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Sexual reproduction is ubiquitous in the natural world, suggesting that sex must have extensive benefits to overcome the cost of males compared to asexual reproduction. One hypothesized advantage of sex with strong theoretical support is that sex plays a role in removing deleterious mutations from the genome. Theory predicts that transitions to asexuality should lead to the suppression of recombination and segregation and, in turn, weakened natural selection, allowing for the accumulation of slightly deleterious mutations. We tested this prediction by estimating the dN/dS ratios in asexual vertebrate lineages in the genus Aspidoscelis using whole mitochondrial genomes from seven asexual and five sexual species. We found higher dN/dS ratios in asexual Aspidoscelis species, indicating that asexual whiptails accumulate nonsynonymous substitutions due to weaker purifying selection. Additionally, we estimated nucleotide diversity and found that asexuals harbor significantly less diversity. Thus, despite their recent origins, slightly deleterious mutations accumulated rapidly enough in asexual lineages to be detected. We provide empirical evidence to corroborate the connection between asexuality and increased amino acid substitutions in asexual vertebrate lineages.

Cyclical parthenogenesis, where females can engage in sexual or asexual reproduction depending on environmental conditions, represents a novel reproductive phenotype that emerged during eukaryotic evolution. The fact that environmental conditions can trigger cyclically parthenogens to engage in distinct reproductive modes strongly suggests that gene expression plays a key role in the origin of cyclical parthenogenesis. However, the genetic basis underlying cyclical parthenogenesis remains understudied. In this study we characterize the female transcriptomic signature of sexual vs. asexual reproduction in the cyclically parthenogenetic microcrustacean Daphnia pulex and D. pulicaria. Our analyses of differentially expressed genes, pathway enrichment, and GO term enrichment clearly show that compared to sexual reproduction the asexual reproductive stage is characterized by both the under-regulation of meiosis and cell-cycle genes and the up-regulation of metabolic genes. We suggest that the under-regulation of meiosis and cell-cycle genes is responsible for the origin of parthenogenesis from meiosis, whereas differentially expressed metabolic genes may mediate choice of asexual vs. sexual reproductive pathway. Furthermore, our analyses identify some cases of divergent expression among gene family members (e.g., doublesex, NOTCH2) associated with asexual or sexual reproductive stage, suggesting potential functional divergence among gene family members.

Summary Perovskite solar cells (PSCs) are one of the emerging solar cell technologies with high conversion efficiency. Several deposition methods had been applied for preparing their hole transport layer (HTL). However, there are few direct evidences to demonstrate whether HTL and its interfaces in PSCs have been influenced by the deposition methods. In this study, the 3D morphology of PSCs has been reconstructed by focused ion beam-scanning electron microscopy from the PSCs in which HTLs are deposited by different methods. The compositional distribution of HTLs is unveiled as well. All these associated layers and interfaces display obvious morphological and compositional differences that are attributed to the HTL components’ solubility differences in the precursor solvent. Our investigation demonstrates the PSCs that HTL fabricated by dynamic spin-coating method have higher efficiency, better film uniformity, and less interfacial roughness than the static spin-coating-based devices.

A new genus and species of colubroid snake is described from the isolated highlands of western Chiapas. This enigmatic little snake possesses a unique suite of characters that defies placi...

Male anuran (frog and toad) advertisement calls associate with fitness and can respond to environmental cues such as rain and air temperature. Moonlight is thought to generally decrease call behaviors – perhaps as a response to increased perceived risk of predation – and this study sought to determine if artificial lighting produces a similar pattern. Using a handheld spotlight, light was experimentally introduced to natural anuran communities in ponds and streams. Custom call surveys where then used to measure anuran calls in paired unlit and lit conditions at six locations in central Texas. Among seven species heard, the number of frogs calling and call index declined in response to the acute light input. Local weather conditions could not explain differences between numbers of frogs calling between species, sites, survey order, or lighting order suggesting the main effect on number calling was light treatment. It appears acute artificial light alone can change calling behavior within several s...

Cancer chiefly occurs in vertebrates. Rare in amphibians, and perhaps common in reptiles, various neoplasms and malignant cancers have been reported with erratic frequency by museums, paleontologists, veterinarians, and pet hobbyists. Unsurprisingly, most herpetofaunal diversity has never been systematically surveyed for the presence of neoplasms owing to the extreme rarity or obscurity of many species. Museum collections can fill these gaps in knowledge, especially when researchers use non-destructive techniques. In this study, we used X-ray computed tomography to discover and characterize an osteosarcoma of the spine in a rare South American coralsnake, Micrurus ancoralis. Two spinal vertebrae were completely fused and adjacent vertebrae showed evidence of corruption. The fused vertebrae contained a hollow inner network thought to be vascular tissue. We also review previous reports of tumors in the Elapidae and all bony tumors in non-avian reptiles. The rarely reported technique of X-ray CT for tumor discovery could greatly improve our understanding of the species diversity and perhaps underlying causes of neoplasia.

Cancer chiefly occurs in vertebrates. Rare in amphibians, and perhaps common in reptiles, various neoplasms and malignant cancers have been reported with erratic frequency by museums, paleontologists, veterinarians, and pet hobbyists. Unsurprisingly, most herpetofaunal diversity has never been systematically surveyed for the presence of neoplasms owing to the extreme rarity or obscurity of many species. Museum collections can fill these gaps in knowledge, especially when researchers use non-destructive techniques. In this study, we used X-ray computed tomography (CT) to discover and characterize a possible osteosarcoma of the spine in a rare South American coralsnake, Micrurus ancoralis. Two spinal vertebrae were completely fused and adjacent vertebrae showed evidence of corruption. The fused vertebrae contained a hollow inner network thought to be vascular tissue. We also review previous reports of neoplasms in the Elapidae and all bony neoplasms in non-avian reptiles. The rarely reported technique of X-ray CT for tumor discovery could greatly improve our understanding of the species diversity and perhaps underlying causes of neoplasia.

Animal navigation allows individuals to efficiently find and use best available habitats. Despite the long history of research into well-studied taxa (e.g., pigeons, salmon, sea turtles), we know relatively little about squamate navigational abilities. Among snakes, documented philopatry (range maintenance) in a non-colubrid species has been rare. In this study, we document the first example of philopatry and homing in a new world elapid snake,Micrurus apiatus. Our data come from the first multi-year mark-recapture study of this species at the open urban preserveZoológico Regional Miguel Álvarez del Toro, in Tuxtla Gutiérrez, Chiapas, Mexico. We show that on average snakes returned to within 144 m of their last capture point. By releasing snakes in one location, we noted that recaptured individuals preferentially returned to their last capture location, compared to a distribution of random locations in the park. We conclude with a preliminary discussion of the evolution of snake homing and potential mechanisms.

During 10-weeks, visual-encounter surveys were conducted on the Georgetown salamander Eurycea naufragia at a spring pool in Williamson County, Texas. There was no significant difference in number of salamanders observed or percentage of objects used as cover between surveys in mornings and afternoons. Number of salamanders detected and percentage of objects used as cover were not correlated significantly with any environmental variable that was assessed. These results suggest that visual-encounter surveys conducted during daylight hours are not biased by time of day.