Egg-laying Behavior Research Articles

Role of TRPV channels in texture discrimination during Bactrocera dorsalis egg-laying behaviour.

Deciding where to lay an egg is critical for the survival of insects' offspring. Compared with our understanding of the chemosensory assessment of egg-laying sites, the mechanisms of texture detection are largely unknown. Here, we show that Bactrocera dorsalis, a notoriously agricultural pest laying its eggs within ripening fruits, can discriminate substrate texture during the egg-laying process. Exposure to drugs targeting transient receptor potential vanilloid (TRPV) mechanosensory channels abolished their oviposition preference for hard textures. BdorNan and BdorIav are two members of the TRPV subfamily, and their transcripts were detected in the labellum, the foreleg tarsi and the ovipositor. Then, we successfully obtained knockout strains of each gene using the CRISPR/Cas9 technique. The results showed that BdorNan is required for the discrimination of stiffness difference. BdorIav knockout had no significant effect on the ability of B. dorsalis to choose harder substrates. Our study thus reveals that BdorNan plays a substantial role in the texture assessment of egg-laying behaviour in B. dorsalis.

Chemotherapeutic Drug Delivery Nanoplatform Development: From Physicochemical to Preclinical Evaluation.

Through this study, the synergistic behavior of small-molecular-weight, amphiphilic surfactant molecules and the triblock copolymer Pluronic 188 was extensively evaluated based on their ability to formulate nanocarriers with novel properties for the delivery of class II and IV (biopharmaceutical classification system) chemotherapeutic compounds. The combination of four different surfactants at multiple weight ratios and twelve initially formulated nanosystems resulted in four hybrid delivery platforms, which were further studied in terms of multiple physicochemical characteristics, as well as their stability in protein-rich media (fetal bovine serum/phosphate-buffer saline). Finally, we obtained a single final nanoformulation that exhibited a high loading capacity (%EE ≥ 75%) and a sustained drug release profile under physiological conditions (model drug methotrexate), without altering the original physicochemical characteristics of the carrier. With a mean hydrodynamic radius (Rh) of less than 70 nm, a polydispersity index of 0.219, and no protein complexation, the system is a suitable candidate for in vivo, intravenous, and/or intramuscular administration. The cytotoxicity and genotoxicity of both loaded and unloaded carriers were evaluated through the examination of the upregulation or downregulation of apoptosis-related pathways. Multiple conventional 2D and 3D spheroidal conformations were used for these assessments, including HEK293, HCT-116, and MCF-7 cell lines, the results of which stressed the safety and biocompatibility of the empty nanocarrier. Additionally, experiments on Caenorhabditis elegans were conducted to evaluate the system's in vivo toxicity, focusing on developmental stages, egg-laying behavior, and locomotion. Nanosystems studied in terms of chemotherapeutic encapsulation have mostly focused on the physiochemical aspect of the development of such novel delivery platforms, with only few exceptions proceeding step-by-step from cellular 2D to 3D to in vivo experimentation. The present study offers a holistic view of the behavior of such a novel system, advancing our understanding of the capabilities of polymeric/surfactant-based nanodelivery platforms.

Captive Breeding Reveals Insights Into the Ecology and Reproductive Biology of 11 Little-Known Malagasy Frog Species.

Amphibians are facing an extinction crisis, with ex situ programs increasingly being used as a tool for their conservation. However, conservation efforts are often limited because we do not understand the ecological, behavioral, and life history traits of many amphibian species. Here, we report on the seasonal breeding patterns, egg-laying behavior, clutch size, and development of 11 frog species maintained at a conservation breeding facility in Andasibe, Madagascar. The frogs exhibited diverse breeding strategies aligned with life history theory. Counting the eggs in 1239 egg masses across these 11 species, we found endotrophic microhylids and terrestrial-breeding species had the smallest clutch size yet completed metamorphosis quickly, whereas species that laid eggs above or in water with exotrophic larvae had larger clutch sizes and took longer to develop. Most reproduction in captivity occurred during the warm, rainy season and followed seasonal patterns in temperature variation. Yet, Mantidactylus betsileanus bred throughout the year, and Heterixalus betsileo required additional environmental stimuli to trigger reproduction. Notably, we confirmed that Gephyromantis mitsinjo lays eggs on land with tadpoles developing terrestrially within jelly, a behavior previously theorized but which until now remained unobserved. Such observations show how captive breeding programs can be used to gain valuable data on the life history traits of species that are otherwise challenging to observe in nature. Our findings can be used to assess threats to closely related species, helping inform conservation efforts in a country harboring exceptional amphibian species richness and endemism.

