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The Neotropical region is the most diverse on the planet, largely owing to its mosaic of tropical rainforests. Multiple tectonic and climatic processes have been hypothesized to contribute to generating this diversity, including Andean orogeny, the closure of the Isthmus of Panama, the GAARlandia land bridge and historical connections among currently isolated forests. Micrathena spiders are diverse and widespread in the region, and thus a complete phylogeny of this genus allows the testing of hypotheses at multiple scales. We estimated a complete, dated phylogeny using morphological data for 117 Micrathena species and molecular data of up to five genes for a subset of 79 species. Employing eventc-based approaches and biogeographic stochastic mapping while considering phylogenetic uncertainty, we estimated ancestral distributions, the timing and direction of dispersal events and diversification rates among areas. The phylogeny is generally robust, with uncertainty in the position of some of the species lacking sequences. Micrathena started diversifying around 25 Ma. Andean cloud forests show the highest in-situ speciation, while the Amazon is the major dispersal source for adjacent areas. The Dry Diagonal generated few species and is a sink of diversity. Species exchange between Central and South America involved approximately 23 dispersal events and started ~20 Ma, which is consistent with a Miocene age for the Isthmus of Panama closure. We inferred four dispersal events from Central America to the Antilles in the last 20 Myr, indicating the spiders did not reach the islands through the GAARlandia land bridge. We identified important species exchange routes among the Amazon, Andean cloud forests and Atlantic forests during the Plio-Pleistocene. Sampling all species of the genus was fundamental to the conclusions above, especially in identifying the Andean forests as the area that generated the majority of species. This highlights the importance of complete taxonomic sampling in biogeographic studies.

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Abstract Accurate distributional information is crucial for studies on systematics, biodiversity and conservation. To improve the knowledge regarding the geographical distribution of Omalonyx in South America, we present updated information based on data from a literature review, institutional collections and malacological surveys. All this information composed the dataset used to predict species distribution employing the Maximum Entropy Algorithm (MaxEnt). The model was run using data on species distribution, altitude and bioclimatic variables (WorldClim database). The model had consistent performance, and areas presenting similar conditions to areas where the species were recorded were considered areas of occurrence. The predicted occurrence areas included those that were already surveyed and those that are considered potential occurrence areas. The results demonstrate that the genus has widespread distribution in the Neotropical region and occurs in the tropical, temperate and arid regions of South America and Lesser Antilles. Omalonyx spp. were recorded in all South American countries and hydrographic regions. However, in some countries, there were only isolated records (ex: Colombia and Ecuador). Here, we also present the first record of Omalonyx spp. in four Brazilian States (Acre, Rondônia, Piaui, and Amapá). The genus was found in all hydrographic regions within Brazil and among 27 federative unities; it was absent from only two unities (Roraima State and Distrito Federal). This work contributes to the knowledge on Omalonyx spp. distribution and provides an important basis for the work of ecologists and taxonomists.

Resumo A informação precisa sobre a distribuição é crucial para os estudos sobre sistemática, biodiversidade e conservação. Para melhorar o conhecimento sobre a distribuição geográfica de Omalonyx na América do Sul, apresentamos informações atualizadas com base em dados de revisão de literatura, coleções institucionais e pesquisas malacológicas. Toda essa informação compôs o conjunto de dados usado para predição da distribuição de espécies empregando o Algoritmo de Entropia Máxima (MaxEnt). O modelo foi executado usando dados de distribuição de espécies, altitude e variáveis bioclimáticas (banco de dados WorldClim). O modelo apresentou um desempenho consistente e as áreas que apresentaram condições semelhantes às áreas onde as espécies foram registradas, foram consideradas áreas de ocorrência. As áreas de ocorrências previstas incluíram aquelas que já foram pesquisadas e aquelas que são consideradas áreas de ocorrência potencial. Os resultados demonstram que o gênero tem uma distribuição Neotropical ampla e que ocorre nas regiões tropical, temperada e árida da América do Sul e nas Pequenas Antilhas. Omalonyx spp. foram registradas em todos os países e bacias sul-americanas. No entanto, em alguns países, apenas registros isolados foram encontrados (ex: Colômbia e Equador). Aqui, também apresentamos o primeiro registro de Omalonyx spp. em quatro estados brasileiros (Acre, Rondônia, Piauí e Amapá). O gênero foi encontrado em todas as regiões hidrográficas no Brasil e nas 27 unidades federativas; sendo ausente em apenas duas unidades federativas (Estado de Roraima e Distrito Federal). Esse trabalho contribui para o conhecimento da distribuição das espécies de Omalonyx e fornece uma importante base para trabalhos de ecólogos e taxonomistas.

