Investigation of egg development in the brown locust, Locustana pardalina (Walk.) (Orthoptera: Acrididae)

• Main Author: Kambule, Innocent Nqaba
• Format: Others
• Language: en
• Published: 2010
• Online Access: http://hdl.handle.net/10539/8276

Locustana pardalina (Walk.) eggs have the ability to survive during drought. Diapause and quiescence, both types of dormancy, play a major role in contributing to brown locust survival under arid conditions by preventing immediate hatching and allowing build-up of eggs in the soil which contributes to swarming. This study investigated the water balance, hydropyle cell structure, tracking of development and the metabolic rate of eggs in different states. The eggs have the ability to resist desiccation and to survive water loss when it occurs. Locustana pardalina eggs consist of 66 % water and can lose almost all the water during desiccation. Hydropyle cell structure showed morphological structures such as lateral infoldings supporting evidence of active rather than passive water uptake. We showed that water absorption was immediate in non-diapause eggs and limited in diapause eggs. There was a general increase in hydropyle cell nuclear area and cell height during water absorption. We measured the metabolic rate of diapause and non-diapause eggs and directly linked these to embryonic development. Day 6 after laying seems to be the point at which some of the embryos in anatrepsis enter diapause and others continue development. The metabolic rate of non-diapause eggs increased exponentially until hatching while that of laboratory and field diapause eggs maintained a low stable metabolic rate. Eggs subjected to alternate drying and hydration showed adaptability by stopping development, lowering their metabolic rate while still maintaining the embryo. Locustana diapause and non-diapause eggs have the ability to control water absorption, resist desiccation and survive water loss. The maintenance of low stable metabolic rate of desiccation resistant diapause eggs contributes to the success of Locustana in harsh environments.