Variation in parental investment preferences for nestlings of the Gray-backed Shrike (Lanius tephronotus) in alpine environments.

In the northeastern edge of the Qinghai-Tibet Plateau, the Gray-backed Shrike, a shrubland bird species of the plateau, confronts harsh living conditions. The impact of such an environment on their reproductive strategies has long intrigued us. This study reveals significant environmental effects on the investment of the Gray-backed Shrike during their nestling-rearing and egg-laying stages. (1) Based on measurements of 215 shrike eggs from 2017 to 2021, we found that under the cold alpine climate, Gray-backed Shrikes opt for a strategy of larger clutches and bigger eggs as average rainfall decreases. Concurrently, parents display a decreasing hatching order strategy, resulting in significant weight differences among newly hatched nestlings. (2) Marginal and core offspring exhibited no significant differences in fledging conditions. Core offspring generally have a slightly larger physique than marginal ones. However, marginal offspring exhibit the highest growth rate, with similar survival rates across different offspring categories. Parental rearing adopts a nest survival strategy. (3) The food provisioning rate by parents correlates strongly with the number of nestlings, the age of the nestling, and the nest's sex ratio. Differences exist between female and male provisioning rates based on begging intensity and average temperature; higher average temperatures lead to more food, with males providing more food. (4) Factors like nest sex ratio, offspring category, nestling age, and nestling sex influence the feeding preferences of parents. When overall nestling ratios skew towards either male or female, parental feeding preferences align with the actual nest sex ratio. Male and female parental feeding preferences differ based on average temperature and nestling sex. Males consistently exhibit a stronger preference for feeding male nestlings, regardless of the nest's sex ratio. In contrast, females don't show a clear preference, leading to differences in survival rates for different nestling sex under male feeding preferences.

RhoprCAPA-2 acts as a gonadotropin regulating reproduction in adult female, Rhodnius prolixus.

CAPA peptides play diverse roles in insects, modulating muscle contraction, regulating fluid balance, and reproduction. In Rhodnius prolixus, a hematophagous insect and a vector for human Chagas disease, three CAPA peptides are encoded by the capability gene, including RhoprCAPA-1, RhoprCAPA-2, and RhoprCAPA-PK-1. RhoprCAPA-2 is an anti-diuretic hormone in R. prolixus. Here, we explore the involvement of RhoprCAPA-2 in reproduction in adult female R. prolixus. Double-label immunohistochemistry reveals co-localization of RhoprCAPA-2-like and the glycoprotein hormone (GPA2/GPB5) subunit GPB5-like immunoreactivity in neurosecretory cells in the mesothoracic ganglionic mass and in their neurohemal sites, suggesting these peptides can be co-released to regulate physiological processes. qPCR analysis reveals changes in transcript expression levels of the RhoprCAPA receptor (CAPAR) in the fat body and reproductive tissues after feeding in adult female R. prolixus. RNA interference-mediated knockdown of CAPAR transcript decreases egg production and reduces hatching rate and survival rate in female R. prolixus. Downregulation of CAPAR decreases vitellogenin RhoprVg1 transcript expression in the fat body and deceases its receptor RhoprVgR transcript level in the ovaries; accompanied by a reduction in vitellogenin content in the fat body and hemolymph. Incubation of fat body and ovaries in vitro with RhoprCAPA-2 increases RhoprVg1 transcript expression in the fat body, vitellogenin content in the fat body culture medium, and increases RhoprVgR transcript in the ovaries. These findings implicate the CAPA signaling pathway in reproduction, with RhoprCAPA-2 acting as a gonadotropin in adult female R. prolixus.

Integrating Genomics and Transcriptomics to Identify Candidate Genes for Egg Production in Taihe Black-Bone Silky Fowls (Gallus gallus domesticus Brisson).

