The influence of the conservation status and changes in the rainfall regime on forest-savanna mosaic dynamics in Northern Brazilian Amazonia

Coupled carbon/climate models are predicting changes in Amazon carbon and water cycles for the near future, with conversion of forest into savanna-like vegetation. However, empirical data to support these models are still scarce for Amazon. Facing this scenario, we investigated whether conservation status and changes in rainfall regime have influenced the forest-savanna mosaic over 20 years, from 1986 to 2006, in a transitional area in Northern Amazonia. By applying a spectral linear mixture model to a Landsat-5-TM time series, we identified protected savanna enclaves within a strictly protected nature reserve (Maracá Ecological Station - MES) and non-protected forest islands at its outskirts and compared their areas among 1986/1994/2006. The protected savanna enclaves decreased 26% in the 20-years period at an average rate of 0.131 ha year-1, with a greater reduction rate observed during times of higher precipitation, whereas the non-protected forest islands remained stable throughout the period of study, balancing the encroachment of forests into the savanna during humid periods and savannization during reduced rainfall periods. Thus, keeping favorable climate conditions, the MES conservation status would continue to favor the forest encroachment upon savanna, while the non-protected outskirt areas would remain resilient to disturbance regimes. However, if the increases in the frequency of dry periods predicted by climate models for this region are confirmed, future changes in extension and directions of forest limits will be affected, disrupting ecological services as carbon storage and the maintenance of local biodiversity.

Radiação solar em superfieies horizontal e vertical com exposição norte

In the field of agrometeorological studies we are in need of the estimation of the solar radiation frequently. At the present study the authors have worked out some dat:t regarding the hours of sunshine during the months of August, September, October, November, December and January of 1957, 1958 and 1959. Based on such hours of sunshine in the Agrometeorological Station, located at the Escola Superior de Agricultura "Luiz de Queiroz" - U.S. P., in Piracicaba, the authors calculated the solar radiation received on a plane and horizontal surface, from the method proposed by Glover and Mc Culloch. With those results the authors estimated the percentual part of radiation that would be received on vertical wall facing north.

Estratificação vertical de formigas em cerrado strictu sensu no Parque Estadual da Serra de Caldas Novas, Goiás, Brasil

Formicidae é um grupo abundante no solo e também largamente distribuído em todos os estratos da vegetação, constituindo-se em um bom modelo biológico para estudos de estratificação vertical. O objetivo geral do trabalho foi determinar os padrões de estratificação da assembléia de formigas em três estratos verticais (solo, estrato arbustivo e estrato arbóreo). Os dados foram coletados no Parque Estadual da Serra de Caldas Novas, em uma área de cerrado strictu sensu. A coleta de formigas foi realizada utilizando-se armadilhas do tipo pitfall. Foram instaladas 11 armadilhas no solo, 17 em plantas do estrato arbustivo e 23 em plantas do estrato arbóreo (uma armadilha por planta). Foi coletado um total de 49 espécies de formigas, pertencentes a 15 gêneros e cinco subfamílias. Através de curvas de acumulação de espécies, pôde-se verificar que existem 37,5% a mais de espécies no solo do que nas árvores e 35% a mais de espécies nas árvores do que nos arbustos. Uma análise de agrupamento indicou uma similaridade mediana entre as espécies de formigas do solo e vegetação (estrato arbustivo e arbóreo). Uma análise de aninhamento demonstrou que as espécies presentes no solo são um subconjunto das espécies presentes nos dois estratos de vegetação. Mesmo sem uma estratificação vertical muito clara, a alta diversidade de formigas encontrada no cerrado pode ser explicada em parte pelo fato de algumas espécies serem especializadas em forragear e/ou nidificar no solo e outras na vegetação.

Seasonal dynamics of a drosophilid (Diptera) assemblage and its potencial as bioindicator in open environments

Drosophila Fallen, 1823 (Diptera, Drosophilidae) is for long a well-established model organism for genetics and evolutionary research. The ecology of these flies, however, has only recently been better studied. Recent papers show that Drosophila assemblies can be used as bioindicators of forested environment degradation. In this work the bioindicator potential of drosophilids was evaluated in a naturally opened environment, a coastal strand-forest (restinga). Data from nine consecutive seasonal collections revealed strong temporal fluctuation pattern of the majority of Drosophila species groups. Drosophila willistoni group was more abundant at autumns, whereas D. cardini and D. tripunctata groups were, respectively, expressive at winters and springs, and D. repleta group at both seasons. The exotic species D. simulans Sturtevant, 1919 (from D. melanogaster group) and Zaprionus indianus Gupta, 1970 were most abundant at summers. Overall, the assemblage structure did not show the same characteristics of forested or urban environments, but was similar to the forests at winters and to cities at summers. This raises the question that this locality may already been under urbanization impact. Also, this can be interpreted as an easily invaded site for exotic species, what might lead to biotic homogenization and therefore can put in check the usage of drosophilid assemblages as bioindicators at open environments.

