Evolution of compound eye morphology underlies differences in vision between closely related Drosophila species.

BACKGROUND: Insects have evolved complex visual systems and display an astonishing range of adaptations for diverse ecological niches. Species of Drosophila melanogaster subgroup exhibit extensive intra- and interspecific differences in compound eye size. These differences provide an excellent opportunity to better understand variation in insect eye structure and the impact on vision. Here we further explored the difference in eye size between D. mauritiana and its sibling species D. simulans. RESULTS: We confirmed that D. mauritiana have rapidly evolved larger eyes as a result of more and wider ommatidia than D. simulans since they recently diverged approximately 240,000 years ago. The functional impact of eye size, and specifically ommatidia size, is often only estimated based on the rigid surface morphology of the compound eye. Therefore, we used 3D synchrotron radiation tomography to measure optical parameters in 3D, predict optical capacity, and compare the modelled vision to in vivo optomotor responses. Our optical models predicted higher contrast sensitivity for D. mauritiana, which we verified by presenting sinusoidal gratings to tethered flies in a flight arena. Similarly, we confirmed the higher spatial acuity predicted for Drosophila simulans with smaller ommatidia and found evidence for higher temporal resolution. CONCLUSIONS: Our study demonstrates that even subtle differences in ommatidia size between closely related Drosophila species can impact the vision of these insects. Therefore, further comparative studies of intra- and interspecific variation in eye morphology and the consequences for vision among other Drosophila species, other dipterans and other insects are needed to better understand compound eye structure-function and how the diversification of eye size, shape, and function has helped insects to adapt to the vast range of ecological niches.

Critical junctions in evolution.

Key traits set the course of de novo visual system evolution in marine mollusks.

Evolution of the Spider Homeobox Gene Repertoire by Tandem and Whole Genome Duplication.

Gene duplication generates new genetic material that can contribute to the evolution of gene regulatory networks and phenotypes. Duplicated genes can undergo subfunctionalization to partition ancestral functions and/or neofunctionalization to assume a new function. We previously found there had been a whole genome duplication (WGD) in an ancestor of arachnopulmonates, the lineage including spiders and scorpions but excluding other arachnids like mites, ticks, and harvestmen. This WGD was evidenced by many duplicated homeobox genes, including two Hox clusters, in spiders. However, it was unclear which homeobox paralogues originated by WGD versus smaller-scale events such as tandem duplications. Understanding this is a key to determining the contribution of the WGD to arachnopulmonate genome evolution. Here we characterized the distribution of duplicated homeobox genes across eight chromosome-level spider genomes. We found that most duplicated homeobox genes in spiders are consistent with an origin by WGD. We also found two copies of conserved homeobox gene clusters, including the Hox, NK, HRO, Irx, and SINE clusters, in all eight species. Consistently, we observed one copy of each cluster was degenerated in terms of gene content and organization while the other remained more intact. Focussing on the NK cluster, we found evidence for regulatory subfunctionalization between the duplicated NK genes in the spider Parasteatoda tepidariorum compared to their single-copy orthologues in the harvestman Phalangium opilio. Our study provides new insights into the relative contributions of multiple modes of duplication to the homeobox gene repertoire during the evolution of spiders and the function of NK genes.

'Distributed' vision and the architecture of animal visual systems.

More than a century of research, of which JEB has published a substantial selection, has highlighted the rich diversity of animal eyes. From these studies have emerged numerous examples of visual systems that depart from our own familiar blueprint, a single pair of lateral cephalic eyes. It is now clear that such departures are common, widespread and highly diverse, reflecting a variety of different eye types, visual abilities and architectures. Many of these examples have been described as 'distributed' visual systems, but this includes several fundamentally different systems. Here, I re-examine this term, suggest a new framework within which to evaluate visual system distribution in both spatial and functional senses, and propose a roadmap for future work. The various architectures covered by this term reflect three broad strategies that offer different opportunities and require different approaches for study: the duplication of functionally identical eyes, the expression of multiple, functionally distinct eye types in parallel and the use of dispersed photoreceptors to mediate visual behaviour without eyes. Within this context, I explore some of the possible implications of visual system architecture for how visual information is collected and integrated, which has remained conceptually challenging in systems with a large degree of spatial and/or functional distribution. I highlight two areas that should be prioritised in future investigations: the whole-organism approach to behaviour and signal integration, and the evolution of visual system architecture across Metazoa. Recent advances have been made in both areas, through well-designed ethological experiments and the deployment of molecular tools.

