DEVELOPMENT OF THE VENOM APPARATUS IN THE ARMED SPIDER, Phoneutria nigriventer (KEYSERLING, 1891):  STRUCTURAL AND MICROANATOMICAL ANALYSIS

SILVA L. M. (1, 2, 3), BOTELHO A. C. C. (3), PIMENTA P. F. P. (3), FORTES-DIAS C. L. (1)

(1) Lab. Molecular and Cell Biology, Research and Development Center (DPD), FUNED, Belo Hte, MG, Brazil; (2) Dep. Morphology, UFMG, Belo Hte,  MG; (3) Lab. Medical Entomology, CPqRR/FIOCRUZ, Belo Hte, MG, Brazil.

The venom of Phoneutria nigriventer spiders is composed of a variety of bioactive substances. It has been considered as a rich source of potential candidates for the development of new drugs for prevention/treatment of a number of physio-pathological conditions or for agricultural use as natural insecticides. Although the venom composition has been extensively studied, secretion pathways are poorly understood. In this study, the presence of venom glands at early development stages of P. nigriventer was investigated. The ultra structure and microanatomy of four intra-cocoon stages (egg, first pre-larva, second pre-larva and pre-nymph) were analyzed by scanning electron (MEV) and confocal laser microscopy (CLM). The samples were fixed with 2.5% glutaraldeyde, 4% sucrose in 0.1 M cacodylate buffer (MEV) or with 4% paraformaldeyde (CLM). Our results demonstrated that the venom glands are among the first organs to be formed in P. nigriventer spiders. They are protected by a double layer of muscle fibers that contracts for venom release. Possibly, this external layer may avoid, also, the toxic action of the stored secretion on the physiological system of the spider itself, considering the known action of the venom toxins on invertebrates. At the pre-nimph stage, the venom apparatus is fully developed showing a pair of chelicera and stingers. Molecular studies are in progress to check for the presence of specific toxins in the venom glands of P. nigriventer spiders at early development stages.

KEY WORDS: Phoneutria nigriventer, armed spider, venom gland, MEV, CLM.

FINANCIAL SUPPORT: CNPq and FAPEMIG

CORRESPONDENCE TO: LUCIANA M. SILVA, Lab. Biologia Celular/DPD, FUNED. R. Conde Pereira Carneiro 80, 30510-010, Belo Hte, MG. E-mail: lucianams@funed.mg.gov.br