Biology subjects

Bass, A. H.

Publications and source records attributed to Bass, A. H..

6 recordsLinked to original sources

bioRxiv2026

Atlas of adult Danionella fish telencephalon reveals retention of larval characters

The adult size of the vertebrate telencephalon typically impedes our interpreting its functions within the context of brain-wide circuit dynamics. Danionella, a genus of miniature and transparent teleost fishes closely related to zebrafish (Danio rerio), holds promise for whole-brain imaging and connectomics in an adult vertebrate. These advantages result from progenesis, a form of heterochrony characterized by early developmental onset of sexual maturation and cessation of growth leading to the retention of larval or juvenile characters in adults. Using molecular markers, tract tracing, and quantitative comparisons of cellular distribution patterns, we report a detailed neuroanatomical atlas of the adult Danionella dracula (Dracula fish) telencephalon. The results demonstrate that adults of Dracula fish and other Danionella species show extreme reduction in cellular migration from periventricular zones and topographic reorganization of major pallial divisions, including a compartment-like caudal pallium reminiscent of insect glomeruli (a dense neuropil surrounded by a thin layer of somata). We further document these characters in larval zebrafish, providing essential evidence corroborating a larval-like telencephalon in Danionella adults. Despite this phenotype, most canonical regions of the adult teleost telencephalon are identified. We also generate a transgenic GCaMP Dracula fish line, an annotated 3-dimensional atlas, and align functional imaging data to demonstrate the usefulness of this atlas as a resource for deciphering how the novel progenetic cytoarchitecture of the adult Danionella telencephalon can support its rich behavioral repertoire.

neuroscience↗

bioRxiv2024

Label-free multiphoton imaging reveals volumetric shifts across development in sensory-related brain regions of a miniature transparent vertebrate

Animals integrate information from different sensory modalities as they mature and perform increasingly complex behaviors. This may parallel differential investment in specific brain regions depending on the demands of changing sensory inputs. To investigate developmental changes in the volume of canonical sensory integration brain regions, we used third harmonic generation imaging for morphometric analysis of forebrain and midbrain regions from 5 to 90 days post fertilization (dpf) in Danionella dracula, a transparent, miniature teleost fish whose brain is optically accessible throughout its lifespan. Relative to whole brain volume, increased volume or investment in telencephalon, a higher order sensory integration center, and torus longitudinalis (TL), a midbrain visuomotor integration center, is relatively consistent from 5 to 30 dpf, until it increases at 60 dpf, followed by another increase at 90 dpf, as animals reach adulthood. In contrast, investment in midbrain optic tectum (TeO), a retinal-recipient target, progressively decreases from 30-90 dpf, whereas investment is relatively consistent across all stages for the midbrain torus semicircularis (TS), a secondary auditory and mechanosensory lateral line center, and the olfactory bulb (OB), a direct target of the olfactory epithelium. In sum, increased investment in higher order integration centers (telencephalon, TL) occurs as juveniles reach adulthood and exhibit more complex cognitive tasks, whereas investment in modality-dominant regions occurs in earlier stages (TeO) or is relatively consistent across development (TS, OB). Complete optical access throughout Danionellas lifespan provides a unique opportunity to investigate how changing brain structure over development correlates with changes in connectivity, microcircuitry, or behavior.

neuroscience↗

bioRxiv2021

Whole-brain optical access in small adult vertebrates with two- and three-photon microscopy

Although optical microscopy has allowed us to study the entire brain in early developmental stages, access to the brains of live, adult vertebrates has been limited. Danionella, a genus of miniature, transparent fish closely related to zebrafish has been introduced as a neuroscience model to study the entire adult vertebrate brain. However, the extent of optically accessible depth in these animals has not been quantitatively characterized. Here, we show that two- and three-photon microscopy can be used to access the entire depth of the adult wild type Danionella dracula brain without any modifications to the animal other than mechanical stabilization. Three-photon microscopy provides high signal to background ratio and optical sectioning through the deepest part of the brain. While vasculature can be observed with two-photon microscopy, the deeper regions have low contrast. We show that multiphoton microscopy is ideal for readily penetrating the entire adult brain within the geometry of these animals head structures and without the need for pigment removal. With multiphoton microscopy enabling optical access to the entire adult brain and a repertoire of methods that allow observation of the larval brain, Danionella provides a model system for readily studying the entire brain over the lifetime of a vertebrate.

