Biomedical subjects

Carl D Schlichting

Publications and source records attributed to Carl D Schlichting.

5 recordsLinked to original sources

PubMed2006

Phenotypic plasticity and evolution by genetic assimilation.

In addition to considerable debate in the recent evolutionary literature about the limits of the Modern Synthesis of the 1930s and 1940s, there has also been theoretical and empirical interest in a variety of new and not so new concepts such as phenotypic plasticity, genetic assimilation and phenotypic accommodation. Here we consider examples of the arguments and counter-arguments that have shaped this discussion. We suggest that much of the controversy hinges on several misunderstandings, including unwarranted fears of a general attempt at overthrowing the Modern Synthesis paradigm, and some fundamental conceptual confusion about the proper roles of phenotypic plasticity and natural selection within evolutionary theory.

Adaptation, Physiological↗

PubMed2006

The importance of Anopheles albitarsis E and An. darlingi in human malaria transmission in Boa Vista, state of Roraima, Brazil.

In several districts of Boa Vista, state of Roraima, Brazil we found Anopheles (Nyssorhynchus) albitarsis E to be the primary vector of human malaria parasites, and during 2001-2002 it was significantly more abundant than An. darlingi (p < 0.001). Other species sampled were An. (Nys.) braziliensis, An. (Ano.) peryassui, An. (Nys.) nuneztovari, An. (Nys.) oswaldoi s.l., and An. (Nys.) triannulatus. As determined by the ELISA technique An. darlingi had a higher overall infection rate (2.1%) compared with An. albitarsis E (1.2%). However a marginally higher proportion of An. albitarsis E was infected with Plasmodium vivax compared with An. darlingi, and the An. albitarsis E biting index was also much higher These results suggest the importance of An. albitarsis E in malaria transmission in a savannah ecoregion of northern Amazonian Brazil, and reconfirm the importance of An. darlingi even if at lower abundance.

Animals↗

PubMed2003

Malaria vectors, epidemiology, and the re-emergence of Anopheles darlingi in Belém, Pará, Brazil.

An evaluation of malaria transmission and epidemiology in the Amazonian city of Belém over the last 70 years shows that (1) Anopheles darlingi, reported to be eradicated in 1968, reappeared in the mid 1990s, with a marked increase in abundance between 1997 to 1999 in two of three districts sampled; (2) An. darlingi and An. aquasalis are each implicated in current malaria transmission in different districts of the city; (3) mosquito species diversity (in Anopheles subgenus Nyssorhynchus) has increased from two in the 1930s to six in the 1940s to 10 in the 1990s; (4) there is no overall correlation between malaria case incidence and human population size from 1940 to 1996 in Belém; (5) however, the total number of malaria cases has increased significantly since the late 1970s and over the short term from 1993 to 1999; and (6) interestingly, the short term increases are due solely to cases of Plasmodium vivax infection; cases of P. falciparum malaria are declining (significantly for Pará state only). The reappearance of An. darlingi may be a result of the continued expansion of Belém into the surrounding forest in the 1990s. In the absence of preventative measures, we predict an increase in local outbreaks of malaria in the DAENT and DAICO districts where the population sizes of An. darlingi are increasing.

Animals↗

PubMed2002

Emergence of a new neotropical malaria vector facilitated by human migration and changes in land use.

In a region of northeastern Amazonia, we find a species previously of minor importance, Anopheles marajoara, to be the principal malaria vector. In a total of five collections during 1996-97 in three replicated sites near the city of Macapá, Amapá state, this species occurs in much greater abundance compared with the presumed vector Anopheles darlingi. Also, a significantly higher proportion of An. marajoara is infected with malaria parasites, determined by the ELISA technique. This appears to be the result of increased abundance of An. marajoara due to alterations in land use, invasion of its primary breeding sites by human immigrants, and its anthropophilic behavior. This discovery highlights one of the challenges of Neotropical malaria control, namely that the targeting of specific vectors may be complicated by a changing mosaic of different locally important vectors and their interactions with human populations.

Animals↗

PubMedDate not supplied

Origins of differentiation via phenotypic plasticity.

How cell types of multicellular organisms came to be differentiated is still an open issue. Here I offer a model that posits that the origins of some cell differentiation patterns were originally passive outcomes of environmental effects. As cells' contact with the external environment was diminished, their patterns of gene expression were altered, due to changes in concentrations of externally supplied substances. Later, as multicellular growth continued, the relationships of cell layers to each other shifted, producing concentration gradients of signaling molecules. These gradients emanated both from the external cell layer toward the inside and from internal cell layers to adjacent layers. In this scenario then, differentiation arose initially as a by-product of the changing patterns of gene expression and of the complex mixtures and changing concentrations of substances passing among layers. Subsequent selection would operate to stabilize the expression patterns in those cell layers whose phenotypes provide a fitness advantage to the organism.

Animals↗