@article {670, title = {Gene expression correlates and mechanistic insights into electric organ discharge duration changes in mormyrid electric fish}, journal = {Journal of Experimental Biology}, volume = {228}, year = {2025}, month = {Jun-01-2025}, abstract = {

Electric organ discharge (EOD) duration in African weakly electric fish (Mormyridae) is the most variable waveform component between species and the basis for distinguishing species-specific signals. EOD duration is thought to be influenced by morphological and physiological features of electrocytes (the cells that comprise the electric organ), but the mechanistic details are poorly understood. It has long been known that EOD duration is modulated by androgen hormones, affording an opportunity to identify gene expression correlates of EOD duration differences. We induced EOD elongation in the mormyrid Brienomyrus brachyistius by administering 17\α-methyltestosterone (17\αMT) to three treatment groups: control (no 17\αMT exposure), T1day and T8day (samples taken 1 and 8 days after a single exposure to 17\αMT, respectively). We then performed RNAseq, differential gene expression and functional enrichment analysis to detect gene expression changes during EOD duration change. Our analyses indicate 44 genes whose expression changed in tandem with EOD elongation and include genes responsible for actin filaments and microtubules, extracellular matrix organization and membrane lipid metabolism. Additionally, we found expression changes in one Na+ channel \β-subunit, and five voltage-gated K+ channels. Together, these genes point toward specific cellular processes that contribute to morphological and physiological changes that contribute to EOD duration changes.

}, keywords = {Androgen hormones, electrocyte, K+ channel, Na+ channel, Testosterone}, issn = {0022-0949, 1477-9145}, doi = {10.1242/jeb.249548}, url = {https://doi.org/10.1242/jeb.249548}, author = {Losilla, Mauricio and Gallant, Jason R.} } @article {665, title = {Distribution, abundance, size and feeding habits of Brienomyrus brachyistius (Gill, 1862) (Teleostei: Mormyridae) in a Nigerian rainforest stream}, journal = {Cybium}, volume = {13}, year = {1989}, pages = {25-36}, chapter = {25}, abstract = {

Brienomyrus brachyistius (Gill, 1862) constitutes 64\% of the total number of all mormyrid species caught from the upper and middle reaches of Ikpa River in the rainforest zone of south-eastern Nigeria. It inhabits shallow marginal areas and swamp-pools with aquatic macrophytes. B. brachyistius\ feeds primarily on benthic invertebrates (with chironomid larvae predominating), algae, detritus and secondarily on zooplankton, miscellaneous invertebrates and mud/sans; allochthonous invertebrates and macrophyte material are of incidental importance. The diet varies slightly with growth and season. Feeding activity is higher in the small-sized guild (\< 10 cm TL) than large-sized guild (\≥ 10 cm TL); it is intense at night but declines during the day and is higher in the dry season than during the rains. Seasonal fluctuations in hydrometeorological regimes (rainfall, water level, flow rate) are critical factors that affect the food and feeding habits of the fish; flood has a depressive influence on food variety and feeding intensity.

}, keywords = {Brienomyrus brachyistius, ecology, Hydrometeological regimes, Ikpa River, Mormyridae, Nigeria}, doi = {10.26028/cybium/1989-131-003}, url = {https://doi.org/10.26028/cybium/1989-131-003}, author = {King, R.P.} } @article {620, title = {The Complete Genome Sequences of 38 Species of Elephantfishes (Mormyridae, Osteoglossiformes)}, year = {2022}, month = {Nov-21-2022}, abstract = {

We present the complete genome sequences of 38 species of elephantfishes from 20 genera. Illumina sequencing was performed on genetic material from single wild-caught individuals. The reads were assembled using a de novo method followed by a finishing step. The raw and assembled data is publicly available via Genbank.

}, issn = {2687-7945}, doi = {10.56179/001c.56077}, url = {http://dx.doi.org/10.56179/001c.56077}, author = {Rose Peterson and John P Sullivan and Stacy Pirro} } @article {537, title = {Behavioral and Single-Neuron Sensitivity to Millisecond Variations in Temporally Patterned Communication Signals}, journal = {Journal of Neuroscience}, volume = {36}, year = {2016}, month = {Feb-16-20162220}, pages = {8985 - 9000}, abstract = {

In many sensory pathways, central neurons serve as temporal filters for timing patterns in communication signals. However, how a population of neurons with diverse temporal filtering properties codes for natural variation in communication signals is unknown. Here we addressed this question in the weakly electric fish Brienomyrus brachyistius, which varies the time intervals between successive electric organ discharges to communicate. These fish produce an individually stereotyped signal called a scallop, which consists of a distinctive temporal pattern of \∼8\–12 electric pulses. We manipulated the temporal structure of natural scallops during behavioral playback and in vivo electrophysiology experiments to probe the temporal sensitivity of scallop encoding and recognition. We found that presenting time-reversed, randomized, or jittered scallops increased behavioral response thresholds, demonstrating that fish\&$\#$39;s electric signaling behavior was sensitive to the precise temporal structure of scallops. Next, using in vivo intracellular recordings and discriminant function analysis, we found that the responses of interval-selective midbrain neurons were also sensitive to the precise temporal structure of scallops. Subthreshold changes in membrane potential recorded from single neurons discriminated natural scallops from time-reversed, randomized, and jittered sequences. Pooling the responses of multiple neurons improved the discriminability of natural sequences from temporally manipulated sequences. Finally, we found that single-neuron responses were sensitive to interindividual variation in scallop sequences, raising the question of whether fish may analyze scallop structure to gain information about the sender. Collectively, these results demonstrate that a population of interval-selective neurons can encode behaviorally relevant temporal patterns with millisecond precision.

SIGNIFICANCE STATEMENT The timing patterns of action potentials, or spikes, play important roles in representing information in the nervous system. However, how these temporal patterns are recognized by downstream neurons is not well understood. Here we use the electrosensory system of mormyrid weakly electric fish to investigate how a population of neurons with diverse temporal filtering properties encodes behaviorally relevant input timing patterns, and how this relates to behavioral sensitivity. We show that fish are behaviorally sensitive to millisecond variations in natural, temporally patterned communication signals, and that the responses of individual midbrain neurons are also sensitive to variation in these patterns. In fact, the output of single neurons contains enough information to discriminate stereotyped communication signals produced by different individuals.

}, issn = {0270-6474}, doi = {10.1523/JNEUROSCI.0648-16.2016}, url = {http://www.jneurosci.org/cgi/doi/10.1523/JNEUROSCI.0648-16.2016}, author = {Baker, C. A. and Ma, L. and Casareale, C. R. and Bruce A Carlson} }