Adult-Juvenile interactions and temporal niche partitioning between life-stages in a tropical amphibian.

Divergence in ecological niche offers organisms the opportunity of exploiting different food and habitat resources, scaling down competition and predation both among species, and within different age or size-classes of the same species. In harsh environments, where abiotic factors determine a clustering of resources during short timespans, competition and predation between organisms is likely to be enhanced. This is the case in tropical dry forests, where amphibians have limited opportunities to feed, their activity being restricted to the short rainy season. One way to maximize resource exploitation while avoiding predation risk is by adopting different diel activity patterns. We tested this hypothesis by comparing activity patterns in adults and recently metamorphosed juveniles of Pacific horned frogs (Ceratophrys stolzmanni) during field surveys and in an experimental study. Field surveys showed that the adults are strictly nocturnal, whereas freshly metamorphosed juveniles can be found active above ground at all hours, with a peak activity during daytime. The average body condition index of juveniles found active during the night was higher than that of juveniles found active during the day, suggesting that the weaker individuals may be constrained to being active during the day. On the other hand, in a laboratory experiment, juveniles that were visually exposed to adults moved less than those in the absence of adults. Both field and experimental observations indicate a temporal niche divergence between life stages. The results of the experiment offer support to the hypothesis that the juveniles in this species display an inverse activity pattern compared to adults, which can reduce competitive interactions and predation pressure from the larger conspecifics.

Nocturnal Activity Rhythm of Nyssomyia intermedia (Diptera: Psychodidae: Phlebotominae) in Campus Fiocruz Mata Atlântica, an American Cutaneous Leishmaniasis Transmission Area, Rio de Janeiro, Brazil.

INTRODUCTION: Nyssomyia intermedia is an important vector of American cutaneous leishmaniasis. METHODS: Sand flies were captured in a Shannon trap and after landing on human collectors and retrieved monthly. Nocturnal activity was estimated using a log-linear model. RESULTS: Peak sand fly collection in the Shannon trap occurred in summer and winter, and peak fly collection on humans occurred in spring and summer. CONCLUSIONS: Ny. intermedia was captured in both the hottest and coldest months, indicating its adaptability to different seasons and the possibility of disease transmission at any time of the year in Campus Fiocruz Mata Atlântica, Brazil.

Nocturnal activity rhythm of nyssomyia intermedia (diptera: psychodidae: phlebotominae) in campus fiocruz mata atlântica, an american cutaneous leishmaniasis transmission area, Rio de Janeiro, Brazil

Abstract INTRODUCTION: Nyssomyia intermedia is an important vector of American cutaneous leishmaniasis. METHODS: Sand flies were captured in a Shannon trap and after landing on human collectors and retrieved monthly. Nocturnal activity was estimated using a log-linear model. RESULTS: Peak sand fly collection in the Shannon trap occurred in summer and winter, and peak fly collection on humans occurred in spring and summer. CONCLUSIONS: Ny. intermedia was captured in both the hottest and coldest months, indicating its adaptability to different seasons and the possibility of disease transmission at any time of the year in Campus Fiocruz Mata Atlântica, Brazil.

Time and seasonal patterns of activity of phyllostomid in fragments of a stational semidecidual forest from the Upper Paraná River, Southern Brazil.

Bats may exhibit different patterns of activity, considering aspects concerning niche dynamics as well as the establishment and permanence of the communities in the ecosystems. In this way, the present study analyzed the time and seasonal patterns of activity in different species of frequent phyllostomid bats in remnants of the stational semidecidual forest from the Upper Paraná River, Southern Brazil. Captures were performed between January and December, 2006, using 32 mist nets set above the soil along the nocturnal period during the four seasons of the year. The daily and seasonal patterns of activity of each species was modeled using generalized linear models with Poisson error. The best model was selected using Akaike's Information Criterion (AICc). Artibeus planirostris (Spix, 1823) did not exhibit a conspicuous time pattern, whereas A. lituratus (Olfers, 1818) was more frequent after the sixth hour and A. fimbriatus Gray, 1838 had an activity increase along the night. Platyrrhinus lineatus (E. Geoffroy, 1810) was registered during all sampling hours. Carollia perspicillata (Linnaeus, 1758) and Sturnira lilium (E. Geoffroy, 1810) were the most active during the first four hours. Concerning seasonal pattern, the highest activity of these species was verified during the summer. These data contribute to the information about the ecology of bats in the region, highlighting the high adaptive potential of the species studied in relation to the use of space throughout the night and in to variations in environmental conditions.

