Constant Temperature and Time Period Effects on Anopheles Gambiae Egg Hatching

Abstract

Anopheles gambiae Giles sensu stricto (Diptera: Culicidae) egg development and its relation to environmental parameters is an understudied aspect of vector biology. Although several studies have illustrated the dramatic effects of temperature on egg development, egg hatching dynamics remain unclear. The objective of this study was to expose An. gambiae eggs to various temperatures for different lengths of time and determine the impact on egg development and hatching count. Batches of mosquito eggs (n = 30 eggs/replicate) were incubated under moist conditions at temperatures of 12, 22, 27, 33, and 42 degrees C for intervals of 1, 3, 7, and 10 days. After that, they were flooded with distilled water at 27 degrees C, and hatching counts were observed for up to 7 days. Mosquito eggs held at 22 and 27 degrees C had the highest overall mean hatching count. During early incubation periods, eggs held at 33 degrees C had hatching counts comparable to 22 and 27 degrees C, but counts decreased drastically during later incubation periods. Temperatures of 12 and 42 degrees C reduced mosquito egg viability, because few eggs hatched in these temperature regimes. Other experiments revealed that during early embryonic development, temperature had a major effect on the developing embryo, while later in embryonic development it had no dramatic effect. Microscopic observation of the An. gambiae embryo showed that extreme low and high temperatures affected the normal development of the embryo. A regression model was developed to describe the effect of incubation temperature and incubation period on egg hatching counts, which demonstrated that the optimum temperature for egg hatching ranges from 24 to 30 degrees C, irrespective of incubation period. The interaction between temperature and time period may have implications for dry-season survival and climate-based models of malaria risk.

Effect of Larval Density and Host Species on Preimaginal Development of Bactrocera tau (Diptera: Tephritidae)

“…Similarly, other study showed that limes were not hosts to the Caribbean fruit ßy (Hennessey et al 1992). Compared with host species, other conditions such as temperature and relative humidity make a greater impact on the egg incubation periods and viability (Impoinvil et al 2007, Mc Donnell et al 2007.…”

Rethinking vector immunology: the role of environmental temperature in shaping resistance

“…Predicting how these environmental variables combine to mechanistically influence the suite of factors involved in resistance is clearly a complex problem. That said, not all environmental parameters will have equal effects on vector fitness, physiology and resistance; evidence 14–18 (Supplementary information S1 (table)) suggests that temperature is a strong driver, whereas other variables can have little or no effect. Unravelling patterns and mechanisms from the complexity of natural systems requires an interdisciplinary perspective drawing on insights from ecology, immunology and molecular biology.…”

“…Second, mosquitoes are small-bodied, ectothermic insects. Many studies have already demonstrated that temperature can markedly affect diverse aspects of mosquito physiology and ecology, including the rate and viability of egg hatching 14 , the rate of development 15–17 , the propensity to feed and the rate of feeding 18 , and survival 15 . It would be surprising if immune function were any different.…”

Temperature during larval development and adult maintenance influences the survival of Anopheles gambiae s.s.

“…Data have been reported on the influence of adult temperature on adult survival [14][15][16][17][18]. Fewer data exist on the influence of juvenile environmental temperature on juvenile survival [19][20][21][22][23], but none exist, to our knowledge, on the influence of environmental temperature during the juvenile stages on adult mortality, although temperature throughout the mosquito's development may have repercussions on its survival [24].…”