Micro-CT visualization of the CNS: Performance of different contrast-enhancing techniques for documenting the spider brain.

Spider brain and central nervous system (CNS) have remained unexplored, due in part to the difficulty of observing these organs, usually only possible through histological preparations. Recently, internal anatomy studies have been supplemented by the inclusion of X- ray micro-CT. Unmineralized tissue such as the body of invertebrates requires a staining process to enhance tissue X-ray absorption and improve contrast during observation. Many current protocols are based on iodine staining requiring critical point drying (CPD) of the sample for optimal contrast. This process induces shrinking of the soft tissue generating artifacts in the morphology, volume, and even position of internal structures. Phosphotungstic acid (PTA) is an alternative staining agent recently used in marine invertebrate and plant studies. Here, we used several specimens of the common spider Araneus diadematus to visualize the spider brain and compare both contrast-enhancing ethanol-based solutions. We assessed a gradient of staining times, observed and tested the repercussions of CPD, and examined the use of vacuum to accelerate PTA diffusion. We show that PTA provides the best contrast on micro-CT scans in ethanol eliminating the need for CPD, and offering more realistic in situ visualizations of the internal organs. In combination with different scanning settings, PTA allowed observation of internal organs like the CNS, digestive system, muscles, and finer structures like the retina, visual nerves, and optic neuropiles. This fast and less invasive method could facilitate the proper documentation of the internal anatomy in the context of evolutionary, developmental and functional studies.

Clindamycin Protects Nonhuman Primates Against Inhalational Anthrax But Does Not Enhance Reduction of Circulating Toxin Levels When Combined With Ciprofloxacin.

BACKGROUND: Inhalational anthrax is rare and clinical experience limited. Expert guidelines recommend treatment with combination antibiotics including protein synthesis-inhibitors to decrease toxin production and increase survival, although evidence is lacking. METHODS: Rhesus macaques exposed to an aerosol of Bacillus anthracis spores were treated with ciprofloxacin, clindamycin, or ciprofloxacin + clindamycin after becoming bacteremic. Circulating anthrax lethal factor and protective antigen were quantitated pretreatment and 1.5 and 12 hours after beginning antibiotics. RESULTS: In the clindamycin group, 8 of 11 (73%) survived demonstrating its efficacy for the first time in inhalational anthrax, compared to 9 of 9 (100%) with ciprofloxacin, and 8 of 11 (73%) with ciprofloxacin + clindamycin. These differences were not statistically significant. There were no significant differences between groups in lethal factor or protective antigen levels from pretreatment to 12 hours after starting antibiotics. Animals that died after clindamycin had a greater incidence of meningitis compared to those given ciprofloxacin or ciprofloxacin + clindamycin, but numbers of animals were very low and no definitive conclusion could be reached. CONCLUSION: Treatment of inhalational anthrax with clindamycin was as effective as ciprofloxacin in the nonhuman primate. Addition of clindamycin to ciprofloxacin did not enhance reduction of circulating toxin levels.

Repeated evolution of male sacrifice behavior in spiders correlated with genital mutilation.

According to sexual cannibalism theory, male complicity in terminal mating can be adaptive when the male's future reproductive value is low relative to the benefits of self sacrifice. Spiders and insects that exhibit male sacrifice behavior (either complicity in cannibalism or spontaneous death associated with copulation) often also have male genitalia that stereotypically become broken or disfigured the first time they are used for copulation, potentially lowering his future reproductive value. Theoretical work on monogamy has identified male bias in the effective sex ratio as a precursor to the evolution of monogamy (including male sacrifice) as an adaptive form of paternity protection. Using phylogeny-based statistics and drawing on several phylogenetic studies of araneoid spiders, I investigate relationships between male sacrifice behavior, genital mutilation, extreme sexual size dimorphism, and the accumulation of multiple males in the female web (as an indicator of a male-based effective sex ratio). This investigation focuses on araneoid spiders because several independent origins of sacrifice behavior are known for this group and the phylogenetic structure of the lineage is relatively well studied. I report that male genital mutilation is significantly correlated with sacrifice behavior and argue that this finding is consistent with sexual cannibalism theory. Male sacrifice behavior is also correlated with male accumulation, a result that is consistent with theoretical work on the evolution of monogamy. Male accumulation and extreme sexual size dimorphism are correlated suggesting that sex-based differences in maturation time can lead to a male biased effective sex ratio. Similar patterns of correlated characters may hold for some insect taxa. Studying traits that have appeared independently in multiple lineages is a powerful method for developing general theories about the evolution of biological phenomena.