Long-term storage and viability of Ochlerotatus albifasciatus (Diptera: Culicidae)

Abstract

The viability of Ochlerotatus albifasciatus (Macquart) eggs stored at room temperature and at 5ºC was studied over 31 months. After 12, 18 Ochlerotatus albifasciatus (Macquart) is a floodwater mosquito of medical importance (Mitchell et al. 1987) distributed from tropical Brazil (Forattini et al. 1988) to cold areas in Argentina (Rossi et al. 2006). Larval sites are temporary, semi-permanent and ephemeral pools, with a high variation in the water level (Maciá et al. 1995). As a consequence of the heterogeneous larval sites, Oc. albifasciatus eggs have adopted strategies that allow them to survive under unfavorable environmental conditions. When eggs are either immersed in cold water or remain dry they enter a quiescence or diapause (Campos & Sy 2006, 2007. When environmental conditions turn favorable a proportion of the eggs hatch while others remain in dormancy until the next flooding (Campos & Sy 2006). This behavior, characterized by the occurrence of partial hatchings, is called installment hatching, and has been interpreted as a reproductive strategy that permits multivoltine species that breed in ephemeral pools to survive for long periods (Andreadis 1990). Thus, installment hatching and resistance to low temperature and lack of water, permit Oc. albifaciatus survive in regions where rainfall and temperature are highly variable (Campos & Sy 2007).Several studies on Aedine mosquitoes, mainly from tree hole and container habitats, have been carried out to estimate egg survival (e. g., Christophers 1960). For example, Gubler (1970) (Gjullin et al. 1950). Survivorship of floodwater mosquito eggs has been studied from different regions all over the world, but is unknown from neotropical species.The objective of this study was to determine the resistance of Oc. albifasciatus eggs to long dry periods, testing the hypothesis that Oc. albifasciatus eggs survive after a long dry period independently of storage temperature.The experiment was carried out with eggs obtained from wild-caught females of Oc. albifasciatus captured with a manual aspirator at Pereyra Iraola Provincial Park (34º 51'S; 58º 08'W), province of Buenos Aires, Argentina, from May to June 2004. Mosquitoes were blood fed on a guinea pig and stored individually in tubes (6 cm in height x 3 cm in diameter) with a moist piece of towel paper resting on a cotton pad at the bottom of the tube. After oviposition, females were withdrawn and the tubes sealed with plastic film to maintain humidity. Eggs remained at room temperature for over nine days to ensure complete maturity of embryos (Fava et al. 2001).Batches (batch = group of eggs laid by a single female during one gonotrophic cycle) were pooled and randomly assigned to one of two treatments. Eggs from one treatment were kept at room temperature, and the other was stored in the dark at 5ºC. All batches with fungal or bacterial contamination during storage were excluded from the experiment.After 12, 18, and 31 months of storage, 20 batches from each group were flooded except for the group of 18 months...

Resistance to freezing temperatures inAedes (Ochlerotatus) albifasciatus(Macquart) eggs (Diptera: Culicidae) from two different climatic regions of Argentina

“…However, the hatching percentage was high regardless of exposure to freezing temperatures, suggesting that an extreme thermal event does not influence egg hatching in either population. The highest percentage of egg hatching occurred after the first flooding, without previous freezing, as earlier noted by Campos ().…”

Coffee and its waste repel gravid Aedes albopictus females and inhibit the development of their embryos

“…The ease of hatching of Aedes eggs is dependent on the adequacy of water uptake during development. Indeed, eggs that absorb sufficient water hatch easily and at a greater rate than those that take up less water [ 89 , 82 ]. In the present study, maturation in the HCE environment resulted in a low hatching rate compared to maturation in low-concentration coffee-contaminated environment (MCE filter paper); almost all eggs maintained in the water environment hatched.…”

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

“…Then, the eggs were placed on plastic trays (12 × 12 × 6 cm 3 ) and flooded with tap water with 10 mL of a solution containing water and dried Brewer's yeast to stimulate hatching (Campos & Sy, 2006;Campos, 2008).…”