Variation in the productivity (Ro), morphology and age specific mortality in Culex quinquefasciatus (Diptera: Culicidae) samples reared at different constant temperatures
Filiz Günay, Ergi Deniz Özsoy and Bulent Alten Hacettepe University Faculty of Science Department of Biology 06800 Beytepe-Ankara-TURKEY
Over the last six years, several vector-borne, parasitic or zoonotic diseases have emerged, re-emerged or spread in the European territory, especially in southern Europe, with major health, ecological, socioeconomical and environmental consequences. Most of these outbreaks are linked to global and local changes
as ecosystems, habitats, rangeland disturbances, mostly instabilities resulting of climatic changes or growth in human populations and their activities.
As we know that the earth’s climate is in a warming phase, a part of which may be due to human activities.
Both local and global changes may independently or in combination have a negative impact on human and animal health by favouring the spread of vector-borne diseases. Recent experiences with West Nile Virus show how diseases may appear in one continent, be transferred to other continents and become widespread
within the space of a very few months. Many of vector-borne diseases are not only dependent upon carriers that are themselves very sensitive to their environment, the local climate and weather, but also have some of the greatest capacities for rapid increase over short periods of time and for rapid evolutionary responses to
new situations.
It is well known that one of the most important factors affecting the biology and morphology of vectors is temperature. Hypothesis is that populations of Cx. quinquefasciatus rearing under different temperature regimes show subtle variations in reproductivity, morphology and also age specific mortality. A purpose of
this work is to evaluate the dissimilarities among cohorts reared at different five constant temperatures (15 oC, 20 oC, 23 oC, 27 oC and 30 oC) using geometric morphometrics and demographic techniques.
Maximum likelihood estimations of the rate of increase in age specific mortality (the b parameter from Gompertz function) were calculated in Culex quinquefasciatus samples reared at different temperatures.
Between temperature comparisons to assess if significant differences in age specific mortality occured rearing the samples at different temperatures were performed via a likelihood ratio test. In that way, variation in age specific mortality in response to temperature was defined in terms of a reaction norm after one
generation of rearing.
Rearing temperatures affected egg, larval and pupal formation and also the lenght of the developmental period from egg to imago. Furthermore, when temperature increased adult longevity decreased for both sexes. While significant differences could be demonstrated among cohorts for predictive parameters such as
net reproductive rate, Ro, and generation time, Tc, no significant differences among the cohorts were found in terms of intrinsic rate of increase, rm, finite rate of increase,, birth (b) and date (d) rates. As we know, the net reproductive rate (Ro), integrates several important variables, and is indicative for the absence (if<1) or
presence (if>1) of potential spread of disease. Therefore, Ro values and the productivity of all cohorts in different temperatures were determined as “presence (if>1)”. Almost 20 parameters in all life stages were used as phsiological variables and these operational taxonomic units were analyzed using Principal
Component Analysis (PCA).
Wing shape was analyzed using 22 wing landmarks following mosquito rearing at constant temperatures.
Geometric morphometric analysis showed that variables in wing shape and size were statistically correlated with rearing temperatures in both sexes..