Early behavioral and molecular events leading to caste switching in the ant Harpegnathos.

Ant societies show a division of labor in which a queen is in charge of reproduction while nonreproductive workers maintain the colony. In Harpegnathos saltator, workers retain reproductive ability, inhibited by the queen pheromones. Following the queen loss, the colony undergoes social unrest with an antennal dueling tournament. Most workers quickly abandon the tournament while a few workers continue the dueling for months and become gamergates (pseudoqueens). However, the temporal dynamics of the social behavior and molecular mechanisms underlining the caste transition and social dominance remain unclear. By tracking behaviors, we show that the gamergate fate is accurately determined 3 d after initiation of the tournament. To identify genetic factors responsible for this commitment, we compared transcriptomes of different tissues between dueling and nondueling workers. We found that juvenile hormone is globally repressed, whereas ecdysone biosynthesis in the ovary is increased in gamergates. We show that molecular changes in the brain serve as earliest caste predictors compared with other tissues. Thus, behavioral and molecular data indicate that despite the prolonged social upheaval, the gamergate fate is rapidly established, suggesting a robust re-establishment of social structure.

Recent Advances in Behavioral (Epi)Genetics in Eusocial Insects.

Eusocial insects live in societies in which distinct family members serve specific roles in maintaining the colony and advancing the reproductive ability of a few select individuals. Given the genetic similarity of all colony members, the diversity of morphologies and behaviors is surprising. Social communication relies on pheromones and olfaction, as shown by mutants of orco, the universal odorant receptor coreceptor, and through electrophysiological analysis of neuronal responses to pheromones. Additionally, neurohormonal factors and epigenetic regulators play a key role in caste-specific behavior, such as foraging and caste switching. These studies start to allow an understanding of the molecular mechanisms underlying social behavior and provide a technological foundation for future studies of eusocial insects. In this review, we highlight recent findings in eusocial insects that advance our understanding of genetic and epigenetic regulations of social behavior and provide perspectives on future studies using cutting-edge technologies.

Substances in the mandibular glands mediate queen effects on larval development and colony organization in an annual bumble bee.

Social organization is commonly dynamic, with extreme examples in annual social insects, but little is known about the underlying signals and mechanisms. Bumble bee larvae with close contact to a queen do not differentiate into gynes, pupate at an earlier age, and are commonly smaller than siblings that do not contact a queen. We combined detailed observations, proteomics, microRNA transcriptomics, and gland removal surgery to study the regulation of brood development and division of labor in the annual social bumble bee Bombus terrestris. We found that regurgitates fed to larvae by queens and workers differ in their protein and microRNA composition. The proteome of the regurgitate overlaps significantly with that of the mandibular (MG) and hypopharyngeal glands (HPG), suggesting that these exocrine glands are sources of regurgitate proteins. The proteome of the MG and HPG, but not the salivary glands, differs between queens and workers, with caste-specificity preserved for the MG and regurgitate proteomes. Queens subjected to surgical removal of the MG showed normal behavior, brood care, and weight gain, but failed to shorten larval development. These findings suggest that substances in the queen MG are fed to larvae and influence their developmental program. We suggest that when workers emerge and contribute to larval feeding, they dilute the effects of the queen substances, until she can no longer manipulate the development of all larvae. Longer developmental duration may allow female larvae to differentiate into gynes rather than to workers, mediating the colony transition from the ergonomic to the reproductive phase.

Genomic and transcriptomic analyses of the subterranean termite Reticulitermes speratus: Gene duplication facilitates social evolution.

