Salience of multisensory feedback regulates behavioral variability

Many animal behaviors are robust to dramatic variations in morphophysiological features, both across and within individuals. The control strategies that animals use to achieve such robust behavioral performances are not known. Recent evidence suggests that animals rely on sensory feedback rather than precise tuning of neural controllers for robust control. Here we examine the structure of sensory feedback, including multisensory feedback, for robust control of animal behavior. We re-examined two recent datasets of refuge tracking responses of Eigenmannia virescens, a species of weakly electric fish. Eigenmannia rely on both the visual and electrosensory cues to track the position of a moving refuge. The datasets include experiments that varied the strength of visual and electrosensory signals. Our analyses show that increasing the salience (perceptibility) of visual or electrosensory signals resulted in more robust and precise behavioral responses. Further, we find that robust performance was enhanced by multisensory integration of simultaneous visual and electrosensory cues. These findings suggest that engineers may achieve better system performance by improving the salience of multisensory feedback rather than solely focusing on precisely tuned controllers.

Spike-frequency dependent coregulation of multiple ionic conductances in fast-spiking cells forces a metabolic tradeoff

ABSTRACTHigh-frequency action potentials (APs) allow rapid information acquisition and processing in neural systems, but create biophysical and metabolic challenges for excitable cells. The electric fish Eigenmannia virescens images its world and communicates with high-frequency (200-600 Hz) electric organ discharges (EODs) produced by synchronized APs generated at the same frequency in the electric organ cells (electrocytes). We cloned three previously unidentified Na+-activated K+ channel isoforms from electroctyes (eSlack1, eSlack2, and eSlick1). In electrocytes, mRNA transcript levels of the rapidly-activating eSlick, but not the slower eSlack1 or eSlack2, correlated with EOD frequency across individuals. In addition, transcript levels of an inward-rectifier K+ channel, a voltage-gated Na+ channel, and Na+,K+-ATPases also correlated with EOD frequency while a second Na+ channel isoform did not. Computational simulations showed that maintaining electrocyte AP waveform integrity as firing rates increase requires scaling conductances in accordance with these mRNA expression correlations, causing AP metabolic costs to increase exponentially.

Dieta de sarapós da família sternopygidae em ambientes de praia no Rio Negro, Amazonas

Os ambientes de praia na Amazônia Central ocorrem de forma aparente nas margens de rios, paranás e lagos, através da alternância do nível da água, que ocorre a partir do ciclo hidrológico, surgindo durante a fase estacional terrestre mais conhecida como os períodos de vazante e seca. Estes habitats proporcionam abrigo e fonte de alimentação para uma diversa e abundante ictiofauna, dentre as espécies de peixes que habitam os ambientes de praias destacam-se os peixes da ordem Gymnotiformes, os quais são conhecidos popularmente como sarapós ou peixes elétricos, sendo este último, devido a capacidade de gerar uma corrente de carga elétrica para eletrolocação e interações sociais, principalmente para a família Sternopygidae, utilizada na presente pesquisa. Estudos acerca dos hábitos alimentares e dieta dos Gymnotiformes são escassos e, essa falta de conhecimento tanto pela história de vida, comportamento e ecologia são os principais pontos para o não entendimento das pesquisas realizadas, sendo assim, este estudo é primordial para a melhor compreensão dos hábitos alimentares das espécies Eigenmannia macrops, Eigenmannia trilineata e Eigenmannia virescens coletadas em praias do rio Negro. Foram analisados ao total 180 estômagos, 60 de cada espécie e todos apresentaram algum item alimentar, estando os estômagos parcialmente cheios (0-25%) até mesmo distendidos (75-100%) como se destacou para os espécimes de E. macrops. O item alimentar mais frequente foi o de inseto, seguido por material indefinido (digerido) e por fim o item material vegetal. A partir do IAi (%) pode-se classificar as espécies E. macrops (>70%) e E. virescens (>70%) na guilda trófica como insetívoras e E. trilineata como onívora com tendência a insetivoria. O valor calculado para amplitude de nicho trófico apresentou nível intermediário para E. trilineata e E. virescens e baixa para E. macrops, portanto tendo a maior dissimilaridade quanto aos itens consumidos. Quanto ao fator de condição, a espécie E. macrops demonstrou que estava em boas condições de bem-estar mesmo em período de seca, já as espécies E. trilineata e E. virescens apresentaram valores abaixo de zero, o que não as impossibilitou de explorar os recursos alimentares.