Extreme Risk Protection Orders in Washington State: Understanding the Role of Health Professionals.

Objective: Extreme Risk Protection Orders (ERPO) allow a petitioner to file a civil order to temporarily restrict access to firearms among individuals ("respondents") deemed to be at extreme risk of harming themselves, others, or both. Although unable to file ERPOs for their clients in most states, health professionals may play a pivotal role in the ERPO process by recommending an eligible petitioner initiate the process. We describe the process of filing an ERPO when a healthcare, mental health, or social service professional contacted an ERPO petitioner. Method: Court documents of ERPOs involving health professionals in Washington State between December 8th, 2016 and May 10th, 2019 were qualitatively analyzed (n=24). We constructed pen portraits from the documents and analyzed them using an inductive qualitative thematic approach. Results: Themes included factors influencing the process by which each professional evaluated respondent behaviors, factors considered during assessment, factors influencing interpretation of respondent behaviors and subsequent provider response during a crisis. These influenced the outcome of the crisis event that led to ERPO filing. Conclusions: Each professional group differed in their approach to risk assessment of respondent behaviors. Strategies to better coordinate and align approaches may improve the ERPO process.

Practices, knowledge, and concerns for out-of-home firearm storage among those with access to firearms: results from a survey in two states.

BACKGROUND: Temporary, voluntary storage of firearms away from the home is a recommended option for individuals with risk of suicide, but it may also be used in other situations (e.g., long trips). Prior work has explored the availability of storage options and the views of storage locations. Little is known about out-of-home storage practices among those who live in homes with firearms (including owners). METHODS: We surveyed English-speaking adults (18 or older) in two states (Colorado and Washington) living in a home with a firearm (June-July 2021). RESULTS: Among the final sample of 1029, most respondents were white (88.1%) and non-Hispanic (85.0%); half were female (50.8%), and the most common age group was ages 35-44 (25.5%). Just over one quarter (27.3%) of respondents indicated they had stored a firearm away from their home/car/garage in the last 5 years. The place most respondents said they were somewhat or very likely to consider was at a family members home (62.7%) or at a self-storage facility (52.5%). CONCLUSION: Out-of-home firearm storage is a relatively common practice and endorsed by many gun-owners, suggesting out-of-home storage is feasible for firearm owners as an approach to suicide prevention.

Evolutionary loss of shell pigmentation, pattern, and eye structure in deep-sea snails in the dysphotic zone.

Adaptations to habitats lacking light, such as the reduction or loss of eyes and pigmentation, have fascinated biologists for centuries, yet have rarely been studied in the deep sea, the earth's oldest and largest light-limited habitat. Here, we investigate the evolutionary loss of shell pigmentation, pattern, and eye structure across a family of deep-sea gastropods (Solariellidae). We show that within our phylogenetic framework, loss of these traits evolves without reversal, at different rates (faster for shell traits than eye structure), and over different depth ranges. Using a Bayesian approach, we find support for correlated evolution of trait loss with increasing depth within the dysphotic region. A transition to trait loss occurs for pattern and eye structure at 400-500 m and for pigmentation at 600-700 m. We also show that one of the sighted, shallow-water species, Ilanga navakaensis, which may represent the "best-case" scenario for vision for the family, likely has poor spatial acuity and contrast sensitivity. We therefore propose that pigmentation and pattern are not used for intraspecific communication but are important for camouflage from visual predators, and that the low-resolution vision of solariellids is likely to require high light intensity for basic visual tasks, such as detecting predators.

