Fluctuating salinity improves survival of the invasive freshwater golden mussel at high salinity: implications for the introduction of aquatic species through estuarine ports

In order to evaluate the resistance to salinity as a factor enhancing freshwater invasiveness, we assessed the tolerance of the mussel Limnoperna fortunei to salinity conditions mimicking changes in an estuary. We tested mussel mortality in 30-day exposures to constant and fluctuating salinities at different temperatures in the laboratory. Test conditions simulated different seasons of the year and locations with increasing influence of marine waters in Río de la Plata, Argentina. Significant mortality (31 % after 30 days) was observed at a constant salinity of 2 ‰, increasing to 45 and 57 % at 5 and 10 ‰, respectively. In contrast, considerably greater tolerances were observed when conditions in the experimental chamber fluctuated between salt water and fresh water. No significant mortality was observed in mussels exposed to a salinity cycle with abrupt salinity changes ranging 1–23 ‰ (mean 2.68 ‰) over a month. Tolerance to this type of regime was unaffected by different temperatures within ambient ranges. Tests at constant salinity underestimate the tolerance of this and probably other freshwater nonindigenous species (NIS) to short-term saltwater exposures. Estuarine ports account for ca. 2/3 of non-marine ports globally, thus constituting donor and recipient hotspots for the spread of NIS propagules into continental aquatic ecosystems via shipping vectors. The tolerance of L. fortunei to estuarine conditions likely contributes to the species’ remarkable invasive success. These results highlight the need to determine causes of invasiveness and to study NIS traits not alone but in combination with transport network properties.     

Reproductive strategy of the invasive Oxalis pes-caprae: distribution patterns of floral morphs, ploidy levels and sexual reproduction

Oxalis pes-caprae, a tristylous flowering plant native to South Africa, is described in the western Mediterranean basin as an asexual—only 5x short-styled morph (5x S-morph) invasive weed losing all mating partners after introduction. The objective of this study was to reassess the patterns of floral morph and cytotype distribution and the sexual reproduction ability in this invaded range. For that, floral morph and cytotype composition were evaluated in 39 populations of O. pes-caprae in a methodical sampling. The reproductive success of natural populations was assessed as fruit and seed production and seed germination for all floral morphs and cytotypes detected. Self- and morph-incompatibility were also studied with controlled hand pollinations. A remarkable diversity in floral morph and cytotype composition was observed. Furthermore, we observed successful sexual reproduction in several localities across the surveyed area. The S-morph is still dominant in this invaded area, and although it was mostly 5x, an additional cytotype (4x) was also recorded. Records of both a mid-styled morph (M-morph) and an area with trimorphic populations of this species are reported here for the first time in the invasive range of the Mediterranean basin. The long-styled morph appears to occur randomly across the surveyed area, while the M-morph is concentrated mainly in Estremadura province (Portugal), where a breakdown in the incompatibility system was observed. These distribution patterns may result from events of sexual reproduction after incompatibility breakdown and/or from multiple introduction events from the native area. The ability to reproduce sexually, undetected so far, may have important impacts in the population dynamics and major consequences for the adaptation and selection potential of O. pes-caprae in this invaded area.     

Alien parasite hitchhikes to Patagonia on invasive bumblebee

The worldwide trade in bumblebees can lead to the spread of diseases, which in turn has been claimed as a factor in bumblebee decline. Populations of the introduced Bombus terrestris, which invaded NW Patagonia, Argentina, in 2006, harbor the highly pathogenic protozoan Apicystis bombi. We asked whether A. bombi had been co-introduced with B. terrestris, and if so, whether spillover occurred to the two resident bumblebee species in the region: the introduced European Bombus ruderatus and the native Bombus dahlbomii. We searched for A. bombi by means of PCR in samples of B. ruderatus and B. dahlbomii collected before and after the invasion of B. terrestris and in samples of the latter. We found no A. bombi in samples of B. ruderatus and B. dahlbomii collected before B. terrestris invasion, whereas post invasion, A. bombi was present in all 3 species. The identity of the parasite was established by sequencing the 18S region, which was identical for the three bumblebee species and also matched the European sequence, confirming it to be A. bombi. This is the first report of A. bombi in B. ruderatus and B. dahlbomii. Moreover, our results suggest that Patagonia had been free of A. bombi until this parasite was co-introduced with B. terrestris, and spilled over in situ to these two previously resident species. Finally, our findings provide indirect circumstantial evidence of a potential link between the population collapse and geographic retraction of B. dahlbomii and the introduction of this novel parasite.     

Assessment of the total effective xenoestrogen burden in extracts of human placentas

We have standardized a method to assess the total effective xenoestrogen burden (TEXB) in human placentas by the extraction and separation by high-performance liquid chromatography of two fractions containing lipophilic xenoestrogens (alpha) and endogenous hormones (beta), followed by assessing their estrogenicity in MCF-7 breast cancer cell-based E-Screen and Yeast Estrogen Screen (YES) bioassays. The means of TEXB alpha concentrations (in estradiol equivalent (Eeq) units) were 1.32 and 0.77 Eeq pM g^?1 placenta in the E-Screen and YES, respectively; TEXB beta concentrations were 6.97 and 11.56 Eeq pM g^?1 placenta, respectively. The interclass correlation coefficient was low and a fair level of agreement was observed after kappa test correction. According to the E-Screen and YES, TEXB alpha was ≥LOD in 70.0 and 55.0% of the placentas and 92.5 and 82.5% in beta, respectively. Although both bioassays can be recommended for assessing TEXB, there is greater experience with the use of the E-Screen for estrogenic assessment after extensive extraction of complex human matrices.     