Variability in locomotor dynamics reveals the critical role of feedback in task control

Animals vary considerably in size, shape, and physiological features across individuals, but yet achieve remarkably similar behavioral performances. We examined how animals compensate for morphophysiological variation by measuring the system dynamics of individual knifefish (Eigenmannia virescens) in a refuge tracking task. Kinematic measurements of Eigenmannia were used to generate individualized estimates of each fish’s locomotor plant and controller, revealing substantial variability between fish. To test the impact of this variability on behavioral performance, these models were used to perform simulated ‘brain transplants’—computationally swapping controllers and plants between individuals. We found that simulated closed-loop performance was robust to mismatch between plant and controller. This suggests that animals rely on feedback rather than precisely tuned neural controllers to compensate for morphophysiological variability.

Variability in Locomotor Dynamics Reveals the Critical Role of Feedback in Task Control

Animals vary considerably in size, shape, and physiological features across individuals, but yet achieve behavioral performances that are virtually indistinguishable between conspecifics. We examined how animals compensate for morphophysiological variation by measuring the system dynamics of individual knifefish (Eigenmannia virescens) in a refuge tracking task. Kinematic measurements of Eigenmannia were used to generate individualized estimates of each fish’s locomotor plant and controller revealing substantial variability between fish. To test the impact of this variability on behavioral performance, these models were used to perform simulated ‘brain transplants’—computationally swapping controllers and plants between individuals. We found that simulated closed-loop performance was robust to mismatch between plant and controller. This suggests that animals rely on feedback rather than precisely tuned neural controllers to compensate for morphophysiological variability.

Closed-Loop Control of Active Sensing Movements Regulates Sensory Slip

SummaryActive sensing involves the production of motor signals for the purpose of acquiring sensory information [1–3]. The most common form of active sensing, found across animal taxa and behaviors, involves the generation of movements—e.g. whisking [4–6], touching [7,8], sniffing [9,10], and eye movements [11]. Active-sensing movements profoundly affect the information carried by sensory feedback pathways [12–15] and are modulated by both top-down goals (e.g. measuring weight vs. texture [1,16]) and bottom-up stimuli (e.g. lights on/off [12]) but it remains unclear if and how these movements are controlled in relation to the ongoing feedback they generate. To investigate the control of movements for active sensing, we created an experimental apparatus for freely swimming weakly electric fish, Eigenmannia virescens, that modulates the gain of reafferent feedback by adjusting the position of a refuge based on real time videographic measurements of fish position. We discovered that fish robustly regulate sensory slip via closed-loop control of active-sensing movements. Specifically, as fish performed the task of maintaining position inside the refuge [17–22], they dramatically up- or down-regulated fore-aft active-sensing movements in relation to a 4-fold change of experimentally modulated reafferent gain. These changes in swimming movements served to maintain a constant magnitude of sensory slip. The magnitude of sensory slip depended on the presence or absence of visual cues. These results indicate that fish use two controllers: one that controls the acquisition of information by regulating feedback from active sensing movements, and another that maintains position in the refuge, a control structure that may be ubiquitous in animals [23,24].

