Biology subjects

Beron de Astrada, M.

Publications and source records attributed to Beron de Astrada, M..

5 recordsLinked to original sources

bioRxiv2026

Ontogenetic expansion and regionalization of the triatomine compound eye supports flight-related vision

Triatomines are the vectors of Chagas disease, one of the main endemic diseases from South to North America, now expanding to other continents. These hemimetabolous insects have been considered poorly visual animals. However, recent findings challenge this idea. Here, we used Rhodnius prolixus as a model species to comprehensively characterize triatomine compound eyes. We found that in the adult stage, eye size significantly exceeds the dimensions predicted by the nymphal eye growth rate. Moreover, while the compound eye grows symmetrically in its dorsal and ventral directions throughout the nymphal instars, in the adult, the eye undergoes greater ventral growth, resulting in a dorsoventrally asymmetrical eye. By studying a bright pseudopupil induced by fluorescence in natural mutant animals, we observed no major differences in sampling resolution between the last nymphal instar and the adult stage. However, the adult eye possesses significantly larger ommatidia, particularly in its ventral region, shifting the area of highest sensitivity from the equatorial region in the nymphal instars to the ventral region in the adult. A similar eye growth pattern was observed in Triatoma infestans and Panstrongylus megistus. The analysis of photographic records from 39 species across 10 genera indicates that an asymmetrical eye is the predominant eye pattern in adult triatomines. Notable exceptions in wingless adults of Mepraia spinolai, reveal a tight association between possessing a large asymmetrical eye and the presence of wings. This suggests that vision might support triatomine dispersal flights among other visual behaviors. Significance StatementKissing bugs are hematophagous insects known for being the vectors of Chagas disease, one of the main endemic diseases in the Americas. Vision was not considered a relevant sensory system in these insects. Here, we show that their eyes increase in size beyond expected by ontogeny and become asymmetrical when transitioning from the last nymphal instar to the adult stage. The eyes undergo a ventral expansion that shifts the region of greatest light sensitivity from the equatorial zone in nymphs to the ventral region in adults. We found this asymmetrical eye only in winged kissing bugs, suggesting that vision supports flight. This is relevant in ecological and epidemiological terms since kissing bugs disperse by flight for habitat colonization and host-seeking.

neuroscience↗

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

Stimulus contrast information modulates sensorimotor decision making in goldfish

Animal survival relays on environmental information gathered by their sensory systems. We found that contrast information of a looming stimulus biases the type of defensive behavior goldfish (Carassius auratus) perform. Low contrast looms only evoke subtle alarm reactions whose probability is independent of contrast. As looming contrast increases, the probability of eliciting a fast escape maneuver, the C-start response, increases dramatically. Contrast information also modulates the decision of when to escape. Although looming retinal size is determinant of response latency, we found that contrast acts as an additional parameter influencing this decision. When presented progressively higher contrast stimuli, animals need shorter periods of stimulus integration to initiate the response. Our results comply the notion that the decision to escape is a flexible process initiated with stimulus detection and followed by assessment of the perceived risk posed by the stimulus. Highly disruptive behaviors as the C-start are only observed when a multifactorial threshold that includes stimulus contrast is surpassed. Summary statementThis study highlights that in fish, the decision of what to do after threat detection is a multifactorial non-binary process that includes assessing the relative contrast of the potential threat. Increasingly higher contrast stimuli produce a progressive increase in C-start escape probability and a decrease in response latency. More subtle alarm reactions are, on the contrary, mostly insensitive to changes in contrast. This might reflect that while subtle reactions have lower thresholds to be executed, disruptive behaviors as the C-start must surpass higher saliency thresholds that integrate multiple aspects including contrast.

neuroscience↗

bioRxiv2018

Polarized light information modulates sensorimotor decision making in goldfish

Animal survival relays on environmental information gathered by their sensory systems. In invertebrates the polarization angle of light is known to provide vital information for a wide range of visual tasks. However, the role of polarization sensitivity in vertebrates remains poorly understood. Here we study if polarization vision enhances threat detection in goldfish. We found that adding a polarization cue to a low intensity contrast looming stimulus biases the type of evasive behavior the animals perform. While low contrast looms mostly evoke subtle alarm reactions, the addition of a polarized cue dramatically increases the probability of eliciting a fast escape maneuver, the C-start response. Goldfish can be startled by polarized light stimuli coming not only from above but also from the sides indicating that polarization sensitivity spans large areas of the retina. In addition, we observed that while low intensity contrast looms preferentially elicit alarm behaviours, high intensity contrast looms rarely induced them, but elicited C-start responses with a high probability. Together, our results show that the addition of a polarized light cue to a low intensity contrast stimulus shifts animals decision making from low threshold alarm responses to the higher threshold C-start escape behaviour. This additional visual cue, thus, might aid underwater threat detection and predator avoidance in the animals natural environment. Summary statementThis study gives the first compelling evidence that fish can use polarized light information to improve their decision making in the context of visual threat detection.

neuroscience↗