Ant diversity decreases during the dry season: A meta-analysis of the effects of seasonality on ant richness and abundance

Tropical studies traditionally describe insect diversity variation throughout the year. The temporally structured responses of insect assemblages to climate seasonality vary across ecosystems due to gradients of resource availability and limiting ecological factors. These idiosyncratic responses might be particularly true across the vast geographical range of the Brazilian territory, including various environments that harbor one of the most diverse ant faunas worldwide. This study addressed the relationship between ant diversity and climatic seasonality, performing a quantitative review of the published data on ant diversity collected in Brazil. We investigated the seasonality effect on ant abundance and richness described in the literature in 47 papers published between 2000 and 2018. These studies were developed mainly in the Atlantic Forest biome and collected ants with pitfall traps on the soil/litter stratum. We initially carried out a vote-counting procedure by comparing the number of significant results describing seasonal differences in the ant assemblage. We found that most papers described a similar pattern of ant abundance, richness, and species composition between seasons. However, when we performed a meta-analysis, we observed a clear pattern of higher ant abundance and richness in the wet/summer season compared with the dry/winter season. Our meta-analysis reveals that the ant diversity decreases in the dry season, strongly in the Cerrado biome. Additionally, we point out differences in the sampling effort across biomes, indicating the need for further investments in studies focused on temporal diversity patterns, including seasonal effects, on the insect assemblage in biomes less investigated so far. Abstract in Portuguese is available with online material.     

Yeast mitochondrial calcium uptake: Regulation by polyamines and magnesium ions

Spermine, spermidine, and magnesium ions modulate the kinetic parameters of the Ca²⁺ transport system ofEndomyces magnusii mitochondria. Mg²⁺ at concentrations up to 5 mM partially inhibits Ca²⁺ transport with a half-maximal inhibiting concentration of 0.5 mM. In the presence of 2 mM MgCl₂, theS _0.5 value of the Ca²⁺ transport system increases from 220 to 490 µM, which indicates decreased affinity for the system. Spermine and spermidine exert an activating effect, having half-maximal concentrations of 12 and 50 µM, respectively. In the case of spermine, theS _0.5 value falls to 50–65 µM, which implies an increase in the transport system affinity for Ca²⁺. Both Mg²⁺ and spermine cause a decrease of the Hill coefficient, giving evidence for a smaller degree of cooperativity. Spermine and spermidine enable yeast mitochondria to remove Ca²⁺ from the media completely. In contrast, Mg²⁺ lowers the mitochondrial buffer capacity. When both Mg²⁺ and spermine are present in the medium, their effects on theS _0.5 value and the free extramitochondrial Ca²⁺ concentration are additive. The ability of spermine and Mg²⁺ to regulate yeast mitochondrial Ca²⁺ transport is discussed.     

Monitoring airborne concentrations of sporangia ofPhytophthora infestans in relation to tomato late blight in Emilia Romagna,Italy

Late blight caused byPhytophthora infestans is one of the most important diseases of tomato crops in Emilia Romagna. In total, 7–8 chemical sprays are applied per season to control the disease without taking into account the risk of infection. An integrated warning service for the prediction of tomato late blight was set up in order to define a more rational disease control strategy. As a part of the warning service, a number of sites monitoringPh. infestans airborne sporangia was set up for a timely disease prediction in the regional tomato growing areas. The results of 3 years monitoring ofPh. infestans sporangia are presented. They suggest that concentrations of airborne sporangia rapidly increase 1–2 weeks prior the blight onset in the field.     

Comparison of melatonin-binding sites in the brain of two amphibians: an autoradiographic study

Neuroanatomic comparison of the binding capability of 2-[¹²⁵I] iodomelatonin in the crested newt Triturus carnifex Laur. and the green frog Rana esculenta, using quantitative autoradiographic techniques, revealed a heterogeneous distribution pattern. The highest and relatively high binding activities were shown to occur in the optic tracts and in the suprachiasmatic area of the hypothalamus and the optic tectum, respectively, of both species. Low or no 2-[¹²⁵I] iodomelatonin binding values were obtained in the preoptic nucleus, the tuberal hypothalamus, the medulla oblongata, the septum and the dorsal pallium. A differential binding pattern was observed in the amygdaloid nucleus pars lateralis, the striatum and the hindbrain of these amphibians. Indeed, notably high binding levels were shown to occur in the former two brain areas of the crested newt, whereas high levels were displayed in the latter brain region of the green frog. On the basis of elevated quantities of melatonin receptors in mesencephalic, hypothalamic and telencephalic sites, it seems plausible to ascribe some important sensory functions to this receptor system in both species. The remarkably different binding activities in the brain of the two amphibians could be correlated with the simpler cytoarchitectonic brain structure of urodeles and with species-specific variations.     