Foraging activity of the free-tailed bat Molossus molossus (Chiroptera; Molossidae) in southeastern Brazil.

Sunset and sunrise regulate the activities of most studied bat species. To verify patterns of foraging activity, 29 bat sampling nights were carried out over a dam in Rio de Janeiro city, which resulted in 363 hours with 730 captures, representing 13 species of insectivorous bats. Molossus molossus constituted the bulk of the captures (79.9%) and was present in 82.8% of the sampling nights. This bat species exhibited crepuscular and nocturnal activity (from -6 minutes to 900 minutes after the time of sunset). A bimodal activity pattern was observed, and two non-overlapping capture peaks. The first peak lasted from 6 minutes before sunset to 420 minutes after sunset. The second peak began at 564 minutes after sunset and ended just after sunrise. The first capture peak was observed in 75.9% of the nights, and the second peak in 62.1% of the nights. The time of the first capture exhibited a positive linear relationship with sunset and the time of the last capture, a positive linear relationship with sunrise. The existence of a relationship between night length and the difference between first and last captures of each night shows that M. molossus has longer activity the longer the night, showing a seasonal variation in the activity period.

Diet and feeding daily rhythm of Pimelodella lateristriga (Osteichthyes, Siluriformes) in a coastal stream from Serra do Mar - RJ.

The present study was carried out in Mato Grosso fluvial system, a costal drainage from Serra do Mar. We analysed the diet and the feeding daily rhythm of Pimelodella lateristriga from samples carried out during 24 hours over a 4 hour fishing interval, in June, July and September, 2006 as well as in January and February, 2007. Diet was described from the Feeding Index (IAi) and feeding daily rhythm was verified through the Gut Fullness Index (GFI). Pimelodella lateristriga diet was composed of 37 items, being aquatic insects the most important ones. IAi analysis revealed that Diptera, Trichoptera and Ephemeroptera amounted to 90% of the diet. Autochthonous invertebrates were the most important consumed items. Pimelodella lateristriga concentrated its feeding activities in the nocturnal period (10:00 PM to 2:00 AM) with marked significant differences (F = 16.11; gl = 5; p < 0.05) between each diurnal and nocturnal periods. Between 6:00 AM and 6:00 PM, foraging activity was gradually reduced. We concluded that P. lateristriga has an insectivorous diet and a nocturnal feeding habit with greater activity between 10:00 PM to 2:00 AM.

Diet and feeding daily rhythm of Pimelodella lateristriga (Osteichthyes, Siluriformes) in a coastal stream from Serra do Mar - RJ / Dieta e ritmo diário da alimentação de Pimelodella lateristriga (Osteichthyes, Siluriformes) de um riacho costeiro da Serra do Mar - RJ

The present study was carried out in Mato Grosso fluvial system, a costal drainage from Serra do Mar. We analysed the diet and the feeding daily rhythm of Pimelodella lateristriga from samples carried out during 24 hours over a 4 hour fishing interval, in June, July and September, 2006 as well as in January and February, 2007. Diet was described from the Feeding Index (IAi) and feeding daily rhythm was verified through the Gut Fullness Index (GFI). Pimelodella lateristriga diet was composed of 37 items, being aquatic insects the most important ones. IAi analysis revealed that Diptera, Trichoptera and Ephemeroptera amounted to 90 percent of the diet. Autochthonous invertebrates were the most important consumed items. Pimelodella lateristriga concentrated its feeding activities in the nocturnal period (10:00 PM to 2:00 AM) with marked significant differences (F = 16.11; gl = 5; p < 0.05) between each diurnal and nocturnal periods. Between 6:00 AM and 6:00 PM, foraging activity was gradually reduced. We concluded that P. lateristriga has an insectivorous diet and a nocturnal feeding habit with greater activity between 10:00 PM to 2:00 AM.