The Taihe Black-Bone Silky Fowl (Gallus gallus domesticus Brisson) possesses significant value in terms of consumption, medicinal applications, and ornamental appeal, representing a precious genetic resource and traditional Chinese medicinal material. However, considerable variation exists within populations regarding egg-laying performance. This study integrates a whole-genome selection signal analysis (SSA) with a transcriptome analysis to identify genes associated with egg-laying traits in Taihe Black-Bone Silky Fowls. We identified 31 candidate genes under selection from the high-yield chicken (HC) and low-yield chicken (LC) groups. Additionally, through RNA-seq analysis, 257 common differentially expressed genes (DEGs) were identified from four comparative groups. Two overlapping genes-LPL and SETBP1-were found in both the selected gene and DEG lists. These selected genes and DEGs were enriched in pathways related to ovarian development, including the lysosome pathway, the ECM-receptor interaction pathway, the TGF-beta signaling pathway, the Wnt signaling pathway, the PPAR signaling pathway, and the glycerolipid metabolism pathway. These research findings contribute to the breeding of Taihe Black-Bone Silky Fowls with high egg production traits and provide a theoretical foundation for exploring the regulatory mechanisms of avian reproduction.

Soluble Guanylate Cyclase α1 Gene Influences Egg-Laying Amount and Hatching Rate in Bombyx mori.

Soluble guanylate cyclase (sGC) serves as a receptor of nitric oxide (NO) and is the core metalloenzyme in the NO signal transduction pathway. sGC plays a key role in the NO-cGMP signal transduction pathway and participates in various physiological processes, including cell differentiation, neuron transmission, and internal environment homeostasis. sGC consists of two subunits, α and ß, each subunit containing multiple isoforms. In this study, we cloned and analyzed the sGC-α1 gene in the silkworm Bombyx mori (BmsGC-α1). The BmsGC-α1 gene was expressed highest at the pupal stages. The highest BmsGC-α1 mRNA expression was observed in the head of fifth instar larvae and in fat body during the wandering stage of B. mori. Furthermore, we observed that feeding fifth instar larvae with thyroid hormone and nitroglycerin induced the expression of the BmsGC-α1 gene. Injection of BmsGC-α1 siRNA into silkworms at the prepupal stage resulted in a significant decrease in BmsGC-α1 expression levels at 48 and 72 h postinjection. After silencing BmsGC-α1, both the egg-laying amount and hatching rate of silkworm eggs were significantly reduced compared to the control group. These results suggest that BmsGC-α1 plays an important role in regulating the reproductive system of silkworms. This finding enhances our understanding of the functional diversity of sGC in insects.

Neurobiology of egg-laying behavior in Drosophila: neural control of the female reproductive system.

Egg-laying is one of the key aspects of female reproductive behavior in insects. Egg-laying has been studied since the dawn of Drosophila melanogaster as a model organism. The female's internal state, hormones, and external factors, such as nutrition, light, and social environment, affect egg-laying output. However, only recently, neurobiological features of egg-laying behavior have been studied in detail. fruitless and doublesex, two key players in the sex determination pathway, have become focal points in identifying neurons of reproductive significance in both central and peripheral nervous systems. The reproductive tract and external terminalia house sensory neurons that carry the sensory information of egg maturation, mating and egg-laying. These sensory signals include the presence of male accessory gland products and mechanical stimuli. The abdominal neuromere houses neurons that receive information from the reproductive tract, including sex peptide abdominal ganglion neurons (SAGs), and send their information to the brain. In the brain, neuronal groups like aDNs and pC1 clusters modulate egg-laying decision-making, and other neurons like oviINs and oviDNs are necessary for egg-laying itself. Lastly, motor neurons involved in egg-laying, which are mostly octopaminergic, reside in the abdominal neuromere and orchestrate the muscle movements required for laying the egg. Egg-laying neuronal control is important in various evolutionary processes like cryptic female choice, and using different Drosophila species can provide intriguing avenues for the future of the field.

Viviparity is associated with larger female size and higher sexual size dimorphism in a reproductively bimodal lizard.

