Efeitos da tilápia do Nilo, Oreochromis niloticus, sobre a biomassa planctônica e a transparência da água ao longo de um gradiente de enriquecimento por nutrientes

The omnivorous filter-feeding fish, Nile tilapia (Oreochromis niloticus), can have negative effects on water quality enhancing the eutrophication process. These effects depend on the nutrient enrichment level in the water. We carried out a mesocosm experiment for five weeks in a tropical man-made lake in Brazil to test ifthe effects of tilapias depend on of the level of nutrient enrichment. The experiment lasted for 5 weeks and a factorial 2x5 experimental design was used where the presence and absence of tilapias were manipulated in combination to 5 different levels of nutrient load in a total of 10 treatments. A two way repeated measure ANOVA was performed to evaluate the effects of time (t), tilapia (F), nutrients (NP) and the interactions among these factors on: chlorophyll a, water transparency, total phosphorous, total nitrogen, N:P ratio, zooplankton biomass and phytoplankton biovolume. The tilapia effect was evident, but nutrient enrichment didn t have any effect on the variables analyzed. Tilapia decreased the water transparency, total zooplankton biomass, calanoid copepod biomass, nauplii copepod biomass and cladocerans biomass. On the other hand, tilapia had no effect on phytoplankton biovolume. This lack of effect on phytoplankton is probably due to tilapia grazing that may counteract the positive effect of tilapia on phytoplankton via trophic cascades and nutrient recycling. Hence, a reduction in tilapia stock would not be an effective way to reduce phytoplankton biomass and improve water quality

Avaliação do desempenho reprodutivo do Cavalo-Marinho Hippocampus reidi (GINSBURG 1933) do estuário do Rio Potengi (Rio Grande do Norte, Brasil) com vistas ao seu cultivo em bases sustentáveis

Os cavalos-marinhos têm cativado a imaginação e a curiosidade dos seres humanos por centenas de anos. No entanto, nos dias de hoje, esses animais correm um sério risco de extinção por fatores como a pesca desordenada para suprir os mercados de peixes ornamentais e da medicina tradicional chinesa e principalmente, a destruição do seu habitat. Nesse contexto, é crescente o número de estudos sobre a ecologia, a biologia (reprodutiva, especialmente) e o cultivo de várias espécies do gênero Hippocampus, inclusive para fins conservacionistas e de recomposição de estoques. Duas espécies de cavalos-marinhos são encontradas no Brasil: Hippocampus reidi Ginsburg 1933 e Hippocampus erectus Perry. No entanto, as informações sobre essas espécies estão basicamente restritas ao seu grau de ocorrência ou a sua área de ocupação. No presente estudo, foi avaliado o desempenho reprodutivo de Hippocampus reidi do estuário do rio Potengi (05° 47' 42'' S; 35° 12' 34'' W), em Natal, Rio Grande do Norte. Para tanto, cavalos-marinhos grávidos (n = 38) foram coletados no referido estuário nos meses de setembro, outubro e novembro de 2008 e julho, agosto, setembro e outubro de 2009 e mantidos em laboratório até que liberassem os filhotes. O comprimento padrão (CPA), altura (ATA), volume da bolsa (VB) e peso úmido (PuA) dos adultos, bem como o comprimento padrão (CPF), altura (ATF), peso úmido (PuF) e peso seco (PsF) dos filhotes foram determinados. Os resultados obtidos mostraram que houve correlações significativas entre o CPA e a ATA (r²=0,171), CPA e PuA (r²=0,624), CPA e VB (r²=0,256), ATA e PuA (r²=0,788), PuA e VB (r²=0,211), CPF e ATF (r²=0,903) e CPF e PsF (r²=0,163). A análise de correspondência (AC) que associou as classes do comprimento padrão dos adultos (CPA) e o volume da bolsa de H. reidi ao número de filhotes mostrou que animais entre 19 cm e 21 cm e com volume de bolsa entre 3 mL e 4 mL foram os que liberaram o maior número de filhotes. Os resultados do presente estudo também indicam que o tamanho mínimo de captura recomendado pela CITES (10 cm de altura) para H. reidi deve ser revisto, uma vez que não foram encontrados animais menores que 13,5 cm que estivessem grávidos. Finalmente, o número médio de filhotes por desova obtido no presente estudo (n = 775 ± 398 filhotes) realçou o potencial reprodutivo de H. reidi e a necessidade de estudos adicionais com esta espécie