DNA BARCODING IKAN HIAS INTRODUKSI

Identifikasi spesies menjadi tantangan dalam pengelolaan ikan hias introduksi baik untuk tujuan budidaya maupun konservasi. Penelitian ini bertujuan untuk melakukan identifikasi molekuler ikan hias introduksi yang beredar di pembudidaya dan pasar ikan hias Indonesia dengan menggunakan barcode DNA gen COI. Sampel ikan diperoleh dari pembudidaya dan importir ikan hias di kawasan Bandung dan Jakarta. Total DNA diekstraksi dari jaringan sirip ekor dengan menggunakan metode kolom. Amplifikasi gen target dilakukan dengan menggunakan primer FishF1, FishF2, FishR1, dan FishR2. Hasil pembacaan untai DNA disejajarkan dengan sekuen yang terdapat pada genbank melalui program BLAST. Identifikasi dilakukan melalui kekerabatan pohon filogenetik dan presentasi indeks kesamaan dengan sekuen genbank. Hasil identifikasi menunjukkan sampel yang diuji terbagi menjadi lima grup, yaitu: Synodontis terdiri atas lima spesies, Corydoras: empat spesies, Phseudoplatystoma: tiga spesies, Botia: tiga spesies, dan Leporinus: tiga spesies dengan nilai boostrap 99-100. Indeks kesamaan sekuen menunjukkan sebanyak 11 spesies memiliki indeks kesamaan 99%-100% dengan data genbank yaitu Synodontis decorus, Synodontis eupterus, Synodontis greshoffi, Botia kubotai, Botia lohachata, Rasbora erythromicron, Corydoras aeneus, Gyrinocheilus aymonieri, Eigenmannia virescens, Leporinus affinis, Phractocephalus hemioliopterus. Dua spesies teridentifikasi sebagai hasil hibridisasi (kawin silang) yaitu Leopard catfish (100% identik dengan Pseudoplatystoma faciatum) dan Synodontis leopard (100% identik dengan Synodontis notatus). Hasil analisis nukleotida penciri diperoleh tujuh nukleotida untuk Synodontis decora, 10 nukleotida untuk Synodontis tanganyicae, 13 nukleotida untuk Synodontis euterus, empat nukleotida untuk Synodontis notatus, dan 14 untuk Synodontis grashoffi. Kejelasan identifikasi spesies ikan menjadi kunci utama dalam budidaya, perdagangan, manajemen, konservasi, dan pengembangan ilmu pengetahuan.Species identification becomes a new challenge in the management of ornamental fish either for cultivation, or for conservation proposes. The objective of this study was to identify currently existing introduced ornamental fish in Indonesian farmers and markets using DNA barcodes COI gene. Fish samples were collected from farmers and importers of ornamental fish in Bandung and Jakarta. Total genome was extracted from caudal fin tissue using the column method. Amplification of the target gene was done by using FishF1, FishF2, FishR1, and FishR2 primers. DNA sequence was aligned with the sequences from genbank by BLAST program. Species identification was decided through the phylogenetic tree and similarity index with genbank sequences. The results showed that all of tested samples fall into five groups; Synodontis consisted of five species, Corydoras four species, Phseudoplatystoma four species, Botia three species, and Leporinus three species with 99-100 boostrap value. Sequence similarity index showed around 11 species have 99%-100% similarity index with sequence data on genbank which are Synodontis decorus, Synodontis eupterus, Synodontis greshoffi, Botia kubotai, Botia lohachata, Rasbora erythromicron, Corydoras aeneus, Gyrinocheilus aymonieri, Eigenmannia virescens, Leporinus affinis, Phractocephalus hemioliopterus. Two species were identified as hybridization product (interbreeding) including leopard catfish (100% identical with Pseudoplatystoma faciatum) and the leopard Synodontis (100% identical with Synodontis notatus). Analysis of nucleotide diagnostic showed Synodontis decora has seven nucleotides diagnostic, Synodontis tanganyicae 10 nucleotides, Synodontis euterus 13 nucleotides, Synodontis notatus four nucleotides, and Synodontis grashoffi 14 nucleotides. The correct identification of fish species is a useful tool for aquaculture, global marketing, management or conservation, and academic/scientific purpose.

Dynamic modulation of visual and electrosensory gains for locomotor control

Animal nervous systems resolve sensory conflict for the control of movement. For example, the glass knifefish, Eigenmannia virescens , relies on visual and electrosensory feedback as it swims to maintain position within a moving refuge. To study how signals from these two parallel sensory streams are used in refuge tracking, we constructed a novel augmented reality apparatus that enables the independent manipulation of visual and electrosensory cues to freely swimming fish ( n = 5). We evaluated the linearity of multisensory integration, the change to the relative perceptual weights given to vision and electrosense in relation to sensory salience, and the effect of the magnitude of sensory conflict on sensorimotor gain. First, we found that tracking behaviour obeys superposition of the sensory inputs, suggesting linear sensorimotor integration. In addition, fish rely more on vision when electrosensory salience is reduced, suggesting that fish dynamically alter sensorimotor gains in a manner consistent with Bayesian integration. However, the magnitude of sensory conflict did not significantly affect sensorimotor gain. These studies lay the theoretical and experimental groundwork for future work investigating multisensory control of locomotion.

A highly polarized excitable cell separates sodium channels from sodium-activated potassium channels by more than a millimeter

The bioelectrical properties and resulting metabolic demands of electrogenic cells are determined by their morphology and the subcellular localization of ion channels. The electric organ cells (electrocytes) of the electric fish Eigenmannia virescens generate action potentials (APs) with Na+ currents >10 μA and repolarize the AP with Na+-activated K+ (KNa) channels. To better understand the role of morphology and ion channel localization in determining the metabolic cost of electrocyte APs, we used two-photon three-dimensional imaging to determine the fine cellular morphology and immunohistochemistry to localize the electrocytes' ion channels, ionotropic receptors, and Na+-K+-ATPases. We found that electrocytes are highly polarized cells ∼1.5 mm in anterior-posterior length and ∼0.6 mm in diameter, containing ∼30,000 nuclei along the cell periphery. The cell's innervated posterior region is deeply invaginated and vascularized with complex ultrastructural features, whereas the anterior region is relatively smooth. Cholinergic receptors and Na+ channels are restricted to the innervated posterior region, whereas inward rectifier K+ channels and the KNa channels that terminate the electrocyte AP are localized to the anterior region, separated by >1 mm from the only sources of Na+ influx. In other systems, submicrometer spatial coupling of Na+ and KNa channels is necessary for KNa channel activation. However, our computational simulations showed that KNa channels at a great distance from Na+ influx can still terminate the AP, suggesting that KNa channels can be activated by distant sources of Na+ influx and overturning a long-standing assumption that AP-generating ion channels are restricted to the electrocyte's posterior face.