The opening-closing rhythms of the subelytral cavity and associated gas exchange patterns were monitored in diapausing Leptinotarsa decemlineata beetles. Measurements were made by means of a flow-through CO2 analyser and a coulometric respirometer. Under the elytra of these beetles there is a more or less tightly enclosed space, the subelytral cavity (SEC). When the cavity was tightly closed, air pressure inside was sub-atmospheric, due to oxygen uptake into the tracheae by the beetle. In about half of the beetles regular opening-closing rhythms of the SEC were observed visually and also recorded; these beetles displayed a discontinuous gas exchange (DGE) pattern. The SEC opened at the start of the CO2 burst and was immediately closed. On opening a rapid passive suction inflow of atmospheric air into the SEC occurred, recorded coulometrically as a sharp upward peak. As the CO2 burst lasted beyond the closure of the SEC, we suggest that most of the CO2 was expelled through the mesothoracic spiracles. In the other half of the beetles the SEC was continually semi-open, and cyclic gas exchange (CGE) was exhibited. The locking mechanisms and structures between the elytra and between the elytra and the body were examined under a stereomicroscope and by means of micro-photography. We concluded that at least some of the L. decemlineata diapausing beetles were able to close their subelytral cavity tightly, and that the cavity then served as a water saving device.
- Received May 4, 2016.
- Accepted August 20, 2016.
- © 2016. Published by The Company of Biologists Ltd