Detecting and modelling delayed density-dependence in abundance time series of a small mammal (Didelphis aurita).

We study the population size time series of a Neotropical small mammal with the intent of detecting and modelling population regulation processes generated by density-dependent factors and their possible delayed effects. The application of analysis tools based on principles of statistical generality are nowadays a common practice for describing these phenomena, but, in general, they are more capable of generating clear diagnosis rather than granting valuable modelling. For this reason, in our approach, we detect the principal temporal structures on the bases of different correlation measures, and from these results we build an ad-hoc minimalist autoregressive model that incorporates the main drivers of the dynamics. Surprisingly our model is capable of reproducing very well the time patterns of the empirical series and, for the first time, clearly outlines the importance of the time of attaining sexual maturity as a central temporal scale for the dynamics of this species. In fact, an important advantage of this analysis scheme is that all the model parameters are directly biologically interpretable and potentially measurable, allowing a consistency check between model outputs and independent measurements.

Organ donation: cross-sectional survey of knowledge and personal views of Brazilian medical students and physicians.

OBJECTIVE: To assess the knowledge, attitudes, and behavior associated with cadaver organ donation and transplantation among medical students and physicians. PATIENTS AND METHODS: We randomly selected 350 medical students, 150 physicians, and 150 intensive care unit physicians. Each completed a questionnaire consisting of 9 self-administered items, from which we gathered data about their knowledge about brain death and criteria for the diagnosis of brain death; their hypothetical behaviors, assuming willingness to donate their own or their family's organs; their trust in physicians; and their confidence in a diagnosis of brain death made by physicians. RESULTS: We observed that knowledge about brain death increased with medical education level; the best results were noted in intensive care unit physicians. Agreement to transplant organs from brain-dead donors (odds ratio [OR], 4.58), confidence in brain-death diagnosis by physicians (OR, 2.17), and knowledge about criteria for the diagnosis of brain death (OR, 2.26) were predictors of willingness to donate one's own organs. CONCLUSION: Enhanced medical knowledge of and involvement in donation are needed to achieve cadaver organ donation.

Reproduction, development and growth of Akodon lindberghi (Hershkovitz, 1990) (Rodentia, Muridae, Sigmodontinae) raised in captivity

The reproduction, development and growth of Akodon lindberghi were studied in captivity. The colony was derived from animals captured in Simão Pereira, Minas Gerais state, which represents a new area of geographical distribution known for this species. Twelve males and twelve females were crossed, producing 144 young in 53 litters. Post-partum oestrus was observed and gestation length was estimated in 23 days. Litter size ranged from 1 to 4 with a mean of 2.72 (SD = 0.97, n = 53) and modal size of 3. Sexual dimorphism was neither present in body mass at birth nor at weaning. There was a significant negative correlation between litter size and mass at birth or weaning. Permanent emergence of adult external appearance occurred at 15 days. Puberty for males and females was 43 and 42 days, respectively, and the first fecundation event for two females was recorded at 47 and 54 days of age. The weight growth was described by fitting a Gompertz model. No significant difference was found in any parameter of growth curves for males and females. Measurements (head-body, tail, hind foot and internal and external ear lengths) obtained for adult individuals also did not reveal the presence of sexual dimorphism.

A reprodução, o crescimento e o desenvolvimento de Akodon lindberghi foram estudados em cativeiro. A colônia foi derivada de animais capturados em Simão Pereira, Minas Gerais, Brasil, localidade que representa uma nova área de distribuição geográfica conhecida para esta espécie. Doze machos e doze fêmeas foram acasalados, produzindo 144 filhotes em 53 ninhadas. Observou-se estro pós-parto e o período de gestação foi estimado em 23 dias. O tamanho médio da ninhada foi de 2,72 (SD = 0,97, n = 53), com amplitude de 1 a 4 e moda de 3 filhotes. Não houve dimorfismo sexual do peso dos filhotes ao nascimento e ao desmame. O tamanho da ninhada foi negativamente correlacionado com o peso ao nascimento e ao desmame. A emergência da aparência externa adulta (pêlos, dentes e olhos e orelhas abertos) ocorreu aos 15 dias. A puberdade em machos e fêmeas ocorreu aos 43 e 42 dias, respectivamente, e a primeira fecundação para duas fêmeas, aos 47 e 54 dias. O crescimento do peso foi descrito através do modelo de Gompertz. Não houve diferença significativa entre machos e fêmeas em nenhum parâmetro das curvas de crescimento, bem como nas medidas corporais (cabeça-corpo, cauda, pé posterior, e orelhas interna e externa) obtidas para animais adultos.