Dopaminergic- and Serotonergic-Dependent Behaviors Are Altered by Lanthanide Series Metals in Caenorhabditis elegans.

The lanthanide series elements are transition metals used as critical components of electronics, as well as rechargeable batteries, fertilizers, antimicrobials, contrast agents for medical imaging, and diesel fuel additives. With the surge in their utilization, lanthanide metals are being found more in our environment. However, little is known about the health effects associated with lanthanide exposure. Epidemiological studies as well as studies performed in rodents exposed to lanthanum (La) suggest neurological damage, learning and memory impairment, and disruption of neurotransmitter signaling, particularly in serotonin and dopamine pathways. Unfortunately, little is known about the neurological effects of heavier lanthanides. As dysfunctions of serotonergic and dopaminergic signaling are implicated in multiple neurological conditions, including Parkinson's disease, depression, generalized anxiety disorder, and post-traumatic stress disorder, it is of utmost importance to determine the effects of La and other lanthanides on these neurotransmitter systems. We therefore hypothesized that early-life exposure of light [La (III) or cerium (Ce (III))] or heavy [erbium (Er (III)) or ytterbium (Yb (III))] lanthanides in Caenorhabditis elegans could cause dysregulation of serotonergic and dopaminergic signaling upon adulthood. Serotonergic signaling was assessed by measuring pharyngeal pump rate, crawl-to-swim transition, as well as egg-laying behaviors. Dopaminergic signaling was assessed by measuring locomotor rate and egg-laying and swim-to-crawl transition behaviors. Treatment with La (III), Ce (III), Er (III), or Yb (III) caused deficits in serotonergic or dopaminergic signaling in all assays, suggesting both the heavy and light lanthanides disrupt these neurotransmitter systems. Concomitant with dysregulation of neurotransmission, all four lanthanides increased reactive oxygen species (ROS) generation and decreased glutathione and ATP levels. This suggests increased oxidative stress, which is a known modifier of neurotransmission. Altogether, our data suggest that both heavy and light lanthanide series elements disrupt serotonergic and dopaminergic signaling and may affect the development or pharmacological management of related neurological conditions.

Fatty acid synthase 2 knockdown alters the energy allocation strategy between immunity and reproduction during infection by Micrococcus luteus in Locusta migratoria

Immunity and reproduction are vital functions for the survival and population maintenance of female insects. However, owing to limited resources, these two functions cannot be fulfilled simultaneously, resulting in an energy tradeoff between them. Notably, the mechanisms underlying this immune-reproductive trade-off, in which energy competition likely plays a central role, remain poorly understood. Fatty acid synthase (FAS), a key gene involved in lipid synthesis and insect energy metabolism, was investigated in this study using Locusta migratoria as the research subject. Bacterial infection and RNA interference (RNAi) technology were used to examine changes in the immunity, fecundity, and energy metabolism patterns of locusts under different treatments. The findings of this study demonstrate that infection with Micrococcus luteus triggers an immune response in locusts, significantly upregulates the expression of defensin 3 (DEF3) and Attacin, and enhances pHenoloxidase (PO) activity. Upon FAS2 silencing, bacterial attack upregulated DEF3 and Attacin expression to a lesser extent, leading to increased lysozyme activity instead of PO. Furthermore, bacterial infection results in a decrease in glycogen and glucose content in the fat body, accompanied by a significant increase in triacylglycerol (TAG) content. However, after FAS2 knockdown, both the lipid and carbohydrate contents were significantly reduced in the fat body. Compared with bacterial infection alone, low FAS2 expression further exacerbated fecundity impairment in locusts. The expression levels of vitellogenin A (VgA) and vitellogenin B (VgB) were significantly low, with severe ovarian atrophy observed. Notably, the ovarian weight was only 21 % compared to that of the control group. Moreover, females exhibited minimal egg-laying behavior. In summary, our findings suggest that following FAS2 gene silencing, there is a greater inclination toward immune stimulation energy activation in locusts, whereas reproductive investment is reduced. The outcomes of this study will contribute to the further exploration of the molecular mechanisms underlying the trade-off between immune and reproductive energy in locusts.