Termites are model social organisms characterized by a polyphenic caste system. Subterranean termites (Rhinotermitidae) are ecologically and economically important species, including acting as destructive pests. Rhinotermitidae occupies an important evolutionary position within the clade representing a transitional taxon between the higher (Termitidae) and lower (other families) termites. Here, we report the genome, transcriptome, and methylome of the Japanese subterranean termite Reticulitermes speratus Our analyses highlight the significance of gene duplication in social evolution in this termite. Gene duplication associated with caste-biased gene expression was prevalent in the R. speratus genome. The duplicated genes comprised diverse categories related to social functions, including lipocalins (chemical communication), cellulases (wood digestion and social interaction), lysozymes (social immunity), geranylgeranyl diphosphate synthase (social defense), and a novel class of termite lineage-specific genes with unknown functions. Paralogous genes were often observed in tandem in the genome, but their expression patterns were highly variable, exhibiting caste biases. Some of the assayed duplicated genes were expressed in caste-specific organs, such as the accessory glands of the queen ovary and the frontal glands of soldier heads. We propose that gene duplication facilitates social evolution through regulatory diversification, leading to caste-biased expression and subfunctionalization and/or neofunctionalization conferring caste-specialized functions.

Social disadvantage, economic inequality, and life expectancy in nine Indian states.

SignificanceIndia is one of the most hierarchical societies in the world. Because vital statistics are incomplete, mortality disparities are not quantified. Using survey data on more than 20 million individuals from nine Indian states representing about half of India's population, we estimate and decompose life expectancy differences between higher-caste Hindus, comprising other backward classes and high castes, and three marginalized social groups: Adivasis (indigenous peoples), Dalits (oppressed castes), and Muslims. The three marginalized groups experience large disadvantages in life expectancy at birth relative to higher-caste Hindus. Economic status explains less than half of these gaps. These large disparities underscore parallels between diverse systems of discrimination akin to racism. They highlight the global significance of addressing social inequality in India.

The genetic determination of alternate stages in polyphenic insects.

Molt-based transitions in form are a central feature of insect life that have enabled adaptation to diverse and changing environments. The endocrine regulation of these transitions is well established, but an understanding of their genetic regulation has only recently emerged from insect models. The pupal and adult stages of metamorphosing insects are determined by the stage specifying transcription factors broad-complex (br) and Ecdysone inducible protein 93 (E93), respectively. A probable larval determinant, chronologically inappropriate metamorphosis (chinmo), has just recently been characterized. Expression of these three transcription factors in the metamorphosing insects is regulated by juvenile hormone with ecdysteroid hormones, and by mutual repression between the stage-specific transcription factors. This review explores the hypothesis that variations in the onset, duration, and tissue-specific expression of chinmo, br, and E93 underlie other polyphenisms that have arisen throughout insects, including the castes of social insects, aquatic stages of mayflies, and the neoteny of endoparasites. The mechanisms that constrain how chinmo, br, and E93 expression may vary will also constrain the ways that insect life history may evolve. I find that four types of expression changes are associated with novel insect forms: (1) heterochronic shift in the turnover of expression, (2) expansion or contraction of expression, (3) tissue-specific expression, and (4) redeployment of stage-specific expression. While there is more to be learned about chinmo, br, and E93 function in diverse insect taxa, the studies outlined here show that insect stages are modular units in developmental time and a substrate for evolutionary forces to act upon.

Coevolution of larval signalling and worker response can trigger developmental caste determination in social insects.

Eusocial insects belong to distinct queen and worker castes, which, in turn, can be divided into several morphologically specialized castes of workers. Caste determination typically occurs by differential nutrition of developing larvae. We present a model for the coevolution of larval signalling and worker task allocation-both modelled by flexible smooth reaction norms-to investigate the evolution of caste determination mechanisms and worker polymorphism. In our model, larvae evolve to signal their nutritional state to workers. The workers evolve to allocate time to foraging for resources versus feeding the brood, conditional on the larval signals and their body size. Worker polymorphism evolves under accelerating foraging returns of increasing body size, which causes selection to favour large foraging and small nursing workers. Worker castes emerge because larvae evolve to amplify their signals after obtaining some food, which causes them to receive more food, while the other larvae remain unfed. This leads to symmetry-breaking among the larvae, which are either well-nourished or malnourished, thus emerging as small or large workers. Our model demonstrates the evolution of nutrition-dependent caste determination and worker polymorphism by a self-reinforcement mechanism that evolves from the interplay of larval signalling and worker response to the signals.

Resource adaptation drives the size-complexity rule in termites.

