphologies are commonly thought to represent specializations to alternative behavioral reproductive tactics-large body size and exaggerated secondary sexual characters should both facilitate territoriality, courtship, and pair-spawning; while small body size and reduced secondary sexual characters should facilitate "sneaky" cuckoldry. Given this postulated relationship between morphology and behavior, we examined the relationship between the morphology of exaggerated males and cuckoldry. In a field and aquarium study of the midshipman fish, a fish with both exaggerated and reduced morphs, we demonstrated cuckoldry in some males of the exaggerated morph. Since the "reduced" morphology is thought to be an adaptation towards sneaky cuckoldry, we predicted that, of males with the exaggerated morph, less-exaggerated (smaller) males would be better able to gain proximity to the spawning pair during cuckoldry. In contrast to that prediction, access to the spawning pair during cuckoldry increased with the body size of the cuckolding exaggerated-morph males. This may be related to our observation that exaggerated males often cuckolded aggressively. Thus the "exaggerated" morphology need not preclude adaptive plasticity to cuckoldry, and may even aid it.

Animals↗

Ultrastructural observations of efferent terminals in the crista Ampullaris of the toadfish, opsanus tau.

The present study was conducted to visualize the ultrastructural features of vestibular efferent boutons in the oyster toadfish, Opsanus tau. The crista ampullaris of the horizontal semicircular canal was processed for and examined by routine transmission electron microscopy. The results demonstrate that such boutons vary in size and shape, and contain a heterogeneous population of lucent vesicles with scattered dense core vesicles. Efferent contacts with hair cells are characterized by local vesicle accumulations in the presynaptic terminal and a subsynaptic cistern in the postsynaptic region of the hair cell. Serial efferent to hair cell to afferent synaptic arrangements are common, particularly in the central portion of the crista. However, direct contacts between efferent terminals and afferent neurites were not observed in our specimens. The existence of serial synaptic contacts, often with a row of vesicles in the efferent boutons lining the efferent-afferent membrane apposition, suggests that the efferent influence on the crista may involve both synaptic and nonsynaptic, secretory mechanisms. Further, it is suggested that differences in more subtle aspects of synaptic architecture and/or transmitter and receptor localization and interaction may render the efferent innervation of the peripheral crista less effective in influencing sensory processing.

Animals↗

Ultrastructural observations of efferent terminals in the crista ampullaris of the toadfish, Opsanus tau.

The present study was conducted to visualize the ultrastructural features of vestibular efferent boutons in the oyster toadfish, Opsanus tau. The crista ampullaris of the horizontal semicircular canal was processed for and examined by routine transmission electron microscopy. The results demonstrate that such boutons vary in size and shape, and contain a heterogeneous population of lucent vesicles with scattered dense core vesicles. Efferent contacts with hair cells are characterized by local vesicle accumulations in the presynaptic terminal and a subsynaptic cistern in the postsynaptic region of the hair cell. Serial efferent to hair cell to afferent synaptic arrangements are common, particularly in the central portion of the crista. However, direct contacts between efferent terminals and afferent neurites were not observed in our specimens. The existence of serial synaptic contacts, often with a row of vesicles in the efferent boutons lining the efferent-afferent membrane apposition, suggests that the efferent influence on the crista may involve both synaptic and nonsynaptic, secretory mechanisms. Further, it is suggested that differences in more subtle aspects of synaptic architecture and/or transmitter and receptor localization and interaction may render the efferent innervation of the peripheral crista less effective in influencing sensory processing.

Animals↗

Synapsin-like immunoreactivity is present in hair cells and efferent terminals of the toadfish crista ampullaris.