Population dynamics of the pea crab Austinixa aidae (Brachyura, Pinnotheridae): a symbiotic of the ghost shrimp Callichirus major (Thalassinidea, Callianassidae) from the southwestern Atlantic

The Pinnotheridae family is one of the most diverse and complex groups of brachyuran crabs, many of them symbionts of a wide variety of invertebrates. The present study describes the population dynamics of the pea crab Austinixa aidae (Righi, 1967), a symbiont associated with the burrows of the ghost shrimp Callichirus major (Say, 1818). Individuals (n = 588) were collected bimonthly from May, 2005 to September, 2006 along a sandy beach in the southwestern Atlantic, state of São Paulo, Brazil. Our data indicated that the population demography of A. aidae was characterized by a bimodal size-frequency distribution (between 2.0 and 4.0 mm and between 8.0 and 9.0 mm CW) that remained similar throughout the study period. Sex ratio does not differ significantly from 1:1 (p > 0.05), which confirms the pattern observed in other symbiontic pinnotherids. Density values (1.72 ± 1.34 ind. • ap.-1) are in agreement with those found for other species of the genus. The mean symbiosis incidence (75.6%) was one of the highest among species of the Pinnotheridae family, but it was the lowest among the three studied species of the genus. Recruitment pattern was annual, beginning in May and peaking in July, in both years, after the peak of ovigerous females in the population (from March to May). Our findings describe ecological and biological aspects of A. aidae similar to those of other species of this genus, even from different geographic localities.

Diel vertical migration of predators (planktivorous fish larvae) and prey (zooplankton) in a tropical lagoon

ABSTRACT Based on the hypothesis that diel vertical migration (DVM) is a mechanism of predator avoidance, the objective of the present study was to test for the occurrence of DVM in planktivorous fish larvae of Hypophthalmus edentatus (Spix, 1829) (Siluriformes, Pimelodidae) and Plagioscion squamosissimus (Heckel, 1840) (Perciformes, Sciaenidae), and zooplankton (rotifers, cladocerans and copepods) in an isolated tropical lagoon in the floodplain of the Upper Paraná River, Brazil (region of Parque Nacional de Ilha Grande). We investigated spatial overlap between predators (planktivorous fish larvae) and prey (zooplankton), and tested which physical and chemical variables of the water are related to the DVM of the studied communities. We performed nocturnal (8:00 pm and 4:00 am) and diurnal sampling (8:00 am and 4:00 pm) in the limnetic region of the lagoon for six consecutive months, from October 2010 to March 2011, which comprises the reproductive period of the fish species analyzed. During the day the larvae tried to remain aggregated in the bottom of the lagoon, whereas at night they tried to disperse in the water column. Especially for cladocerans, the diel vertical migration is an important behavior to avoid predation larvae of H. edentatus and P. squamosissimus once decreased spatial overlap between secured and its potential predators, which corroborates the hypothesis that DVM is a mechanism of predator avoidance. Although significant correlations were observed between the abiotic factors and WMD of microcrustaceans at certain times of day, the effect of predation of fish larvae on zooplankton showed more important in this environment, because the small depth and isolation not allow great variation of abiotic factors seasonally and between strata the lagoon.

Morphology and dynamics of male gametogenesis in Sympterygia bonapartii (Chondrichthyes, Rajidae) from Northern Patagonia

ABSTRACT The smallnose fanskate, Sympterygia bonapartii Müller & Henle, 1841 is one of the most disembarked items in commercial harbors in Argentina. In this work, the microscopic architecture of mature male gonads and the dynamics of cysts development are analyzed as a contribution to awareness of the reproductive biology of the species. Some biological data related to reproduction are given as well. Two seasons were sampled (fall and spring) and length classes's frequency distribution and maturity stages frequency distribution are given. Size at first sexual maturation for males was estimated at 57 cm of total length. Testes are symmetric, peer, lobed, with several germinal zones. Inside the gonads, there are many spermatocysts, containing reproductive cells at the same developmental stage. On the basis of their cytological and microanatomical features, several maturative degrees of the spermatogenic series were differentiated. Few Leydig cells were recognized at the interstitial tissue among cysts. The microscopic and semiquantitative analysis performed in this work provides morphological information about male gametogenesis and some biological data for the North Patagonian population of this economically and ecologically important species.