Squamate reptiles are central for studying phenotypic correlates of evolutionary transitions from oviparity to viviparity because these transitions are numerous, with many of them being recent. Several models of life-history theory predict that viviparity is associated with increased female size, and thus more female-biased sexual size dimorphism (SSD). Yet, the corresponding empirical evidence is overall weak and inconsistent. The lizard Zootoca vivipara, which occupies a major part of Northern Eurasia and includes four viviparous and two non-sister oviparous lineages, represents an excellent model for testing these predictions. We analysed how sex-specific body size and SSD is associated with parity mode, using body length data for nearly 14,000 adult individuals from 97 geographically distinct populations, which cover almost the entire species' range and represent all six lineages. Our analyses controlled for lineage identity, climatic seasonality (the strongest predictor of geographic body size variation in previous studies of this species) and several aspects of data heterogeneity. Parity mode, lineage and seasonality are significantly associated with female size and SSD; the first two predictors accounted for 14%-26% of the total variation each, while seasonality explained 5%-7%. Viviparous populations exhibited a larger female size than oviparous populations, with no concomitant differences in male size. The variation of male size was overall low and poorly explained by our predictors. Albeit fully expected from theory, the strong female bias of the body size differences between oviparous and viviparous populations found in Z. vivipara is not evident from available data on three other lizard systems of closely related lineages differing in parity mode. We confront this pattern with the data on female reproductive traits in the considered systems and the frequencies of evolutionary changes of parity mode in the corresponding lizard families and speculate why the life-history correlates of live-bearing in Z. vivipara are distinct. Comparing conspecific populations, our study provides the most direct evidence for the predicted effect of parity mode on adult body size but also demonstrates that the revealed pattern may not be general. This might explain why across squamates, viviparity is only weakly associated with larger size.

Multi-omics analysis reveals associations between host gene expression, gut microbiota and metabolites in chickens.

Egg-laying is an important trait in chickens, and it is affected by many factors, such as hormones regulated by the hypothalamic-pituitary axis and precursors synthesized by the liver. Recent studies showed that gut microbiota was associated with egg-laying, however, its underlying mechanism remains unclear. We comprehensively analyzed the host transcriptome, gut microbiota and metabolome in broiler breeder hens during the pre-laying, peak-laying and late-laying periods. The transcriptome analysis of the tissues related to the hypothalamic-pituitary-liver (HPL) axis revealed dynamic gene expression during egg-laying periods. Differentially expressed genes (DEGs) (i.e., PENK, NPY, AVP, PRL, RLN3, and FST) from the hypothalamus and pituitary gland were involved in female gonadal development, hormone secretion, response to endogenous stimulus, liver development, and amide metabolism. In liver, DEGs (i.e., FABP3, VTG1, LPL, APOA5, APOV1, and RBP5) were enriched in efferocytosis, sphingolipid metabolism, amide and peptide biosynthesis. Alpha and beta diversity changed significantly in cecum microbiota during different laying periods. The abundance of Firmicutes was decreased and the abundance of Bacteroidota was increased during the peak-laying period. Functional analysis showed that the biosynthesis of secondary metabolites, amino acids, purine, and steroid hormones were altered during laying. The metabolome analysis from cecal contents showed that amino acid metabolism and steroid hormone biosynthesis changed during laying. Integrated analysis of the cecal microbiota and metabolites showed the genus Megasphaera was involved in amino acid metabolism, which included 3-phenyllatic acid, quinic acid, caffeic acid, and folic acid, and the genus Hungatella participated in steroid hormone biosynthesis through its strong correlation with estradiol. These results explored the dynamic changes in tissues related to the HPL axis and cecal microbiota, and provided new insights into the interaction between the host and microbiota during egg-laying in chickens.

Taste cells expressing Ionotropic Receptor 94e reciprocally impact feeding and egg laying in Drosophila.

Chemosensory cells across the body of Drosophila melanogaster evaluate the environment to prioritize certain behaviors. Previous mapping of gustatory receptor neurons (GRNs) on the fly labellum identified a set of neurons in L-type sensilla that express Ionotropic Receptor 94e (IR94e), but the impact of IR94e GRNs on behavior remains unclear. We used optogenetics and chemogenetics to activate IR94e neurons and found that they drive mild feeding suppression but enhance egg laying. In vivo calcium imaging revealed that IR94e GRNs respond strongly to certain amino acids, including glutamate, and that IR94e plus co-receptors IR25a and IR76b are required for amino acid detection. Furthermore, IR94e mutants show behavioral changes to solutions containing amino acids, including increased consumption and decreased egg laying. Overall, our results suggest that IR94e GRNs on the fly labellum discourage feeding and encourage egg laying as part of an important behavioral switch in response to certain chemical cues.