O presente estudo foi desenvolvido no sistema fluvial do rio Mato Grosso que compõe uma drenagem costeira da Serra do Mar. Foi analisado o hábito alimentar e o ritmo alimentar diário de Pimelodella lateristriga a partir de amostras obtidas em coletas de 24 horas, com intervalos de 4 horas, em junho-julho-setembro/2006 e janeiro- fevereiro/2007. A dieta foi avaliada a partir do Índice Alimentar (IAi) e o ritmo alimentar diário, com base no Índice de Repleção Estomacal (GFI) dos peixes. A dieta de P. lateristriga foi composta por 37 itens, sendo os insetos aquáticos os mais abundantes. O IAi revelou que Diptera, Trichoptera e Ephemeroptera somaram 90 por cento da dieta, sendo, portanto, os invertebrados autóctones os itens mais consumidos. Pimelodella lateristriga concentrou sua atividade alimentar no período noturno (10:00 até 14:00 horas) com diferenças significativas (F = 16,11; gl = 5; p < 0,05) entre os horários diurnos e noturnos. Entre os horários 6 am e 6 pm a atividade de forrageamento foi gradualmente reduzida. Concluímos que P. lateristriga possui dieta insetívora e ritmo alimentar noturno com pico de atividade entre 10:00 até 14:00 horas.

Foraging activity of the free-tailed bat Molossus molossus (Chiroptera; Molossidae) in southeastern Brazil / Atividade de forrageio do morcego-cauda-de-rato Molossus molossus (Chiroptera; Molossidae) no Sudeste do Brasil

Sunset and sunrise regulate the activities of most studied bat species. To verify patterns of foraging activity, 29 bat sampling nights were carried out over a dam in Rio de Janeiro city, which resulted in 363 hours with 730 captures, representing 13 species of insectivorous bats. Molossus molossus constituted the bulk of the captures (79.9 percent) and was present in 82.8 percent of the sampling nights. This bat species exhibited crepuscular and nocturnal activity (from -6 minutes to 900 minutes after the time of sunset). A bimodal activity pattern was observed, and two non-overlapping capture peaks. The first peak lasted from 6 minutes before sunset to 420 minutes after sunset. The second peak began at 564 minutes after sunset and ended just after sunrise. The first capture peak was observed in 75.9 percent of the nights, and the second peak in 62.1 percent of the nights. The time of the first capture exhibited a positive linear relationship with sunset and the time of the last capture, a positive linear relationship with sunrise. The existence of a relationship between night length and the difference between first and last captures of each night shows that M. molossus has longer activity the longer the night, showing a seasonal variation in the activity period.

A atividade dos morcegos inicia-se imediatamente antes, durante ou imediatamente após o pôr do sol. O início e o término das atividades dos morcegos são reguladas respectivamente pelo pôr e nascer do sol. Nesse trabalho, 29 noites de amostragem foram realizadas (total de 363 horas) sobre um açude na Cidade do Rio de Janeiro para avaliar a atividade de forrageio de Molossus molossus. Esse esforço resultou em 730 capturas de 13 espécies de morcegos insetívoros. Molossus molossus constituiu a maior parte das capturas e representou 79,9 por cento da amostragem, presente em 82,8 por cento das noites de coleta. Esta espécie apresenta atividade crepuscular e noturna (de -6 minutes a 900 minutos após o pôr do sol). Foi observado um padrão bimodal de atividade com picos de capturas sem superposição, sendo o primeiro 6 minutos antes do pôr do sol a 420 minutos após o pôr do sol, e o segundo aos 564 minutos após o pôr do sol e término imediatamente após o nascer do sol. O primeiro pico de captura ocorreu em 75,9 por cento das noites e o segundo em 62,1 por cento das noites. O horário da primeira captura resultou em uma relação linear positiva com o pôr do sol e o horário da última captura, com o nascer do sol. A existência de relação entre a duração da noite e a diferença entre a primeira e a última captura de cada noite demonstra que M. molossus tem maior período de atividade quanto mais longa é a noite, sustentando uma variação estacional do período de atividade.

