23736 research outputs found
Sort by
He leaps, she beats: The role of social interactions on the overland movements of an Amazonian amphibious killifish
No full textAmphibious habits are present in a variety of fish and are allowed by a set of physiological, morphological and behavioural adaptations. The most intriguing question, however, is what motivates an aquatic organism to venture into the land? Unfavourable abiotic and biotic conditions in the aquatic environment have been reported as main stimuli for fish to emerge from water. However, few attempts have been made to disentangle the effects of different social contexts on the propensity of amphibious fishes to leave the water. Trying to separate the effects of predator threat, intraspecific competition and mate searching on overland movement of amphibious fish, we ran a mesocosm experiment with the Amazonian killifish Anablepsoides micropus. Overland movement was quantified based on fish leaps between artificial pools set in enclosures in a primary forest area. Males moved overland more frequently than females and their movement depended on the social context, being higher in the presence of predators and lower in the presence of females. Females, instead, showed context-independent movement rates. This suggests that males move between pools searching for mates, stopping when successful in this search. On the other hand, occasional encounters with predators may force males to abandon the pool as a defence mechanism. Female aggressiveness towards the predator may influence its low movement in the presence of the predator. Such differential responses may play important ecological and evolutionary roles, allowing A. micropus to occupy a wide range of environmental conditions under varied ecological and social contexts. © 2018 John Wiley & Sons A/S. Published by John Wiley & Sons Lt
Primeiro Registro De Dna Ambiental De Lagos De Várzea Da Amazônia Central: Definição E Validação De Método De Extração
No full textComparative cytogenetics of nine populations of the Rhinella genus (Anura, Bufonidae) with a highlight on their conservative karyotype
Get PDFThe genus Rhinella is one of the most diverse groups of bufonid toads, currently composed by 93 valid species and naturally distributed throughout different Neotropical ecoregions. Here, we analyze nine Brazilian populations of toads representing species of the Rhinella margaritifera and Rhinella marina groups. These new data include the first description of the R. hoogmoedi and R. proboscidae karyotypes, as well as other taxonomically unresolved forms. Chromosomal analysis of the populations revealed pronounced chromosomal uniformity (2n=22), including the diploid number and chromosomal morphology. Three different NOR-bearing chromosomes were identified: in the subterminal region of pair 10q in R. hoogmoedi, Rhinella sp. 1 and Rhinella sp. 2, in subterminal region of 7p in R. proboscidae and Rhinella cf. margaritifera while in R. henseli and R. icterica was detected in interstitial region of 7p. Karyotypic uniformity of the genus permits the inference of interspecific chromosome homologies and evolutionary changes in the NOR-bearing chromosome may represent an informative character in species group level. The review of the cytogenetic data of the Rhinella species together with the new karyotypes reported here contributes to the understanding of the chromosomal evolution of these toads, which karyotypes are highly conserved despite the ample distribution of many forms. © 2019, Sociedade Brasileira de Genética
Análise do teor de saponinas em tubérculos amazônicos com potencial utilização na redução de colesterol e obesidade.
No full textDiversification history in the Dendrocincla fuliginosa complex (Aves: Dendrocolaptidae): Insights from broad geographic sampling
No full textDendrocincla woodcreepers are ant-following birds widespread throughout tropical America. Species in the genus are widely distributed and show little phenotypic variation. Notwithstanding, several subspecies have been described, but the validity of some of these taxa and the boundaries among them have been discussed for decades. Recent genetic evidence based on limited sampling has pointed to the paraphyly of D. fuliginosa, showing that its subspecies constitute a complex that also includes D. anabatina and D. turdina. In this study we sequenced nuclear and mitochondrial markers for over two hundred individuals belonging to the D. fuliginosa complex to recover phylogenetic relationships, describe intraspecific genetic diversity and provide historical biogeographic scenarios of diversification. Our results corroborate the paraphyly of D. fuliginosa, with D. turdina and D. anabatina nested within its recognized subspecies. Recovered genetic lineages roughly match the distributions of described subspecies and congruence among phylogenetic structure, phenotypic diagnosis and distribution limits were used to discuss current systematics and taxonomy within the complex, with special attention to Northern South America. Our data suggest the origin of the complex in western Amazonia, associated with the establishment of upland forests in the area during the early Pliocene. Paleoclimatic cycles and river rearrangements during the Pleistocene could have, at different times, both facilitated dispersal across large Amazonian rivers and the Andes and isolated populations, likely playing an important role in differentiation of extant species. Previously described hybridization in the headwaters of the Tapajós river represents a secondary contact of non-sister lineages that cannot be used to test the role of the river as primary source of diversification. Based on comparisons of D. fuliginosa with closely related understory upland forest taxa, we suggest that differential habitat use could influence diversification processes in a historically changing landscape, and should be considered for proposing general mechanisms of diversification. © 201
Uma nova espécie de Paralithoxus é descrita do rio ajarani, um pequeno tributário da bacia do Rio Branco, Estado de Roraima, Amazônia Brasileira
Get PDFA new species of Paralithoxus is described from the Ajarani River, a small tributary of the Branco River basin, Roraima State, Brazilian Amazon. The genus Paralithoxus comprises species described from the Essequibo drainage in Guyana, Approuague and Maroni in French Guiana, Suriname River in Surinam, and more recently, from Jari and Amapá rivers, in Brazil. Despite occurring in a rock-bottomed fast-flowing stream as the other species of Paralithoxus, this is the first species of the genus collected at 900 m altitude, in the Serra da Mocidade highlands, an isolated and poorly accessible small mountain chain at the southern border of the Guiana Shield. The new species is distinguished from its congeners by having truncate teeth, color pattern with green spots on dark olive-brown background, alternating dark and light blotches on fins and by the pelvic fin being as long as or longer than the pectoral fin. Sex dimorphism of the species is described. Comments on morphology and osteology are provided and compared with congeners. © 2019 Sociedade Brasileira de Ictiologia
Boto (Inia geoffrensis-Cetacea: Iniidae) aggregations in two provisioning sites in the lower Negro River-Amazonas, Brazil: Are they related?
