Label-free, whole-brain in vivo mapping in an adult vertebrate with third harmonic generation microscopy.

Comprehensive understanding of interconnected networks within the brain requires access to high resolution information within large field of views and over time. Currently, methods that enable mapping structural changes of the entire brain in vivo are extremely limited. Third harmonic generation (THG) can resolve myelinated structures, blood vessels, and cell bodies throughout the brain without the need for any exogenous labeling.

A tale of two males: Behavioral and neural mechanisms of alternative reproductive tactics in midshipman fish.

An amalgam of investigations at the interface of neuroethology and behavioral neuroendocrinology first established the most basic behavioral, neuroanatomical, and neurophysiological characters of vocal-acoustic communication morphs in the plainfin midshipman fish, Porichthys notatus Girard. This foundation has led, in turn, to the repeated demonstration that neuro-behavioral mechanisms driving reproductive-related, vocal-acoustic behaviors can be uncoupled from gonadal state for two adult male phenotypes that follow alternative reproductive tactics (ARTs).

Midbrain node for context-specific vocalisation in fish.

Vocalizations communicate information indicative of behavioural state across divergent social contexts. Yet, how brain regions actively pattern the acoustic features of context-specific vocal signals remains largely unexplored. The midbrain periaqueductal gray (PAG) is a major site for initiating vocalization among mammals, including primates.

Sound production biomechanics in three-spined toadfish and potential functional consequences of swim bladder morphology in the Batrachoididaea).

The relationship between sound complexity and the underlying morphology and physiology of the vocal organ anatomy is a fundamental component in the evolution of acoustic communication, particularly for fishes. Among vertebrates, the mammalian larynx and avian syrinx are the best-studied vocal organs, and their ability to produce complex vocalizations has been modeled. The range and complexity of the sounds in mammalian lineages have been attributed, in part, to the bilateral nature of the vocal anatomy.

California singing fish.

Bass describes the fascinating life history, behavior, and neurobiology of the California singing fish, including its remarkable vocal abilities.

Whole-brain optical access in a small adult vertebrate with two- and three-photon microscopy.

Although optical microscopy has allowed scientists to study the entire brain in early developmental stages, access to the brains of live, adult vertebrates has been limited. , a genus of miniature, transparent fish closely related to zebrafish has been introduced as a neuroscience model to study the adult vertebrate brain. However, the extent of optically accessible depth in these animals has not been quantitatively characterized.

Acoustic and postural displays in a miniature and transparent teleost fish, Danionella dracula.

Acoustic behavior is widespread across vertebrates, including fishes. We report robust acoustic displays during aggressive interactions for a laboratory colony of Danionella dracula, a miniature and transparent species of teleost fish closely related to zebrafish (Danio rerio), which are hypothesized to be sonic based on the presence of a hypertrophied muscle associated with the male swim bladder. Males produce bursts of pulsatile sounds and a distinct postural display - extension of a hypertrophied lower jaw, a morphological trait not present in other Danionella species - during aggressive but not courtship interactions.

Noise-induced hearing loss correlates with inner ear hair cell decrease in larval zebrafish.

Anthropogenic noise can be hazardous for the auditory system and wellbeing of animals, including humans. However, very limited information is known on how this global environmental pollutant affects auditory function and inner ear sensory receptors in early ontogeny. The zebrafish (Danio rerio) is a valuable model in hearing research, including investigations of developmental processes of the vertebrate inner ear.

Oxytocin-like receptor expression in evolutionarily conserved nodes of a vocal network associated with male courtship in a teleost fish.

Neuropeptides, including oxytocin-like peptides, are a conserved group of hormones that regulate a wide range of social behaviors, including vocal communication. In the current study, we evaluate whether putative brain sites for the actions of isotocin (IT), the oxytocin (OT) homolog of teleost fishes are associated with vocal courtship and circuitry in the plainfin midshipman fish (Porichthys notatus). During the breeding season, nesting males produce advertisement calls known as "hums" to acoustically court females at night and attract them to nests.

Vocal and Electric Fish: Revisiting a Comparison of Two Teleost Models in the Neuroethology of Social Behavior.

The communication behaviors of vocal fish and electric fish are among the vertebrate social behaviors best understood at the level of neural circuits. Both forms of signaling rely on midbrain inputs to hindbrain pattern generators that activate peripheral effectors (sonic muscles and electrocytes) to produce pulsatile signals that are modulated by frequency/repetition rate, amplitude and call duration. To generate signals that vary by sex, male phenotype, and social context, these circuits are responsive to a wide range of hormones and neuromodulators acting on different timescales at multiple loci.

To hum or not to hum: Neural transcriptome signature of male courtship vocalization in a teleost fish.