The size-complexity rule posits that the evolution of larger cooperative groups should favour more division of labour. Examples include more cell types in larger multicellular organisms, and more polymorphic castes in larger eusocial colonies. However, a correlation between division of labour and group size may reflect a shared response of both traits to resource availability and/or profitability. Here, this possibility was addressed by investigating the evolution of sterile caste number (worker and soldier morphotypes) in termites, a major clade of eusocial insects in which the drivers of caste polymorphism are poorly understood. A novel dataset on 90 termite species was compiled from the published literature. The analysis showed that sterile caste number did increase markedly with colony size. However, after controlling for resource adaptations and phylogeny, there was no evidence for this relationship. Rather, sterile caste number increased with increasing nest-food separation and decreased with soil-feeding, through changes in worker (but not soldier) morphotype number. Further, colony size increased with nest-food separation, thus driving the false correlation between sterile caste number and colony size. These findings support adaptation to higher energy acquisition as key to the rise of complex insect societies, with larger size being a by-product.

Minibrain plays a role in the adult brain development of honeybee (Apis mellifera) workers.

The brain of adult honeybee (Apis mellifera) workers is larger than that of queens, facilitating behavioural differentiation between the castes. This brain diphenism develops during the pharate-adult stage and is driven by a caste-specific gene expression cascade in response to unique hormonal milieus. Previous molecular screening identified minibrain (mnb; DYRK1A) as a potential regulator in this process. Here, we used RNAi approach to reduce mnb transcript levels and test its role on brain diphenism development in honeybees. White-eyed unpigmented cuticle worker pupae were injected with dsRNA for mnb (Mnb-i) or gfp, and their phenotypes were assessed two and 8 days later using classic histological and transcriptomic analyses. After 2 days of the injections, Mnb-i bees showed 98% of downregulation of mnb transcripts. After 8 days, the brain of Mnb-i bees showed reduction in total volume and in the volume of the mushroom bodies (MB), antennal, and optic lobes. Additionally, signs of apoptosis were observed in the Kenyon cells region of the MB, and the cohesion of the brain tissues was affected. Our transcriptomic analyses revealed that 226 genes were affected by the knockdown of mnb transcripts, most of which allowing axonal fasciculation. These results suggest the evolutionary conserved mnb gene has been co-opted for promoting hormone-mediated developmental brain morphological plasticity generating caste diphenism in honeybees.

Sex- and caste-specific developmental responses to juvenile hormone in an ant with maternal caste determination.

Juvenile hormone is considered to be a master regulator of polyphenism in social insects. In the ant Cardiocondyla obscurior, whether a female egg develops into a queen or a worker is determined maternally and caste-specific differentiation occurs in embryos, so that queens and workers can be distinguished in a non-invasive manner from late embryogenesis onwards. This ant also exhibits two male morphs - winged and wingless males. Here, we used topical treatment with juvenile hormone III and its synthetic analogue methoprene, a method that influences caste determination and differentiation in some ant species, to investigate whether hormone manipulation affects the development and growth of male, queen- and worker-destined embryos and larvae. We found no effect of hormone treatment on female caste ratios or body sizes in any of the treated stages, even though individuals reacted to heightened hormone availability with increased expression of krüppel-homolog 1, a conserved JH first-response gene. In contrast, hormone treatment resulted in the emergence of significantly larger males, although male morph fate was not affected. These results show that in C. obscurior, maternal caste determination leads to irreversible and highly canalized caste-specific development and growth.

An orthology-based methodology as a complementary approach to retrieve evolutionarily conserved A-to-I RNA editing sites.