Avaliação da atividade turística sobre a composição e a distribuição das macroalgas marinhas nos recifes de Pirangi (Rio Grande do Norte, Brasil)

The reef area of Pirangi beach has been experiencing antropogenic actions, mainly due to tourism activity. In order to evaluate these effects, surveys on seaweeds were conducted at nine stations located over the fringing reef. Benthic community (seaweeds/corals) were identified using the photoquadrat method, with 50 meters random transects located paralleled to the coast. The general categories evaluated in each transect were: rock, sand, seaweeds, corals and mollusks. Data achieved were processed at Coral Point Count with Excel Extensions software. A total of 30 seaweed species, 5 coral species and 1 mollusk species were identified. There was a high dominance of short algae at stations with high tourism pressure, whereas frondose algae usually occurred at places without human interference. Seaweeds with the highest percent cover were composed by Sargassum vulgare (59%), Caulerpa racemosa (47%) and Dictyopteris delicatula (33%). Cluster analyses considering benthic organisms revealed five benthic features: (1) submersed area characterized by a diversified marine flora; (2) area with dominance of Caulerpa racemosa and presence of Millepora alcicornis; (3) area with high cover of Sargassum vulgare; (4) trampling area characterized by bare rocks, short algae and Zoanthus sociatus and (5) area with high coverage of Palythoa caribaeroum. Obtained data suggest that the studied area has been damaged by tourism activities. Furthermore, observed differences in algal communities may be a good indicator of ecosystem health of Pirangi reefs

Respostas funcionais de diferentes tamanhos de Tilápia do Nilo; Oreochromis niloticus; predando zooplâncton

The Nile tilapia, Oreochromis niloticus, is an important omnivorous fish in the reservoirs of the semi-arid region of Brazil. Throughout its growth tilapia s feeding behavior changes from a visual predator of zooplankton to a filter-feeder, collecting suspended particulate matter, including planktonic organisms, through pumping. This feature results in different impacts of tilapia on plankton community as the fish grows. Aiming to quantify the functional response of different sizes of Nile tilapia on zooplankton experiments in microcosms scale in the laboratory and in mesocosm scale in the field were carried out. The data were fitted to four different models of functional response. The best fits were obtained for nonlinear models in laboratory experiments. While the experiments in mesocosms were the best settings for responses of type I (juvenile and adult tilapia) and type III (fry). The Manly's alpha index was used to evaluate the feeding selectivity of tilapia on the three main groups of the zooplankton in the experiments in mesocosms. The results show that: (i) rotifers were the preferred prey of fingerlings,(ii) copepods were rejected by fry and juvenile tilapia and (iii) adult fish fed non-selectively on copepods, cladocerans and rotifers. The functional response models obtained in this research can be applied to population models and help in modeling the dynamics of interactions between Nile tilapia and the planktonic communities in the reservoirs of the semi-arid

Diversificação evolutiva de gobídeos no litoral brasileiro: padrões citogenéticos e ecomorfológicos

