Cavanaugh, J. | bioRxiv Science

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↗

bioRxiv2021

Kismet/CHD7/CHD8 affects gut biomechanics, the gut microbiome, and gut-brain axis in Drosophila melanogaster

The gut-brain axis may contribute to the pathophysiology of neurodevelopmental disorders, yet it is often unclear how risk genes associated with these disorders affect gut physiology in a manner that could impact microbial colonization. We addressed this question using Drosophila melanogaster with a null mutation in kismet, the ortholog of chromodomain helicase DNA-binding protein (CHD) family members CHD7 and CHD8. In humans, CHD7 and CHD8 are risk genes for neurodevelopmental disorders with co-occurring gastrointestinal symptoms. We found kismet mutant flies have a significant increase in gastrointestinal transit time, indicating functional homology of kismet with CHD7/CHD8 in vertebrates. To measure gut tissue mechanics, we used a high-precision force transducer and length controller, capable of measuring forces to micro-Newton precision, which revealed significant changes in the mechanics of kismet mutant guts, in terms of elasticity, strain stiffening, and tensile strength. Using 16S rRNA metagenomic sequencing, we also found kismet mutants have reduced diversity of gut microbiota at every taxonomic level and an increase in pathogenic taxa. To investigate the connection between the gut microbiome and behavior, we depleted gut microbiota in kismet mutant and control flies and measured courtship behavior. Depletion of gut microbiota rescued courtship defects of kismet mutant flies, indicating a connection between gut microbiota and behavior. In striking contrast, depletion of gut microbiome in the control strain reduced courtship activity. This result demonstrated that antibiotic treatment can have differential impacts on behavior that may depend on the status of microbial dysbiosis in the gut prior to depletion. We propose that Kismet influences multiple gastrointestinal phenotypes that contribute to the gut-brain axis to influence behavior. Based on our results, we also suggest that gut tissue mechanics should be considered as an element in the gut-brain communication loop, both influenced by and potentially influencing the gut microbiome and neuronal development.

developmental biology↗