Ecofaunistic Study and Egg Morphology: Egg Laying Behavior of Hydrometra stagnorum (Linnaeus, 1753) (Gerromorpha: Heteroptera) Newly Recorded From the Karabük Province of Western Black Sea (Türkiye).

This study examines the egg-laying behavior and egg morphology of Hydrometra stagnorum (Linnaeus, 1753) (Gerromorpha: Heteroptera) to provide ecofaunistic information about the species. Newly recorded H. stagnorum samples were collected from the Karabük province of Western Black Sea region of Türkiye. Physicochemical parameters of the water were also recorded. The morphology and egg-laying behavior of H. stagnorum eggs were identified using a stereo, light and electron microscopy. Mature eggs were observed to be blackish dark brown in color. The study reveals distinctive characteristics of the egg structure and micropyle areas, which may contribute to the classification of the species at the subfamily level. Additionally, it was found that H. stagnorum inhabits high-quality waters.

Flexible oviposition behavior enabled the evolution of terrestrial reproduction

Among vertebrates, nearly all oviparous animals are considered to have either obligate aquatic or terrestrial oviposition, with eggs that are specialized for developing in those environments. The terrestrial environment has considerably more oxygen but is dry and thus presents both opportunities and challenges for developing embryos, particularly those adapted for aquatic development. Here, we present evidence from field experiments examining egg-laying behavior, egg size, and egg jelly function of 13 species of Central and South American treefrogs in the genus Dendropsophus, which demonstrates that flexible oviposition (individuals laying eggs both in and out of water) and eggs capable of both aquatic and terrestrial development are the likely factors which enable the transition from aquatic to terrestrial reproduction. Nearly half of the species we studied had previously undescribed degrees of flexible oviposition. Species with obligate terrestrial reproduction have larger eggs than species with aquatic reproduction, and species with flexible reproduction have eggs of intermediate sizes. Obligate terrestrial breeding frogs also have egg masses that absorb water more quickly than those with flexible oviposition. We also examined eight populations of a single species, Dendropsophus ebraccatus, and document substantial intraspecific variation in terrestrial oviposition; populations in rainy, stable climates lay fewer eggs in water than those in drier areas. However, no differences in egg size were found, supporting the idea that the behavioral component of oviposition evolves before other adaptations associated with obligate terrestrial reproduction. Collectively, these data demonstrate the key role that behavior can have in facilitating major evolutionary transitions.

Phenotypic Identification, Genetic Characterization, and Selective Signal Detection of Huitang Duck.

The Huitang duck (HT), a long-domesticated elite local breed from Hunan Province, China, with excellent meat quality, has not had its population genetic structure and genomic selective sweeps extensively studied to date. This study measured the phenotypic characteristics of HT and conducted comparative analysis between HT and 16 different duck breeds, including wild, indigenous, and meat breeds, to characterize its population structure and genetic potential. The results revealed that HT is a dual-purpose indigenous breed with a genetic background closely related to the Youxian sheldrake and Linwu ducks. In the selective sweep analysis between HT and Linwu ducks, genes such as PLCG2, FN1, and IGF2BP2, which are associated with muscle growth and development, were identified near the 27 selection signals. The comparison between HT and Jinding ducks revealed 68 selective signals that contained important genes associated with ovarian development (GRIK4, MAP3K8, and TGIF1) and egg-laying behaviors (ERBB4). Selective sweep analysis between HT and Youxian sheldrake ducks found 93 selective regions covering genes related to both meat (IGF1R and IGFBP5) and egg-production (FOXO3 and ITPR1) traits. Our study may provide novel knowledge for exploring the population structure and genetic potential of HT, offering a theoretical basis for its breeding strategies in the future.

Orthologs of NOX5 and EC-SOD/SOD3: dNox and dSod3 Impact Egg Hardening Process and Egg Laying in Reproductive Function of Drosophila melanogaster.