The fishes of the order Perciformes are characterized as an important model for understanding the genetic structure of marine populations, because besides they present examples of conservation chromosomal, also they present the karyotype diversification for some groups. Gobiidae family is the most specious in the marine environment. Among its representatives, many species are part of a cryptic fauna little noticed and studied, a wide distribution with behavioral and reproductive characteristics, that make them conducive to the action of biogeographical barriers. Morphologically this family presents reduced body structures through simplification and regressions. Despite their importance in evolutionary inferences, cytogenetics data are incipient facing their species diversity, especially with western Atlantic species. In order to estimate the evolutionary diversity in Gobiidae, it were developed cytogenetic analysis and the standards body, through geometric morphometrics in five species on the Brazilian coast, Coryphopterus glaucofraenum, Bathygobius mystacium, B. soporator, Ctenogobius smaragdus e C. Boleosoma. The data show significant karyotype and morphological diversity among the species. The pericentric inversions and mergers play an important role in chromosomal evolution of this family, causing karyotypic structural and numerical differences in all species. Karyotypic and morphological comparisons among geographic samples of B. soporator from the coast of Maranhão, Rio Grande do Norte and Bahia showed cytogenetics patterns commons, but different morphological patterns. A sample from the Atol das Rocas revealed conspicuous morphological and karyotypic differentiation of another continental populations, confirming the presence of a new island species. The approaches done reveal diversification consistent with characteristics of a group of low vagile and largely able to environmental selection due from peculiar ecological requirements

Análise dos remanescentes de mata atlântica do Estado do Rio Grande do Norte : uma perspectiva em alta resolução

The habitat loss and fragmentation are considered the main threats to the biodiversity. These threats operate at the landscape level, which drives the need to manage entire landscapes, not just its components. Although systematic monitoring of the Atlantic Forest biome has been ongoing since the late eighties, current data on forest fragmentation for the sub-region of Pernambuco are practically nonexistent. This study aimed to map out, with high spatial resolution, the remnants of Atlantic forest in Rio Grande do Norte, and conduct a landscape level analysis. The results show that the landscape is highly fragmented, where about 13.6% to 17% of biome remains. Most of the fragments is less than 10 ha, while a few fragments have area larger than 100 ha. Although the high degree of fragmentation, the average distance between fragments found was small (128 m), this estimate is lower than has been observed for the biome (1440m). There is evidence that abrupt changes in the quantification of landscape structure can occur when one observes the fragmentation at high spatial resolution. The results presented here can be used in management actions, in order to make the scenario more conducive to maintaining biodiversity.

Padrões distintos de congruência climática em duas espécies invasoras de prosopis em zonas semi-áridas da América do Sul

Based on climate data and occurrence records, ecological niche models (ENM) are an important opportunity to identify areas at risk or vulnerable to biological invasion. These models are based on the assumption that there is a match between the climatic characteristic of native and invaded regions predicting the potential distribution of exotic species. Using new methods to measure niche overlap, we chose two exotic species fairly common in semi-arid regions of South America, Prosopis juliflora (Sw.) D.C. and Prosopis pallida (H. ; B. ex. Willd) HBK, to test the climate matching hypothesis. Our results indicate that both species occur with little niche overlap in the native region while the inverse pattern is observed in the invaded region on South America, where both species occur with high climatic overlap. Maybe some non-climate factor act limiting the spread of P. pallida on the native range. We believe that a founder effect can explain these similarities between species niche in the invaded region once the seeds planted in Brazil came from a small region on the Native range (Piura in Peru), where both species occur sympatric. Our hypothesis of a founder effect may be evident when we look at the differences between the predictions of the models built in the native and invaded ranges. Furthermore, our results indicate that P. juliflora shows high levels of climate matching between native and invaded ranges. However, conclusions about climate matching of P. pallida should be taken with caution. Our models based on climatic variables provide multiple locations suitable for occurrence of both species in regions where they still don t have occurrence records, including places of high interest for conservation.