Sôbre a distribuição vertical dos criadouros de Anopheles do subgênero Kerteszia, no Sul do Brasil

Analisando dados sôbre a distribuição vertical das Bromeliáceas onde se criam Anopheles do subgênero Kerteszia, o autor obteve as seguintes conclusões: 1 - A influência da luminosidade, na distribuição das Bromeliáceas, e a umidade, com respeito áquelas que são criadouros de Kerteszia, se bem que conspícuas, não se apresentam da maneira esquemática como foram observadas em Trinidad F.I.O); 2 - As alturas preferenciais das três espécies de kerteszia variam de acôrdo com as condições de umidade reinantes na mata, porém, na maior parte da área de distribuição dêsses mosquitos, o A. bellator é uma espécies dos níveis mais elevados, o A. homunculus prefere as bromeliáceas mais baixas e o A. cruzii prolifera em qualquer nível, sendo, entretanto, mais encontradiço nas alturas preferenciais das duas outras espécies; 3 - Como foi mostrado, anteriormente por PITTENDRIGH (1950a) em Trinidad, a densidade de cada espécie está na dependência da amplitude da faixa de alturas que ela pode explorar e, portanto, do número de criadouros de que dispõe; assim, apesar da predominância quase total do A. cruzii, o A. bellator é abundante na orla litorânea, onde pode se criar até ao nível do solo, e o A. homunculus chega a ser a espécie mais numerosa em algumas várzeas da área de relêvo movimentado, onde os seus criadouros são encontrados até nos esgalhamentos das árvores; 4 - As distribuições de freqüência das Bromeliáceas em geral e daquelas que são criadouros de Kerteszia, apresentaram diferenças estatísticamente significativas; 5 - O fato do A. cruzii apresentar duas alturas preferenciais e o de sua distribuição vertical ser significativamente diferente daquela observada para as bromeliáceas das mesmas matas, sugere a hipótese de tratar-se de duas entidades biológicas difíceis de serem distinguidas pelos caracteres morfológicos, atualmente, utilizados na classificação dêsses mosquitos.

The vertical dispersión of Anopheles (Kerteszia) cruzi in a forest in southern Brazil suggests that human cases of malaria of simian origin might be expected

By staining females of Anopheles cruzi with fluorescent coloured powders in a forest in the State of Santa Catarina, we showed that they move from canopy to ground and vice-versa to feed. This suggests that in areas where this mosquito is a vector of human and simian malarias sporadic infections of man with monkey plasmodia might be expected.

Orientation to light of juvenile and adult forms of melanic and albino populations of Biomphalaria glabrata (Say, 1818)

The process of light orientation by the snail Biomphalaria glabrata was studied using the selection technique in a Y-shaped aquarium under vertical or horizontal lighting schemes. Snail behavior was measured on the basis of distance (cm) covered per hour, direction of locomotion, and localization of the animal in the aquarium. A comparison was made of the action of the light stimulus on young and adult animals of albino populations from Santa Luzia (State of Minas Gerais, Brazil) and of a melanic population from Touros (State of Rio Grande do Norte) studied in groups and separately. All groups studied were attracted to light. Analysis of the data suggests the exitence of two orientation mechanisms with respect to light in these animals, i.e. high photo-orthokinesia and positive phototaxis, which influence their motion in the environment. This evidence permitted us to discuss features of the distribution dynamics of these mollusks in the environment and their relationship with the larval phases of Schistosoma mansoni, for which they act as intermediated hosts.

Mosquitos no Parque Nacional da Serra dos Orgãos, Estado do Rio de Janeiro, Brasil: II. Distribuição vertical

Em prosseguimento aos estudos sobre a ecologia de culicídeos que vimos realizando no Parque Nacional da Serra dos Orgãos (PNSO), apresentamos nesta oportunidade a sua distribuição vertical. Por meio de capturas feitas em isca humana concomitantemente ao nível do solo e nas imediações da copa das árvores, estabelecemos as tendências das espécies que ali ocorreram de março de 1981 a fevereiro de 1982, por se alimentarem de sangue na copa da floresta ou junto ao solo. A distribuição é analisada comparativamente em ambos os níveis levando-se em consideração as variações de temperatura, umidade, precipitações pluviométricas e estações do ano. Dentre as espécies com nítida preferência à acrodendrofilia encontramos alguns importantes transmissores de doenças: Anopheles cruzii - malária humana e simiana; Culex nigripalpus - encefalite de São Luis (SLE); Haemagogus leucocelaenus e Haemagogus capricornii - febre amarela silvestre, todas também sendo obtidas, embora em menor número, a nível do solo. Os sabetíneos - Wyeomyia Knabi, Phoniomyia theobaldi, Sabethes tarsopus, Sabethes quasicyaneus, Sabethes chloropterus - completam a relação das principais espécies que preferem a copa. Por outro lado, Aedes fluviatilis, Trichoprosopon digitatum, Tr. similis, Tr. frontosus, Tr. theobaldi, Wy, arthrostigma, Wy. aporonoma, Wy. personata, Wy undulata, Wy. mystes, Limatus durhami, Li. pseudomethisticus, Sa. identicus e Sa. undosus foram capturados em grande maioria próximo ao solo.