Obstacle negotiation in female desert locust oviposition digging.

The female locust lays its eggs deep within soft substrate to protect them from predators and provide optimal conditions for successful development and hatching. During oviposition digging, the female's abdomen is pooled and extends into the ground, guided by a dedicated excavation mechanism at its tip, comprising two pairs of specialized digging valves. Little is known about how these active valves negotiate the various obstacles encountered on their path. In this study, female locusts oviposited their eggs in specialized sand-filled tubes with pre-inserted 3D-printed plastic obstacles. The subterranean route taken by the abdomen and digging valves upon encountering the obstacles was investigated, characterized, and compared to that in control tubes without obstacles. Data were obtained by way of visual inspection, by utilizing cone beam computed tomography scans in high-definition mode, and by making paraffin casts of the oviposition burrows (after egg hatching). We demonstrate, for the first time, the subterranean navigation ability of the female locust's excavation mechanism and its ability to circumvent obstacles during oviposition. Finally, we discuss the role of active sensory-motor mechanisms versus the passive embodied function of the valves, central control, and decision-making.

The Influence of Male Biostimulation on Cloacal Anatomy and Egg-Laying Behavior in Young Female Muscovy Ducks (Cairina moschata forma domestica).

The importance of Muscovy ducks in industrial poultry production is growing; however, little is known about the physiology of their reproductive cycles. This study investigated the influence of male biostimulation on female ducks before the commencement of the laying phase. A total of 30 muscovy ducks, hatched in the same year at 289-341 days of age, were divided into two groups of 15 birds each and kept with and without contact with a male duck until the day of first egg-laying-319 ± 14 and 335 ± 13, respectively. Before reaching egg-laying maturity, the cloacae of 29 adult ducks were subjected to daily clinical assessments. The evaluations yielded four unique categories of outcomes, determined by assessing factors such as the degree of redness and protrusion of the mucous membrane, the moisture level, and swelling of the cloacal sphincter muscle. The results of this study on biostimulation revealed that, on average, female ducks that had contact with males laid their first egg 16 days earlier, weighing 78.7 ± 3.0 g, compared to the isolated female ducks, weighing 79.1 ± 7.0 g. Furthermore, there was no significant difference observed in the mean initial egg weight between the groups (p = 0.841). The cloacal morphology indicated significant morphological changes 25-26 days before laying. Efforts to improve Muscovy production and develop biotechnological techniques to modify these ducks' reproductive cycle will benefit from these advancements.

Sequence variations and accessory proteins adapt TMC functions to distinct sensory modalities.

Transmembrane channel-like (TMC) proteins are expressed throughout the animal kingdom and are thought to encode components of ion channels. Mammals express eight TMCs (mTMC1-8), two of which (mTMC1 and mTMC2) are subunits of mechanotransduction channels. C. elegans expresses two TMCs (TMC-1 and TMC-2), which mediate mechanosensation, egg laying, and alkaline sensing. The mechanisms by which nematode TMCs contribute to such diverse physiological processes and their functional relationship to mammalian mTMCs is unclear. Here, we show that association with accessory proteins tunes nematode TMC-1 to divergent sensory functions. In addition, distinct TMC-1 domains enable touch and alkaline sensing. Strikingly, these domains are segregated in mammals between mTMC1 and mTMC3. Consistent with these findings, mammalian mTMC1 can mediate mechanosensation in nematodes, while mTMC3 can mediate alkaline sensation. We conclude that sequence diversification and association with accessory proteins has led to the emergence of TMC protein complexes with diverse properties and physiological functions.

Dynamic Changes in Intestinal Gene Expression and Microbiota across Chicken Egg-Laying Stages.