Contribuição à citogenética de testudines e análise de assimetria flutuante em Eretmochelys imbricata, Cheloniidae

This work has contributed to knowledge of the order Testudines from cytogenetic and morphological point of view. With regard to the aspects proposed cytogenetic characterization of the species Mesoclemmys tuberculata (n = 5), endemic to the Caatinga biomes, through conventional techniques of cytogenetics and molecular levels. This species presented 2n = 58, NF = 64, the first submetacentric pair, the second metacentric and third subtelocentric, and the other microchromosome telocentric. This species showed a nucleolar bearing pair, coincident with the 18S ribosomal rDNA and that proved to be heterochromatic. Small heterochromatic blocks were also found in the centromeres of the largest chromosomes, as well as terminal regions in most other chromosomes of the complement, that were GC +. Telomeric sequences showed variable patterns of signal intensity, with some repeats more intense in microchromosomes and subtly in the larger ones. When compared with other species of the genus, the G-banding patterns showed a marked similarity between them. The first karyotypic description of the species will aid in future studies and the understanding of evolutionary aspects of this family. From the morphological point of view, we carried out studies of fluctuating asymmetry in sea turtle Eretmochelys imbricata, using methods of benchmarking between hatchlings and adults and their implications for natural selection. Data were collected at two different times: first during the spawning female and the second during the outbreak and birth of the nest. The analyzed characteristics consisted of measurements of length and width of front and rear flippers (CANT, LANT, CPOS and LPOS) also collected data on the number of hull plates, side plates (NPL), the surrounding plates (NPCIRC), and plastron; plates power plants (NPP), inframarginais plates (NPIM). With the values of asymmetry we calculated the value of strict heritability for these traits, the calculation was based on only one parent. A nonparametric analysis Mann-Whitneywas performed to compare the groups (females X hatchlings, newborn hatchlings X dead hatchlings). Adult females showed no bilateral fluctuating asymmetry (FA = 0) on the number plates of the hull and plastron, while offspring, living and dead, showed a greater level of variation in these meristic parameters. In the analysis of females x hatchlings we found a significant difference between the levels of asymmetry in hoof plates (p=0.006) an the width of hindlimbs (p=0.001). Levels of FA suggest an accurate indicator as to the viability or maintenance of the individual to the reproductive phase. The coefficient of heritability (h2) of FA , obtained from the regression analysis, showed that both have low and not statistically significant values(p> 0.1). In the case of exclusion of the effective role of genetics in the generation of FA, reproductive strategies based on high number of subsidiaries products, such as those observed in E. imbricata seems to implicate the production of individuals with high level of developmental instability

A diversidade de lagartos na Caatinga é mediada pelos térmitas?

Intending to explain the extraordinary lizard coexistence levels found in Australian deserts, Morton & James (1988) figured out a hypothesis which defends that the termite diversity would bring about lizard radiation. This study aims to verify the validation of that hypothesis in Caatinga lizard assemblages. This study also objectives verifying if the termite defense mechanisms influence their consuming levels by lizards and if this pattern differs between different lizard lineages. Termites were collected using a standardized sampling protocol of termites. Besides using haphazard sampling, we collect lizards with 108 pitfall traps in each area. Intending to check the linkage between the termite and lizard assemblages, the lizard stomach contents were analyzed and then a canonical correspondence analysis was performed. The presence of nonrandom patterns of diet overlap among the lizard species was also examined. Aiming to check if the defense mechanisms of termite influence their consuming pattern by lizards it was performed a laboratory experiment where termite with different defense mechanisms were offered to lizards of two different lineages. We verified that lizard assemblages do not consume termites according to termite abundance in ecosystems. Furthermore, mean niche overlap lizard species did not differ significantly from that expected by chance. We found that termite chemical defense mechanism does influence the termite s pattern consuming by lizards. These results do not corroborate premises which support Morton & James hypothesis (1988) and point out that lizard do not chose termites based on their abundance, but, trying to avoid consuming termites which exhibit chemical defense mechanisms. This defense mechanism, however, may not be the only explanation to patterns of termite s consuming by lizards.