Adar-mediated adenosine-to-inosine (A-to-I) mRNA editing is a conserved mechanism that exerts diverse regulatory functions during the development, evolution, and adaptation of metazoans. The accurate detection of RNA editing sites helps us understand their biological significance. In this work, with an improved genome assembly of honeybee (Apis mellifera), we used a new orthology-based methodology to complement the traditional pipeline of (de novo) RNA editing detection. Compared to the outcome of traditional pipeline, we retrieved many novel editing sites in CDS that are deeply conserved between honeybee and other distantly related insects. The newly retrieved sites were missed by the traditional de novo identification due to the stringent criteria for controlling false-positive rate. Caste-specific editing sites are identified, including an Ile>Met auto-recoding site in Adar. This recoding was even conserved between honeybee and bumblebee, suggesting its putative regulatory role in shaping the phenotypic plasticity of eusocial Hymenoptera. In summary, we proposed a complementary approach to the traditional pipeline and retrieved several previously unnoticed CDS editing sites. From both technical and biological aspects, our works facilitate future researches on finding the functional editing sites and advance our understanding on the connection between RNA editing and the great phenotypic diversity of organisms.

Dynamics of caste and early childbearing in India: a perspective of three decades.

BACKGROUND: Early childbearing disrupts girls' otherwise healthy growth into adulthood and adversely affects their education, livelihood, and health. Individual, sociocultural, economic, environmental, and health service-related factors contribute to childbearing among young females. In India, caste affects health outcomes despite several affirmative policies aimed at improving the health and welfare of the backward castes/tribes. However, there is a dearth of empirical evidence about the impact of caste on early childbearing, more specifically, regarding the trajectory of inter-caste disparities in early childbearing. METHOD: This study used data from all five rounds of the National Family Health Survey (NFHS) in India to assess the association between caste and early childbearing over the last three decades. All women aged 20-24 [NFHS-1 (n = 17,218), NFHS-2 (n = 15,973), NFHS-3 (n = 22,807), NFHS-4 (n = 122,955) and NFHS-5 (n = 118,700)] were considered to create a pooled data set (n = 297,653) for analysis. Bivariate analysis and binary logistic regression were conducted using Stata (v17). ArcMap (v10.8) presented the caste-wise prevalence of early childbearing among the states and Union Territories (UTs). RESULTS: Many women continue to have early childbearing despite a considerable reduction over the last three decades from 47% in 1992-93 to 15% in 2019-21. Compared to NFHS-1, the odds of early childbearing increased by 15% in NFHS-2 and, after that, declined by 42% in NFHS-3 and 64% in NFHS-4 and NFHS-5. The inter-caste disparity in early childbearing persists, albeit with a narrowing gap, with the Scheduled castes (SC) remaining the most vulnerable group. Adjusting the effects of socio-demographic and economic characteristics, SC women had significantly higher odds of early childbearing (OR = 1.07, CI = 1.04-1.11) than those from the General caste. CONCLUSION: To decrease early childbirth, a focus on adolescent marriage prevention and increasing contraceptive use among young SC women is necessary. Strengthening ongoing programs and policies targeting educational and economic empowerment of the socially weaker castes/tribes will help in reducing early childbearing. Efforts to prevent early childbearing will accelerate the achievement of the Sustainable Development Goals (SDGs)-especially those related to health, poverty, nutrition, education, and general wellbeing, in addition to protecting women's reproductive rights.

Effect of Solenopsis invicta virus 3 on brood mortality and egg hatch in Solenopsis invicta.

Solenopsis invicta virus 3 (SINV-3) has been shown to cause significant mortality among all stages of its host, Solenopsis invicta. One impact of the virus is alteration of worker ant foraging behavior, which results in colony starvation and collapse over time. Additionally, it has been hypothesized that SINV-3 infection of S. invicta may disrupt worker ant brood care behavior. To investigate this possibility, various combinations of SINV-3-infected and -uninfected adult (worker) and immature (brood) stages were placed together and monitored using the response variables, mortality, egg hatch, and virus load. While significant differences in percent cumulative S. invicta worker ant mortality among six combinations of SINV-3-infected and -uninfected stages were observed, no significant differences in percent cumulative mortality of S. invicta larvae or pupae were observed. No significant differences in egg hatch were observed among SINV-3-uninfected, SINV-3-infected (colony-treated and queen-treated), and starved colonies. Eggs hatched normally in 10-12 days for all treatments indicating that egg care by worker ants was unaffected by SINV-3 infection status. The study further clarifies SINV-3 pathogenesis in its host, S. invicta. Larval mortality in SINV-3-infected colonies does not appear to be caused by worker ant neglect. S. invicta brood under the care of SINV-3-infected worker ants did not exhibit higher mortality rates compared with those tended by SINV-3-uninfected worker ants.