Small mammal populations of an agroecosystem in the Atlantic Forest domain, southeastern Brazil.

This study reports 2 years of the population dynamics and reproduction of a small mammal community using the removal method. The study was conducted in a rural area of the Atlantic Forest, in Sumidouro, Rio de Janeiro State, Brazil. The population sizes, age structure and reproduction were studied for the four most common species in the study area. The overall diversity was 1.67 and ranged between 0.8 to 1.67. The species richness was 13 considering the whole study. The most abundant species were the rodents Nectomys squamipes (n = 133), Akodon cursor (n = 74), Oligoryzomys nigripes (n = 25) and the marsupials Didelphis aurita (n = 58) and Philander frenatus (n = 50). Seven other rodents were captured once: Necromys lasiurus, Akodon montensis, Sooretamys angouya, Oecomys catherine, Oxymycterus judex, Euryzygomatomys spinosus and Trinomys iheringi. There were higher peaks for diversity and species richness during the winter (dry) months, probably due to higher food availability. The marsupials had a seasonal reproduction with highest population sizes at the end of the rainy seasons. Nectomys squamipes reproduced mostly during rainy periods. Akodon cursor reproduced predominantly in the winter with the highest population peaks occurring during this season. The analysis of the population dynamics of the rodent species indicated that no species behaved as an agricultural pest, probably due to the heterogeneous landscape of high rotativity of vegetable cultivation. Rodent populations were more susceptible to the removal procedure than marsupial ones.

Small mammal populations of an agroecosystem in the Atlantic Forest domain, southeastern Brazil

This study reports 2 years of the population dynamics and reproduction of a small mammal community using the removal method. The study was conducted in a rural area of the Atlantic Forest, in Sumidouro, Rio de Janeiro State, Brazil. The population sizes, age structure and reproduction were studied for the four most common species in the study area. The overall diversity was 1.67 and ranged between 0.8 to 1.67. The species richness was 13 considering the whole study. The most abundant species were the rodents Nectomys squamipes (n = 133), Akodon cursor (n = 74), Oligoryzomys nigripes (n = 25) and the marsupials Didelphis aurita (n = 58) and Philander frenatus (n = 50). Seven other rodents were captured once: Necromys lasiurus, Akodon montensis, Sooretamys angouya, Oecomys catherine, Oxymycterus judex, Euryzygomatomys spinosus and Trinomys iheringi. There were higher peaks for diversity and species richness during the winter (dry) months, probably due to higher food availability. The marsupials had a seasonal reproduction with highest population sizes at the end of the rainy seasons. Nectomys squamipes reproduced mostly during rainy periods. Akodon cursor reproduced predominantly in the winter with the highest population peaks occurring during this season. The analysis of the population dynamics of the rodent species indicated that no species behaved as an agricultural pest, probably due to the heterogeneous landscape of high rotativity of vegetable cultivation. Rodent populations were more susceptible to the removal procedure than marsupial ones.

Este estudo reporta dois anos da dinâmica populacional e reprodução de uma comunidade de pequenos mamíferos através de método de remoção. O estudo foi realizado numa área rural na Mata Atlântica, em Sumidouro, Rio de Janeiro, Brasil. Os tamanhos populacionais, a estrutura etária e a reprodução foram estudados para as quatro espécies mais comuns na área de estudo. A diversidade total foi de 1,67 e variou entre 0,8 e 1,67. A riqueza de espécies foi de 13, considerando-se o estudo todo. As espécies mais abundantes foram os roedores Nectomys squamipes (n = 133), Akodon cursor (n = 74) e Oligoryzomys nigripes (n = 25) e os marsupiais Didelphis aurita (n = 58) e Philander frenatus (n = 50). Sete outras espécies de roedores foram capturadas somente uma vez: Necromys lasiurus, Akodon montensis, Sooretamys angouya, Oecomys catherine, Oxymycterus judex, Euryzygomatomys spinosus and Trinomys iheringi. Houve maiores picos de diversidade e riqueza de espécies durante os meses de inverno (secos), provavelmente devido ao aumento na disponibilidade de recursos. Os marsupiais apresentaram reprodução estacional com maiores tamanhos populacionais no final das estações chuvosas. Nectomys squamipes reproduziu-se predominantemente durante períodos chuvosos. Akodon cursor reproduziu-se predominantemente no inverno, com os maiores picos populacionais ocorrendo durante esta estação. A análise da dinâmica populacional das espécies de roedores indicou que nenhuma se comportou como praga agrícola, provavelmente devido ao ambiente heterogêneo de alta rotatividade de cultivos de legumes. As populações dos roedores foram mais suscetíveis ao procedimento de remoção do que as dos marsupiais.

