Characterization of the larval habitat of mosquitoes in Northern Patagonia, Argentina

Patagonia has a cold climate with a dry season during the mosquito breeding period. Little is known about the reproductive habitats in Patagonia and Aedes aegypti was found in Neuquén. Climate change could encourage mosquito migration to cold areas. Objective: to characterize the reproductive habitats of mosquitoes and identify the genera in Junín de los Andes. Methodology: hydrosphere and biosphere protocols of the GLOBE Program were applied. Results: Only the genus Culex sp. was found. The puddles are protected by trees and herbs, the water quality between the puddles is similar, with little oxygen, high turbidity and alkalinity. The diversity of macroinvertebrates is low compared to the river. Knowing the breeding habitats allows to design prevention and control systems.

When the Aedes mosquito was detected in Patagonia, we were alarmed. Before it was a problem in the North of Argentina, then in the Center and now in the South. We were investigating the quality of the river water and began investigating puddles with mosquito larvae characterizing their habitats.

Mosquitoes are considered the most dangerous animal in the world due to the large number of deaths they cause each year. Mosquitoes are disease vectors because they can be infected by various pathogens that transmit them through bites. Their life cycle begins when the female lays the eggs in places with water (which can be very diverse from small plastic containers discarded such as garbage, tires, temporary puddles, holes in trees that accumulate water or permanent puddles, etc.). A larva emerges from the eggs, which passes to the pupal stage and then the adult emerges that has air-ground life. Adults feed on sugary substances such as flower nectar and females also require blood for the development of their eggs. The bites are caused by females. Mosquitoes are distributed around the world. The modification of natural habitats, climatic factors and the high mobility of people and goods in the world favors dispersal to other areas. Some diseases like dengue have increased 30-fold on a global scale in the last 30 years and more countries are reporting their first outbreaks of the disease. Zika, dengue, chikungunya, and yellow fever are transmitted to humans by the Aedes aegypti mosquito. In 2012, the presence of Aedes aegypti was reported for the first time in the city of Neuquén (North Patagonia region), extending south of its previously reported limit. Environmental factors such as temperature, land cover, dissolved oxygen, conductivity, and pH can affect the number of macroinvertebrate mosquito predators and the larvae that are their prey. These fluctuating abiotic factors affect predators and prey differentially. Understanding the biological limits of mosquito species to abiotic factors, as well as the structure of their habitat in environmental gradients, can provide useful information for developing prevention and control strategies for mosquito populations. The objective of this work was to characterize the habitat of mosquitoes in the North Patagonia region, the quality of the water where they develop and the environmental conditions that allow them to survive in cold and arid environments. In the summer of 2020, the puddles formed by the Chimehuín River in the vicinity of Junín de los Andes were sampled. Physical-chemical analyzes of water quality (temperature, pH, alkalinity, turbidity, dissolved oxygen, electrical conductivity and nitrates) were carried out in the mosquito puddles and in the Chimehuín river near each puddle. In addition, the macroinvertebrates present were identified at the sampled sites. A land cover classification was made at each sampling site and environmental data was analyzed from satellite images and meteorological data. In the summer of 2021, the evolution of a puddle was followed to document changes in populations of mosquitoes and other macroinvertebrates. Both samplings were limited in time due to the restrictions of the covid-19 pandemic. The results show that the topography of the area with many slopes hinders the formation of puddles and the accumulation of water. Puddles are short-lived and run rapidly down slopes or through evaporation. Puddles only form on the banks of the Chimehuín River when its flow decreases in summer. Most of the puddles sampled did not contain mosquito larvae, only a few puddles had larvae and pupae. The water in the puddles has a very low oxygen level, high alkalinity, turbidity and conductivity, unlike the Chimehuín River. The temperature is similar, since the puddles are in areas with trees and canopy cover. The pH is similar and no nitrates were detected in any of the samples. Puddles with mosquitoes, in general, are characterized by being closed, ephemeral, with high turbidity, alkalinity and conductivity. The dissolved oxygen content is very low. Mosquito larvae are not found in puddles with flowing water, even if it is small. The alkalinity, turbidity and conductivity values are slightly lower than in mosquito puddles. The water quality of the Chimehuín River is better than in the puddles, where mosquito larvae develop. The diversity of macroinvertebrates is also greater in the river than in the puddles. In the puddles with mosquito larvae, only amphipods are usually found, but cases with large populations of daphnia and other macroinvertebrates were found in smaller numbers. The data indicate that female Culex mosquitoes are choosing critical environments for other macroinvertebrates that could prey on them. It is recommended to carry out a greater number of investigations to know the species and habitats of mosquitoes in Patagonia. Knowing the characteristics of habitats can be useful to design larval control systems and mitigate the effects of mosquito movements due to climate change towards areas that are currently extreme for their development.