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PubMedDate not supplied

Population dynamics and feeding behavior of Triatoma brasiliensis and Triatoma pseudomaculata, main vectors of chagas disease in Northeastern Brazil.

Biological parameters of Triatoma brasiliensis and T. pseudomaculata that could influence the epidemiological importance of these insects as vectors of Trypanosoma cruzi were compared. The parameters studied were incubation period, interval between hatching or moulting and first feeding, number of blood meals, development time, mortality, net reproductive rate, instantaneous daily reproductive rate, time-lapse before starting feeding, duration of feeding, blood ingestion capacity, occurrence of defecation and blood ingestion velocity. Most aspects of feeding were similar for the two species, although T. pseudomaculata had a longer life cycle than T. brasiliensis producing one and two generations per year, respectively. The two species had similar instantaneous daily rates of population growth.

Animals↗
PubMedDate not supplied

Effect of two solanaceous plants on developmental and population parameters of the tomato leaf miner, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae).

Tuta absoluta (Meyrick) is an important tomato pest that also feeds on other host-plants from the Solanceae family. We studied the effect of two cultivated plants, tomato (Lycopersicum esculentum Mill.) and potato Solanum tuberosum L. on the development and populational parameters of T. absoluta related with host-plant suitability. Larval developmental time, pupal weight, mean fecundity and an index of host-plant quality (IPQ = pupal weight / frass weight) were estimated. Age-specific survivorship and fecundity life tables were constructed in the laboratory to evaluate the following populational parameters: net reproductive rate (Ro), intrinsic rate of increase (r) and generation time (T). Larval developmental time was shorter and pupal weight was higher (P < 0.0001) for larvae reared on tomato (P < 0.0001). Mean fecundity was not significantly different on both plants (P = 0.07) and food quality of host-plant was higher for tomato (P = 0.02). Mean population parameters on tomato were: Ro = 48.92; T = 27.98, r = 0.14; and on potato: Ro = 14.43; T = 32.35, r = 0.08. Although results showed that tomato was a more suitable host-plant and had a better nutritional quality than potato, when T. absoluta fed on potato the potential population increase requires attention. Under appropriate climatic conditions, spatial and temporal coincidence between crop and pest, T. absoluta could become a pest for the potato crop.

Animals↗
PubMed2000

Statistical inference on associated fertility life table parameters using jackknife technique: computational aspects.

Knowledge of population growth potential is crucial for studying population dynamics and for establishing management tactics for pest control. Estimation of population growth can be achieved with fertility life tables because they synthesize data on reproduction and mortality of a population. The five main parameters associated with a fertility life table are as follows: (1) the net reproductive rate (Ro), (2) the intrinsic rate of increase (rm), 3) the mean generation time (T), (4) the doubling time (Dt), and (5) the finite rate of increase (lambda). Jackknife and bootstrap techniques are used to calculate the variance of the rm estimate, which can be extended to the other parameters of life tables. Those methods are computer-intensive, their application requires the development of efficient algorithms, and their implementation is based on a programming language that encompasses quickness and reliability. The objectives of this article are to discuss statistical and computational aspects related to estimation of life table parameters and to present a SAS program that uses jackknife to estimate parameters for fertility life tables. The SAS program presented here allows the calculation of confidence intervals for all estimated parameters, as well as provides one-sided and two-sided t-tests to perform pairwise or multiple comparison between groups, with their respective P values.

Animals↗
PubMed2000

Influence of sublethal exposure to abamectin on the biological performance of Neoseiulus longispinosus (Acari: Phytoseiidae).