Heteronormative geographies and other sexual practices in rural Haryana, India.

Kinship patterns and caste structures have a significant effect on Indian people's lives. Rural Haryana has a strong caste-based kinship system organised around a heteronormative narrative that shapes associated societal and cultural values. This narrative centres on heterosexual marriage, which is arranged within the rules of kinship patterns. Such marital arrangements are viewed as the only space in which people can realise their sexual desires. This article aims to understand the diverse practices of people in rural Haryana that subvert this narrative to realise their sexual desires. The study adopted an ethnographic approach, using casual conversations as a data source to understand how sexuality is practised in rural areas under a strong kinship structure. In the paper, we argue that while the practices documented may seem subversive and countervailing, they contribute to concretising and maintaining the dominant social structure.

Who is Anaemic in India? Intersections of class, caste, and gender.

Anaemia severely impacts physical and mental abilities, raises health risks, and diminishes the quality of life and work capacity. It is a leading cause of adverse pregnancy outcomes and maternal mortality, especially in developing nations like India, where recent data on anaemia from National Family and Health Survey (NFHS-4) (2015-16) and NFHS-5 (2019-21) indicate a tremendous rise. Anaemia is a marker of poor nutrition and health, and socio-economic factors such as gender norms, race, income, and living conditions influence its impact. As a result, there are disparities in how anaemia affects different segments of society. However, existing research on health inequity and anaemia often employs a single-axis analytical framework of social power. These studies operate under the assumption that gender, economic class, ethnicity, and caste are inherently distinct and mutually exclusive categories and fail to provide a comprehensive understanding of anaemia prevalence. Therefore, the study has adopted the theoretical framework of intersectionality and analysed the NFHS-5 (2019-21) data using bivariate cross-tabulations and binary logistic regression models to understand how gender, class, caste, and place of residence are associated with the prevalence of anaemia. The results suggest that the women of Scheduled Tribes (ST) and Scheduled Castes (SC) share a disproportionate burden of anaemia. This study confirms that economic class and gender, geographical location, level of education, and body mass index significantly determine the prevalence of anaemia. The ST and SC women who are economically marginalised and reside in rural areas with high levels of poverty, exclusion, and poor nutritional status have a higher prevalence of anaemia than other population groups. Thus, the study suggests that intersections of multiple factors such as caste, class, gender, and place of residence significantly determine 'who is anaemic in India'.

Olfactory sensitivity differentiates morphologically distinct worker castes in Camponotus floridanus.

BACKGROUND: Camponotus floridanus ant colonies are comprised of a single reproductive queen and thousands of sterile female offspring that consist of two morphologically distinct castes: smaller minors and larger majors. Minors perform most of the tasks within the colony, including brood care and food collection, whereas majors have fewer clear roles and have been hypothesized to act as a specialized solider caste associated with colony defense. The allocation of workers to these different tasks depends, in part, on the detection and processing of local information including pheromones and other chemical blends such as cuticular hydrocarbons. However, the role peripheral olfactory sensitivity plays in establishing and maintaining morphologically distinct worker castes and their associated behaviors remains largely unexplored. RESULTS: We examined the electrophysiological responses to general odorants, cuticular extracts, and a trail pheromone in adult minor and major C. floridanus workers, revealing that the repertoire of social behaviors is positively correlated with olfactory sensitivity. Minors in particular display primarily excitatory responses to olfactory stimuli, whereas major workers primarily manifest suppressed, sub-solvent responses. The notable exception to this paradigm is that both minors and majors display robust, dose-dependent excitatory responses to conspecific, non-nestmate cuticular extracts. Moreover, while both minors and majors actively aggress non-nestmate foes, the larger and physiologically distinct majors display significantly enhanced capabilities to rapidly subdue and kill their adversaries. CONCLUSIONS: Our studies reveal the behavioral repertoire of minors and majors aligns with profound shifts in peripheral olfactory sensitivity and odor coding. The data reported here support the hypothesis that minors are multipotential workers with broad excitatory sensitivity, and majors are dedicated soldiers with a highly specialized olfactory system for distinguishing non-nestmate foes. Overall, we conclude that C. floridanus majors do indeed represent a physiologically and behaviorally specialized soldier caste in which caste-specific olfactory sensitivity plays an important role in task allocation and the regulation of social behavior in ant colonies.

