Article
Physical features and chitin content of eggs from the mosquito vectors Aedes aegypti, Anopheles aquasalis and Culex quinquefasciatus: Connection with distinct levels of resistance to desiccation
Registro en:
FARNESI, Luana Cristina; et al. Physical features and chitin content of eggs from the mosquito vectors Aedes aegypti, Anopheles aquasalis and Culex quinquefasciatus: Connection with distinct levels of resistance to desiccation. Journal of Insect Pathology, v.83, p.43-52, Dec. 2015.
0022-1910
10.1016/j.jinsphys.2015.10.006
1879-1611
Autor
Farnesi, Luana Cristina
Menna-Barreto, Rubem Figueiredo Sadok
Martins, Ademir Jesus
Valle, Denise
Rezende, Gustavo Lazzaro
Resumen
Mosquito eggs are laid in water but freshly laid eggs are susceptible to dehydration, if their surroundings
dry out at the first hours of development. During embryogenesis of different mosquito vectors the serosal
cuticle, an extracellular matrix, is produced; it wraps the whole embryo and becomes part of the eggshell.
This cuticle is an essential component of the egg resistance to desiccation (ERD). However, ERD is variable
among species, sustaining egg viability for different periods of time. While Aedes aegypti eggs can survive
for months in a dry environment (high ERD), those of Anopheles aquasalis and Culex quinquefasciatus in the
same condition last, respectively, for one day (medium ERD) or a few hours (low ERD). Resistance to desiccation
is determined by the rate of water loss, dehydration tolerance and total amount of water of a
given organism. The ERD variability observed among mosquitoes probably derives from diverse traits.
We quantified several attributes of whole eggs, potentially correlated with the rate of water loss: length,
width, area, volume, area/volume ratio and weight. In addition, some eggshell aspects were also evaluated,
such as absolute and relative weight, weight/area relationship (herein called surface density) and
chitin content. Presence of chitin specifically in the serosal cuticle as well as aspects of endochorion
external surface were also investigated. Three features could be related to differences on ERD levels:
chitin content, directly related to ERD, the increase in the egg volume during embryogenesis and the eggshell
surface density, which were both inversely related to ERD. Although data suggest that the amount of
chitin in the eggshell is relevant for egg impermeability, the participation of other yet unidentified eggshell
attributes must be considered in order to account for the differences in the ERD levels observed
among Ae. aegypti, An. aquasalis and Cx. quinquefasciatus.