TOLERANCE OF DESICCATION IN BEETLES FROM THE HIGH ATLAS MOUNTAINS

Resistance to desiccation was studied in eight species of beetles from Oukaimeden at 2600-3200 m in the High Atlas Mountains, Morocco. Lowes t water loss rates and high tolerance to water losses were found in fi ve species of tenebrionids. Seven of the eight species were diurnal, a nd only the tenebrionid Pimeli thomsoni was seen to be active in direc t sunlight. The carabid Harpalus dissitus had a high water loss rate a nd low tolerance to water loss. The chrysomelid Timarcha mairei and th e curculionid Gonocleonus insculpturatus represented an intermediate p osition. The tenebrionids Pimelia sp., P. thomsoni and Opatrum rhaticu m were non-regulators and tolerated dehydration of more than 50%. Tima rcha spp regulated haemolymph osmolality which remained almost unchang ed for water losses up to 46%. In nocturnal O. rhaticum, the O-2 consu mption was highest during the night and higher in beetles from 3100 m than from 2600 m. Pimelia sp., P. thomsoni and T. mairei displayed the highest respiratory rates during the day. A smaller rise in O-2 consu mption between 15 and 20 degrees C than between 10 and 15 degrees C wa s seen in the diurnal species. This may also be of adaptive significan ce in a hot and dry environment. It was also concluded that respiratio n is the main source of water loss in most of the species.