Reproduction, development and growth of Akodon lindberghi (Hershkovitz, 1990) (Rodentia, Muridae, Sigmodontinae) raised in captivity.

The reproduction, development and growth of Akodon lindberghi were studied in captivity. The colony was derived from animals captured in Simão Pereira, Minas Gerais state, which represents a new area of geographical distribution known for this species. Twelve males and twelve females were crossed, producing 144 young in 53 litters. Post-partum oestrus was observed and gestation length was estimated in 23 days. Litter size ranged from 1 to 4 with a mean of 2.72 (SD = 0.97, n = 53) and modal size of 3. Sexual dimorphism was neither present in body mass at birth nor at weaning. There was a significant negative correlation between litter size and mass at birth or weaning. Permanent emergence of adult external appearance occurred at 15 days. Puberty for males and females was 43 and 42 days, respectively, and the first fecundation event for two females was recorded at 47 and 54 days of age. The weight growth was described by fitting a Gompertz model. No significant difference was found in any parameter of growth curves for males and females. Measurements (head-body, tail, hind foot and internal and external ear lengths) obtained for adult individuals also did not reveal the presence of sexual dimorphism.

Study of hantavirus infection in captive breed colonies of wild rodents.

Wild sigmondontine rodents are known to be the reservoir of several serotypes of New World hantaviruses. The mechanism of viral transmission is by aerosol inhalation of the excreta from infected rodents. Considering that the captive breed colonies of various wild mammals may present a potential risk for hantaviral transmission, we examined 85 specimens of Thrichomys spp. (Echimyidae) and 17 speciemens of Nectomys squamipes (Sigmodontinae) from our colony for the presence of hantavirus infections. Blood samples were assayed for the presence of antibodies to Andes nucleocapsid antigen using enzyme-linked immunosorbent assay (ELISA). Additionally, serum samples from workers previously exposed to wild rodents, in the laboratories where the study was conducted, were also tested by ELISA to investigate prevalence of anti-hantavirus IgG antibodies. All blood samples were negative for hantavirus antibodies. Although these results suggest that those rodent's colonies are hantavirus free, the work emphasizes the need for hantavirus serological monitoring in wild colonized rodents and secure handling potentially infected rodents as important biosafety measures.

Study of hantavirus infection in captive breed colonies of wild rodents

Wild sigmondontine rodents are known to be the reservoir of several serotypes of New World hantaviruses. The mechanism of viral transmission is by aerosol inhalation of the excreta from infected rodents. Considering that the captive breed colonies of various wild mammals may present a potencial risk for hantaviral transmission, we examined 85 speciemens of Thrichomys spp. (Echimyidae) and 17 speciemens of Nectomys squamipes (Sigmodontinae) from our colony for the presence of hantavirus infections. Blood samples were assayed for the presence of antibodies to Andes nucleocapsid antigen using enzyme-linked immunosorbent assay (ELISA). Additionally, serum samples from workers previously exposed to wild rodents, in the laboratories where the study was conducted, were also tested by ELISA to investigate prevalence of anti-hantavirus IgG antibodies. All blood samples were negative for hantavirus antibodies. Although these results suggest that those rodent's colonies are hantavirus free, the work emphasizes the need for hantavirus serological monitoring in wild colonized rodents and secure handling potentially infected rodents as important biosafety measures.

Nectomys squamipes microsatellites and homologous loci in sigmodontine rodents.

Three monomorphic and four highly polymorphic microsatellites of Nectomys squamipes were isolated and characterised in a sample of 141 specimens from eight different Brazilian localities. These seven microsatellites and four others previously described in this species were tested in seven other nonfocus sigmodontine species. At least three loci were successfully amplified in every species, but none was amplified in all species. All sequenced products in nonfocus species showed (GT)(n) motifs as in N. squamipes. Several loci were amplified in Nectomys rattus and Oligoryzomys nigripes, while absence of PCR products was observed more frequently in Oxymycterus dasythricus and Akodon cursor. Two of three monomorphic loci in N. squamipes were polymorphic in other species.

Inheritance of litter size at birth in the Brazilian grass mouse (Akodon cursor, Sigmodontinae, Rodentia).