Time and seasonal patterns of activity of phyllostomid in fragments of a stational semidecidual forest from the Upper Paraná River, Southern Brazil / Padrões de atividade horária e sazonal de morcegos filostomídeos em fragmentos de floresta estacional semidecidual do alto rio Paraná, sul do Brasil

Bats may exhibit different patterns of activity, considering aspects concerning niche dynamics as well as the establishment and permanence of the communities in the ecosystems. In this way, the present study analyzed the time and seasonal patterns of activity in different species of frequent phyllostomid bats in remnants of the stational semidecidual forest from the Upper Paraná River, Southern Brazil. Captures were performed between January and December, 2006, using 32 mist nets set above the soil along the nocturnal period during the four seasons of the year. The daily and seasonal patterns of activity of each species was modeled using generalized linear models with Poisson error. The best model was selected using Akaike's Information Criterion (AICc). Artibeus planirostris (Spix, 1823) did not exhibit a conspicuous time pattern, whereas A. lituratus (Olfers, 1818) was more frequent after the sixth hour and A. fimbriatus Gray, 1838 had an activity increase along the night. Platyrrhinus lineatus (E. Geoffroy, 1810) was registered during all sampling hours. Carollia perspicillata (Linnaeus, 1758) and Sturnira lilium (E. Geoffroy, 1810) were the most active during the first four hours. Concerning seasonal pattern, the highest activity of these species was verified during the summer. These data contribute to the information about the ecology of bats in the region, highlighting the high adaptive potential of the species studied in relation to the use of space throughout the night and in to variations in environmental conditions.

Os morcegos podem exibir diferentes padrões de atividade, considerando-se aspectos relacionados à dinâmica de nicho e ao estabelecimento e permanência das comunidades nos ecossistemas. Assim, o presente estudo teve por objetivo investigar o padrão de atividade horária e sazonal em diferentes espécies de morcegos, frequentes em remanescentes de floresta estacional semidecidual do alto rio Paraná, sul do Brasil. As coletas foram realizadas entre janeiro e dezembro de 2006, com o auxílio de 32 redes armadas acima do solo, ao longo de todo o período noturno e nas quatro estações do ano. A análise dos dados contemplou o uso de modelos lineares generalizados Akaike's Information Criterion (AICc) e distribuição de Poisson. Artibeus planirostris (Spix, 1823) não exibiu um padrão horário conspícuo, enquanto A. lituratus (Olfers, 1818) foi mais frequente após a sexta hora e A. fimbriatus Gray, 1838 teve aumento da atividade ao longo da noite. Platyrrhinus lineatus (E. Geoffroy, 1810) foi registrado durante todas as horas de amostragem. Carollia perspicillata (Linnaeus, 1758) e Sturnira lilium (E. Geoffroy, 1810) foram mais ativos nas quatro primeiras horas. Em relação ao padrão sazonal, constatou-se maior atividade dessas espécies durante o verão. Esses dados contribuem com as informações acerca da ecologia dos morcegos na região e evidenciam o alto potencial adaptativo das espécies estudadas à variação de tempo e condições ambientais.

Influence of seasonality on circadian motor activity rhythm in common marmosets during puberty.

The effect of puberty on circadian rhythmicity in nonhuman primates has been little studied, even though it has been demonstrated that puberty-related changes in circadian activity rhythm occur in a number of species, including humans. To characterize the motor activity rhythm during puberty in common marmosets (Callithrix jacchus), six animals was continuously monitored by actimeters between their 5th and 12th months of age. The animals were housed with their families in outdoor cages under seminatural conditions. Onset of puberty was determined from fecal estrogen and progesterone levels in females and androgen levels in males. The spectral power of the circadian component stabilized later in the last two animals to enter puberty. The bimodal characteristic of the active phase in this species became progressively more apparent over the course of the months in which the mean temperature was highest, irrespective of the animal's age. Although the onset of activity advanced after entry into puberty, this parameter showed a strong correlation with sunrise, indicating that seasonality influences this variable. Neither age nor climatic factors included in the regression model influenced the differences in phase angles between sunrise and onset of activity, and between sunset and offset of activity. Total activity was the only parameter influenced by age in the regression model, showing an increase after entry into puberty. Despite the evidence of pubertal influence on both the circadian component and total activity, under seminatural conditions seasonal factors may have a more important effect on motor activity rhythm in common marmosets.

