Thermal response in pre‐imaginal biology of Ochlerotatus albifasciatus from two different climatic regions

Abstract

The biological processes on mosquito could be variable in response to local climatic characteristics. The thermal effects on time and the rate larval development, immature survival and adult size in local populations of Ochlerotatus albifasciatus (Macquart) (Diptera: Culicidae) from cold (Sarmiento) and temperate (Buenos Aires) regions from Argentina were evaluated. This species affects livestock production and human health. Larvae of both regions were placed in breeding thermal baths (11-32 °C range). Development and survival were recorded daily until adult emergence. The development temperature threshold and thermal constant for Sarmiento (4.59 ± 3.08 °C, 204.08 ± 7.83 degree days) was lower and higher than Buenos Aires, respectively (8.06 ± 1.81 °C, 149.25 ± 2.6 degree days). At cold temperatures (11-16 °C), Sarmiento larvae demonstrated 5 days faster development and higher survival (56%) than Buenos Aires (15%), whereas at warm temperatures (20-32 °C) were up to 2 days slower and similar survival (16% vs. 18%). The size did not show differences between populations. An Ochlerotatus albifasciatus population seems to present local thermal responses. The favourable temperature for survival and rate of development would vary within a cold or warm range, and these differential responses would explain the wide geographical distribution in different climatic regions of southern South America.

Wing morphometrics of Aedes (Ochlerotatus) albifasciatus (Macquart, 1838) (Diptera: Culicidae) from different climatic regions of Argentina

“…The slopes indicate that the response of size change (centroid) to the temperatures for both sexes are the same. This would indicate the same metabolic response, where the physical assimilation of nutrients is lower with the increase in temperature, since the development is more accelerated [ 15 , 56 ].…”

“…This characteristic could be a local adaptation to the local climatic region (Patagonian) where the larval state must resist the daily thermal amplitude [ 36 ]. Local adaptations have also been suggested for other life-cycle parameters such as development time and survival [ 15 ].…”

“…Eggs were induced to hatch by immersing them in a yeast solution. Then, approximately 30 larvae were placed randomly in individual containers (cylindrical containers measuring 3 cm in diameter and 5 cm high with 10 ml of dechlorinated tap water) in thermal trays at constant temperatures in a range of 10–29 °C (3° C step) until they reached their adult form [ 15 ]. As the temperatures of the trays could be affected by ambient conditions, we placed temperature data loggers (Hobo®, Onset Computer Corporation, Bourne, MA, USA) in the trays, and took the mean recorded temperature instead of the system thermostat sensor reading.…”

“…To evaluate the geographical variation and sexual dimorphism as a function of the thermal range, the temperatures tested were divided into two sub-ranges: cool (10–17 °C) and warm (19–29 °C), based on the fact that the populations studied respond differently to the time of development as a function of warm or cool temperatures [ 15 ], which directly affects their size.…”

“…albifasciatus are related to gene flow restrictions between breeding areas of different geographical populations [ 13 , 14 ]. Otherwise, some temperature-dependent life-cycle parameters, such as development time and survival, present geographical variations [ 15 ]. These genetic and eco-physiological variations may result in local morphological forms (relative to size and shape) in response to contrasting climatic regions [ 16 , 17 ].…”