Callose pattern and polarization phenomena in the ovules in the F2-hybrids betweenOenothera hookeri andOe. suaveolens

The pattern of callose formation in meiotic cell walls and the order of megaspore degeneration and polarity during embryo sac development are investigated in F₂-plants ofOe. hookeri ×suaveolens and the reciprocal cross. All investigated characters are variable between the ovules in the same ovary. Plants differ in the frequency of the types of callose pattern and polarity of the embryo sacs. In segregating progenies different combinations of both characters are found. The genetic basis of the polarity phenomena during the embryo sac development is discussed. In our material no correlation can be seen between the callose pattern in the surrounding wall of the meiotic cell and the development of polarity in the later stages.     

Phase transitions in nuclei and chromatin

Changes in the volume of rat liver nuclei have been monitored as a function of modifications in ionic environment (from 0 to 20 mM), temperature (from 4 to 37°C) and pH (from 1 to 8). An abrupt reduction of nuclear volume occurred with increasing ion concentration, this contraction being more pronounced with bivalent (either Ca²⁺ or Mg²⁺) than with monovalent (either Na⁺ or K⁺) cations. The lowering of pH produced a similar effect. Parallel changes in chromatin structure took place at the same time as phase-like transitions. Atomic absorption spectroscopy allowed determination of free and nuclei-bound ions, pointing to the presence of a sizeable number of free binding sites for chromatin-DNA even within intact nuclei. DNA-phosphate sites appear to be neutralized by ions strictly according to the size of the electric charge and polyelectrolyte theory. Partial digestion (by micrococcal nuclease) or simple breaks (by chemical carcinogens) of the chromatin-DNA fiber caused respectively elimination or reduction of the abrupt volume changes in the intact nuclei. The apparent role of chromatin structure versus nuclear matrix in determining the shape and volume of intact nuclei is briefly discussed.     

Properties and incompatibility behavior of miniplasmids derived from the bireplicon plasmid pCG86

Summary Many plasmids belonging to the F incompatibility groups contain more than one basic replicon. The chimeric plasmid pCG86 is an example of such a multireplicon plasmid. The two basic replicons of pCG86, RepFIIA/FIC and RepFIB have been cloned and re-ligated, the copy numbers of the clones have been determined, and the incompatibility behavior of plasmids containing the ligated replicons and the individual replicons has been studied. The bireplicon plasmids are not expected to be incompatible as recipients with monoreplicon RepFIB or RepFIIA/RepFIC plasmids, since when one replicon is challenged by an incoming replicon, the other should be able to handle the plasmid's replication. In our studies, we found that challenge with either monoreplicon plasmid resulted in incompatibility. This incompatibility was increased in bireplicon plasmids in which RepFIB was duplicated. We conclude that in the bireplicon plasmids, challenging the replication control of one replicon by an incompatible plasmid can interfere with the replication originating from the second replicon.     

Distribution of different cell types within the rat thymus in the neonatal period of life

Summary This study attempted to define reciprocal positions of cell types within the thymus. Random or non-random contacts between specific cell types were analyzed by means of graph theory. For analysis, thymus blocks were sectioned serially and, then, thymus cells were categorized into types, based on morphological criteria. The distribution of individual cell types within the cortex, cortico-medullary zone and medulla was presented in form of a map. In the analysis, three types of epithelial cell, characteristic of each thymus zone, macrophages, Langerhans-like cells and lymphocytes were found in non-random relations to one another. Moreover, characteristic groups of cells associated with one another were also demonstrated.This study was supported by the Polish Academy of Sciences     

Expression and localization of myotonic dystrophy protein kinase in human skeletal muscle cells determined with a novel antibody: possible role of the protein in cytoskeleton rearrangements during differentiation

Myotonic dystrophy is a multisystemic disorder, due to a CTG triplet expansion at the 3'UTR of the DM1 gene encoding for myotonic dystrophy protein kinase. Recent studies indicate that decreased DMPK levels could account for part of the symptoms suggesting a role of this protein in skeletal muscle differentiation. To investigate this aspect, polyclonal antibodies were raised against two peptides of the catalytic domain and against the human full-length DMPK (DMFL). In western blots, anti-hDMFL antibody was able to detect low amounts of purified human recombinant protein and recognized the splicing isoforms in heart and stomach of overexpressing mice. In human muscle extracts, this antibody specifically recognized a protein of apparent molecular weight of 85 kDa and it specifically stained neuromuscular junctions in skeletal muscle sections. In contrast, both anti-peptide antibodies demonstrated low specificity for either denatured or native DMPK, suggesting that these two epitopes are probably cryptic sites. Using anti-hDMFL, the expression and localization of DMPK was studied in human skeletal muscle cells (SkMC). Western blot analysis indicated that the antibody recognizes a main protein of apparent MW of 75 kDa, which appears to be expressed during differentiation into myotubes. Immunolocalization showed low levels of DMPK in the cytoplasm of undifferentiated cells; during differentiation the staining became more intense and was localized to the terminal part of the cells, suggesting that DMPK might have a role in cell elongation and fusion.