Nucleolar organizer regions in Sittasomus griseicapillus and Lepidocolaptes angustirostris (Aves,Dendrocolaptidae): Evidence of a chromosome inversion

Cytogenetic studies in birds are still scarce compared to other vertebrates. Woodcreepers (Dendrocolaptidae) are part of a highly specialized group within the Suboscines of the New World. They are forest birds exclusive to the Neotropical region and similar to woodpeckers, at a comparable evolutionary stage. This paper describes for the first time the karyotypes of the Olivaceous and the Narrow-billed Woodcreeper using conventional staining with Giemsa and silver nitrate staining of the nucleolar organizer regions (Ag-NORs). Metaphases were obtained by fibular bone marrow culture. The chromosome number of the Olivaceous Woodcreeper was 2n = 82 and of the Narrow-billed Woodcreeper, 2n = 82. Ag-NORs in the largest macrochromosome pair and evidence of a chromosome inversion are described herein for the first time for this group.     

Mantel test in population genetics

The comparison of genetic divergence or genetic distances, estimated by pairwise F_ST and related statistics, with geographical distances by Mantel test is one of the most popular approaches to evaluate spatial processes driving population structure. There have been, however, recent criticisms and discussions on the statistical performance of the Mantel test. Simultaneously, alternative frameworks for data analyses are being proposed. Here, we review the Mantel test and its variations, including Mantel correlograms and partial correlations and regressions. For illustrative purposes, we studied spatial genetic divergence among 25 populations of Dipteryx alata (“Baru”), a tree species endemic to the Cerrado, the Brazilian savannas, based on 8 microsatellite loci. We also applied alternative methods to analyze spatial patterns in this dataset, especially a multivariate generalization of Spatial Eigenfunction Analysis based on redundancy analysis. The different approaches resulted in similar estimates of the magnitude of spatial structure in the genetic data. Furthermore, the results were expected based on previous knowledge of the ecological and evolutionary processes underlying genetic variation in this species. Our review shows that a careful application and interpretation of Mantel tests, especially Mantel correlograms, can overcome some potential statistical problems and provide a simple and useful tool for multivariate analysis of spatial patterns of genetic divergence.     

Proteomic approach of adaptive response to arsenic stress in Exiguobacterium sp. S17, an extremophile strain isolated from a high-altitude Andean Lake stromatolite

The North-Western part of Argentina is particularly rich in wetlands located in the Puna in an altitude between 3,600 and 4,600 m above sea level. Most of these high-altitude Andean lakes are inhospitable areas due to extreme habitat conditions such as high contents of toxic elements, particularly arsenic. Exiguobacterium sp. S17, isolated from stromatolites in Laguna Socompa, exhibited remarkable tolerance to high arsenic concentration, i.e., it tolerated arsenic concentration such as 10 mM of As(III) and 150 mM of As(V). A proteomics approach was conducted to reveal the mechanisms that provide the observed outstanding resistance of Exiguobacterium sp. S17 against arsenic. A comparative analysis of S17, exposed and unexposed to arsenic revealed 25 differentially expressed proteins. Identification of these proteins was performed by MALDI-TOF/MS revealing upregulation of proteins involved in energy metabolism, stress, transport, and in protein synthesis being expressed under arsenic stress. To our knowledge, this work represents the first proteomic study of arsenic tolerance in an Exiguobacterium strain.     

miR-125b Acts as a Tumor Suppressor in Breast Tumorigenesis via Its Novel Direct Targets ENPEP,CK2-α, CCNJ,and MEGF9

MicroRNAs (miRNAs) play important roles in diverse biological processes and are emerging as key regulators of tumorigenesis and tumor progression. To explore the dysregulation of miRNAs in breast cancer, a genome-wide expression profiling of 939 miRNAs was performed in 50 breast cancer patients. A total of 35 miRNAs were aberrantly expressed between breast cancer tissue and adjacent normal breast tissue and several novel miRNAs were identified as potential oncogenes or tumor suppressor miRNAs in breast tumorigenesis. miR-125b exhibited the largest decrease in expression. Enforced miR-125b expression in mammary cells decreased cell proliferation by inducing G2/M cell cycle arrest and reduced anchorage-independent cell growth of cells of mammary origin. miR-125b was found to perform its tumor suppressor function via the direct targeting of the 3’-UTRs of ENPEP, CK2-α, CCNJ, and MEGF9 mRNAs. Silencing these miR-125b targets mimicked the biological effects of miR-125b overexpression, confirming that they are modulated by miR-125b. Analysis of ENPEP, CK2-α, CCNJ, and MEGF9 protein expression in breast cancer patients revealed that they were overexpressed in 56%, 40–56%, 20%, and 32% of the tumors, respectively. The expression of ENPEP and CK2-α was inversely correlated with miR-125b expression in breast tumors, indicating the relevance of these potential oncogenic proteins in breast cancer patients. Our results support a prognostic role for CK2-α, whose expression may help clinicians predict breast tumor aggressiveness. In particular, our results show that restoration of miR-125b expression or knockdown of ENPEP, CK2-α, CCNJ, or MEGF9 may provide novel approaches for the treatment of breast cancer.