Who eats last? Intra-household gender inequality in food allocation among children in educationally backward areas of India.

The practice of women eating after men is a common gender-inequitable food allocation mechanism among adults in Indian households and has been associated with poor health and nutritional outcomes for women. However, empirical evidence on whether a similar practice of girls eating after boys is prevalent among children is scarce. Using primary data from a household survey conducted in educationally backward areas of four Indian states, we provide new evidence of this practice among children. Almost 28 per cent of the sample households follow the mealtime custom of girls eating after boys. Scheduled Tribes and households with higher incomes are less likely to follow this practice. Other relevant factors include children's relative ages by sex and an interplay between family size and children's sex composition. While our findings may not be generalizable, they suggest an intersectionality between gender and other dimensions of inequality, namely social identity and economic class.

Odorant Receptors Expressing and Antennal Lobes Architecture Are Linked to Caste Dimorphism in Asian Honeybee, Apis cerana (Hymenoptera: Apidae).

Insects heavily rely on the olfactory system for food, mating, and predator evasion. However, the caste-related olfactory differences in Apis cerana, a eusocial insect, remain unclear. To explore the peripheral and primary center of the olfactory system link to the caste dimorphism in A. cerana, transcriptome and immunohistochemistry studies on the odorant receptors (ORs) and architecture of antennal lobes (ALs) were performed on different castes. Through transcriptomesis, we found more olfactory receptor genes in queens and workers than in drones, which were further validated by RT-qPCR, indicating caste dimorphism. Meanwhile, ALs structure, including volume, surface area, and the number of glomeruli, demonstrated a close association with caste dimorphism. Particularly, drones had more macroglomeruli possibly for pheromone recognition. Interestingly, we found that the number of ORs and glomeruli ratio was nearly 1:1. Also, the ORs expression distribution pattern was very similar to the distribution of glomeruli volume. Our results suggest the existence of concurrent plasticity in both the peripheral olfactory system and ALs among different castes of A. cerana, highlighting the role of the olfactory system in labor division in insects.

Introduction to a special section: Racial disparities in health care.

Papers in the Special Section on Racial Disparities in Health Care stemmed from. the 60th Anniversary of Family Process Conference, The Heart of the Matter: Systemic Imperatives to Address Health Disparities and Racism in the Time of COVID, which took place in Washington, DC in September 2021. Of the 12 presenters at the conference, these four were asked to recreate their talks into articles. They address key issues that help to explain health disparities in people of color, particularly African Americans, in the United States, as well as suggest innovations to clinical interventions and health care delivery systems to better serve people who have suffered adversity from the racial inequities in the American system.

Counter-stories in the way of caste: towards an anti-casteist public health praxis in contemporary India.

How can ethnographic methods track implicit & explicit forms of structural casteism in Indian public health policy and praxis? How can a critical attention to ordinary stories and subjectivities of casted lives reveal the underlying Brahmanical moralities, assumptions and imaginations of public health but equally also unravel anti-caste counter-framings/counter-theorizations of symptoms, afflictions, injuries and chronic wounds wrought by caste? How, in other words, can the horizons of anti-colonial theory-making be expanded to capaciously conceptualize casteism as a core determinant of community health outcomes and life-chances in India? By mobilizing 'counter-storytelling' as a concept and method for critical medical anthropology from the Global South, and case studies from longitudinal ethnography in northern India, this paper provides a dual critique of: 1. Public health praxis in relation to questions of caste, addiction, respiratory debilitation, air pollution and TB. And, 2. Epistemologies of health policy making pertaining to wellness for 'the poor' and the gendered and casted labour of community care workers like ASHAs and non-institutionalized health actors.