Repeated evolution of queen parthenogenesis and social hybridogenesis in Cataglyphis desert ants

Over the last decade, genetic studies on social insects have revealed a remarkable diversity of unusual reproductive strategies, such as male clonality, female clonality, and social hybridogenesis. In this context, Cataglyphis desert ants are useful models because of their unique reproductive systems. In several species, queens conditionally use sexual reproduction and parthenogenesis to produce sterile workers and reproductive queens, respectively. In social hybridogenesis, two distinct genetic lineages coexist within a population, and workers result from mating between partners of different lineages; in contrast, queens and males are both produced asexually by parthenogenesis. Consequently, nonreproductive workers are all interlineage hybrids, whereas reproductives are all pure lineage individuals. Here, we characterized the reproductive systems of 11 species to investigate the distribution of the conditional use of sex and social hybridogenesis in Cataglyphis. We identified one new case in which sexual reproduction was conditionally used in the absence of dependent‐lineage reproduction. We also discovered five new instances of social hybridogenesis. Based on our phylogenetic analyses, we inferred that both the conditional use of sex and social hybridogenesis independently evolved multiple times in the genus Cataglyphis.     

Hotspots of stream tadpole diversity in forest and agricultural landscapes in Ranomafana,Madagascar

Landscape and Ecological Engineering - Logging and human-induced conversion of natural forests into agricultural areas are major drivers of biodiversity loss in the tropics. Anuran larvae can be...     

Nav1.5-dependent persistent Na+ influx activates CaMKII in rat ventricular myocytes and N1325S mice

Late Na(+) current (I(NaL)) and Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) are both increased in the diseased heart. Recently, CaMKII was found to phosphorylate the Na(+) channel 1.5 (Na(v)1.5), resulting in enhanced I(NaL). Conversely, an increase of I(NaL) would be expected to cause elevation of intracellular Ca(2+) and activation of CaMKII. However, a relationship between enhancement of I(NaL) and activation of CaMKII has yet to be demonstrated. We investigated whether Na(+) influx via Na(v)1.5 leads to CaMKII activation and explored the functional significance of this pathway. In neonatal rat ventricular myocytes (NRVM), treatment with the I(NaL) activators anemone toxin II (ATX-II) or veratridine increased CaMKII autophosphorylation and increased phosphorylation of CaMKII substrates phospholamban and ryanodine receptor 2. Knockdown of Na(v)1.5 (but not Na(v)1.1 or Na(v)1.2) prevented ATX-II-induced CaMKII phosphorylation, providing evidence for a specific role of Na(v)1.5 in CaMKII activation. In support of this view, CaMKII activity was also increased in hearts of transgenic mice overexpressing a gain-of-function Na(v)1.5 mutant (N(1325)S). The effects of both ATX-II and the N(1325)S mutation were reversed by either I(NaL) inhibition (with ranolazine or tetrodotoxin) or CaMKII inhibition (with KN93 or autocamtide 2-related inhibitory peptide). Furthermore, ATX-II treatment also induced CaMKII-Na(v)1.5 coimmunoprecipitation. The same association between CaMKII and Na(v)1.5 was also found in N(1325)S mice, suggesting a direct protein-protein interaction. Pharmacological inhibitions of either CaMKII or I(NaL) also prevented ATX-II-induced cell death in NRVM and reduced the incidence of polymorphic ventricular tachycardia induced by ATX-II in rat perfused hearts. Taken together, these results suggest that a Na(v)1.5-dependent increase in Na(+) influx leads to activation of CaMKII, which in turn phosphorylates Na(v)1.5, further promoting Na(+) influx. Pharmacological inhibition of either CaMKII or Na(v)1.5 can ameliorate cardiac dysfunction caused by excessive Na(+) influx.     

Expression of Dystrophins and the Dystrophin-Associated-Protein Complex by Pituicytes in Culture

The dystrophin-associated-protein complex (DAPC) has been extensively characterized in the central nervous system where it is localized both in neuronal and glial cells. Few studies have characterized this complex in the neurohypophysis. To further study this complex in pituicytes, the resident astroglia of the neurophypophysis, we used adult pituicyte cultures and determined the expression and localization of dystrophins/utrophins and the DAPC by RT–PCR, western blotting and immunofluorescence. Our data show that the pituicytes express dystrophins, utrophins and several members of the DAPC including dystroglycans, δ-, γ-sarcoglycans, α-dystrobrevin-1 and α1-syntrophin. Double immunofluorescence analysis shows that laminin colocalizes with dystroglycan, suggesting that similarly to muscle and astrocytes, the DAPC interacts with the extracellular matrix in pituicytes. Collectively these findings show that dystrophins/utrophins and members of the DAPC are expressed in pituicytes where they may form multiprotein complexes and play a role in the retraction-reinsertion of pituicyte endfeet during specific physiological conditions.     

Seasonal pulses of migratory prey and annual variation in small mammal abundance affect abundance and reproduction by arctic foxes

We examined how large seasonal influxes of migratory prey influenced population dynamics of arctic foxes and how this varied with fluctuations in small mammal (lemming and vole) abundance—the main prey of arctic foxes throughout most of their range. Specifically, we compared how arctic fox abundance, breeding density and litter size varied inside and outside a large goose colony and in relation to annual variation in small mammal abundance. Information-theoretic model selection showed that (1) breeding density and fox abundance were 2–3 times higher inside the colony than they were outside the colony and (2) litter size, breeding density and annual variation in fox abundance in the colony tracked fluctuations in lemming abundance. The influence of lemming abundance on reproduction and abundance of arctic foxes outside the colony was inconclusive, largely because fox densities outside the colony were low, which made it difficult to detect such relationships. Lemming abundance was, thus, the main factor governing reproduction and abundance of arctic foxes in the colony, whereas seasonal influxes of geese and their eggs provided foxes with external subsidies that elevated breeding density and fox abundance above that which lemmings could support. This study highlights (1) the relative importance of migratory prey and other foods on the abundance and reproduction by local consumers and (2) how migratory animals function as vectors of nutrient transfer between distant ecosystems such as Arctic environments and wintering areas by geese thousands of kilometres to the south.     

Green chiral HPLC enantiomeric separations using high temperature liquid chromatography and subcritical water on Chiralcel OD and Chiralpak AD

We report here the application of subcritical water in chiral separations on two popular polysaccharide chiral stationary phases (CSPs): Chiralpak AD and Chiralcel OD. The behavior of these two CSPs was studied under reversed phase conditions at room temperature to discover the maximum percentage of water in the mobile phase, which provided the separation of enantiomers of flavanone and benzoin, respectively, in a reasonable time (i.e., less than 1 h). Then, the stability of Chiralpak AD and Chiralcel OD versus temperature was investigated and discussed. Chiralcel OD separation of flavanone racemate was obtained at 120 °C with water and 2-propanol (80/20) as the mobile phase, while benzoin racemate was separated in pure water at 160 °C. Separations of several racemates were also presented, and advantages and limitations of the technique were discussed.     

Difluoroethylamines as an amide isostere in inhibitors of cathepsin K

The trifluoroethylamine group found in cathepsin K inhibitors like odanacatib can be replaced by a difluoroethylamine group. This change increased the basicity of the nitrogen which positively impacted the log D. This translated into an improved oral bioavailability in pre-clinical species. Difluoroethylamine compounds exhibit a similar potency against cathepsin K and selectivity profile against other cathepsins when compared to trifluoroethylamine analogs.