Voluntary, temporary out-of-home firearm storage: A survey of firearm retailers and ranges in two states.

Out-of-home storage of personal firearms is one recommended option for individuals at risk of suicide, and statewide online maps of storage locations have been created in multiple states, including Colorado and Washington. We sought to examine both the extent to which firearm retailers and ranges offer temporary, voluntary firearm storage and the perceived barriers to providing this service. We invited all firearm retailers and ranges in Colorado and Washington to complete an online or mailed survey; eligible sites had to have a physical location where they could provide storage. Between June-July 2021, 137 retailers/ranges completed the survey (response rate = 25.1%). Nearly half (44.5%) of responding firearm retailers/ranges in Colorado and Washington State indicated they had ever provided firearm storage. Among those who had ever offered storage, 80.3% currently offered storage while 19.7% no longer did. The majority (68.6%) of participants had not heard of the Colorado/Washington gun storage maps and 82.5% did not believe they were currently listed on the maps. Respondents indicated liability waivers would most influence their decision about whether to start or continue providing temporary, voluntary storage of firearms. Understanding current practices, barriers, and concerns about providing out-of-home storage by retailers and ranges may support development of more feasible approaches for out-of-home firearm storage during times of suicide risk.

Civilian Petitioners and Extreme Risk Protection Orders in the State of Washington.

OBJECTIVE: Extreme risk protection orders (ERPOs) are civil orders designed to temporarily restrict access to firearms when people are at substantial risk of harm to themselves or others. A minority of ERPOs in the United States have been filed by civilians, with most filed by law enforcement. The authors examined barriers and facilitators to the ERPO filing process from the perspective of the civilian petitioner. METHODS: Semistructured interviews of civilian petitioners who filed ERPOs in Washington State from December 2016 to September 2020 were conducted. The interviews examined both barriers and facilitators to filing an ERPO. A descriptive and qualitative approach with inductive-deductive thematic analysis was used to identify and code themes. RESULTS: Fifteen civilian petitioners were interviewed. Barriers to ERPO filing included perceived lack of help connecting with social services to address the potential for harmful behavior, confusion regarding the filing and court process, and petitioner distress. Facilitators included having previous legal experience, having assistance from advocates who helped shepherd petitioners through the process, and simplification of the ERPO process. CONCLUSIONS: ERPO is a useful tool for suicide and violence prevention, but several barriers may be inhibiting ERPO use among civilian petitioners. Better educational resources and advocacy programs, as well as simplified filing steps, could improve the process and make ERPOs more accessible for civilians.

A Qualitative study on diverse perspectives and identities of firearm owners.

OBJECTIVE: Research surrounding firearm ownership is often contextualised within the perspectives of older white men. We expand this description using the perceptions of a diverse group of firearm-owning stakeholders. METHODS: We conducted semistructured interviews from October 2020 to May 2021 with Colorado/Washington State stakeholders representing (1) firearm ranges/retailers; (2) law enforcement agencies or (3) relevant state/national firearm organisations. Data were analysed using standard qualitative techniques and included 25 participants, representing varied sociocultural groups including racial and ethnic minorities, political minorities and sexual minorities. RESULTS: Participants for this analysis were of different self-identified sociocultural groups including racial and ethnic minorities (African American, Hispanic and Asian), political minorities (liberal) and sexual minorities, defined as Lesbian, Gay, Bisexual, and Transgender (LGBT). Perspectives on firearm ownership included an idea of gun culture as a component of (1) personal identity, (2) an expression of full citizenship and (3) necessary for self-protection. A strong subtheme was the intersection of minority group and firearm owner identities, creating a need for divergent social communities because of ideas on traditional gun culture. These communities are a safe place for individuals belonging to minority groups to escape negative external and internal group associations with firearms. CONCLUSION: Perspectives on firearms and firearm ownership in the secondary analysis were heterogeneous and related to personal experiences, external and internal group pressures that influence individual behaviour. Understanding the breadth of perspectives on firearm ownership is imperative to engaging individuals for risk reduction. This study adds to the literature by expanding an understanding of the motivation for firearm ownership among diverse communities.