Regulación circadiana del comportamiento: diferencias entre especies diurnas y nocturnas / Circadian regulation of behavior: differences between diurnal and nocturnal species

La mayoría de los organismos, incluyendo los humanos, exhiben ritmos diarios de aproximadamente 24 horas en fisiología, funciones hormonales y conducta. En mamíferos, estos ritmos son controlados por un marcapasos circadiano endógeno ubicado en el núcleo supraquiasmático (NSQ) del hipotálamo que determina la organización temporal de varias conductas y procesos fisiológicos. El control circadiano de ritmos diarios difiere en especies diurnas y nocturnas pero los mecanismos que pueden explicar dichas diferencias se desconocen aún. El objetivo de esta revisión es resumir el estado actual del conocimiento sobre los relojes circadianos y de las diferencias entre especies diurnas y nocturnas.

Most organisms, including humans, show daily rhythms of about 24 hours in physiology, hormonal function, and behavior. In mammals, these rhythmsare controlled by an endogenous circadian pacemaker localized in the suprachiasmatic nucleus (SCN) of the hypothalamus that determines thetemporal organization of several behaviors and physiological processes.Circadian control of daily rhythms differs in diurnal and nocturnal speciesbut many of the mechanisms that may explain these differences remain stillunknown. The aim of this review is to summarize our current knowledge of the circadian clocks and the differences between diurnal and nocturnal species.

Differences in diet and activity pattern between two groups of Alouatta palliata associated with the availability of big trees and fruit of top food taxa.

The threat that forest fragmentation and habitat loss presents for several Alouatta taxa requires us to determine the key elements that may promote the persistence of howler monkeys in forest fragments and to evaluate how changes in the availability of these elements may affect their future conservation prospects. In this study we analyzed the relationship between the availability of both big trees of top food taxa (BTTFT) (diameter at breast height>60) and fruit of top food taxa (FrTFT) in the home ranges of two groups of Alouatta palliata mexicana occupying different forest fragments in Los Tuxtlas, Mexico, and their diet and activity pattern. Both study groups preferred big trees for feeding and the group with lower availability of BTTFT in their home range fed from more, smaller food sources. Furthermore, both study groups also increased the number of food sources when their consumption of fruit decreased, and the group with lower availability of FrTFT in their home range fed from more food sources. The increase in the number of food sources used under such conditions, in turn, set up a process of higher foraging effort and lower rest. In summary, our results support other studies that suggest that the availability of big trees and fruit may be two important elements influencing the persistence of howler monkeys in forest fragments.

Environmental, seasonal, and social modulations of basal activity in a weakly electric fish.

The electric organ discharge (EOD) of weakly electric fish encodes information about species, sex, behavioral, and physiological states throughout the lifetime. Its central command is crucial for sensory-motor coordination, and is therefore the target of plastic mechanisms that adapt fish to environmental and social challenges. The EOD waveform of Brachyhypopomus pinnicaudatus is modulated by environmental factors and the neuroendocrine system. In this study we investigate the effects of water temperature and day-night cycle upon EOD rate in this species during the breeding and non-breeding seasons. During the non-breeding season, EOD rate is a linear function of water temperature and exhibits counterclockwise hysteresis. During breeding, a thermal resistance strategy prevents the decrease of EOD rate to cooling. A nocturnal increase of EOD basal rate independent of water temperature and locomotor activity was demonstrated in isolated non-breeding adults and in male-female dyads all year round. An additional increase of nocturnal EOD rate, probably acting as a social courtship signal, was found in breeding dyads. This additional increase of nocturnal EOD rate could not be fully explained by gonadal maturation and was modulated by social stimuli. This study provides novel data on the complex interactions between environment, reproductive cycle, social behavior, and electromotor output in an advantageous model of the vertebrate central nervous system.

[Sleep-wake cycle mechanisms]. / Mecanismos do ciclo sono-vigília.

Neurochemically distinct systems interact regulating sleep and wakefulness. Wakefulness is promoted by aminergic, acetylcholinergic brainstem and hypothalamic systems. Each of these arousal systems supports wakefulness and coordinated activity is required for alertness and EEG activation. Neurons in the pons and preoptic area control rapid eye movement and non-rapid eye movement sleep. Mutual inhibition between these wake- and sleep-regulating systems generate behavioral states. An up-to-date understanding of these systems should allow clinicians and researchers to better understand the effects of drugs, lesions, and neurologic disease on sleep and wakefulness.