By means of complex segregation analysis we studied the inheritance of litter size in two large pedigrees of captive-bred colonies of the Brazilian grass mouse Akodon cursor. Genetic analysis has revealed a highly significant influence of genetic factors on the variation of litter size (heritability, h2, was estimated as 0.44). The inheritance followed the classical polygene model: neither the major-gene model nor the polygene with unequal contribution model described the data significantly better.

A device and standard variables to describe microhabitat structure of small mammals based on plant cover

Studies quantifying habitat structure generally use several instruments. This paper aims to propose a new and efficient device to characterize microhabitat structure of small mammals. Seven measurements were taken: plant cover, litter cover, rock cover, canopy cover, and vegetative obstruction at three heights. The device is a 0.25 m² square wooden frame (0.50 m x 0.50 m) divided in to 100 open squares by wire mesh. Average time spent to measure each trapping station was six minutes. This new device is efficient, i.e., quick, practical, simple, and reliable. It can be used in any kind of forest. We propose this method as a standard method to describe habitat structure

A device and standard variables to describe microhabitat structure of small mammals based on plant cover.

Studies quantifying habitat structure generally use several instruments. This paper aims to propose a new and efficient device to characterize microhabitat structure of small mammals. Seven measurements were taken: plant cover, litter cover, rock cover, canopy cover, and vegetative obstruction at three heights. The device is a 0.25 m2 square wooden frame (0.50 m x 0.50 m) divided in to 100 open squares by wire mesh. Average time spent to measure each trapping station was six minutes. This new device is efficient, i.e., quick, practical, simple, and reliable. It can be used in any kind of forest. We propose this method as a standard method to describe habitat structure.

A device and standard variables to describe microhabitat structure of small mammals based on plant cover

Studies quantifying habitat structure generally use several instruments. This paper aims to propose a new and efficient device to characterize microhabitat structure of small mammals. Seven measurements were taken: plant cover, litter cover, rock cover, canopy cover, and vegetative obstruction at three heights. The device is a 0.25 m² square wooden frame (0.50 m x 0.50 m) divided in to 100 open squares by wire mesh. Average time spent to measure each trapping station was six minutes. This new device is efficient, i.e., quick, practical, simple, and reliable. It can be used in any kind of forest. We propose this method as a standard method to describe habitat structure.

Os estudos que quantificam a estrutura do habitat geralmente usam vários instrumentos. Este artigo objetiva propor um novo e eficiente instrumento para caracterizar a estrutura do microhabitat de pequenos mamíferos. Sete medidas foram tomadas: cobertura vegetal (herbáceos e lenhosos), cobertura de folhiço, cobertura de pedras, cobertura de dossel e obstrução foliar vertical em três alturas. O instrumento é uma tela quadrada de 0,25 m² (0,50 m x 0,50 m) de madeira, dividida por arame em 100 quadrados abertos. O tempo médio para medir cada estação de captura foi de 6 minutos. Este novo instrumento é eficiente, isto é, rápido, prático, simples e confiável. Ele pode ser usado em qualquer tipo de floresta. Propomos este método como padrão para descrever a estrutura do habitat.

The parasitism of Schistosoma mansoni (Digenea-Trematoda) in a naturally infected population of water rats, Nectomys squamipes (Rodentia-Sigmodontinae) in Brazil.

Schistosomiasis is a health problem in Brazil and the role of rodents in maintaining the schistosome life-cycle requires further clarification. The influence of Schistosoma mansoni on a population of Nectomys squamipes was studied by capture-recapture (1st phase, from June 1991 to November 1995) and removal (2nd phase, from April 1997 to March 1999) studies at Sumidouro, Rio de Janeiro, Brazil. During both phases coproscopic examinations were performed. At the 2nd phase the rodents were perfused and worms were counted. The population dynamics of parasites was studied. During the 1st phase, female reproductive parameters, longevity, recruitment and survivorship rates and migration patterns were studied in relation to schistosome prevalence. Water contamination (source of miracidia), abundance intermediate host and rodent migration were related to prevalence. The N. squamipes population was not obviously influenced by the infection, as shown by the high number of reproductive infected females, high longevity of infected individuals and the absence of a relationship between recruitment or survivorship rates and the intensity of schistosome infection. The data indicate that N. squamipes can increase transmission of S. mansoni in endemic areas and carry it to non-infected areas. Furthermore, this rodent can be used as an indicator of a transmission focus.

Santo Inácio revisited: protozoan diseases in an isolated village in northeastern Brazil after twenty years.