The occurrence of ovarian dysfunction is often due to the imbalance between the formation of reactive oxygen species (ROS) and the ineffectiveness of the antioxidative defense mechanisms. Primary sources of ROS are respiratory electron transfer and the activity of NADPH oxidases (NOX) while superoxide dismutases (SOD) are the main key regulators that control the levels of ROS and reactive nitrogen species intra- and extracellularly. Because of their central role SODs are the subject of research on human ovarian dysfunction but sample acquisition is low. The high degree of cellular and molecular similarity between Drosophila melanogaster ovaries and human ovaries provides this model organism with the best conditions for analyzing the role of ROS during ovarian function. In this study we clarify the localization of the ROS-producing enzyme dNox within the ovaries of Drosophila melanogaster and by a tissue-specific knockdown we show that dNox-derived ROS are involved in the chorion hardening process. Furthermore, we analyze the dSod3 localization and show that reduced activity of dSod3 impacts egg-laying behavior but not the chorion hardening process.

Olfactory preference of the litchi fruit borer for oviposition on two litchi varieties.

The litchi fruit borer Conopomorpha sinensis Bradley is a major destructive pest of litchi and longan plants in China, India and South East Asia. Given its strong olfactory-based oviposition behaviour, interfering with the chemical communication between this insect pest and its host plant may serve as a potential control strategy. However, the chemical compounds associated with its egg-laying behaviour remain poorly understood. In this study, we investigated the olfactory preference of female C. sinensis for oviposition on intact mature fruits of the Feizixiao (FZX) and Guiwei (GW) varieties. Results showed that female C. sinensis preferred to lay eggs on FZX compared with GW fruits, and this preference was olfactory-induced. In addition, we identified differences in the chemical composition of the volatile blend and proportions between FZX and GW fruits, with terpenes being the main volatile components contributing to this divergence. Compounds that induced electrophysiological activity in female borers were subsequently screened from FZX. d-Limonene exhibited the strongest oviposition attraction among four candidates. Furthermore, this compound served as a volatile olfactory cue for recognition and orientation in female C. sinensis. The results of this study provide a deeper understanding of the olfactory preferences of female C. sinensis for oviposition on specific litchi varieties. © 2024 Society of Chemical Industry.

Bacterial peptidoglycan serves as a critical modulator of the gut-immune-brain axis in Drosophila

Metabolites and compounds derived from gut-associated bacteria can modulate numerous physiological processes in the host, including immunity and behavior. Using a model of oral bacterial infection, we previously demonstrated that gut-derived peptidoglycan (PGN), an essential constituent of the bacterial cell envelope, influences female fruit fly egg-laying behavior by activating the NF-κB cascade in a subset of brain neurons. These findings underscore PGN as a potential mediator of communication between gut bacteria and the brain in Drosophila, prompting further investigation into its impact on all brain cells. Through high-resolution mass spectrometry, we now show that PGN fragments produced by gut bacteria can rapidly reach the central nervous system. In Addition, by employing a combination of whole-genome transcriptome analyses, comprehensive genetic assays, and reporter gene systems, we reveal that gut bacterial infection triggers a PGN dose-dependent NF-κB immune response in perineurial glia, forming the continuous outer cell layer of the blood–brain barrier. Furthermore, we demonstrate that persistent PGN-dependent NF-κB activation in perineurial glial cells correlates with a reduction in lifespan and early neurological decline. Overall, our findings establish gut-derived PGN as a critical mediator of the gut-immune-brain axis in Drosophila.

A novel oviposition trap for studying the egg-laying behavior of emerald ash borer

A novel oviposition trap for studying the egg-laying behavior of emerald ash borer

Diverse memory paradigms in Drosophila reveal diverse neural mechanisms.

In this review, we aggregated the different types of learning and memory paradigms developed in adult Drosophila and attempted to assess the similarities and differences in the neural mechanisms supporting diverse types of memory. The simplest association memory assays are conditioning paradigms (olfactory, visual, and gustatory). A great deal of work has been done on these memories, revealing hundreds of genes and neural circuits supporting this memory. Variations of conditioning assays (reversal learning, trace conditioning, latent inhibition, and extinction) also reveal interesting memory mechanisms, whereas mechanisms supporting spatial memory (thermal maze, orientation memory, and heat box) and the conditioned suppression of innate behaviors (phototaxis, negative geotaxis, anemotaxis, and locomotion) remain largely unexplored. In recent years, there has been an increased interest in multisensory and multicomponent memories (context-dependent and cross-modal memory) and higher-order memory (sensory preconditioning and second-order conditioning). Some of this work has revealed how the intricate mushroom body (MB) neural circuitry can support more complex memories. Finally, the most complex memories are arguably those involving social memory: courtship conditioning and social learning (mate-copying and egg-laying behaviors). Currently, very little is known about the mechanisms supporting social memories. Overall, the MBs are important for association memories of multiple sensory modalities and multisensory integration, whereas the central complex is important for place, orientation, and navigation memories. Interestingly, several different types of memory appear to use similar or variants of the olfactory conditioning neural circuitry, which are repurposed in different ways.