Effects of sublethal exposure to abamectin on the biological performance of Neoseiulus longispinosus (Evans) were studied under ambient laboratory conditions of 28 +/- 2 degrees C and 80 +/- 15% RH with 24 h light. The red form of the twospotted spider mite, Tetranychus urticae Koch, complex (Acari: Tetranychidae), was offered as prey. The LC50 obtained from the contact bioassay at 48 h after treatment was 0.015 ppm (AI). A big change in kill for a given variation in dosage for the regression slope probably indicated that abamectin was unlikely selective. Sublethal exposure to abamectin caused a reduction in survival with the female reaching 50% mortality by the sixth day and the male 4 d later. The mean preoviposition period was extended by almost 1 d, whereas the mean oviposition period was shortened by almost 5 d causing a reduction in the mean fecundity female-1 to almost half that of the untreated females. The net reproductive rate (Ro), the intrinsic rate of increase (rm), and the finite rate of increase (lambda) of the treated females were markedly inferior. Treated males were seriously affected; the mean life span was almost half that of the untreated.

Animals↗
PubMed2000

Temperature dependent development of the parasitoid Colpoclypeus florus (Hymenoptera: Eulophidae) in the laboratory.

Development, fecundity, and longevity of Colpoclypeus florus (Walker), a parasitoid of Adoxophyes orana (Fischer von Röslerstamm) (Lepidoptera: Tortricidae), were studied under laboratory conditions at different constant temperatures. Developmental time from egg to adult was inversely related to temperature and at 25 degrees C was 12.81 +/- 0.19 d. No adults emerged at 30 degrees C. The thermal units required for development from egg to adult were 232.56 +/- 19.5 degree-days. Female C. florus oviposited (mean +/- SEM) on average 30.7, 57.4, 46.6, and 34.1 eggs at 15, 17, 20, and 25 degrees C. respectively. Adult longevity was 11 +/- 1.25 d at 17, whereas it decreased to 4.5 +/- 0.4 at 25 degrees C. Honey significantly increased longevity for both males and females. The highest net reproductive rate was 30.739 at 17 degrees C, whereas the highest intrinsic rate of increase and the shortest doubling time occurred at 25 degrees C.

Animals↗
PubMed2006

Age-dependent fecundity and fertility life tables of the predator Brontocoris tabidus (Heteroptera: Pentatomidae) under field conditions.

Reproductive potential, longevity, life expectancy, and fertility life tables of Brontocoris tabidus (Signoret) (Heteroptera: Pentatomidae), a predator of lepidopteran defoliators in eucalyptus (Eucalyptus spp.) plantations, were studied in the field. After a 50-d preoviposition period (emergence of adults to the deposition of the first egg mass), ovipositional activity of B. tabidus continued until females died at 160 d. Females laid an average of 4.2 eggs per day and 601.1 eggs in a lifetime. Gross and net reproductive rates were 216.7 and 75.8 females, respectively. Generation time was 146.1 d, the period for doubling the population was 23.4 d, intrinsic rate was 0.03, and finite population increase was 1.03. Number of females per generation increased at 33.4 times. Results from our field studies indicate that B. tabidus has greater potential reproduction, oviposition period, and longevity than was expected from previous laboratory experiments. This suggests that B. tabidus has potential as a biological control agent to limit economically damaging pests in eucalyptus plantations.

Aging↗
PubMed2005

Importance of acclimation to environmentally relevant zinc concentrations on the sensitivity of Daphnia magna toward zinc.

Daphnia magna was acclimated for six generations to an acclimation range of 0.02 to 74 microg/L of Zn2+. This range was determined by combining physicochemical water characteristics of European surface waters with total Zn concentrations in these waters in such a way that they resulted in minimal and maximal free (i.e., assumed bioavailable) Zn ion activities. No significant differences were found in acute Zn tolerance between the different acclimation concentrations: Average 48-h median effective concentration (EC50) values ranged from 608+/-94 to 713+/-249 microg/L of Zn2+. Also, no significant shifts in chronic tolerance were observed: Average 21-d EC50 (based on net reproductive rate) ranged from 91+/-20 to 124+/-22 microg/L of Zn2+. However, at test concentrations less than the 21-d EC50, acclimation significantly increased the reproductive capacity of the offspring produced. This indicates that metal acclimation is not necessarily accompanied by an increase in tolerance but also may manifest in other responses (e.g., reproduction rate). Organisms acclimated to a range from 6 to 22 microg/L of Zn2+ produced significantly more offspring than organisms acclimated to lower and higher Zn concentrations in test concentrations up to 50 microg/L of Zn2+. This range corresponds to a previously established optimal concentration range for D. magna. Bioconcentration factors indicated that Zn was actively regulated in the acclimation range tested.

