Animal models for studying neural crest development: is the mouse different?

The neural crest is a uniquely vertebrate cell type and has been well studied in a number of model systems. Zebrafish, Xenopus and chick embryos largely show consistent requirements for specific genes in early steps of neural crest development. By contrast, knockouts of homologous genes in the mouse often do not exhibit comparable early neural crest phenotypes. In this Spotlight article, we discuss these species-specific differences, suggest possible explanations for the divergent phenotypes in mouse and urge the community to consider these issues and the need for further research in complementary systems

Shape of Evasive Prey Can Be an Important Cue That Triggers Learning in Avian Predators

Advertising escape ability could reduce predatory attacks. However, the effectiveness of certain phenotypic cues (e.g., color, shape, and size) in signaling evasiveness is still unknown. Understanding the role of such signals in driving predator learning is important to infer the evolutionary mechanisms leading to convergent evasiveness signals among prey species (i.e., evasive mimicry). We aim to understand the role of the color pattern (white patches on dark background) and morphology (extended butterfly hindwings) in driving learning and avoidance of escaping prey by surrogate avian predators, the European blue tit. These cues are common in butterflies and have been suspected to advertise escape ability in nature. We use dummy butterflies harboring shape and color patterns commonly found in skippers (family Hesperiidae). The prey models displayed the studied phenotypical cues (hindwing tails and white bands) in factorial combinations, and we tested whether those cues were learned as evasive signals and were generalised to different phenotypes. Our results suggest that hindwing tails and white bands can be associated with prey evasiveness. In addition, wild blue tits might learn and avoid attacking prey models bearing the studied phenotypic cues. Although blue tits seem to have an initial preference for the phenotype consisting of white patches and hindwing tails, the probability of attacking it was substantially reduced once the cues were associated with escaping ability. This suggests that the same morphological cues might be interchangeable as preference/avoidance signals. Further investigation of the salience of hindwing tails vs. white bands as cues for escaping ability, revealed that predators can associate both color pattern and shape to the difficulty of capture, and possibly generalize their aversion to other prey harboring those cues. More studies with larger sample sizes are needed to confirm this trend. Altogether, our results highlight the hitherto overlooked role of shape (butterfly hindwing tails) for signaling prey unprofitability.Peer reviewe

Mutualistic interactions shape global spatial congruence and climatic niche evolution in Neotropical mimetic butterflies

Understanding the mechanisms underlying species distributions and coexistence is both a priority and a challenge for biodiversity hotspots such as the Neotropics. Here, we highlight that Mullerian mimicry, where defended prey species display similar warning signals, is key to the maintenance of biodiversity in the c. 400 species of the Neotropical butterfly tribe Ithomiini (Nymphalidae: Danainae). We show that mimicry drives large-scale spatial association among phenotypically similar species, providing new empirical evidence for the validity of Muller's model at a macroecological scale. Additionally, we show that mimetic interactions drive the evolutionary convergence of species climatic niche, thereby strengthening the co-occurrence of co-mimetic species. This study provides new insights into the importance of mutualistic interactions in shaping both niche evolution and species assemblages at large spatial scales. Critically, in the context of climate change, our results highlight the vulnerability to extinction cascades of such adaptively assembled communities tied by positive interactions