neuroscience↗

bioRxiv2021

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

Acoustic communication is widespread across vertebrates, including among fishes. We report robust acoustic displays during aggressive interactions for a laboratory colony of Danionella dracula, a relatively recently discovered miniature and transparent species of teleost fish closely related to zebrafish (Danio rerio). Males produce bursts of pulsatile, click-like sounds and a distinct postural display, extension of a hypertrophied lower jaw, during aggressive but not courtship interactions. Females lack a hypertrophied lower jaw and show no evidence of sound production or jaw extension in such contexts. Novel pairs of size-matched or -mismatched males were combined in resident-intruder assays where sound production and jaw extension could be linked to individuals. Resident males produce significantly more sound pulses and extend their jaw more often than intruders in both dyad contexts, and relatively larger males are significantly more sonic and exhibit more jaw extensions in size-mismatched pairs. The majority of highest sound producers in both contexts also show increased jaw extension during periods of heightened sonic activity. These studies firmly establish D. dracula as a sound-producing species that modulates both acoustic and postural displays during aggressive interactions based on either residency or body size, providing a foundation for further investigating the role of multimodal displays in a new model clade for neurogenomic studies of aggression, courtship, and other social interactions.

animal behavior and cognition↗

bioRxiv2020

Gap junction mediated feed-forward inhibition ensures ultra 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 signalling. We show that extreme temporal precision in motoneuronal firing within a hindbrain network that directly determines call duration, pulse repetition rate and fundamental frequency in a teleost fish, the Gulf toadfish, depends on gap junction-mediated, feed-forward glycinergic inhibition that generates a period of reduced probability of motoneuron activation. Super-resolution microscopy confirms glycinergic release sites contacting motoneuron somata and dendrites. Synchronous motoneuron activity can also induce action potential firing in pre-motoneurons, a feature that could figure prominently into motor timing. Gap junction-mediated, feed-forward glycinergic inhibition provides a novel means for achieving temporal precision in the millisecond range for rapid modulation of an acoustic signal and perhaps other motor behaviors.

neuroscience↗

bioRxiv2018

Antioxidant Gene Expression in Vocal Hindbrain of a Teleost Fish

Plainfin midshipman fish (Porichthys notatus) have a remarkable capacity to generate long duration advertisement calls known as hums, each of which may last for close to two hours and be repeated throughout a night of courtship activity during the breeding season. The midshipmans striking sound production capabilities provide a unique opportunity to investigate the mechanisms that motor neurons require for withstanding high-endurance activity. The temporal properties of midshipman vocal behaviors are largely controlled by a hindbrain central pattern generator that includes vocal motor neurons (VMN) that directly determine the activity pattern of target sonic muscles and, in turn, a sounds pulse repetition rate, duration and pattern of amplitude modulation. Of the two adult midshipman male reproductive phenotypes -- types I and II-- only type I males acoustically court females with hums from nests that they build and guard, while type II males do not produce courtship hums but instead sneak or satellite spawn to steal fertilizations from type I males. A prior study using next generation RNA sequencing showed increased expression of a number of cellular respiration and antioxidant genes in the VMN of type I males during the breeding season, suggesting they help to combat potentially high levels of oxidative stress linked to this extreme behavior. This led to the question of whether the expression of these genes in the VMN would vary between actively humming versus non-humming states as well as between male morphs. Here, we tested the hypothesis that to combat oxidative stress, the VMN of reproductively active type I males would exhibit higher mRNA transcript levels for two superoxide dismutases (sod1, sod2) compared to the VMN of type II males and females that do not hum and in general both of which have a more limited vocal repertoire than type I males. The results showed no significant difference in sod1 transcript expression across reproductive morphs in the VMN and the surrounding hindbrain, and no difference of sod2 across the two male morphs and females in the SH. However, we observed a surprising, significantly lower expression of sod2 transcripts in the VMN of type I males as compared to type II males. We also found no significant difference in sod1 and sod2 expression between actively humming and non-humming type I males in both the VMN and surrounding hindbrain. These findings overall lead us to conclude that increased transcription of sod1 and sod2 is not necessary for combatting oxidative stress from the demands of the midshipman high-endurance vocalizations, but warrant future studies to assess protein levels, enzyme activity levels, as well as the expression of other antioxidant genes. These results also eliminate one of the proposed mechanisms that male midshipman use to combat potentially high levels of oxidative stress incurred by motor neurons driving long duration vocalization and provide more insight into how motor neurons are adapted to the performance of extreme behaviors.

neuroscience↗