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At least 685 records · Page 38Linked to original sources
PubMed1976

Seasonal variation in the population dynamics of Caryophyllaeus laticeps.

The biological parameters which generate seasonal fluctuations in the size of populations of Caryophyllaeus laticeps are examined in detail. A mathematical model is formulated to describe the dynamics of the adult parasite within the fish host Abramis brama, and the predictions of the model are compared with observed population data. The seasonality of parasite population size is shown to be caused by the combined effects of a temperature dependent mortality rate and flucate of larval parasites. The observed overdispersed distribution of adult parasite numbers within the host population is shown to be generated by variability in feeding habits between individual members of the fish population. The theoretical population model is used as a framework for the investigation of, among other factors, the comparative influences of the immigration and death rates on the dynamics of the adult parasite, the future behaviour of the system under altered environmental conditions and the importance of chance effects in the dynamics of individual parasite populations within a single host. The stability of the dynamics of the complete life-cycle of C. laticeps is discussed in relation to the inherent biological complexity of host/helminth parasite interactions.

Animals↗
PubMed1997

RNA virus evolution, population dynamics, and nutritional status.

Trace elements exert a strong influence on immune function. Debilitated humoral and cellular immune responses may impair virus clearance in infected organisms, and favor the generation of virus variants with altered biological properties. The population size in evolving viral quasispecies, as well as increased mutagenesis triggered by oxidative stress, may contribute to altering the outcome of quasispecies evolution in infected hosts. The genetic plasticity of RNA viruses is one of the main obstacles for the control of the diseases they cause and probably a major force in the emergence of new viral pathogens. Recent results suggest links between nutritional deficiencies and the generation of variant viruses, a possibility that is addressed in the present article.

Animals↗
PubMed2000

Longitudinal studies of Aedes aegypti (Diptera: Culicidae) in Thailand and Puerto Rico: population dynamics.

Aspiration collections of adult Aedes aegypti (L.) were made weekly from inside and outside of houses for 3 yr in a rural Thai village (n = 9,637 females and n = 11,988 males) and for 2 yr in a residential section of San Juan, Puerto Rico (n = 5,941 females and n = 6,739 males). In Thailand, temperature and rainfall fell into distinct seasonal categories, but only temperature was correlated with fluctuations in female abundance. Average weekly temperature 6 wk before mosquitoes were collected and minimum weekly temperature during the week of collection provided the highest correlations with female abundance. Accounting for annual variation significantly improved Thai models of temperature and mosquito abundance. In Puerto Rico, temperature, but not rainfall, could be categorized into seasonal patterns. Neither was correlated with changes in female abundance. At both sites the vast majority of females were collected inside houses and most contained a blood meal. Most teneral females were collected outside. Wing length--an indicator of female size--and parity, egg development or engorgement status were not correlated, indicating that feeding success and survival were not influenced by female size. At both sites, females fed almost exclusively on human hosts (> or = 96%), a pattern that did not change seasonally. In Puerto Rico more nonhuman blood meals were detected in mosquitoes collected outside than inside houses; no such difference was detected in Thailand. Gut contents of dissected females indicated that females in the Thai population had a younger age distribution and fed more frequently on blood than did Ae. aegypti in Puerto Rico. Our results indicated that aspects of this species' biology can vary significantly from one location to another and 1 yr to the next.

Aedes↗
PubMed1995

Some unknown episodes in the history of population dynamics concerning the logistic law: the lesson of the great epidemiologists.

The author discusses the work of "the two great epidemiologists R. Ross and A. G. McKendrick. This talk is basically devoted to their 'lesson' about logistic theory and it is organised as follows: section 2 is devoted to McKendrick's [1911] contribution to the growth of microorganism populations, a paper which was not widely acclaimed, but which marks the first experimental laboratory verification of the logistic law. Section 3 is also devoted to McKendrick and to the way he repeatedly derived the logistic equation as a model for 'simple epidemics'. Finally, in section 4, we present Ross's 'A priori pathometry' theory that really emphasizes...the role played by the logistic law as the 'first principle' of the mathematical epidemiology."

Demography↗
PubMed2006

Population dynamics of an endogenous meiotic drive system in Aedes aegypti in Trinidad.

An endogenous meiotic drive system was previously reported to be segregating in the yellow fever mosquito Aedes aegypti L. (Diptera: Culicidae) population in Trinidad. The meiotic driver (M(D)) is tightly linked to the male determining locus and selectively targets sensitive responders linked to the female determining allele, causing fragmentation of female gametes. This results in highly male-biased progeny. The M(D) system was initially studied as a genetic tool for population control with limited success, but recently interest has focused on its potential for population replacement. This study examines the distribution and dynamics of the M(D) system in Trinidad natural populations. We obtained ovitrap samples from seven geographically distinct regions and determined the allele frequencies of the driver (M(D)) and sensitive (m(s)) versus insensitive (m(i)) responders, respectively. Frequencies of the M(D) allele ranged from 0.1 to 0.5 and were low at the two major port cities, Port of Spain and San Fernando, suggesting the effects of frequent immigration by non-driving genotypes. Frequencies of the m(i) allele ranged from 0.4 to 0.7, suggesting the effects of strong selection by the driver. In addition, our results show that the driver and sensitivity of responders in the Trinidad populations are highly polymorphic. Continued studies of the dynamics of the M(D) system in natural populations are critical to considerations of its use in population replacement.

Aedes↗