Influence of long-term food restriction on sleep pattern in male rats.

The present purpose was to determine the effects of different schedules of long-term food restriction (FR) applied to rats from weaning to the 8th week. Rats were distributed into FR and ad libitum groups at weaning and fed at 7 am, at 7 pm, and finally, restricted rats fed ad libitum. The restricted rats started with 6 g/day and the food was increased by 1 g per week until reaching 15 g/day by adulthood. The rats were implanted with electrodes to record electrocorticogram/eletromyogram signals. Their wake-sleep cycles were monitored over 3 consecutive days (72 h of recording). The FR group fed at 7 am showed an increase in awake time, and decrease in slow wave sleep (SWS) and paradoxical sleep (PS) during the three light periods compared with the control recordings whereas in the dark periods, these sleep parameters were the opposite. The restricted group fed in the evening showed no statistical significances at diurnal periods; however, a significant decrease was observed in the dark recordings for awake time, but the SWS and PS were increased in relation to controls. The analysis of the 24-h period demonstrated that both FR groups presented increase in SWS time. After being FR, the rats were fed ad libitum and their sleep was monitored for 3 additional days. During the first dark recording, the decrease in awake time and increase in SWS were still present; however, as ad libitum food continued, these sleep parameters returned to control values, reestablishing the normal sleep pattern. These results suggest that dietary restriction, regardless to the feeding schedule, caused increase in total sleep time, during the active period.

Sleep homeostasis in rats assessed by a long-term intermittent paradoxical sleep deprivation protocol.

Numerous studies have evaluated the sleep homeostasis of rats after short- or long-periods of sleep deprivation, but none has assessed the effects of prolonged sleep restriction on the rat's sleep pattern. The purpose of the present study, therefore, was to evaluate the sleep homeostasis of rats under a protocol of chronic sleep restriction. Male Wistar rats were implanted with electrodes for EEG and EMG recordings. Using the single platform method, the animals were submitted to 18 h of sleep restriction, beginning at 16:00 h (lights on at 07:00 h), followed by a 6 h sleep window (from 10:00 h to 16:00 h) for 21 days. Immediately after this period, rats were allowed to sleep freely for 4 days (recovery period). The sleep-wake cycle was recorded throughout the entire experiment and the results showed that during the 6h sleep window there was an increase on the percentage of sleep time, reflected by augmented time in high amplitude slow wave sleep and in paradoxical sleep, when compared to baseline sleep, whereas bouts of awakening longer than 1.5 min were greatly reduced, with the animals exhibiting a monophasic-type sleep pattern. During the deprivation period, paradoxical sleep was abolished. High amplitude slow wave sleep was also greatly affected by the protocol. Nonetheless, one day of recovery was sufficient to restore the normal sleep pattern. These findings indicate that this protocol was capable to induce many changes in the rat's sleep patterns, suggesting that during the 6h sleep window there is a sleep adaptive homeostatic process.

Mecanismos do ciclo sono-vigília / Sleep-wake cycle mechanisms

Três sub-divisões hipotalâmicas são importantes no ciclo sono-vigília: o hipotálamo anterior (núcleos gabaérgicos e núcleos supraquiasmáticos), o hipotálamo posterior (núcleo túbero-mamilar histaminérgico) e o hipotálamo lateral (sistema hipocretinas). O sistema gabaérgico inibitório do núcleo pré-óptico ventro-lateral (VLPO) do hipotálamo anterior é responsável pelo início e manutenção do sono NREM. Os neurônios supraquiasmáticos (NSQs) do hipotálamo anterior são responsáveis pelo ritmo circadiano do ciclo sono-vigília. Os núcleos aminérgicos, histaminérgicos, as hipocretinas e núcleos colinérgicos do prosencéfalo basal apresentam-se ativos durante a vigília, inibindo o núcleo pré-óptico ventro-lateral, promovendo a vigília. O processo de inibição-estimulação é a base do modelo da interação recíproca entre os grupos de células wake-off-sleep-on e células wake-off-sleep-on reguladores do ciclo sono-vigília. O modelo da interação recíproca também se aplica aos núcleos colinérgicos (células REM-on) e aminérgicos (células REM-off) do tronco cerebral no controle temporal do sono REM-NREM.