Regulation of Eye Determination and Regionalization in the Spider Parasteatoda tepidariorum.

Animal visual systems are enormously diverse, but their development appears to be controlled by a set of conserved retinal determination genes (RDGs). Spiders are particular masters of visual system innovation, and offer an excellent opportunity to study the evolution of animal eyes. Several RDGs have been identified in spider eye primordia, but their interactions and regulation remain unclear. From our knowledge of RDG network regulation in Drosophila melanogaster, we hypothesize that orthologs of Pax6, eyegone, Wnt genes, hh, dpp, and atonal could play important roles in controlling eye development in spiders. We analyzed the expression of these genes in developing embryos of the spider Parasteatodatepidariorum, both independently and in relation to the eye primordia, marked using probes for the RDG sine oculis. Our results support conserved roles for Wnt genes in restricting the size and position of the eye field, as well as for atonal initiating photoreceptor differentiation. However, we found no strong evidence for an upstream role of Pax6 in eye development, despite its label as a master regulator of animal eye development; nor do eyg, hh or dpp compensate for the absence of Pax6. Conversely, our results indicate that hh may work with Wnt signaling to restrict eye growth, a role similar to that of Sonichedgehog (Shh) in vertebrates.

Voluntary, temporary, out-of-home firearm storage: A qualitative study of stakeholder views.

BACKGROUND: Reducing firearm access during times of risk is a key component of suicide prevention, including the person at risk voluntarily, temporarily storing firearms outside the home. However, this approach relies on the participation of storage providers (ranges/retailers and law enforcement agencies (LEAs)). Our objective was to describe stakeholders' views and experiences surrounding voluntary, temporary out-of-home firearm storage for suicide prevention. METHOD: We conducted individual interviews with (1) firearm ranges/retailers; (2) LEAs (in Colorado or Washington State); and (3) state/national organizations involved in policy development or enactment; public health; or firearm rights. Transcripts were analyzed using a team-based mixed inductive-deductive approach. RESULTS: Across 100 interviews (October-May 2021), potential storage providers were supportive of voluntary storage programs, often reporting a desire to help their customers and community. However, potential storage suppliers cited civil liability, regulatory, and legal concerns associated with storing and/or returning firearms (to people who had previously expressed suicide risk). Stakeholders offered suggested strategies meant to address liability and increase storage accessibility. CONCLUSIONS: Understanding stakeholder views supports the development of acceptable, feasible programs for out-of-home firearm storage during times of suicide risk. Clarification of existing regulations or creation of new policies is necessary to address potential providers' concerns.

Widespread retention of ohnologs in key developmental gene families following whole-genome duplication in arachnopulmonates.

Whole-genome duplications (WGDs) have occurred multiple times during animal evolution, including in lineages leading to vertebrates, teleosts, horseshoe crabs, and arachnopulmonates. These dramatic events initially produce a wealth of new genetic material, generally followed by extensive gene loss. It appears, however, that developmental genes such as homeobox genes, signaling pathway components and microRNAs are frequently retained as duplicates (so-called ohnologs) following WGD. These not only provide the best evidence for WGD, but an opportunity to study its evolutionary consequences. Although these genes are well studied in the context of vertebrate WGD, similar comparisons across the extant arachnopulmonate orders are patchy. We sequenced embryonic transcriptomes from two spider species and two amblypygid species and surveyed three important gene families, Hox, Wnt, and frizzled, across these and 12 existing transcriptomic and genomic resources for chelicerates. We report extensive retention of putative ohnologs, further supporting the ancestral arachnopulmonate WGD. We also found evidence of consistent evolutionary trajectories in Hox and Wnt gene repertoires across three of the six arachnopulmonate orders, with interorder variation in the retention of specific paralogs. We identified variation between major clades in spiders and are better able to reconstruct the chronology of gene duplications and losses in spiders, amblypygids, and scorpions. These insights shed light on the evolution of the developmental toolkit in arachnopulmonates, highlight the importance of the comparative approach within lineages, and provide substantial new transcriptomic data for future study.

