Ultrastructure of Spiracles of Rhizopertha dominica
The insect spiracle is in depression of integument,specialized from the body wall,is the gateway of the insect trachea system to the outside world.However,there are few reports on the ultrastructure of stored product pests.In the study,the distribution and morphological structure characteristics of spiracle in the last larvaes and a-dults were investigated using scanning electron microscope(SEM).It was found that there were 9 pairs of spiracles on the larvaes body surface,1 pair in the thorax and 8 pairs in the abdomen,the larval spiracles were located on both sides of the back,and each pair of spiracles was an effective spiracle,being multi-spiracle type,all of which were internal closing apparatus,the thoracic spiracle was significantly larger than the abdominal spiracle,the long axis of prothorax spiracle was(13.23±1.25)μm,the abdominal spiracles was between 5.38 μm and 10.89 μm.The ex-ternal view of the thorax and abdominal spiracles were irregular and round,and filter apparatus was spiny;there were 6 pairs of spiracles in adults,2 pairs in the thorax and 4 pairs in the abdomen;there were a pair of spiracles on the lateral membranes of mesothorax and metathoracic,a pair of spiracles on the lateral membrane of the abdominal 1~4 segments,all of which were internal closing apparatus.The spiracles were significantly smaller from the chest to the abdomen,the long axis of mesothorax spiracle was(19.09±2.00)μm,the abdominal spiracles was between 11.04 and 17.78 μm,except for the long axis of the third abdominal segment,the long axis of spiracle was(15.13±1.28)μm,similar in size to the first abdominal segment.The thoracic spiracles and the abdominal 1~3 throttle spi-racles were semicircular in appearance,and the spiracle of abdominal 4 segment was oblong,and filter apparatus was folding.In conclusion,the spiracle structure characteristics of different stages of R.dominica were analyzed,provi-ding reference for further research on respiratory activity,energy metabolism,phosphine resistance and hypoxia toler-ance and also enrich the spiracles database of Coleoptera insects.