Get PDFThe Negro River currently has seven floating houses where tourists can feed and interact with botos, each with its own history of how these aggregations were formed. Some keepers say these groups are familial, even reporting individuals being born into the group. However, behavioral studies have shown that botos are solitary, only forming groups at feeding areas and during the mating season. In the present study we used 12 microsatellite and molecular sex markers to characterize relationships within and between two boto aggregations (ten and seven botos each) in the lower Negro River. Molecular sexing revealed that all botos sampled from both aggregations were males. This may be explained by habitat preference, as male botos are primarily found in the main channels of large rivers, whereas females prefer more protected areas, such as flooded forests and its channels and lakes. Most of the animals were unrelated within each aggregation, demonstrating that these aggregations are not normally formed due to kinship bonds, but are exclusively for feeding, as botos learn that these places provide easy access to food. This study provides important information that helps us understand how human interaction is affecting the social structure and behavior of these animals. © 2019 PeerJ Inc.. All rights reserved
A moratória da piracatinga (Calophysus macropterus, Siluriformes: Pimelodidae) está sendo cumprida?
No full textMorphological and anatomical characteristics and temporal pattern of initial growth in Astrocaryum acaule Mart
No full textAstrocaryum acaule Mart. is a palm with underground stem, common in lowland forests, known in Brazil as tucumã-í. The objective of this work was to perform the description and characterization of seeds and of the seedling emergence process, revealing morphological and anatomical patterns of A. acaule. Seedlings were obtained by sowing in vermiculite. The seed is spherical, with variations in shape and size according to the number of seeds in the fruit. Germination is adjacent, with formation of a coleoptile above the cotyledonary sheath. The germinative bud is emitted within between 30 and 130 days. The proximal and distal regions differentiate with growth, forming the seedling and the haustorium that transfers reserves through the reduced apocole. The initial root system differs in the hypocotyl-radicle region, below the insertion of leaf primordia, forming a lateral root and a late primary root. The first eophyll is expanded 120 days after the protrusion of the germinative button, with aculeate petiole, amphistomatic leaf blade, papillose epidermis, homogeneous mesophyll, and vascular system covered by fibers. Morphoanatomical characters reported in this study increase our knowledge about Amazonian palms and on organogenesis in their early stages of growth. © 2019 Elsevier Gmb
Characterization of Bacterial Communities in Breeding Waters of Anopheles darlingi in Manaus in the Amazon Basin Malaria-Endemic Area
Get PDFThe microbiota in mosquito breeding waters can affect ovipositing mosquitoes, have effects on larval development, and can modify adult mosquito-gut bacterial composition. This, in turn, can affect transmission of human pathogens such as malaria parasites. Here, we explore the microbiota of four breeding sites for Anopheles darlingi, the most important malaria vector in Latin America. The sites are located in Manaus in the Amazon basin in Brazil, an area of active malaria transmission. Using 16S rRNA gene sequencing by MiSeq, we found that all sites were dominated by Proteobacteria and Firmicutes and that 94% of the total number of reads belonged to 36 operational taxonomic units (OTUs) identified in all sites. Of these, the most common OTUs belonged to Escherichia/Shigella, Staphylococcus, and Pseudomonas. Of the remaining 6% of the reads, the OTUs found to differentiate between the four sites belonged to the orders Burkholderiales, Actinomycetales, and Clostridiales. We conclude that An. darlingi can develop in breeding waters with different surface-water bacteria, but that the common microbiota found in all breeding sites might indicate or contribute to a suitable habitat for this important malaria vector. © 2019, The Author(s)