Biology subjects

Frigard, R.

Publications and source records attributed to Frigard, R..

5 recordsLinked to original sources

bioRxiv2026

Extended pregnancy during matrotrophy in cockroaches increases progeny survival during dry periods

Animals reproduce across a spectrum from oviparity to viviparity. Internal gestation and live birth have inherent advantages despite their costs. However, comparative analyses of key drivers, such as resilience to dehydration, lack taxonomic breadth. In this study, we assessed whether live birth improves the ability to proliferate in environments with limited access to water. To do so, we used the viviparous cockroach, Diploptera punctata, as a model of viviparity to assess dehydration-induced damage during extended periods of water deprivation. During pregnancy, maternal survival did not decline during dry periods compared with non-pregnant individuals, suggesting that pregnancy has minimal impact on resistance to dehydration stress. When mothers are deprived of water for 2 weeks, they show an increase in osmolality after one week, while their embryos show no change in osmolality until after two weeks, at which point abortions occur. Periods of dehydration increased the duration of pregnancy, likely due to a slower production of in utero milk, but there was no change in the size of progeny. After birth, viviparous D. punctata newborns showed increased survival under dry conditions compared to two other ovoviviparous species, which are much smaller and dehydrate more quickly. The combined impact of increased dehydration resistance during pregnancy and during the first independent phase indicates a benefit of prolonged viviparity in Diploptera punctata. This study provides evidence that viviparity in animal systems could enable progeny survival during drought.

ecology↗

bioRxiv2025

Discovery of an Adaptive Neuroimmune Response Driving Itch and Fast Tick Removal with Implications for Preventing Pathogen Transmission

Acquired tick resistance (ATR) is well characterized in tick-exposed animals, compromising tick fitness through antibody-mediated activation of basophils. Yet, anti-tick vaccines inducing ATR have had limited success. Here, we describe a neuroimmune event preceding ATR that leads to rapid host-mediated tick removal. Tick-sensitized guinea pigs mechanically remove ticks within 3-6 hours via an acquired neuroimmune-induced itch response that correlates with increased dermal expression of itch-associated genes like OSM and skin infiltration by T cells and macrophages, independently of IgG and IgE antibodies. When we expose humans to ticks, a similar immune response is observed. Blocking T cells before tick sensitization prevents immune cell infiltration to bite sites and abrogates scratching and tick removal. This neuroimmune response is independent of Trpv1 as tick-sensitized guinea pigs treated with resiniferatoxin remove ticks effectively. Itch-induced tick removal or IITR offers a novel approach to tick-borne disease prevention through early tick detection and removal.

neuroscience↗

bioRxiv2025

Daily activity rhythms, sleep, and pregnancy are fundamentally related in the Pacific beetle mimic cockroach, Diploptera punctata

Sleep and pregnancy are contentious bedfellows; sleep disorders and disturbances are associated with adverse pregnancy outcomes, although much is still unknown about this relationship. Sleep and pregnancy have been studied in many models, but most focus heavily on mammals. However, pregnancy is ubiquitous across the animal kingdom - a hallmark of convergent evolution; similarly sleep is a shared feature across diverse species. Here, we present an ideal model in which to study the dynamics between sleep and pregnancy in invertebrates. The Pacific beetle mimic cockroach, Diploptera punctata, is a viviparous cockroach species that uses milk proteins to nourish its young with a broodsac over a three month pregnancy. However, little is known about the relationship between this unique reproductive biology and daily rhythms of activity and sleep. We established that D. punctata displayed a peak in activity shortly following sunset, with males significantly more active than females. When scavenging behavior was examined, males and non-pregnant females emerged more often and traveled further from a shelter compared to pregnant females, suggesting reduced risk-taking behavior in late pregnancy. Chronic disturbance of sleep during pregnancy negatively impacted embryo development by increasing gestational duration and decreasing the transcription of milk proteins. These findings indicate that sleep is key to embryo development and that pregnancy has a significant impact on the daily rhythms of activity in Diploptera punctata. More broadly, we present a tractable invertebrate model for understanding the relationship between sleep and pregnancy, which will aid in the exploration of the poorly understood interface between these two ubiquitous and highly conserved traits.

physiology↗

bioRxiv2024

Impaired humidity sensing reduces tick survival by preventing water homeostasis

Off-host periods are critical for ticks, representing a time when environmental stress, particularly dehydration, can impact tick survival. To prevent dehydration, ticks must be able to detect and move into high humidity areas to allow for water vapor uptake. Ionotropic receptor 93a (Ir93a), which is highly expressed in the front forelegs (location of Hallers organ), increases expression following dehydration, suggesting a role for the forelegs in humidity detection. Although the Hallers organ is suggested as the site of humidity detection in ticks, humidity detection has not been extensively examined for ticks. Here, we assessed the ability of ticks to sense humidity and how altered humidity detection impacts tick survival by manipulating the Hallers organ. Permanent (cutting or heat ablation) or temporary blocking (silicone covering) of the Hallers organ impairs the ability of the American dog tick, Dermacentor variabilis, to rest in areas necessary to maintain hydration. Impaired detection of humidity did not impact tick survival when individuals were held under stable optimal conditions. Still, variable conditions (low and high humidity gradient) reduced survival through dehydration stress and decreased energy reserves, as chronic water vapor uptake is energetically expensive. Field validation of these studies in D. variabilis confirmed that humidity detection is critical to tick survival. Lastly, modeling indicates impaired humidity detection will reduce questing tick populations, specifically in the adult stages. These studies confirm that the Hallers organ is critical for humidity sensing in ticks. Without this ability, tick survival will be impaired by potential dehydration or more rapid depletion of energy reserves.

physiology↗

bioRxiv2023

Tyrosine transfer RNA levels and modifications during blood-feeding and vitellogenesis in the mosquito, Aedes aegypti

Mosquitoes such as Aedes aegypti must consume a blood meal for the nutrients necessary for egg production. Several transcriptome and proteome changes occur post blood meal that likely corresponds with codon usage alterations. Transfer RNA (tRNA) is the adapter molecule that reads messenger RNA (mRNA) codons to add the appropriate amino acid during protein synthesis. Chemical modifications to tRNA enhance codons decoding, improving the accuracy and efficiency of protein synthesis. Here, we examined tRNA modifications and transcripts associated with the blood meal and subsequent periods of vitellogenesis in A. aegypti. More specifically, we assessed tRNA transcript abundance and modification levels in the fat body at critical times post blood-feeding. Based on a combination of alternative codon usage and identification of particular modifications, we identified that increased transcription of tyrosine tRNAs is likely critical during the synthesis of egg yolk proteins in the fat body following a blood meal. Altogether, changes in both the abundance and modification of tRNA are essential factors in the process of vitellogenin production after blood-feeding in mosquitoes.

biochemistry↗