Understanding the Process, Context, and Characteristics of Extreme Risk Protection Orders: A Statewide Study.

Research summary. Extreme risk protection orders (ERPOs) allow police, family, and household members to file an order to temporarily remove firearms or prevent purchasing among individuals at high risk for harming themselves or others. Using inductive qualitative content analysis, we examined 241 ERPOs filed December 8, 2016 through May 10, 2019 in Washington State. Focusing on recurring themes, we explored the circumstances and behaviors that led to an ERPO filing. Extreme risk protection orders were filed over concerns for domestic violence, mass shooting threats, direct threats to oneself or others, and other concerning behavior with a firearm. Factors at all levels of the social-ecological model were found to play a role in the dangerous behaviors of respondents that led to an ERPO petition. Policy implications. Extreme risk protection orders can serve an important role in both protecting people and facilitating the provision of care for substance use, mental illness, and assistance to vulnerable individuals.

Run and hide: visual performance in a brittle star.

Spatial vision was recently reported in a brittle star, Ophiomastix wendtii, which lacks discrete eyes, but little is known about its visual ecology. Our aim was to better characterize the vision and visual ecology of this unusual visual system. We tested animal orientation relative to vertical bar stimuli at a range of angular widths and contrasts, to identify limits of angular and contrast detection. We also presented dynamic shadow stimuli, either looming towards or passing the animal overhead, to test for potential defensive responses. Finally, we presented animals lacking a single arm with a vertical bar stimulus known to elicit a response in intact animals. We found that O. wendtii orients to large (≥50 deg), high-contrast vertical bar stimuli, consistent with a shelter-seeking role and with photoreceptor acceptance angles estimated from morphology. We calculate poor optical sensitivity for individual photoreceptors, and predict dramatic oversampling for photoreceptor arrays. We also report responses to dark stimuli moving against a bright background - this is the first report of responses to moving stimuli in brittle stars and suggests additional defensive uses for vision in echinoderms. Finally, we found that animals missing a single arm orient less well to static stimuli, which requires further investigation.

The Evolution of Sox Gene Repertoires and Regulation of Segmentation in Arachnids.

The Sox family of transcription factors regulates many processes during metazoan development, including stem cell maintenance and nervous system specification. Characterizing the repertoires and roles of these genes can therefore provide important insights into animal evolution and development. We further characterized the Sox repertoires of several arachnid species with and without an ancestral whole-genome duplication and compared their expression between the spider Parasteatoda tepidariorum and the harvestman Phalangium opilio. We found that most Sox families have been retained as ohnologs after whole-genome duplication and evidence for potential subfunctionalization and/or neofunctionalization events. Our results also suggest that Sox21b-1 likely regulated segmentation ancestrally in arachnids, playing a similar role to the closely related SoxB gene, Dichaete, in insects. We previously showed that Sox21b-1 is required for the simultaneous formation of prosomal segments and sequential addition of opisthosomal segments in P. tepidariorum. We studied the expression and function of Sox21b-1 further in this spider and found that although this gene regulates the generation of both prosomal and opisthosomal segments, it plays different roles in the formation of these tagmata reflecting their contrasting modes of segmentation and deployment of gene regulatory networks with different architectures.

Continuous and Regular Expansion of a Distributed Visual System in the Eyed Chiton Tonicia lebruni.