The synapsins are presynaptic membrane-associated proteins involved in neurotransmitter release. They are differentially expressed in tissues and cells of the central and peripheral nervous system. In vestibular end organs of mammals, synapsin I-like immunoreactivity has been reported in efferent and afferent terminals and in afferent nerve calyces surrounding type I hair cells. In addition, synapsin I has recently been described in several non-neural cell lines. The present study was conducted to locate synapsin-like immunoreactivity in the neuronal and non-neuronal cells of the fish crista ampullaris, to examine the possibility that the non-neuronal sensory receptor cells express synapsins in vivo. Synapsin-like immunostaining was visualized by immunofluorescence detection in wholemounts of the toadfish crista ampullaris using multiphoton laser scanning microscopy and by electron microscopic visualization of post-embedding immunogold labeling. The results demonstrate that synapsin-like immunoreactivity is present in vestibular hair cells and efferent boutons of the toadfish crista ampullaris. Afferent endings are not labeled. Staining in hair cells is not associated with the synaptic ribbons, suggesting that there is an additional, non-synaptic role for the synapsins in some non-neuronal cells of vertebrates. Moreover, while the cristae of amniote and anamniote species share many functional attributes, differences in their synaptic vesicle-associated protein profiles appear to reflect their disparate hair cell populations.

Animals↗

Polycyclic aromatic hydrocarbon metabolites in the bile of a territorial benthic fish, oyster toadfish (Opsanus tau) from the Elizabeth River, Virginia.

Reverse-phase high-performance liquid chromatographic analyses of bile of a territorial benthic fish, oyster toadfish (Opsanus tau), indicated that fish from reference stations in the York and Elizabeth Rivers, Virginia, contained lower concentrations of polycyclic aromatic hydrocarbon (PAH) metabolites than fish from polluted stations. PAH metabolite levels in the bile of fish from mildly polluted stations were 7 to 10 times greater than those from reference stations. PAH metabolite levels in fish from a moderately polluted station and a highly polluted station were, respectively, 20 and 50 times greater than those from reference stations. Differential patterns of five major PAH metabolites in fish from the same station suggested individual variability in metabolic pathways possibly further convoluted by the differential inductions or suppressions of hepatic mixed-function oxygenase isozyme systems under various natural or anthropogenic habitat parameters. PAH metabolite levels in the bile of oyster toadfish correlated well with the gradient of PAH contamination in the Elizabeth River sediments. High levels of biliary PAH metabolites were not detected in muskrats (Ondatra zibethicus) collected along the polluted sections of the Elizabeth River, probably due to their primarily herbivorous nature. Assuming that the hepatobiliary system and the gastrointestinal tract are the major routes of biotransformation and excretion of PAHs in the muskrats, the contaminated diet appears to be a more important routes of exposure of muskrats (and possibly oyster toadfish) to PAHs than the transdermal transfer. Occurrence permitting, we propose oyster toadfish as a useful biological sentinel for early detection of estuarine PAH pollution.

Adaptation, Physiological↗

Directionality and frequency tuning of primary saccular afferents of a vocal fish, the plainfin midshipman (Porichthys notatus).

While particle motion is thought to directly stimulate the inner ear of most fish species, it is difficult to measure and might not be predictable from pressure measurements in a small tank. It is therefore important to replicate experiments conducted relative to pressure measurements using stimuli of known particle motion, to ensure that unmeasured components of the stimulus field do not produce misleading frequency response profiles. The frequency sensitivity of the inner ear of the plainfin midshipman fish, Porichthys notatus, in response to isopressure stimuli has been described. This study now examines the frequency and directional response properties of midshipman saccular afferents in response to whole-body displacements simulating acoustic particle motion. Best frequencies were distributed bimodally, with peaks at 50 Hz and 100 Hz. Most units had cosinusoidally shaped directional response profiles in the horizontal and vertical planes, though some units showed slight deviations from this pattern. A few units (probably saccular efferents) had omnidirectional directional response profiles and did not phase lock to the stimulus waveform. These results are consistent with responses of the midshipman saccular nerve to isopressure stimuli, and strengthen the hypothesis that the frequency sensitivity of the midshipman ear matches the frequency content of behaviorally relevant vocalizations.

Acoustic Stimulation↗