The adaptative value of hatching towards the end of the night: lessons from eggs of the haematophagous bug, Rhodnius prolixus

SCHILMAN, P.E., MINOLI, S.A. & LAZZARI, C.R.

PHYSIOLOGICAL ENTOMOLOGY (PRINT)

Blackwell Publishing

Lugar: Oxford, England; Año: 2009 vol. 34 p. 231 - 237

0307-6962

The daily hatching rhythm of Rhodnius prolixus eggs is established under LD 12:12 h. The endogenous nature of this rhythm is demonstrated under continuous darkness. Hatching takes place during the last half of the night, when the maximum environmental relative humidity (RH) and minimum temperature (i.e. combination that yields the lower water vapour saturation deficits) occur in wild habitats. This temporal window of about 7 h recurs at 24-h intervals producing a hatching rhythm in the population. The effects of the RH upon egg-hatching are analysed. In agreement with previous reports, hatching success is strongly affected by environmental RH. Whilst 88% of eggs hatch at 75% RH, only 4% and 10% hatch at 0 or 100% RH, respectively. These results support the hypothesis that temporal synchronisation is related to the avoidance of low environmental RHs, high environmental temperatures, or high water vapour saturation deficit during hatching, thus minimising their deleterious effects. Given that eggs cannot choose optimum microclimatic conditions, selective pressures seem to have originated from an adaptive temporal rather than spatial hygropreference.