AbstractChitons have a distinctive armature of eight articulating dorsal shells. In all living species, the shell valves are covered by a dense array of sensory pores called aesthetes; but in some taxa, a subset of these are elaborated into lensed eyes, which are capable of spatial vision. We collected a complete ontogenetic series of the eyed chiton Tonicia lebruni de Rochebrune, 1884 to examine the growth of this visual network and found that it expands continuously as eyes are added at the margin during shell growth. Our dataset ranged from a 2.58-mm juvenile with only 16 eyes to adults of 25-31 mm with up to 557 eyes each. This allowed us to investigate the organization (and potential constraints therein) of these sensory structures and their development. Chiton eyes are constrained to a narrowly defined region of the shell, and data from T. lebruni indicate that they are arranged roughly bilaterally symmetrically. We found deviations from symmetry of up to 10%, similar to irregularity reported in some other animals with multiplied eyes. Distances separating successive eyes indicate that, while shell growth slows during the life of an individual chiton, eyes are generated at regular time intervals. Although we could not identify a specific eye-producing tissue or organ, we propose that the generation of new eyes is controlled by a clock-like mechanism with a stable periodicity. The apparent regularity and organization of the chiton visual system are far greater than previously appreciated. This does not imply the integration of shell eyes to form composite images, but symmetry and regular organization could be equally beneficial to a highly duplicated system by ensuring even and comprehensive sampling of the total field of view.

Light adaptation mechanisms in the eye of the fiddler crab Afruca tangeri.

A great diversity of adaptations is found among animals with compound eyes and even closely related taxa can show variation in their light-adaptation strategies. A prime example of a visual system evolved to function in specific light environments is the fiddler crab, used widely as a model to research aspects of crustacean vision and neural pathways. However, questions remain regarding how their eyes respond to the changes in brightness spanning many orders of magnitude, associated with their habitat and ecology. The fiddler crab Afruca tangeri forages at low tide on tropical and semi-tropical mudflats, under bright sunlight and on moonless nights, suggesting that their eyes undergo effective light adaptation. Using synchrotron X-ray tomography, light and transmission electron microscopy and in vivo ophthalmoscopy, we describe the ultrastructural changes in the eye between day and night. Dark adaptation at dusk triggered extensive widening of the rhabdoms and crystalline cone tips. This doubled the ommatidial acceptance angles and increased microvillar surface area for light capture in the rhabdom, theoretically boosting optical sensitivity 7.4 times. During daytime, only partial dark-adaptation was achieved and rhabdoms remained narrow, indicating strong circadian control on the process. Bright light did not evoke changes in screening pigment distributions, suggesting a structural inability to adapt rapidly to the light level fluctuations frequently experienced when entering their burrow to escape predators. This should enable fiddler crabs to shelter for several minutes without undergoing significant dark-adaptation, their vision remaining effectively adapted for predator detection when surfacing again in bright light.

Characterization of the Genetic Architecture Underlying Eye Size Variation Within Drosophila melanogaster and Drosophila simulans.

The compound eyes of insects exhibit striking variation in size, reflecting adaptation to different lifestyles and habitats. However, the genetic and developmental bases of variation in insect eye size is poorly understood, which limits our understanding of how these important morphological differences evolve. To address this, we further explored natural variation in eye size within and between four species of the Drosophila melanogaster species subgroup. We found extensive variation in eye size among these species, and flies with larger eyes generally had a shorter inter-ocular distance and vice versa We then carried out quantitative trait loci (QTL) mapping of intra-specific variation in eye size and inter-ocular distance in both D. melanogaster and D. simulans This revealed that different genomic regions underlie variation in eye size and inter-ocular distance in both species, which we corroborated by introgression mapping in D. simulans This suggests that although there is a trade-off between eye size and inter-ocular distance, variation in these two traits is likely to be caused by different genes and so can be genetically decoupled. Finally, although we detected QTL for intra-specific variation in eye size at similar positions in D. melanogaster and D. simulans, we observed differences in eye fate commitment between strains of these two species. This indicates that different developmental mechanisms and therefore, most likely, different genes contribute to eye size variation in these species. Taken together with the results of previous studies, our findings suggest that the gene regulatory network that specifies eye size has evolved at multiple genetic nodes to give rise to natural variation in this trait within and among species.