Acclimatization↗
PubMed2001

The presence of chemicals exuded by fish affects the life-history response of Ceriodaphnia cf. dubia to chemicals with different mechanisms of action.

The toxicity of chemicals with different mechanisms of action (3,4-dichloroaniline, fenoxycarb, and chlorpyrifos) to the cladoceran Ceriodaphnia cf. dubia was examined in the presence and absence of chemicals exuded by fish, termed fish kairomones. A range of life-history traits were examined, including mean brood sizes, survival, net reproductive rate (Ro) and population growth rate (r). Cladocerans exposed to 3,4-dichloroaniline showed similar sensitivities in the presence and absence of fish kairomones with respect to all of the life-history traits examined. The presence of fish kairomones reduced the sensitivity of cladocerans to fenoxycarb with respect to mean brood sizes and r but increased their sensitivity in terms of Ro. The presence of fish kairomones increased the sensitivity of cladocerans to chlorpyrifos with respect to survival, r, Ro, and mean brood sizes. The general trends observed were similar to those shown when C. cf. dubia was exposed to these chemicals under low food conditions, and it is suggested that the effects of fish kairomones on toxicity may be attributed to the reduction in feeding rates observed when C. cf. dubia is exposed to fish kairomones.

Aniline Compounds↗
PubMed1991

Epidemio-entomological survey of Japanese encephalitis in Korea.

In order to determine the seasonal prevalence and population dynamics of Culex tritaeniorhynchus in relation to the epidemics of Japanese encephalitis, and ecology of these vector mosquito in Kyungpook Province, Korea, studies were conducted during the period of 7 years from 1984 to 1990. Cx. tritaeniorhynchus first collected in June between 4th and 28th, and trapped in large numbers during the period from mid-August to early September, showed a simple sharply pointed one-peaked curve. There was a gradual decrease from mid-September, with a very small number of them collected until early October in every year. The average number of Cx. tritaeniorhynchus rapidly decreased after 1985, and the number became particularly low in 1989. The highest population density, which was observed in August during the initial three years, was found to be delayed in the following years, accompanied by a decrease in the number of mosquitoes. In the trend of nocturnal activity of Cx. tritaeniorhynchus, with oncoming darkness they become very active, gradually decreasing in activity toward mid night, but slightly increasing toward dawn. The immature stages of Cx. tritaeniorhynchus were first found in rice fields contributing to peak adult densities in mid-July. The highest average densities of Cx. tritaeniorhynchus was 14,900 per m2 on mid-August 19th. The larval Cx. tritaeniorhynchus showed high resistance levels and resistance ratios against 5 organophosphorus compounds. In the adult horizontal life table characteristics of Kyungsan colonies of Cx. tritaeniorhynchus under insectary conditions, life expectancy was 28.3 days for males and 59.8 days for females. The net reproductive rate was 7.8 and generation time was 25.6 days.

Animals↗
PubMed2006

Variation in life table characteristics among populations of Phlebotomus papatasi at different altitudes.

