Biology subjects

Barrozo, R. B.

Publications and source records attributed to Barrozo, R. B..

6 recordsLinked to original sources

bioRxiv2026

Automated analysis of feeding dynamics from electromyographic recordings in a blood-sucking insect

Feeding behavior in blood-sucking insects relies on gustatory evaluation to decide on sustained ingestion, yet quantifying this process from electromyogram (EMG) recordings is labor-intensive. Here we developed MyoRec, an automated computational framework employing machine learning to analyse EMG signals from the triatomine bug Rhodnius prolixus. Using recordings under appetitive and aversive conditions, a convolutional neural network detected ingestion events with 97.7% accuracy. Automated analysis revealed distinct feeding dynamics, with prolonged ingestion and higher pumping frequency under appetitive stimuli, compared to rapid feeding cessation under aversive stimuli. MyoRec substantially reduces analysis time while maintaining accuracy, providing a scalable tool to investigate how gustatory cues modulate feeding decisions in hematophagous insects.

zoology↗

bioRxiv2026

Subjective rather than absolute reward value determines long-term memory formation in honey bees

How animals evaluate reward quality is a fundamental question in neuroscience and behavioral biology. Here we show that in honey bees (Apis mellifera), the value of a sucrose reward is not processed in absolute terms but relative to prior experience, and that this subjective evaluation strongly influences long-term memory formation. Using appetitive olfactory conditioning of the proboscis extension reflex (PER), we demonstrate that memory performance is determined by the contrast between a previously experienced reward and the reward used during training, rather than by the absolute concentration of sucrose received. This effect operates across multiple timescales, from contrasts between successive trials within a single session to differences between rewards experienced 24 hours apart. We further show that prior exposure to sucrose solutions of different concentrations modulates gustatory responsiveness and alters the sensitivity of antennal gustatory receptor neurons, suggesting that peripheral sensory plasticity contributes to experience-dependent changes in reward evaluation. Dissociating pre- and post-ingestive reward components revealed that the contrast between the sucrose concentration sensed by the antennae and the concentration ingested is sufficient to modulate memory formation. Together, our results indicate that bees form an internal expectation of reward quality based on experience, and that this expectation rescales the perceived value of subsequent rewards, thereby shaping associative memory strength. These findings provide a mechanistic framework for understanding how invertebrates perform relative reward comparisons across multiple temporal scales, with implications for flexible foraging strategies in dynamic environments.

neuroscience↗

bioRxiv2023

Mosquitoes do not like bitter: new perspectives for biorational repellents

Chemical repellents play a crucial role in personal protection, serving as essential elements in reducing the transmission of vector-borne diseases. A biorational perspective that extends beyond the olfactory system as the classical target may be a promising direction to move. The taste system provides reliable information regarding food quality, helping animals discriminate between nutritious and potentially harmful food sources, often associated with a bitter taste. Understanding how bitter compounds affect feeding in blood-sucking insects could unveil novel molecules with the potential to reduce biting and feeding. Here, we investigated the impact of two naturally occurring bitter compounds, caffeine and quinine, on the feeding decisions in female Aedes aegypti mosquitoes at two distinctive phases: (1) when the mosquito explores the biting substrate using external taste sensors and (2) when the mosquito takes a sip of food and tastes it using internal taste receptors. We assessed the aversiveness of bitter compounds through both an artificial feeding condition (artificial feeder test) and a real host (arm-in-cage test). Our findings revealed different sensitivities in the external and internal sensory pathways responsible for detecting bitter taste in Ae. aegypti. Internal detectors exhibited responsiveness to lower doses compared to the external sensors. Quinine exerted a more pronounced negative impact on biting and feeding activity than caffeine. The implications of our findings are discussed in the context of mosquito food recognition and the potential practical implications for personal protection.

zoology↗

bioRxiv2022

Food recognition in a blood-feeding insect: characterization of the pharyngeal taste organ

