Comparison of three methods for age-grading of female neotropical phlebotomine sandflies.

ABSTRACT

Changes in appearance of the accessory glands (AG), ovaries (OV) and the absence or presence of crease marks at the edges of the genital atrium armature (GA) were compared as methods to age-grade female laboratory-bred (Lutzomyia migonei) and wild-caught (Lu.youngi, Lu.spinicrassa, Lu.ovallesi) Neotropical sandflies. Dissections at different physiological stages revealed that all parous and high proportions of nulliparous (4/38) unmated, 12/12 mated) females showed similar residual AG secretions. Hence AG appearance (nullipars with AG translucent, versus yellowish opaque granulated AG previously regarded as signs of parousness) is unreliable for age-grading. Readily recognizable changes in both GA (98% creased) and the OV (100% yellowish with loose ovarioles) indicated that these organs could be employed to discriminate between nulliparous and parous females. Despite finding one misdiagnosed female (a nullipar having creased GA indicative of parity), the GA method of age-grading is recommended because females may be examined satisfactorily at any stage of the gonotrophic cycle. Moreover, the GA characteristics of pickled or dry preserved sandflies as well as fresh slide-mounted specimens can be determined easily. Among sixty-five wild-caught Lutzomyia females dissected (mostly Lu.spinicrassa and Lu.youngi), the proportions of specimens yielding preparations suitable for examination were 97% for GA, 89% for OV, but only 58% for AG, which reinforces GA as the preferred character for age-grading.