Biology subjects

Berthet, M.

Publications and source records attributed to Berthet, M..

4 recordsLinked to original sources

bioRxiv2026

Supra-regular recursion in primate vocal sequences

Complex syntax is the widely accepted demarcation between animal and human communication. Although animal vocal systems occasionally contain pockets of syntax-like structures, their grammars are thought to be at best regular, whereas human language is supra-regular, i.e., including at least context-free computational complexity. Leveraging a new likelihood method for probabilistic formal grammars, we show that the call sequences of three phylogenetically diverse nonhuman primates (bonobos, olive colobus monkeys, common marmosets) include parts that are most likely generated by supra-regular recursive grammars, similar to human language. These findings challenge syntax as the major transition in hominid evolution and opens up prospects for alternative evolutionary scenarios.

animal behavior and cognition↗

bioRxiv2025

An updated vocal repertoire of wild adult bonobos (Pan paniscus )

While research over the last 20 years has shed important light on the vocal behaviour of our closest living relatives, bonobos and chimpanzees, a quantitative description of their full vocal repertoire is absent. Such data are critical for a holistic understanding of a species communication system and unpacking how these systems compare more broadly with other primate and non-primate species. Here we make key progress by providing the first quantitative Pan vocal repertoire, specifically for wild bonobos. Using data comprising over 1500 calls from 53 adult individuals collected over 33 months, we employ machine-learning-based random forest analyses and describe 11 acoustically distinguishable call types. We discuss issues associated with resolving vocal repertoires from wild data in great apes and highlight potential future approaches to further capture the complexity of the bonobo vocal system.

animal behavior and cognition↗

bioRxiv2020

Do l'Hoest's monkeys show sensitivity to conspecifics' informational state?

A series of field studies in chimpanzees have shown that the examination of communicative behaviour (e.g. alarm calling) could be particularly fruitful to help uncover mind-reading abilities in non-human animals. In this study, we sought to extend communication-based protocols to one species of Cercopithecids. Specifically, we looked at whether social gazing behaviour of LHoests monkeys (Allochrocebus lhoesti) is sensitive to the informational state of conspecifics using an original experimental design, thereby focusing on their ability to represent conspecifics rather than human experimenters mental states. We presented a group of 11 zoo-housed monkeys with a box that contained either an appetitive (mealworms), aversive (raptor stuffed toy) or neutral stimulus (wood bark chips). The discoverer (the first individual that inspected the content of the box) emitted more social gazes in the aversive condition than in the neutral and appetitive conditions. Besides, social gazing was related to the informational state of the conspecifics in the appetitive and neutral conditions, with more social gazes directed towards informed individuals (who had inspected the box) rather than uninformed ones (who had not inspected the box yet). Additional examination of the behaviour of the discoverers revealed that they were likely addressing social gazes to individuals who were in close proximity to them, suggesting that they preferentially gaze at informed conspecifics because the latter remained in proximity. Our study calls for a more widespread assessment of mind-reading capacities in primates, to further reveal the evolutionary history of traits that were thought to be uniquely human until fairly recently.

animal behavior and cognition↗

bioRxiv2019

Midgut barriers prevent the replication and dissemination of the yellow fever vaccine in Aedes aegypti

BackgroundTo be transmitted to vertebrate hosts via the saliva of their vectors, arthropod-borne viruses have to cross several barriers in the mosquito body, including the midgut infection and escape barriers. Yellow fever virus (YFV) belongs to the genus Flavivirus, which includes human viruses transmitted by Aedes mosquitoes, such as Dengue and Zika viruses. The live-attenuated YFV-17D vaccine has been used safely and efficiently on a large scale since the end of World War II. Early studies have shown, using viral titration from salivary glands of infected mosquitoes, that YFV-17D can infect Aedes aegypti midgut, but does not disseminate to other tissues.\n\nMethodology/Principal FindingsHere, we re-visited this issue using a panel of techniques, such as RT-qPCR, Western blot, immunofluorescence and titration assays. We showed that YFV-17D replication was not efficient in Aedes aegypti midgut, as compared to the clinical isolate YFV-Dakar. Viruses that replicated in the midgut failed to disseminate to secondary organs. When injected into the thorax of mosquitoes, viruses succeeded in replicating into midgut-associated tissues, suggesting that, during natural infection, the block for YFV-17D replication occurs at the basal membrane of the midgut. Our NGS analysis revealed that YFV-Dakar genome exhibited a greater diversity than the vaccine strain; a trait that may contribute to its ability to infect and disseminate efficiently in Ae. aegypti.\n\nConclusions/SignificanceThe two barriers associated with Ae. aegypti midgut prevent YFV-17D replication. Our study contributes to our basic understanding of vector-pathogen interactions and may also aid in the development of non-transmissible live virus vaccines.\n\nAuthor summaryMost flaviviruses, including yellow fever virus (YFV), are transmitted between hosts by mosquito bites. The yellow fever vaccine (YFV-17D) is one of the safest and most effective live virus vaccine ever developed. It is also used as a platform for engineering vaccines against other health-threatening flaviviruses, such as Japanese encephalitis, West Nile, Dengue and Zika viruses. We studied here the replication and dissemination of YFV-17D in mosquitoes. Our data showed that YFV-17D replicates poorly in mosquito midgut and is unable to disseminate to secondary organs, as compare to a YFV clinical isolate. Our study contributes to our basic understanding of the interactions between viruses and their vectors, which is key for conceiving new approaches in inhibiting virus transmission and designing non-transmissible live virus vaccines.

microbiology↗