Hard to catch : experimental evidence supports evasive mimicry

Most research on aposematism has focused on chemically defended prey, but the signalling difficulty of capture remains poorly explored. Similar to classical Batesian and Mullerian mimicry related to distastefulness, such 'evasive aposematism' may also lead to convergence in warning colours, known as evasive mimicry. A prime candidate group for evasive mimicry are Adelpha butterflies, which are agile insects and show remarkable colour pattern convergence. We tested the ability of naive blue tits to learn to avoid and generalize Adelpha wing patterns associated with the difficulty of capture and compared their response to that of birds that learned to associate the same wing patterns with distastefulness. Birds learned to avoid all wing patterns tested and generalized their aversion to other prey to some extent, but learning was faster with evasive prey compared to distasteful prey. Our results on generalization agree with longstanding observations of striking convergence in wing colour patterns among Adelpha species, since, in our experiments, perfect mimics of evasive and distasteful models were always protected during generalization and suffered the lowest attack rate. Moreover, generalization on evasive prey was broader compared to that on distasteful prey. Our results suggest that being hard to catch may deter predators at least as effectively as distastefulness. This study provides empirical evidence for evasive mimicry, a potentially widespread but poorly understood form of morphological convergence driven by predator selection.Peer reviewe

Variation of chemical compounds in wild Heliconiini reveals ecological factors involved in the evolution of chemical defenses in mimetic butterflies.

Evolutionary convergence of color pattern in mimetic species is tightly linked with the evolution of chemical defenses. Yet, the evolutionary forces involved in natural variations of chemical defenses in aposematic species are still understudied. Herein, we focus on the evolution of chemical defenses in the butterfly tribe Heliconiini. These neotropical butterflies contain large concentrations of cyanogenic glucosides, cyanide-releasing compounds acting as predator deterrent. These compounds are either de novo synthesized or sequestered from their Passiflora host plant, so that their concentrations may depend on host plant specialization and host plant availability. We sampled 375 wild Heliconiini butterflies across Central and South America, covering 43% species of this clade, and quantify individual variations in the different CGs using liquid chromatography coupled with tandem mass spectrometry. We detected new compounds and important variations in chemical defenses both within and among species. Based on the most recent and well-studied phylogeny of Heliconiini, we show that ecological factors such as mimetic interactions and host plant specialization have a significant association with chemical profiles, but these effects are largely explained by phylogenetic relationships. Our results therefore suggest that shared ancestries largely contribute to chemical defense variation, pointing out at the interaction between historical and ecological factors in the evolution of Müllerian mimicry

Developmental, cellular, and biochemical basis of transparency in the glasswing butterfly Greta oto

Numerous species of Lepidoptera have transparent wings, which often possess scales of altered morphology and reduced size, and the presence of membrane surface nanostructures that dramatically reduce reflection. Optical properties and anti-reflective nanostructures have been characterized for several ‘clearwing’ Lepidoptera, but the developmental basis of wing transparency is unknown. We apply confocal and electron microscopy to create a developmental time-series in the glasswing butterfly, Greta oto, comparing transparent and non-transparent wing regions. We find that scale precursor cell density is reduced in transparent regions, and cytoskeletal organization differs between flat scales in opaque regions, and thin, bristle-like scales in transparent regions. We also reveal that sub-wavelength nanopillars on the wing membrane are wax-based, derive from wing epithelial cells and their associated microvillar projections, and demonstrate their role in enhancing-anti-reflective properties. These findings provide insight into morphogenesis of naturally organized micro- and nanostructures and may provide bioinspiration for new anti-reflective materials

Predictors of Program Participation in a Nutrition-Sensitive Agroecological Intervention in Singida, Tanzania