For many animal species, vocal communication is a critical social behavior and often a necessary component of reproductive success. Additionally, vocalizations are often demanding motor acts. Wanting to know whether a specific molecular toolkit might be required for vocalization, we used RNA-sequencing to investigate neural gene expression underlying the performance of an extreme vocal behavior, the courtship hum of the plainfin midshipman fish (Porichthys notatus).

Gap junction-mediated glycinergic inhibition ensures precise temporal patterning in vocal behavior.

Precise neuronal firing is especially important for behaviors highly dependent on the correct sequencing and timing of muscle activity patterns, such as acoustic signaling. Acoustic signaling is an important communication modality for vertebrates, including many teleost fishes. Toadfishes are well known to exhibit high temporal fidelity in synchronous motoneuron firing within a hindbrain network directly determining the temporal structure of natural calls.

Neuroanatomical and neurophysiological mechanisms of acoustic and weakly electric signaling in synodontid catfish.

To what extent do modifications in the nervous system and peripheral effectors contribute to novel behaviors? Using a combination of morphometric analysis, neuroanatomical tract-tracing, and intracellular neuronal recording, we address this question in a sound-producing and a weakly electric species of synodontid catfish, Synodontis grandiops, and Synodontis nigriventris, respectively. The same peripheral mechanism, a bilateral pair of protractor muscles associated with vertebral processes (elastic spring mechanism), is involved in both signaling systems. Although there were dramatic species differences in several morphometric measures, electromyograms provided strong evidence that simultaneous activation of paired protractor muscles accounts for an individual sound and electric discharge pulse.

Mating Behavioral Function of Preoptic Galanin Neurons Is Shared between Fish with Alternative Male Reproductive Tactics and Tetrapods.

Understanding the contribution of neuropeptide-containing neurons to variation in social behavior remains critically important. Galanin has gained increased attention because of the demonstration that galanin neurons in the preoptic area (POA) promote mating and parental care in mammals. How widespread these mechanisms are among vertebrates essentially remains unexplored, especially among teleost fishes, which comprise nearly one-half of living vertebrate species.

Galanin immunoreactivity is sexually polymorphic in neuroendocrine and vocal-acoustic systems in a teleost fish.

Galanin is a peptide that regulates pituitary hormone release, feeding, and reproductive and parental care behaviors. In teleost fish, increased galanin expression is associated with territorial, reproductively active males. Prior transcriptome studies of the plainfin midshipman (Porichthys notatus), a highly vocal teleost fish with two male morphs that follow alternative reproductive tactics, show that galanin is upregulated in the preoptic area-anterior hypothalamus (POA-AH) of nest-holding, courting type I males during spawning compared to cuckolding type II males.

Co-opting evo-devo concepts for new insights into mechanisms of behavioural diversity.

We propose that insights from the field of evolutionary developmental biology (or 'evo-devo') provide a framework for an integrated understanding of the origins of behavioural diversity and its underlying mechanisms. Towards that goal, in this Commentary, we frame key questions in behavioural evolution in terms of molecular, cellular and network-level properties with a focus on the nervous system. In this way, we highlight how mechanistic properties central to evo-devo analyses - such as weak linkage, versatility, exploratory mechanisms, criticality, degeneracy, redundancy and modularity - affect neural circuit function and hence the range of behavioural variation that can be filtered by selection.

FoxP2 Expression in a Highly Vocal Teleost Fish with Comparisons to Tetrapods.

Motivated by studies of speech deficits in humans, several studies over the past two decades have investigated the potential role of a forkhead domain transcription factor, FoxP2, in the central control of acoustic signaling/vocalization among vertebrates. Comparative neuroanatomical studies that mainly include mammalian and avian species have mapped the distribution of FoxP2 expression in multiple brain regions that imply a greater functional significance beyond vocalization that might be shared broadly across vertebrate lineages. To date, reports for teleost fish have been limited in number and scope to nonvocal species.

Inhibitory and modulatory inputs to the vocal central pattern generator of a teleost fish.

Vocalization is a behavioral feature that is shared among multiple vertebrate lineages, including fish. The temporal patterning of vocal communication signals is set, in part, by central pattern generators (CPGs). Toadfishes are well-established models for CPG coding of vocalization at the hindbrain level.

"Singing" Fish Rely on Circadian Rhythm and Melatonin for the Timing of Nocturnal Courtship Vocalization.

The patterning of social acoustic signaling at multiple timescales, from day-night rhythms to acoustic temporal properties, enhances sender-receiver coupling and reproductive success [1-8]. In diurnal birds, the nocturnal production of melatonin, considered the major vertebrate timekeeping hormone [9, 10], suppresses vocal activity but increases song syllable duration over circadian and millisecond timescales, respectively [11, 12]. Comparable studies are lacking for nocturnal vertebrates, including many teleost fish species that are also highly vocal during periods of reproduction [4, 13-20].