Uso e conservação da fauna por populações humanas no Rio Grande do Norte, Nordeste do Brasil

Muitos países subdesenvolvidos são caracterizados por uma significativa diversidade sociocultural e por uma acentuada pobreza em grande parte da população, que fazem uso da caça de animais como uma fonte alternativa de alimento e para outros fins. O estudo objetivou investigar se a distância das populações humanas da zona rural em relação à zona urbana e fatores socioeconômicos podem ser preditores de um maior conhecimento sobre as espécies da fauna utilizadas. Além disso, o estudo objetivou também testar uma ferramenta capaz de gerar uma lista da fauna prioritária para a conservação local a partir do conhecimento local. Os dados foram coletados por meio de 30 entrevistas utilizando formulários semi-estruturados em quatro comunidades rurais no município de Pedro Avelino, RN. Foram calculados o fator de consenso dos informantes (ICF), a importância relativa (IR) e o nível de fidelidade (FL). Adicionalmente, foi calculado o índice de Shannon-Wiener para as categorias de uso: estimação, alimentar, medicinal e para a multiplicidade de uso por informante. Os entrevistados reconhecem 83 espécies pertencentes a 45 famílias de animais. As espécies citadas pertencem a seis grandes grupos taxonômicos: aves, mamíferos, répteis, anfíbios, peixes e insetos. O conhecimento sobre a utilização de animais para as categorias de uso definidas neste trabalho não mostrou relação significativa com os fatores socioeconômicos e nem com a distância das comunidades da zona rural para a zona urbana de Pedro Avelino. Os resultados sugerem, portanto, que a pobreza nivela o conhecimento sobre o uso da fauna independente da distância que as comunidades encontram-se da zona urbana. As listas geradas permitirão direcionar estudos ecológicos mais aprofundados visando à conservação das espécies do bioma Caatinga. Desta forma, é importante considerar as interações existentes entre as pessoas e os animais para melhor entender a dinâmica de utilização e fornecer, assim, subsídios para a conservação das espécies.

Influência da matéria orgânica dissolvida alóctone e autóctone sobre o balanço de carbono em sistemas aquáticos: um experimento em mesocosmos

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Uso da biodiversidade por populações humanas na caatinga e na Mata Atlântica, Rio Grande do Norte, Nordeste do Brasil

The use of animals is a common activity but it can be really variable between human populations. This work analyzed the knowledge about useful animal species between human communities in Caatinga and Atlantic Forest considering the influence of socioeconomics and environmental factors on the species selection. Forty people were interviewed in Caraúbas community (Atlantic Forest) and thirty were interviewed in Barrocas community (Caatinga). A total of 193 animals were cited. The communities showed a low degree of similarity (20%) and the general diversity of mentioned species was significantly bigger in Caraúbas. Men cited a diversity of species greater than women for food category in Caraúbas and pet category in Caraúbas and Barrocas. Women cited greater species diversity for medicinal use in Caraúbas. In general, in both communities, the age group >60 years showed a greater knowledge than the others. The multiple regression analysis showed the age as the only socioeconomic factor which influenced significantly the knowledge about animals for the food category in both communities. Considering the richness of known species, there were differences only between gender for sum of uses and food category in Caraúbas and for the pet category in Barrocas with men showing a greater knowledge than women. The results showed that local environmental differences are fundamental at the species selection but they also showed that within communities there are other factors like gender and age that tend to influence the knowledge about species. It is important to consider cultural, economic, social and environmental factors to understand better the interactions between people and animals so that this information can be used to facilitate the implementation of conservation measures

Movimento de borboletas frugívoras e conectividade funcional em uma paisagem de Mata Atlântica

An organisms movement within and between habitats is an essential trait of life history, one that shapes population dynamics, communities and ecosystems in space and time. Since the ability to perceive and react to specific conditions varies greatly between organisms, different movement patterns are generated. These, in turn, will reflect the way species persist in the original habitat and surrounding patches. This study evaluated patterns of movement of frugivorous butterflies in order to estimate the connectivity of a landscape mosaic in an area of Atlantic Forest. For this purpose, we used the capture-mark-recapture method on butterflies trapped with fermented fruit bait in three distinct habitats. The first represents a typical Atlantic forest fragment, while the other two represent man-made matrix habitats. One contains a coconut plantation and the other a plantation of the exotic Acacia mangium species. Five traps were randomly placed in each landscape unit in areas of 40 x 40m. Using recapture data and relating it to distance between captures and habitat structure, I found that movement frequencies, both within and between landscape units were different for the analyzed species, suggesting that they do not interpret and react to the landscape in the same way. Thus this study was able to measure landscape functional connectivity. For most species, the exchange between forest and coconut plantations occurred with low frequency compared to exchanges between the forest and acacia plantations, which share more structural similarities. This seems to indicate that a matrix that is more similar to patches of native vegetation can shelter species, permit their movement and, consequently, contribute to the landscape connectivity