Aspectos da ecologia dos flebótomos do Parque Nacional da Serra dos Orgãos, Rio de Janeiro: II. Distribuição vertical (Diptera, Psychodidae, Phlebotominae)

Durante um ano completo efetuamos capturas de flebótomos em isca humana, simultaneamente no solo e na copa da floresta em plataforma a dez metros de altura. Lutzomyia fischeri foi a espécie mais numerosa na copa. L.sp. 1 (espécie ainda não descrita) também foi mais freqüente neste nivel; L.shannoni, apesar de ser mais ativa ao nivel do solo, compareceu várias vezes na copa; L.pessoai, L.ayrozai, L.davisi. L.sp.2 (espécie também não identificada), L.microps e L.monticola só picaram iscas situadas no solo; L.hirsuta esteve pouco representada na copa, porém sua maior densidade foi no solo, onde figura como espécie dominante nos meses mais frios e secos do ano. Dois aspectos devem ser enfatizados com relação à distribuição vertical: a acrodendrofilia de L. fischeri e, ao contrário, o fato de L.ayrozai alimentar-se exclusivamente ao nível do solo. Este comportamento de L.ayrozai e sua preferência em sugar nas partes mais baixas do corpo fazem supor que seus abrigos naturais sejam as folhas caídas no solo florestal. Dentre os fatores mesológicos que influenciam na estratificação dos flebótomos consideramos que a luminosidade seja preponderante, pois em noites mais claras (lua crescente ou cheia) a atividade foi nula, todos os flebotomíneos capturados na copa das árvores foram obtidos em noites mais escuras (lua nova ou minguante).

Population dynamics of aquatic snails in Pampulha reservoir

An attempt was made to determine more accurately the density of molluskan populations in the Pampulha reservoir, using the quadrate method, intending to detect the fluctuation of the populations density, the habitat conditions and the possible competitive interactions among Biomphalaria tenagophila, Melanoides tuberculata, Pomacea haustrum and Biomphalaria glabrata, through the analysis of populational parameters. Among the most significative facts observed in the reservoir it has to be mentioned: the almost disappearance of B. glabrata; the invasion, colonization, fixation and fast growing of M. tuberculata population until reaching about 11,000 individuals/[square metre]; the density fluctuations of B. tenagophila, P. haustrum and M. tuberculata alives and deads; differences on the habitat preference of these three molluskan species at the edge (at the limit earth-water, at 0.70m and 1.40m from the shore line); monthly mortality rates and reproduction seasons of the species.

Rheotaxis of Biomphalaria glabrata on vertical substrates and its role in the recolonization of habitats treated with molluscicides

The authors observed specimens of Biomphalaria glabrata climbing up the vertical wall of a ditch against the current. The snails that showed this behavior during application of a molluscicide in the breeding site survived and probably played a role in repopulation, which was observed three months later. These observations motivated field and laboratory investigations which led the authors to conclude that: a) this species is able to climb vertical surfaces both in field and laboratory situations; b) the current of water, as a physical stimulus, is sufficient to trigger this behavior (rheotaxis); c) rheotaxis on vertical surfaces depends on the presence of a necessarily moderate current; d) there are indications that B. glabrata may undergo habituation with respect to rheotaxis on vertical walls, e) the relationship between rheotaxis and habituation should be considered as a factor causing snail grouping in water bodies which may contribute to their localization in the field; f) rheotaxis on vertical surfaces may facilitate population dispersal, and its occurrence should be considered when campaigns for the control of schistosomiasis transmission are planned. The authors present some proposals to avoid the manifestation of this behavior in some filed situations.

Dynamics of fibrosis production and resorption in intestinal schistosomiasis of mice

A histological, morphometric and immunocytochemical study of schistosomal periovular granulomas in the liver and intestines of mice revealed that intestinal granulomas are smaller and contain less collagen than those in the liver. After curative treatment intestinal granulomas undergo a relatively more rapid resorption, although the general pattern of collagen degradation apparently does not differ from that observed in the liver. Tendency to form scattered, usually isolated granulomas that are only mildly fibrogenic, coupled with a well-balanced process of resorption appear as the explanation why intestinal fibrosis is not an outstanding feature of schistosomiasis as it is in the liver.