The pyrexia channel remodels egg-laying of Liriomyza huidobrensis in response to temperature change.

The pea leafminer, Liriomyza huidobrensis, is one of the most important insect pests on vegetables and ornamentals. The survival and egg-laying behavior of leafminers are markedly affected by the environment temperature. However, the mechanisms underlying the relationship between egg-laying and temperature are still largely unknown. Here, we find that leafminers have evolved an adaptive strategy to overcome the stress from high or low temperature by regulating oviposition-punching plasticity. We further show that this oviposition-punching plasticity is mediated by the expression of pyx in the ovipositor when subjected to disadvantageous temperature. Specifically, down-regulation of pyx expression in leafminers under low temperature stress led to a significant decrease in the swing numbers of ovipositor and puncture area of the egg spot, and consequently the lower amount of egg-laying compared to leafminers at ambient temperature. Conversely, activation of pyx expression under high temperature stress increased the swing numbers and puncture area, still resulting in a reduction of egg-laying amount. Thereby, leafminers are able to coordinate pyx channel expression level and accordingly depress the oviposition. Our study uncovers a molecular mechanism underlying the adaptive strategy in insects that can avoid disadvantageous temperature for reproducing offspring. © 2024 Society of Chemical Industry.

Hypergravity Impact on Fertility of Apis mellifera carnica Queens – Case Study

The launch is considered the most stressful rocket flight stage due to the hypergravity occurrences. The possibility of using honey bees (Apis mellifera) as the extraterrestrial pollinator depends on their ability to reproduce correctly after experiencing hypergravity. The described study aims to verify the impact of a launching rocket’s acceleration on honey bee queen’s egg-laying behavior. Four artificially inseminated A. mellifera carnica queens were placed in the Human Training Centrifuge and given to the acceleration pattern of the launching Soyuz rocket. Next, the data on the number of food stores, eggs, larvae, and worker and drone pupae were collected from the test and control hives using the modified Liebefeld method. The pilot study results imply that accelerated queen’s egg-laying behavior may change twofold: limiting or maximizing the number of laid eggs, with the control queen egg-laying rate remaining stable for all samples. The number of drone pupae is greater for the test sample colonies, with its earlier appearance in the hive. No impact on overwintering success was observed. Authors indicate limitations of the results and a need to continue the study to verify the occurrence of anomalies potentially related to the examined factor.

Chewing ability, courtship and egg-laying behaviors of the parasitoid wasp Melittobia sosui Dahms, 1984 (Hymenoptera: Eulophidae)

We present observations on Melittobia sosui Dahms chewing ability, courtship and egg-laying behaviors. Under laboratory conditions and with 12 tested different hosts, the parasitoid took a successful chewing on cocoons of four Sphecidae wasps and puparia of Drosophilidae and Muscidae flies. The highest successful chewing proportion was 83.3% on Chalybion bengalense (Sphecidae) cocoons. During courtship, the male mounted the female’s back by grasping her pronotum with his forelegs, his hindlegs straddling her abdomen, his midlegs raising upwards, and clasping the female’s antennal tips into his antennal scapes. The male tapped his midlegs on the female’s midlegs or pronotum, shook his antennae and simultaneously fluttered the wings. A male of M. sosui could courtship many females, even female pupae. After feeding on hemolymph exuded from the wounds made by her sting, the physogastric female laid batches of eggs. To oviposit, the female extended her legs to the sides and her wings were raised to an angle of about 45° from the body. She exposed and lowered her ovipositor often perpendicular to the host surface and laid eggs; after each oviposition her abdominal apex was slightly raised upwards.

Natural variation in the Caenorhabditis elegans egg-laying circuit modulates an intergenerational fitness trade-off.