Determinantes locais da decomposição foliar e de raízes finais em um ecossistema semiárido do nordeste brasileiro

The decomposition process exercises an extensive control over the carbon cycle, affecting its availability and nutrient cycling in terrestrial ecosystems. The understanding of leaf decomposition patterns above the soil and fine roots decomposition below the soil is necessary and essential to identify and quantify more accurately the flow of energy and matter in forest systems. There is still a lack of studies and a large gap in the knowledge about what environmental variables act as local determinants over decomposition drivers. The knowledge about the decomposition process is still immature for Brazilian semiarid region. The aim of this study was to analyze the decomposition process (on leaves and fine roots) of a mixture of three native species for 12 months in a semiarid ecosystem in Northeast Brazil. We also examined whether the rate of decomposition can be explained by local environmental factors, specifically plant species richness, plant density and biomass, soil macro-arthropods species richness and abundance, amount of litterfall and fine root stock. Thirty sampling points were randomly distributed within an area of 2000 m x 500 m. To determine the decomposition rate, the litterbag technique was used and the data analysis were made with multiple regressions. There was a high degradation of dead organic matter along the experiment. Above ground plant biomass was the only environmental local factor significantly related to leaf decomposition. The density of vegetation and litter production were positively and negatively related to decay rates of fine roots, respectively. The results suggest that Caatinga spatial heterogeneity may exert strong influences over the decomposition process, taking into account the action of environmental factors related to organic matter exposure of and the consequent action of solar radiation as the decomposition process main controller in this region

A perda de grupos funcionais em comunidades virtuais: efeito das interações entre espécies e grupos funcionais

High levels of local, regional, and global extinctions has progressively simplified communities in terms of both species and ecosystem functioning. Theoretical models demonstrated that the degree of functional redundancy determines the rates of functional group loss in response to species extinctions. Here, we improve the theoretical predictions by incorporating in the model interactions between species and between functional groups. In this study, we tested the effect of different scenarios of interspecific interactions and effects between functional groups on the resistance to loss of community functional groups. Virtual communities have been built with different distribution patterns of species in functional groups, both with high and low evenness. A matrix A was created to represent the net effect of interspecific interactions among all species, representing nesting patterns, modularity, sensitive species, and dominant species. Moreover, a second matrix B was created to represent the interactions between functional groups, also exhibiting different patterns. The extinction probability of each species was calculated based on community species richness and by the intensity of the interspecific interactions that act upon it and group to which it belongs. In the model, successive extinctions decrease the community species richness, the degree of functional redundancy and, consequently, the number of functional groups that remain in the system. For each scenario of functional redundancy, A, and B, we ran 1000 simulations to generate an average functional extinction curve. Different model assumptions were able to generate remarkable variation on functional extinction curves. More extreme variations occurred when the matrix A and B caused a higher heterogeneity in the species extinction probability. Scenarios with sensitive species, positive or negative, showed a greater variation than the scenarios with dominant species. Nested interactions showed greater variation than scenarios where the interactions were in modules. Communities with maximal functional evenness can only be destabilized by the interactions between species and functional groups. In contrast, communities with low functional evenness can have its resistance either increased or decreased by the interactions. The concentration of positive interactions in low redundancy groups or negative interactions in high redundancy groups was able to decrease the functional extinction rates. In contrast, the concentration of negative interactions in low redundancy groups or positive interactions in high redundancy groups was able to increase the functional extinction rates. This model shows results that are relevant for species priorization in ecosystem conservation and restoration