This research article was published in the Current Developments in Nutrition Volume 4, SUPPLEMENT 2, June 2020Objectives Nutrition-sensitive agricultural interventions are theorized to improve child’s diet through asset provision and program participation. Although some programs measure participation, predictors of participation are understudied. We therefore investigated predictors of men’s and women’s program participation in Singida Nutrition and Agroecology Project (SNAP-Tz; NCT02761876). Methods In SNAP-Tz, ‘mentor farmers’ led their peers (smallholder farmers with children < 1 year at baseline) in learning about agroecology, nutrition, and gender equity through meetings and household visits. At baseline, we collected data on demographics, Household Food Insecurity Access Scale (0–27), men’s involvement in 7 household tasks (0–7), and Abbreviated Women’s Empowerment in Agriculture Index (AWEAI). Participating men (n = 262) and women (n = 283) were asked to recall their program participation biannually. Predictors of high participation, defined as attendance in ≥60% participant meetings and household visits, were identified using multiple logistic regressions, controlling for clustering at the village level. Results Only 59% and 37% of women and men, respectively, had high participation. Women’s high participation was associated with their spouse’s participation (OR = 4.23, P < 0.01), greater food insecurity (OR = 1.03, P = 0.03), years of education (OR = 1.13, P = 0.02), and being empowered (OR = 5.88, P < 0.01). Men’s high participation was associated with their spouse’s participation (OR = 4.22, P < 0.01), greater food insecurity (OR = 2.23, P = 0.01), involvement in household tasks (OR = 1.25, P = 0.04), and age (OR = 1.03, P < 0.01). Conclusions Associations between an individual’s and their spouse’s participation indicate the importance of spousal dynamics. The association between participation and baseline gender equity (i.e., women’s empowerment, men’s involvement in household tasks) highlights the challenges of gender programming in nutrition-sensitive interventions. Analysis of program participation was simple and revealed valuable lessons for program implementation and design; more programs should therefore analyze participation

A Participatory Agroecological Intervention Reduces Women’s Risk of Probable Depression Through Improvements in Food Security in Singida, Tanzania

This research article was published in the Current Developments in Nutrition Volume 4, Supplement 2, June 2020In 2015, depressive disorders led to over 50 million disability-adjusted life years lost globally, with more than 80% occurring in low- and middle-income countries. Depressive disorders are also risk factors of a number of adverse maternal and child health outcomes. To our knowledge, the Singida Nutrition and Agroecology Project (SNAP-Tz), is the first nutrition-sensitive agriculture (NSA) intervention identified to improve women’s probable depression (2020). Food security has been posited to play an important role in the relationship between NSA interventions and depression, yet causal factors have not yet been analyzed quantitatively. Therefore, we investigated food security’s mediating role on this impact

Cardiovascular Risk Reduction After Renal Denervation According to Time in Therapeutic Systolic Blood Pressure Range

Background: Renal denervation (RDN) has been shown to lower blood pressure (BP), but its effects on cardiovascular events have only been preliminarily evaluated. Time in therapeutic range (TTR) of BP is associated with cardiovascular events. Objectives: This study sought to assess the impact of catheter-based RDN on TTR and its association with cardiovascular outcomes in the GSR (Global SYMPLICITY Registry). Methods: Patients with uncontrolled hypertension were enrolled and treated with radiofrequency RDN. Office and ambulatory systolic blood pressure (OSBP and ASBP) were measured at 3, 6, 12, 24, and 36 months postprocedure and used to derive TTR. TTR through 6 months was assessed as a predictor of cardiovascular events from 6 to 36 months using a Cox proportional hazard regression model. Results: As of March 1, 2022, 3,077 patients were enrolled: 42.2% were female; mean age was 60.5 ± 12.2 years; baseline OSBP was 165.6 ± 24.8 mm Hg; and baseline ASBP was 154.3 ± 18.7 mm Hg. Patients were prescribed 4.9 ± 1.7 antihypertensive medications at baseline and 4.8 ± 1.9 at 36 months. At 36 months, mean changes were −16.7 ± 28.4 and −9.0 ± 20.2 mm Hg for OSBP and ASBP, respectively. TTR through 6 months was 30.6%. A 10% increase in TTR after RDN through 6 months was associated with significant risk reductions from 6 to 36 months of 15% for major adverse cardiovascular events (P < 0.001), 11% cardiovascular death (P = 0.010), 15% myocardial infarction (P = 0.023), and 23% stroke (P < 0.001). Conclusions: There were sustained BP reductions and higher TTR through 36 months after RDN. A 10% increase in TTR through 6 months was associated with significant risk reductions in major cardiovascular events from 6 to 36 months. (Global SYMPLICITY Registry [GSR] DEFINE; NCT01534299