Eggs are a vital dietary component for humans, and it is beneficial to increase egg production to support poultry farming. Initially, the egg production rate rises rapidly with young hens until it reaches its peak, and then it declines gradually. By extending the duration of peak egg production, the hens' performance can be enhanced significantly. Previous studies found dynamic changes in gut microbiota during egg-laying, and several species of microbiota isolated from the chicken gut improved egg-laying performance. However, the interaction between microbes and host gene expression is still unclear. This study provides a more comprehensive understanding of chicken egg-laying by examining dynamic alterations in the microbiota of the entire intestinal tract (i.e., duodenum, jejunum, and ileum) and gene expression. The microbial community in the intestine underwent significant changes during different egg-laying periods (i.e., pre-, peak-, and late-laying periods). Metagenomic functional analysis showed that the relative abundance of biosynthesis of amino acids, secondary metabolites, and cofactors decreased significantly in the duodenum, jejunum, and ileum of aging hens. The relative levels of aldosterone, GnRH, insulin, growth hormone, and other hormone-related pathways increased dramatically in the intestinal microbiota during egg-laying, but only in the microbiota located in the duodenum and ileum. Transcriptome analysis suggested that genes associated with various transport processes were upregulated consistently in the small intestine during egg-laying; genes involved in the development of intestinal structure were down-regulated; and genes involved in response to DNA damage and stress were consistent with changes in laying rate. The abundance of Lactobacillus was related to the expression of ANGPTRL1, ANGPTRL2, ANGPT1L, and NOXO1 in the duodenum; Muricomes was correlated significantly with NFKBIZ, LYG2, and IRG1L expression in the jejunum; and Campylobacter was correlated positively with the expression of KMT2A and USF3 in the ileum. These results indicated that the intestinal microbiota and host gene expression may influence egg production jointly.

Plant Essential Oils: Dual Action of Toxicity and Egg-Laying Inhibition on Tetranychus urticae (Acari: Tetranychidae), Unveiling Their Potential as Botanical Pesticides.

Tetranychus urticae, a prominent pest mite in strawberry and vegetable cultivation in China, has developed escalating resistance due to extensive chemical pesticide application. Consequently, there is an urgent need to identify safe and efficacious methods to reduce resistance development. In this study, 38 commercially available plant essential oils (EOs) were screened for their acaricidal potential and ability to inhibit oviposition. The findings revealed that 13 EOs exhibited notable acaricidal activity, with lemon EO demonstrating the highest toxicity, followed by sage, patchouli, frankincense, lemongrass, palmarosa, and oregano EOs. In addition, 18 EOs displayed significant inhibitory effects on oviposition, with lemon EO exhibiting the highest inhibition rate (99.15%) and inhibition index (0.98). Subsequently, sage, frankincense, clove, lemongrass, oregano, patchouli, myrrh, black pepper, palmarosa, and geranium EOs also showed inhibition rates exceeding 50%. Despite black pepper, clove, myrrh, and oregano EOs demonstrating relatively low toxicity against T. urticae, they exhibited heightened efficacy in inhibiting oviposition and suppressing population expansion. This study conducted a comparative assessment of the acaricidal and oviposition inhibition activities of EOs and their principal constituents, thus providing a theoretical basis for the development of botanical acaricides against T. urticae.

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.

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

BACKGROUND: 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. RESULTS: 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. CONCLUSION: 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.

Effect of Perilla seeds inclusion on the performance, egg quality characteristics, biochemical parameters and egg yolk fatty acid composition of laying hens.

This study investigates the effect of supplementation of Perilla seeds (PS) on the performance, egg quality, blood biochemical parameters, and egg yolk fatty acids composition in the diet of egg-laying chicken. A total of 1600 Lohmann laying hens were randomly assigned to four different groups with 4 replicates each (100 chickens/replicate) and were subjected to varying PS concentrations (PS0, PS6, PS12, and PS18; 0%, 6%, 12%, and 18%, respectively) for four weeks, including an acclimation period of one week. The results showed no significant differences among the groups for average egg weight (P > 0.005). The laying rate (%), feed conversion ratio (FCR) and average feed intake (AFI) decreased significantly for birds fed on 18% PS as compared to the other treatments (P < 0.005). Haugh unit, albumin height, egg-shape index and eggshell thickness among hens fed PS diets were greater averaging 80.53, 7.00, 1.29, 0.34 compared to 76.84, 6.86, 1.25 and 0.32 from Control hen eggs (P < 0.05). Serum analysis showed a trend towards elevated levels of glucose (Glu), total protein (TP) and aspartate aminotransferase (AST) among treatments. Total cholesterol (TC), low-density lipoprotein (LDL), and high-density lipoprotein (HDL) decreased for the birds fed on 6% PS. The fatty acid composition of egg yolk showed a substantial reduction for α-linolenic acid and docosahexaenoic acid increased significantly by the incorporating PS in the diet (P < 0.001). PS incorporation in diets resulted in significant improvements in both performance indicators and greater amounts of α-linolenic acid and DHA in egg yolks. These findings indicate that PS at 6% inclusion has the potential to improve fatty acid profiles of egg yolk without any adverse effect on performance of egg quality.

