No abstract

A statistical evaluation of the population dynamics of R. neivai is based on six cohorts experiments conducted under controlled laboratory conditions. Two blood sources were offered to animals: rabbit and hen. Egg hatching, nymphal development time and mortality, adult longevity and age-specific mortality, female age-specific fecundity and fertility were determined. In addition, some population parameters were evaluated, such as: life expectancy, intrinsic rate of natural increase, net reproduction rate, finite rate of increase, reproductive value and stable age distribution. Life cycle was longer in the animals fed on rabbit, nymphal survival was slightly higher in the individuals fed on hen. Age of first reproduction was lower in the insects fed on hen, but reproductive output and total number of reproductive weeks were greater in the cohorts fed on rabbit. Intrinsic and finite rate of increase were greater in the animals fed on hen. Generation time was slightly greater in the cohorts fed on rabbit. Net reproduction rate was similar on both blood sources, although it was slightly bigger in the individuals fed on rabbit. Reproductive value in the insects fed on rabbit was twice as much as the registered in the animals fed on hen.

A statistical evaluation of the population dynamics of Panstrongylus geniculatus is based on a cohort experiment conducted under controlled laboratory conditions. Animals were fed on hen every 15 days. Egg incubation took 21 days; mean duration of 1st, 2nd, 3rd, 4th, and 5th instar nymphs was 25, 30, 58, 62, and 67 days, respectively; mean Panstrongylus geniculatus (Latreille 1811), is widely distributed in America; it is found from southern Mexico to northern Argentina. It has epidemiological importance since it has been found naturally infected with Trypanosoma cruzi from the beginning of this century (Chagas 1912).In Venezuela, it has been captured in many states (Ramírez Pérez 1987). Pifano (1986) studying the urban Chagas' disease in the valley of Caracas reported individuals of P. geniculatus in human dwellings, apparently associated to the marsupial Didelphis marsupialis.It is attracted by light and has been collected in human dwellings, but it does not colonize them (Miles et al. 1981); it is a sylvatic species (Lent & Wygodzinsky 1979, Zeledón 1983.It has been little studied because of the difficulties for rearing and maintenance, and for the low number of collected specimens (Miles et al. 1981, Ramírez Pérez 1987; therefore, very little literature has been published on its biology, ecology and epidemiology. Barreto (1967) studied some ecological aspects and indicated a close association with some mammals like armadillo. Lent and Jurberg (1969) Here we present the results of a study of P. geniculatus fed only on hen, under controlled constant environmental conditions, with special emphasis on its demographic characteristics, in order to contribute to the kwowledge of the population dynamics of this species. MATERIALS AND METHODSThe population of P. geniculatus used in this experiment was obtained from a colony founded by a single female collected in a human dwelling in the area of San Jacinto, located in the city of Trujillo, Trujillo State, Venezuela. The colony was kept in a climatic chamber at 26±3°C and 90±10% RH, and fed on hens.Vital statistics described in this study were based on a cohort constituted by 63 recently laid eggs (0 to 48 hr old); these were kept in 150 cm 3 glass containers until all viable eggs hatched; then, all 1st instar nymphs were transferred to a 3,785 l broad mouth jar, covered with nylon mesh and provided with vertically placed strips of paper in order to allow insects to climb to the jar top at feeding time and provide them resting places and serve as laying sites.

No abstract

Changes in life tables of

No abstract

After changing feeding frequency to a weekly and biweekly basis, a statistical evaluation of the variation of some population and reproductive parameters was conducted. It was based on four cohorts experiments of Rhodnius neivai fed on hen or rabbit. We found a direct relationship between blood feeding frequency and the parameters adult average longevity, maximum longevity and life expectancy in the animals fed on hen. On the other hand, in the insect fed biweekly on rabbit, these three values were higher than the registered in the cohorts fed weekly. Reproductive output got bigger and age-specific fertility showed a small decrease when feeding frequency was weekly. Every population parameter, except generation time, was greater in the individuals fed weekly.

Abstract. The population dynamics of the small forest rice rat Microryzomys minutus, a murid rodent that occurs in the high altitudes of the northern and central Andes, was studied in disturbed and primary environments in a cloud forest of the Venezuelan Andes (Juan Pablo Peñaloza National Park, 8º11'N, 71º49'W). We collected 121 animals (66 and 55 ) between 1995 and 1998, using pitfall traps with formalin. Adult males were heavier than adult females. Relative abundance was much greater in the disturbed environments (over 10 individuals in some periods) than in the primary cloud forest: 4-8 individuals. In the disturbed environments, the rats were extremely abundant in the first sampling period, and less frequent afterwards. In the cropland, abundance showed some fluctuations during the study and displayed two small abundance peaks in March-June 1997 and 1998. In the mined area, the rats had irregular fluctuations until March-June 1997 and were not recorded in July-October 1997. The occurrence of this rat in both disturbed and natural habitats confirms the wide ecological tolerance of this species. Rev. Biol. Trop. 54(2): 651-. Epub 2006 Jun 01.