Variation in hybrid gene expression: Implications for the evolution of genetic incompatibilities in interbreeding species

Interbreeding species often produce low-fitness hybrids due to genetic incompatibilities between parental genomes. Whether these incompatibilities reflect fixed allelic differences between hybridizing species, or, alternatively, standing variants that segregate within them, remains unknown for many natural systems. Yet, evaluating these alternatives is important for understanding the origins and nature of species boundaries. We examined these alternatives using spadefoot toads (genus Spea), which naturally hybridize. Specifically, we contrasted patterns of gene expression in hybrids relative to pure-species types in experimentally produced tadpoles from allopatric parents versus those from sympatric parents. We evaluated the prediction that segregating variation should result in gene expression differences between hybrids derived from sympatric parents versus hybrids derived from allopatric parents, and found that 24% of the transcriptome showed such differences. Our results further suggest that gene expression in hybrids has evolved in sympatry owing to evolutionary pressures associated with ongoing hybridization. Although we did not measure hybrid incompatibilities directly, we discuss the implications of our findings for understanding the nature of hybrid incompatibilities, how they might vary across populations over time, and the resulting effects on the evolutionary maintenance - or breakdown - of reproductive barriers between species

Modes, mechanisms and evidence of bet hedging in rotifer diapause traits

In this contribution, we review our knowledge on bet-hedging strategies associated with rotifer diapause. First, we describe the ecological scenario under which bet hedging is likely to have evolved in three diapause-related traits in monogonont rotifer populations: (1) the timing of sex (because diapausing eggs are produced via sexual reproduction), (2) the sexual reproduction ratio (i.e. the fraction of sexually reproducing females) and (3) the timing of diapausing egg hatching. Then, we describe how to discriminate among bet-hedging modes and discuss which modes and mechanisms better fit the variability observed in these traits in rotifers. Finally, we evaluate the strength of the empirical evidence for bet hedging in the scarce studies available, and we call for the need of research at different levels of biological complexity to fully understand bet hedging in rotifer diapause

Evaluation and Treatment of Iron Deficiency Anemia: A Gastroenterological Perspective

A substantial volume of the consultations requested of gastroenterologists are directed towards the evaluation of anemia. Since iron deficiency anemia often arises from bleeding gastrointestinal lesions, many of which are malignant, establishment of a firm diagnosis usually obligates an endoscopic evaluation. Although the laboratory tests used to make the diagnosis have not changed in many decades, their interpretation has, and this is possibly due to the availability of extensive testing in key populations. We provide data supporting the use of the serum ferritin as the sole useful measure of iron stores, setting the lower limit at 100 μg/l for some populations in order to increase the sensitivity of the test. Trends of the commonly obtained red cell indices, mean corpuscular volume, and the red cell distribution width can provide valuable diagnostic information. Once the diagnosis is established, upper and lower gastrointestinal endoscopy is usually indicated. Nevertheless, in many cases a gastrointestinal source is not found after routine evaluation. Additional studies, including repeat upper and lower endoscopy and often investigation of the small intestine may thus be required. Although oral iron is inexpensive and usually effective, there are many gastrointestinal conditions that warrant treatment of iron deficiency with intravenous iron

Superhydrophobicity from the Inside

The nature of trapped air on submersed ultra-water-repellent interfaces has been investigated. These gaseous layers (plastrons) can last from hours to, in some examples such as the <i>Salvinia molesta</i> fern, months. The interface of submerged superhydrophobic surfaces with carefully controlled micropatterned surface roughness has been probed using synchrotron-based high-resolution X-ray phase tomography. This technique looks in situ, through the aqueous/gas interface in three dimensions. Long-term plastron stability appears to correlate with the appearance of scattered microdroplets <20 μm in diameter that are sandwiched within the 30 μm thick gaseous interfacial layer. These microdroplets are centered on defects or damaged sections within the substrate surface approximately 20–50 μm apart. Such irregularities represent heterogeneous micro/nano-hierarchical structures with varying surface structures and chemistry. The stability of microdroplets is governed by a combination of electrostatic repulsion, contact angle limitations, and a saturated vapor pressure, the latter of which reduces the rate of diffusion of gas out of the air layer, thus increasing underwater longevity. Homogenous surfaces exhibiting purely nano- or micro-regularity do not support such microdroplets, and, as a consequence, plastrons can disappear in <20 h compared with >160 h for surfaces with scattered microdroplets. Such behavior may be a requirement for long-term nonwetting in any system