The northeastern highlands of Brazil are endemic for several tropical diseases, especially American trypanosomiasis (Chagas' disease) and schistosomiasis. Twenty years ago, we measured the seroprevalence of protozoan diseases in Santo Inácio, a village of approximately 1,000 inhabitants located 1,000 m above sea level. We detected small numbers of sera with antibodies against Trypanosoma cruzi and Toxoplasma gondii, and the area had a low prevalence both of American trypanosomiasis (3.54%) and toxoplasmosis (27.43%) compared with nearby Brazilian areas. This was attributed to a specific triatomine vector and local housing conditions. Twenty years later, we again determined the prevalences of both diseases and compared these results with those from Iraquara, a larger town with the same ethnic and social background but with a higher prevalence of rural activities. The incidence of Chagas' disease in San Inácio showed the same low level, i.e., 3.78% (5 of 132) with only adult males affected in contrast with Iraquara, which had an incidence of 34.5%, but a low prevalence of only one of 22 among children up to 14 years of age. Santo Inácio maintained a low (25.8%) seroprevalence for toxoplasmosis. Housewives presented a higher incidence of toxoplasmosis during both periods, probably due to related risk factors. Cats were found less frequently in Santo Inácio than in Iraquara, which showed an incidence of 65.5% seropositivity for Toxoplasma gondii. These results suggest that the environmental conditions of Santo Inácio were preserved after 20 years, with a low incidence of these selected protozoan diseases.

Breeding of Philander frenata (Didelphimorphia, Didelphidae) in captivity.

Data on the reproductive biology and laboratory management of Philander frenata are presented here. Sensory contact before pairing increased breeding success and reduced aggression between pairs. Gestation period was 13-14 days, with a post-lactation oestrous. Births occurred only between August and February. Mean litter size at birth and at weaning was 5.5 (SD = 2.4) and 4.0 (SD = 1.9), respectively. Sex ratio at birth was statistically biased toward males. The timing of weaning was established at between 70 and 80 days old, with the young weighing from 24 g to 49 g.

Early blood pressure level as a mark of familial aggregation of metabolic cardiovascular risk factors--the Rio de Janeiro Study.

OBJECTIVE: To investigate the familial aggregation of metabolic risk factors (RF) according to blood pressure (BP) percentile of children and adolescents. DESIGN AND METHODS: Normal BP was established in 3906 children and adolescents in 1987. From this population two groups of target individuals were separated: group A (n = 327) with systolic and/or diastolic BP percentile > 95 and group B (n = 327) with systolic and diastolic BP percentile < or = 50. Ten years later, familial aggregation of metabolic RF was evaluated using clinical and laboratorial data from 785 individuals, divided into two groups: group 1 with 135 target individuals (BP percentile > 95), 181 parents, 100 siblings and 16 grandparents; and group 2: 106 target individuals (BP percentile < or = 50), 145 parents, 84 siblings and 18 grandparents. RESULTS: (1) The longitudinal study 10 years later (tracking effect) showed that 34.8% of target individuals of group 1 and 90.5% of group 2 remained at the same BP percentile. (2) Comparing the two groups of target individuals, group 1 had higher weight and body mass index (BMI), systolic BP (SBP), diastolic BP (DBP), and heart rate (HR) (P < 0.001) and lower HDL (P < 0.003). (3) Comparing target individuals' and their relatives' measurements together, group 1 had higher BMI, HR, SBP, DBP (P < 0.03) and lower HDL (P < 0.001). (4) SBP and DBP showed significant correlation with all metabolic variables even when BMI was controlled in a multiple regression analysis (P < 0.04). CONCLUSION: BP level in children and adolescents was a good marker for familial aggregation of metabolic RF, suggesting an interaction of genetic and environmental factors. Primary intervention should be carried out in early stages of life.

Breeding of the water rat (Nectomys squamipes) in the laboratory.

The water rat, Nectomys squamipes, is reported as a natural host of Schistosoma mansoni in Brazil. This paper presents some reproductive, growth and developmental data, and laboratory management of a breeding programme for N. squamipes. The colony was derived from animals captured at Sumidouro, Rio de Janeiro state. The animals' diploid number was 56, conception rate was 66.7% and gestation period was 30 days. Litter size ranged from 1 to 6, with a mean of 4.1 (SD +/- 1.2) and a mode of 4 and 5. Sex ratio at birth and at weaning was not significantly different from the expected ratio of 1:1. There were no significant differences between mean body weights at birth for males and females. The minimum age for weaning was between 20-25 days. The growth curves of body weight, head-body length and tail length, for both sexes, comprise at least three linear segments representing different phases of approximately constant growth rates. Facilities for colony maintenance and its potential for use as experimental model are reported.