Structures involved in production, secretion and injection of the venom produced by the caterpillar Lonomia obliqua (Lepidoptera, Saturniidae)

The number of accidents caused by injection of the venom of Lonomia obliqua caterpillars in Southern Brazil has increased in the last years. Even thou gh this kind of envenomation has an important social and medical impact, no thing is known about the cellular structures responsible for the production and secretion of this venom. Here we identify and analyse morphological st ructures possibly responsible for the production and secretion of the activ e principles of the venom, as well as the histological relationship of thes e structures with the urticating spines of L. obliqua. Detailed microscopic observations showed that: (a) L. obliqua has a complex tegument, with seve ral cuticular specializations, (b) there are no pores along the tegument ne ither in the spines and (c) the spines bear a hollow canal-where the venom is deposited-and an area that can be easily broken when touched, releasing the venom. Histological and histochemical techniques revealed that: (a) the re is no single gland cell that produces the venom, (b) a secretory epithel ium, composed of cells containing Vesicles that increase in size and number as they reach the apical region, underlies the tegument and the spines and is responsible for secretion of the venomous substances and (c) the venom is deposited in the subcuticular space and at the tips of the spines. (C) 2 001 Elsevier Science Ltd. All rights reserved.