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.

Parasitoid cues modulate Drosophila germline development and stem cell proliferation.

Environmental factors influence an organism's reproductive ability by regulating germline development and physiology. While the reproductive adaptations in response to extrinsic stress cues offer fitness and survival advantages to individuals, the mechanistic understanding of these modifications remains unclear. Here, we find that parasitoid wasps' stress signaling regulates Drosophila melanogaster oogenesis. We show that fruit flies dwelling in the wasp-infested area elevate their fecundity, and the observed reproductive response is specific to Pachycrepoideus sp., a pupal parasitoid wasp. Pachycrepoideus-specific olfactory and visual cues recruit the signaling pathways that promote germline stem cell proliferation and accelerate follicle development, increasing egg production in Drosophila females. Downregulation of signaling engaged in oocyte development by shifting flies to a non-wasp-infested environment increases apoptosis of the developing follicles. Thus, this study establishes host germline responsiveness to parasitoid-specific signals and supports a predator strategy to increase hosts for infection.

GCY-20 signaling controls suppression of Caenorhabditis elegans egg laying by moderate cold.

Organisms sensing environmental cues and internal states and integrating the sensory information to control fecundity are essential for survival and proliferation. The present study finds that a moderate cold temperature of 11°C reduces egg laying in Caenorhabditis elegans. ASEL and AWC neurons sense the cold via GCY-20 signaling and act antagonistically on egg laying through the ASEL and AWC/AIA/HSN circuits. Upon cold stimulation, ASEL and AWC release glutamate to activate and inhibit AIA interneurons by acting on highly and lowly sensitive ionotropic GLR-2 and GLC-3 receptors, respectively. AIA inhibits HSN motor neuron activity via acetylcholinergic ACR-14 receptor signaling and suppresses egg laying. Thus, ASEL and AWC initiate and reduce the cold suppression of egg laying. ASEL's action on AIA and egg laying dominates AWC's action. The biased opposite actions of these neurons on egg laying provide animals with a precise adaptation of reproductive behavior to environmental temperatures.

Expression and potential regulatory functions of Drosophila octopamine receptors in the female reproductive tract.

Aminergic signaling is known to play a critical role in regulating female reproductive processes in both mammals and insects. In Drosophila, the ortholog of noradrenaline, octopamine, is required for ovulation as well as several other female reproductive processes. Two octopamine receptors have already been shown to be expressed in the Drosophila reproductive tract and to be required for egg-laying: OAMB and Octß2R. The Drosophila genome contains 4 additional octopamine receptors-Octα2R, Octß1R, Octß3R, and Oct-TyrR-but their cellular patterns of expression in the reproductive tract and potential contribution(s) to egg-laying are not known. In addition, the mechanisms by which OAMB and Octß2R regulate reproduction are incompletely understood. Using a panel of MiMIC Gal4 lines, we show that Octα2R, Octß1R, Octß3R, and Oct-TyrR receptors are not detectable in either epithelium or muscle but are clearly expressed in neurons within the female fly reproductive tract. Optogenetic activation of neurons that express at least 3 types of octopamine receptors stimulates contractions in the lateral oviduct. We also find that octopamine stimulates calcium transients in the sperm storage organs and that its effects in spermathecal, secretory cells, can be blocked by knock-down of OAMB. These data extend our understanding of the pathways by which octopamine regulates egg-laying in Drosophila and raise the possibility that multiple octopamine receptor subtypes could play a role in this process.