Baseline biological growth data were obtained under laboratory conditions for four local populations of the phlebotomine sand fly R papatasi (Scopoli, 1786) (Diptera: Psychodidae) in different eco-regions at altitudes between 368 and 1117 m in the Sanliurfa province of Turkey. The developmental time from egg to adult was found to be significantly different among the populations: 36 days for the AKL population (368 m), 43 days for the HHR population (488 m), 45 days for the HMD population (644 m), and 49 days for the ALT population (1117 m), respectively. Based on cohorts of adults in each population, horizontal life tables were constructed. The average longevity was determined to be in the range of 8.75 +/- 2.39 to 11.60 +/- 3.48 days for adult females, and it was found to be slightly longer for adult males. No significant difference was found in life expectancy at emergence, e(x) when x=1, between females and males in general (P>0.05) in all the populations. While significant differences could be demonstrated among populations for predictive parameters such as net reproductive rate, Ro, and generation time, Tc, no significant differences among the populations were found in terms of intrinsic rate of increase, r(m), finite rate of increase, lambda, birth (b) and death (d) rates (P>0.05). Populations that produced offspring earlier in life also produced more total female offspring, since Tc was negatively correlated with Ro among the populations (r = -0.686, 0.01<P<0.05). Twenty-seven parameters in all life stages, both pre-adult and adult features of R papatasi, were used as physiological variables and these operational taxonomic units were analyzed using Principal Component Analysis. Analyses confirmed results from the previous morphometric and molecular studies that the Alitas population orientated and clustered as a distinct group along the first two PCs.

Altitude↗
PubMedDate not supplied

Knowledge and attitudes of rural adolescent girls regarding reproductive health issues.

BACKGROUND: Adolescent girls (10-19 years old) comprise about 22% of women in India. They are the mothers of tomorrow and the burden of planned reproduction rests on them. Yet very little is known about their knowledge and attitudes towards reproductive health issues--a crucial aspect if India is to achieve the net reproduction rate of 1 by AD 2016. This study aimed to gather information on areas required for the planning of family life education strategies. METHODS: This cross-sectional study was conducted in the government schools and anganwadi premises of three villages of the primary health centre, Chhainsa, under the Comprehensive Rural Health Services Project Area (CRHSP), Ballabgarh, Haryana. The participants were 254 girls aged 13 to 17 years, who had attained menarche. A pre-tested interview schedule was administered to each girl after taking permission from the principals and parents and with the consent of the participants. The knowledge and attitudes regarding age at marriage, concept of small family norm, family size and preference for a son were assessed. RESULTS: All the girls were aware that there is a law regarding legal age of marriage but only 165 (65%) of them knew the correct legal age. Early marriage was preferred by 19 (7.6%). Though 214 (84.3%) girls were aware of the small family norm, only 19 (8.8%) knew the exact norm. A preferred family size of two or less was reported by 151 (59.2%). Preference for a son was reported by 233 (91.7%). CONCLUSION: All the girls were aware of the small family norm, but few could correctly define it. Though most girls preferred a two-child family, almost all of them had a preference for at least one son. This preference for a son could dominate their future decision-making. As attitude development is a long-term process, there is indeed a long way to go.

Adolescent↗
PubMed1987

Effect of declining fertility on population aging in India: an application of Coale's analytical model.

This paper attempts to gauge the effect of constantly declining fertility on population aging in India through the application of an analytical model proposed by Ansley Coale (1972), which employs stable population theory. The author has assumed a linearly constant fertility decline in India to obtain a net reproduction rate equals 1 by the year 2001. The projected age distribution in 2001 shows that the proportions of males and females aged 65+ will be 3.66% and 3.98% respectively. This means that there would be an increase of 7.3% in the proportion of males (65+) from 1971 to 2001. The corresponding increase for females is more, 17.4%. The median age of males increases from 16.59 to 22.92 years during the same period. For females, the increase is from 16.64 to 22.75 years. Although the proportional increase of the aged is not very substantial, the absolute magnitude it implies is very large. It has far reaching implications in the development process in India.

Adult↗
PubMed1982

Long-range global population projections, as assessed in 1980.