Nocturnal activity rhythms of Lutzomyia intermedia and Lutzomyia whitmani (Diptera: Psychodidae) in a transmission area of American cutaneous leishmaniasis in Rio de Janeiro State, Brazil.

The phlebotomine sand flies Lutzomyia (Nyssomyia) intermedia (Lutz & Neiva) and Lutzomyia (Nyssomyia) whitmani (Coutinho & Antunes) are important vectors of Leishmania (Vianna) braziliensis, the etiological agent of American cutaneous leishmaniasis. In some areas, both species occur in sympatry, and their relative roles as vectors in these areas are not clear. We studied the nocturnal activity and biting rhythms of both species in Posse, a locality in Rio de Janeiro State, Brazil. Our results show differences between the activity patterns of Lu. intermedia and Lu. whitmani that might be epidemiologically important. Although the activity profiles vary between seasons and microhabitats (peridomestic versus forest), the two species show marked differences in their tendencies to bite humans in the early morning (0400-0600 hours), with Lu. whitmani showing higher feeding rates than Lu. intermedia.

Allometric scaling of biological rhythms in mammals

A wide spectrum of cyclic functions in terrestrial mammals of different size, from the 3-gram shrew to the 3-ton elephant, yields an allometric exponent around 0.25, which is correlated - as a kind of common denominator - with the specific metabolic rate. Furthermore, the applicability of these empirical findings could be extrapolated to chronological events in the sub-cellular realm. On the other hand, the succession of growth periods (T98 percent) until sexual maturity is reached also follows the 1/4 power rule. By means of Verhulst's logistic equation, it has been possible to simulate three different biological conditions, which means that by modifying the numerical value of only one parameter, revertible physiological and pathological states can be obtained, as for instance isostasis, homeostasis and heterostasis.

Retinal morphology and electrophysiology of two caprimulgiformes birds: the cave-living and nocturnal oilbird (Steatornis caripensis), and the crepuscularly and nocturnally foraging common pauraque (Nyctidromus albicollis).

Oilbirds (Steatornis caripensis) breed in the total darkness of caves and forage at night on fruits. Common pauraques (Nyctidromus albicollis) are crepuscular and nocturnal foragers on flying insects. We examined if their retinal structure and function can be correlated with their types and periods of activity. Electroretinograms (ERGs) were obtained from anesthetized birds in photopic and scotopic conditions to a wide range of light intensities, following which the retinas were processed for histological analysis. Retinal sensitivity is higher in oilbirds than in common pauraques. Under scotopic conditions with maximum flash luminance, the average (+/- 95% CI) b-wave amplitude of oilbirds is double that of common pauraques (500.4 +/- 49.8 and 245.4 +/- 40.9 microV, respectively) but, under photopic conditions, the results are the reverse (common pauraque: 69.4 +/- 18.1; oilbird: 23.0 +/- 4.4 microV). On the other hand, the retina of both species is highly rod-dominated, but rods are highly more numerous in oilbirds than in common pauraques (rods:cones ratio: 123:1 and 5:1, respectively). In oilbirds, rods are largely thinner and their outer segments are 1.0 microm in diameter and 18.6 microm in length. They are distributed over various levels in the photoreceptor layers, an arrangement known for deep-sea fishes, but so far unknown for birds. In common pauraques, rods are patchily distributed and their outer segments are 4.0 microm in diameter and 53 microm in length. The oilbirds rod thinness allows more rods per area unit, and thus to catch more photons per area unit under darkness, while the low cone number suggests that the species has poor daytime vision, which concurs with the species cavernicolous daytime habits. The lower rod number of common pauraques, compared to oilbirds, appears counterbalanced by their patchiness and longer and thicker outer segments to provide high retinal sensitivity. In addition, common pauraques also have a tapetum. These features, combined with a higher proportion of cones, show that common pauraques are well equipped for crepuscular and nocturnal foraging on flying insects in an open environment.