BackgroundObligate blood-feeding insects obtain the nutrients and water necessary to ensure survival from the vertebrate blood. The internal taste sensilla, situated in the pharynx, evaluate the suitability of the ingested food. Here, through multiple approaches, we characterized the pharyngeal organ (PO) of the hematophagous kissing bug Rhodnius prolixus to determine its role in food assessment. The PO, located antero-dorsally in the pharynx, comprises 8 taste sensilla that become bathed with the incoming blood. ResultsWe showed that these taste sensilla house gustatory receptor neurons projecting their axons through the labral nerves to reach the subesophageal zone in the brain. We found that these neurons are electrically activated by relevant appetitive and aversive gustatory stimuli such as NaCl, ATP and caffeine. Using RNA-Seq, we examined the expression of sensory-related gene families in the PO. We identified gustatory receptors, ionotropic receptors, transient receptor potential channels, pickpocket channels, opsins, takeouts, neuropeptide precursors, neuropeptide receptors and biogenic amine receptors. RNA interference assays demonstrated that the pickpocket channel Rproppk014276 is necessary for salt detection during feeding. ConclusionWe provide evidence of the role of the pharyngeal organ in food evaluation. This work shows the first comprehensive characterization of a pharyngeal taste organ in a hematophagous insect.

neuroscience↗

bioRxiv2021

Salty surfaces deter feeding in a blood-sucking disease vector

Salts are essential nutrients required for many physiological processes, and deficient or excessive salt results in adverse health problems. Taste is the ultimate sensory modality involved in resource quality assessment, resulting in acceptance or rejection. Here, we show that detection of high-salt substrates by a salt-sensitive antennal gustatory receptor neuron, S1-GRN, results in feeding avoidance in the hematophagous bug Rhodnius prolixus. Knock-down of two antennal-expressed amiloride-sensitive pickpocket channel receptors (PPKs; RproPPK014276 and RproPPK28) using RNA interference, prevents avoidance of bugs to high-salt substrates. Tracing antennal GRNs to the central nervous system reveals the antennal lobes as a gustatory processing center. The identification of the gustatory basis of high-salt detection in a blood feeder provides novel targets to prevent biting and feeding, as well as to promote substrate avoidance in a relevant disease vector. Significance StatementDetection of aversive gustatory stimuli induces avoidance responses in animals. Avoidance acquires particular interest if it reduces the biting rates of blood-feeding insects of medical relevance. Here we describe the molecular and physiological basis of high-salt detection in the blood-sucking disease vector Rhodnius prolixus. We show that detection of high-salt substrates through two PPK receptors expressed in an antennal gustatory receptor neuron produces feeding avoidance. Understanding these gustatory-driven aversive responses allows the hitherto overlooked use of gustatory molecules as a complement to known olfactory repellents.

physiology↗

bioRxiv2019

Perception of aversive stimuli of different gustatory modalities in an haematophagous insect, Rhodnius prolixus.

Sensory aversion is an essential link for avoiding potential dangers. Here, we studied the chemical perception of aversive compounds of different gustatory modalities (salty and bitter) in the haematophagous kissing bug, Rhodnius prolixus. Over a walking arena, insects preferred a substrate embedded with 0.3 M NaCl or KCl rather than with distilled water. Same salts were avoided when prepared at 1 M. When NaCl and KCl were confronted, no preferences were evinced by insects. A pre-exposure to amiloride interfered with the repellency of NaCl and KCl equally, suggesting that amiloride-sensitive receptors are involved in the detection of both salts. Discriminative experiments were then performed to determine if R. prolixus can distinguish between these salts. An aversive operant conditioning involving either NaCl or KCl modulated the repellency of the conditioned salt, but also of the novel salt. A chemical pre-exposure to the salts did not to modify their repellency levels. When we crossed gustatory modalities by confronting NaCl to caffeine (i.e. a bitter stimulus) no innate preferences were evinced. Aversive operant conditionings with either NaCl or Caf rendered unspecific changes in the repellency of both compounds. A chemical pre-exposure to Caf modulated the response to Caf but not to NaCl, suggesting the existence of two independent neural pathways for the detection of salts and bitter compounds. Overall results suggest that R. prolixus cannot distinguish between NaCl and KCl but can distinguish between NaCl and Caf and generalizes the response between these two aversive stimuli of different gustatory modality.\n\nSummary statementKissing-bugs use contact chemo-perception to avoid aversive substrates. They can sensory distinguish between salty (sodium chloride) and bitter (caffeine) tastes, but not between different salts (sodium and potassium chloride).

animal behavior and cognition↗