Chromosomal evidence for a putative cryptic species in the Gymnotus carapo species-complex (Gymnotiformes, Gymnotidae)

<p>Abstract</p> <p>Background</p> <p>In this study we examined the karyotypes of morphologically indistinguishable populations of the electric knifefish <it>Gymnotus carapo sensu stricto </it>from the Eastern Amazon of Brazil. These were identified unambiguously on the basis of external morphology, meristics, and pigmentation.</p> <p>Results</p> <p>Specimens from one of five localities exhibited a karyotype previously not documented for <it>Gymnotus </it>species in the Amazon basin: 2n = 40 (34M/SM+6ST/A). Samples from the other four localities exhibited a different karyotype: 2n = 42 (30M/SM+12ST/A), which we had previously described. Specimens from all five localities presented constitutive heterochromatin in the centromeric region of almost all chromosomes, including in the distal and interstitial regions. Staining with 4'6-Diamidino-2-phenylindole revealed C-positive banding. In both karyotypes the Nucleolar Organizer Region (NOR) was located on the short arm of pair 20, and Chromomycin A₃stained the NORs. Fluorescent <it>in situ </it>hybridization with telomeric probes showed an Interstitial Telomeric Sequence (ITS) in the proximal short arm of a metacentric pair in the 2n = 40 karyotype.</p> <p>Conclusion</p> <p>The difference between the two karyotypes on the diploid number and chromosome morphology can be explained by rearrangements of the fusion-fission type and also by pericentric inversions. The presence of ITS in a metacentric pair of the 2n = 40 karyotype suggests that the difference in the diploid number of the karyotypes results from a fusion. The consistent 2n = 42 karyotype at four localities suggests an interbreeding population. However, because fusion-fission and pericentric inversions of this nature typically result in reproductive isolation, we speculate that the form with the 2n = 40 karyotype is a different species to that of the 2n = 42 form. Nonetheless, we did not observe evident differences in external morphology, meristics and pigmentation between the two forms, which suggest that they represent cryptic sympatric species in the <it>G. carapo </it>species complex. We speculate that the chromosomal speciation occurred recently, allowing insufficient time for the fixation of other differences following post-zygotic isolation.</p

Effects of riparian plant diversity loss on aquatic microbial decomposers become more pronounced at longer times

We examined the potential long-term impacts of riparian plant diversity loss on diversity and activity of aquatic microbial decomposers. Microbial assemblages were obtained in a mixed-forest stream by immersion of mesh bags contain-ing three leaf species (alder, oak and eucalyptus), commonly found in riparian corridors of Iberian streams. Simulation of species loss was done in microcosms by including a set of all leaf species, retrieved from the stream, and non-colonized leaves of three, two or one leaf species. Leaves were renewed every month throughout six months, and microbial inoculum was ensured by a set of colonized leaves from the previous month. Microbial diversity, leaf mass loss and fungal biomass were assessed at the second and sixth months after plant species loss. Molecular diversity of fungi and bacteria, as the total number of operational taxonomic units per leaf diversity treatment, decreased with leaf diversity loss. Fungal biomass tended to decrease linearly with leaf species loss on oak and eucalyptus, suggesting more pronounced effects of leaf diver-sity on lower quality leaves. Decomposition of alder and eucalyptus leaves was affected by leaf species identity, mainly after longer times following diversity loss. Leaf decomposi-tion of alder decreased when mixed with eucalyptus, while decomposition of eucalyptus decreased in mixtures with oak. Results suggest that the effects of leaf diversity on microbial decomposers depended on leaf species number and also on which species were lost from the system, especially after longer times. This may have implications for the management of riparian forests to maintain stream ecosystem functioning.FEDER-POFC-COMPETE and the Portuguese Foundation for Science and Technology supported this study (PEst-C/ BIA/UI4050/2011, PTDC/AAC-AMB/113746/2009 and PTDC/AAC-AMB/117068/2010), S. Duarte (SFRH/BPD/47574/2008) and I. Fernandes (SFRH/BD/42215/2007)

Identification and quantification of prosthetic mitral regurgitation by flow convergence method using transthoracic approach

The present case report illustrates the clinical applicability of the proximal isovelocity surface area (PISA) method in identifying, locating and assessing paravalvular prosthetic mitral regurgitation by transthoracic echocardiography

Uncertainties in projecting climate-change impacts in marine ecosystems

Projections of the impacts of climate change on marine ecosystems are a key prerequisite for the planning of adaptation strategies, yet theyare inevitablyassociated withuncertainty.Identifying,quantifying,andcommunicatingthisuncertaintyis keytobothevaluatingtherisk associated with a projection and building confidence in its robustness. Wereview howuncertainties in such projections are handled in marine science. We employan approach developedin climatemodelling by breaking uncertainty down into(i) structural (model) uncertainty,(ii) initialization and internalvariabilityuncertainty,(iii)parametricuncertainty,and(iv)scenariouncertainty.Foreachuncertaintytype,wethenexaminethecurrent state-of-the-art in assessing and quantifying its relative importance. We consider whether the marine scientific community has addressed these types of uncertainty sufficiently and highlight the opportunities and challenges associated with doing a better job. We find that even within a relatively small field such as marine science, there are substantial differences between subdisciplines in the degree of attention given to each type of uncertainty. We find that initialization uncertainty is rarely treated explicitly and reducing this type of uncertainty may deliver gainsontheseasonal-to-decadaltime-scale.Weconcludethatallpartsofmarinesciencecouldbenefitfromagreaterexchangeofideas,particularly concerningsuchauniversalproblemsuchasthetreatmentofuncertainty.Finally,marinescienceshouldstrivetoreachthepointwherescenario uncertainty is the dominant uncertainty in our projections

Sports Participation and Health Care Costs in Older Adults Aged 50 Years or Older

Brazilian Ministry of Science and Technology; São Paulo Research Foundatio