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Corbicula largillierti is a native mollusk from China. In Brazil, this species was first recorded in the Pantanal of Mato Grosso. This short communication reports the occurrence of C. largillierti for the first time in the Paraíba river basin (Brazilian semi-arid), and also considers the risk of introduction of other molluscs invaders in this basin due to the diversion of water from the São Francisco River. Densities of individuals ranged from 33 to 65 ind.m-2 (maximum values of 484 ind.m-2) in coarse sediment (gravel, 2-4 mm). The diversion of waters from the São Francisco river can lead to the introduction of new species, enhancing ecological problems in the Paraiba river basin.

Corbicula largillierti é um molusco nativo da China. No Brasil esta espécie foi registrada primeiramente no Pantanal do Mato Grosso. Esta nota registra a primeira ocorrência de C. largillierti na bacia do Rio Paraíba (semiárido brasileiro). Considera também os riscos potenciais de introdução de outros moluscos invasores nesta bacia devido è transposição das águas do Rio São Francisco. As densidades do molusco variaram de 33 a 65 ind.m-2 (atingindo valor máximo de 484 ind.m-2) em sedimentos grossos (cascalho, 2-4 mm). A transposição das águas do Rio São Francisco pode ocasionar a introdução de novas espécies exóticas potencializando problemas ecológicos na bacia do Rio Paraíba.

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The Brazilian Caatinga is part of the seasonally dry tropical forests, a vegetation type disjunctly distributed throughout the Neotropics. It has been suggested that during Pleistocene glacial periods, these dry forests had a continuous distribution, so that these climatic shifts may have acted as important driving forces of the Caatinga biota diversification. To address how these events affected the distribution of a dry forest species, we chose Sicarius cariri, a spider endemic to the Caatinga, as a model. We studied the phylogeography of one mitochondrial and one nuclear gene and reconstructed the paleodistribution of the species using modelling algorithms. We found two allopatric and deeply divergent clades within S. cariri, suggesting that this species as currently recognized might consist of more than one independently evolving lineage. Sicarius cariri populations are highly structured, with low haplotype sharing among localities, high fixation index and isolation by distance. Models of paleodistribution, Bayesian reconstructions and coalescent simulations suggest that this species experienced a reduction in its population size during glacial periods, rather than the expansion expected by previous hypotheses on the paleodistribution of dry forest taxa. In addition to that, major splits of intraspecific lineages of S. cariri took place in the Pliocene. Taken together, these results indicate S. cariri has a complex diversification history dating back to the Tertiary, suggesting the history of dry forest taxa may be significantly older than previously thought.

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Introns are common among all eukaryotes, while only a limited number of introns are found in prokaryotes. Globin and globin-like proteins are widely distributed in nature, being found even in prokaryotes and a wide range of patterns of intron-exon have been reported in several eukaryotic globin genes. Globin genes in invertebrates show considerable variation in the positions of introns; globins can be found without introns, with only one intron or with three introns in different positions. In this work we analyzed the introns in the myoglobin gene from Biomphalaria glabrata, B. straminea and B. tenagophila. In the Biomphalaria genus, the myoglobin gene has three introns; these were amplified by PCR and analyzed by PCR-RFLP. Results showed that the size (number or nucleotides) and the nucleotide sequence of the coding gene of the myoglobin are variable in the three species. We observed the presence of size polymorphisms in intron 2 and 3; this characterizes a homozygous/heterozygous profile and it indicates the existence of two alleles which are different in size in each species of Biomphalaria. This polymorphism could be explored for specific identification of Biomphalaria individuals.