UN medium range projections prepared in the 1980 assessment projected the population of individual countries up to the year 2025. The long range projections discussed here were prepared by projecting the population of 8 major world regions from 2025-2100. The purpose of the projection was to observe the implications of the changes from the 1978 assessment made in the 1980 medium range projections on the long range projections of the world's populations. As in previous projections, high, medium, and low variants were prepared in which fertility is assumed to be constant at the replacement level but at different times in the future. In addition, these projections contain 2 variants not previously prepared--namely, the growth and decline variants, in which the ultimate net reproduction rate is 1.05 and 0.95, respectively. In all the variants, expectation of life at birth is assumed to reach 75 years for males and 80 for females. According to the current medium variant projection, the earth's population will become stationary after 2095 at 10.2 billion persons, compared with a total of 10.5 billion projected in the 1978 assessment. The lower projection is largely attributable to a recent decline in the growth rate of several countries in South Asia which was greater than previously assumed. When the world population becomes stationary, both crude birth and death rates would be about 13/1000. In the decline variant, total population would peak at 7.7 billion in 2055, then decline gradually to 7.2 billion in 2100. The total population as projected by the growth variant would equal 14.9 billion in 2100 and would still be growing slowly. Between 1980 and 2050, 95% of the world's growth will occur in the currently less developed regions. Their share of total population will increase from 75-85% during that period. The age structure in all regions is expected to converge to 1 in which the median age is 39 years, the proportion both below age 15 and above age 64 is about 19% each, and the dependency ratio is about 60. A precise degree of accuracy cannot be specified, but the argument is made that the actual future population of the world is very likely to fall within the range of the projection variants and probably not far from the medium variant.

Africa↗
PubMed1986

[Age, parity, and time in fertility].

The authors analyze fertility trends in Japan from 1935 to 1969 using "vital statistics data upon which age-parity adjusted net reproduction tables were constructed for 35 different female birth cohorts." These tables are used to calculate "cohort net reproduction rate and total fertility rate by parity and age, [as well as] mean age at first birth, second birth, etc. and average length of birth interval in each cohort." (summary in ENG)

Age Factors↗
PubMed2004

Pathogenicity of the fungus, Verticillium lecanii, to the green peach aphid, Myzus persicae (Hom.: Aphididae).

Pathogenicity of the hyphomycete, Verticillium lecanii (DAOM 198499), was investigated to aphid, Myzus persicae under laboratory conditions. Analysis of lethal effect of six various concentrations 0, 10(4), 10(5), 10(6), 10(7) and 10(8) conidia/ml of V. lecanii against third nymphal stage of M. persicae, indicated significant mortality on aphids. Mean comparisons showed that there was significant difference between treatments. Three days after treatment, aphid mortality observed and after 12 days minimal mortality was 17.77 in control and maximum was 100 percent related to 10(7) and 10(8) conidia/ml. LC50 and LT50 values were estimated by probit analysis and life test. LC50 value for aphid mortality was 1.4 x 10(4) conidia/ml, LT50 values for concentrations 10(4), 10(6), 10(6), 10(7) and 10(8) conidla/ml was 10, 10, 9, 8 and 6 days, respectively. In this experiment, net reproduction rate of aphid's (R0) decreased significantly when concentration increased. These observations showed that V. lecanii (DAOM 198499) can be an active biological agent against aphids.

Animals↗
PubMed2005

Virulence evolution in emerging infectious diseases.

Models of virulence evolution generally consider the outcome of competition between resident and mutant parasite strains at or near endemic equilibrium. Less studied is what happens during the initial phases of invasion and adaptation. Understanding initial adaptive dynamics is particularly important in the context of emerging diseases in wildlife and humans, for which rapid and accurate intervention may be of the essence. To address the question of virulence evolution in emerging diseases, we employ a simple stochastic modeling framework. As is intuitive, the pathogen strains most likely to emerge are those with the highest net reproductive rates (R0). We find, however, that stochastic events shape the properties of emerging pathogens in sometimes unexpected ways. First, the mean virulence of emerging pathogens is expected to be larger in dense host populations and/or when transmission is high, due to less restrictive conditions for the spread of the pathogen. Second, a positive correlation between average virulence and transmissibility emerges due to a combination of drift and selection. We conclude that at least in the initial phases of adaptation, special assumptions about constraints need not be invoked to explain some virulence-transmission correlations and that virulence management practices should consider how residual variation in transmission and virulence can be selected to reduce the prevalence and/or virulence of emerging infectious diseases.

Biological Evolution↗