Evolutionary transitions from egg laying (oviparity) to live birth (viviparity) are common across various taxa. Many species also exhibit genetic variation in egg-laying mode or display an intermediate mode with laid eggs containing embryos at various stages of development. Understanding the mechanistic basis and fitness consequences of such variation remains experimentally challenging. Here, we report highly variable intra-uterine egg retention across 316 Caenorhabditis elegans wild strains, some exhibiting strong retention, followed by internal hatching. We identify multiple evolutionary origins of such phenotypic extremes and pinpoint underlying candidate loci. Behavioral analysis and genetic manipulation indicates that this variation arises from genetic differences in the neuromodulatory architecture of the egg-laying circuitry. We provide experimental evidence that while strong egg retention can decrease maternal fitness due to in utero hatching, it may enhance offspring protection and confer a competitive advantage. Therefore, natural variation in C. elegans egg-laying behaviour can alter an apparent trade-off between different fitness components across generations. Our findings highlight underappreciated diversity in C. elegans egg-laying behavior and shed light on its fitness consequences. This behavioral variation offers a promising model to elucidate the molecular changes in a simple neural circuit underlying evolutionary shifts between alternative egg-laying modes in invertebrates.

Natural variation in the Caenorhabditis elegans egg-laying circuit modulates an intergenerational fitness trade-off

Evolutionary transitions from egg laying (oviparity) to live birth (viviparity) are common across various taxa. Many species also exhibit genetic variation in egg-laying mode or display an intermediate mode with laid eggs containing embryos at various stages of development. Understanding the mechanistic basis and fitness consequences of such variation remains experimentally challenging. Here, we report highly variable intra-uterine egg retention across 316 Caenorhabditis elegans wild strains, some exhibiting strong retention, followed by internal hatching. We identify multiple evolutionary origins of such phenotypic extremes and pinpoint underlying candidate loci. Behavioral analysis and genetic manipulation indicates that this variation arises from genetic differences in the neuromodulatory architecture of the egg-laying circuitry. We provide experimental evidence that while strong egg retention can decrease maternal fitness due to in utero hatching, it may enhance offspring protection and confer a competitive advantage. Therefore, natural variation in C. elegans egg-laying behaviour can alter an apparent trade-off between different fitness components across generations. Our findings highlight underappreciated diversity in C. elegans egg-laying behavior and shed light on its fitness consequences. This behavioral variation offers a promising model to elucidate the molecular changes in a simple neural circuit underlying evolutionary shifts between alternative egg-laying modes in invertebrates.

A sweet tooth makes a fly a pest

The major insect pest of soft and stone fruits, the spotted-wing drosophila, Drosophila suzukii, has evolved a greater preference for laying eggs on ripe fruits over fermented ones. In a recent study, Cavey et al. found that higher responsiveness to low sugar concentrations has had an important role in this evolutionary shift in egg-laying behavior.

Mercuric sulfide nanoparticles suppress the neurobehavioral functions of Caenorhabditis elegans through a Skp1-dependent mechanism

Cinnabar is the naturally occurring mercuric sulfide (HgS) and concerns about its safety have been grown. However, the molecular mechanism of HgS-related neurotoxicity remains unclear. S-phase kinase-associated protein 1 (Skp1), identified as the target protein of HgS, plays a crucial role in the development of neurological diseases. This study aims to investigate the neurotoxic effects and molecular mechanism of HgS based on Skp1 using the Caenorhabditis elegans (C. elegans) model. We prepared the HgS nanoparticles and conducted a comparative analysis of neurobehavioral differences in both wild-type C. elegans (N2) and a transgenic strain of C. elegans (VC1241) with a knockout of the SKP1 homologous gene after exposure to HgS nanoparticles. Our results showed that HgS nanoparticles could suppress locomotion, defecation, egg-laying, and associative learning behaviors in N2 C. elegans, while no significant alterations were observed in the VC1241 C. elegans. Furthermore, we conducted a 4D label-free proteomics analysis and screened 504 key proteins significantly affected by HgS nanoparticles through Skp1. These proteins play pivotal roles in various pathways, including SNARE interactions in vesicular transport, TGF-beta signaling pathway, calcium signaling pathway, FoxO signaling pathway, etc. In summary, HgS nanoparticles at high doses suppress the neurobehavioral functions of C. elegans through a Skp1-dependent mechanism.