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Angiostrongylus costaricensis can infect several mollusks, and its migration route in intermediate hosts has been studied only in Sarasinula marginata. To verify the susceptibility of Omalonyx sp. as an intermediate host of A. costaricensis and to analyze the nematode migration route, individuals were infected with stage 1 larvae. Obtained stage 3 larvae were orally inoculated in mice, and after 30 days, adult worms and stage 1 larvae were recovered, demonstrating Omalonyx susceptibility and suitability to infection. To define the parasite migration routes, specimens of Omalonyx with 30 min, 1 h, 2 h, 4 h, 6 h, 8 h, 2 days, 5 days, 10 days, 12 days, 15 days, 20 days, 21 days, 25 days, 28 days, and 30 days of infection were fixed and serially sectioned. Histological sections were stained with hematoxylin-eosin. The results were compared to those described in S. marginata. Oral and cutaneous infections were noted. After the penetration, larvae were retained, mainly in the fibromuscular tissue, by hemocytes, or they spread to the whole organism through the circulation, following the anatomical structure of the vasculature. The perilarval hemocyte reaction in Omalonyx was more intense until stage 2 larva instar, decreasing in the presence of stage 3 larvae. Differences in some aspects of hemocyte reaction between S. marginata and Omalonyx exemplify interspecific peculiarities in snail response to the same parasite.

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A simple and single-step technique based on multiplex PCR (multiplex polymerase chain reaction) has been developed for simultaneous identification of Brazilian Biomphalaria species, the intermediate hosts of Schistosoma mansoni, and their diagnosis of infection by the trematode. We used species-specific primers directed both to the internal transcribed spacer 2 (ITS2) of ribosomal DNA from 3 of the S. mansoni host species and to the mitochondrial DNA (mtDNA) from the trematode. Those primers were used simultaneously in a single multiplex-PCR reaction, and template DNA was obtained from S. mansoni-infected and noninfected snails. The results were visualized in silver stained polyacrylamide gels, revealing the presence of specific bands. The methodology has shown to be efficient, fast, and reproducible for Biomphalaria species identification and diagnosis of snails infected by S. mansoni during prepatent periods.

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The first and second internal transcribed spacer regions (ITS1 and ITS2) of the ribosomal DNA of Biomphalaria tenagophila complex (B. tenagophila, B. occidentalis, and B. t. guaibensis) were sequenced and compared. The alignment lengths of these regions were about 655 bp and 481 bp, respectively. Phylogenetic relationships among the Biomphalaria species were inferred by Maximum Parsimony and Neighbor-joining methods. The phylogenetic trees produced, in most of the cases, were in accordance with morphological systematics and other molecular data previously obtained by polymerase chain reaction and restriction fragment length polymorphism analysis. The present results provide support for the proposal that B. tenagophila represents a complex comprising B. tenagophila, B. occidentalis and B. t. guaibensis.

Assuntos

RESUMO

The first and second internal transcribed spacer regions (ITS1 and ITS2) of the ribosomal DNA of Biomphalaria tenagophila complex (B. tenagophila, B. occidentalis, and B. t. guaibensis) were sequenced and compared. The alignment lengths of these regions were about 655 bp and 481 bp, respectively. Phylogenetic relationships among the Biomphalaria species were inferred by Maximum Parsimony and Neighbor-joining methods. The phylogenetic trees produced, in most of the cases, were in accordance with morphological systematics and other molecular data previously obtained by polymerase chain reaction and restriction fragment length polymorphism analysis. The present results provide support for the proposal that B. tenagophila represents a complex comprising B. tenagophila, B. occidentalis and B. t. guaibensis.

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RESUMO

The intermediate hosts of Schistosoma mansoni, in Brazil, Biomphalaria glabrata, B. tenagophila and B. straminea, were identified by restriction fragment length polymorphism analysis of the mitochondrial gene cytochrome oxidase I (COI). We performed digestions with two enzymes (AluI and RsaI), previously selected, based on sequences available in Genbank. The profiles obtained with RsaI showed to be the most informative once they were polymorphic patterns, corroborating with much morphological data. In addition, we performed COI digestion of B. straminea snails from Uruguay and Argentina.

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