Structural Analysis of the Venom Glands of the Armed Spider Phoneutria nigriventer

¹Silva, L.M., ²Pimenta, P. F. P., ²Secundino, N.F.C., ¹Diniz, M.R.V., ¹Fortes-Dias C.L.

1 Serviço de Biologia Celular e Molecular, Fundação Ezequiel Dias (FUNED), Belo Horizonte, MG; 2 Lab. de Entomologia Médica, Centro de Pesquisas René Rachou (CPqRR/FIOCRUZ), Belo Horizonte, MG.

Spiders in the genus Phoneutria, most commonly known as “armed” or “banana” spiders are among the most dangerous species in Brazil due to the high toxicity of their venom, associated to their habit to invade domestic or specific areas such as banana plantations (von Eickstedt, 1994). However, accidents leading to death are restricted to debilitated patients and children due to the low dose of venom inoculated (Schemberg & Pereira-Lima, 1976). A pair of venom glands of Phoneutria nigriventer spiders is located in their cephalothorax, connected to the chelicera by two independent ducts. Two types of epithelial secretory cells are present in these ampoule-form glands, as described by Bücherl (1971) using light microscopy and histological tools. The objective of the present study is to extend the study of Phoneutria nigriventer venom glands using light, scanning electron (SEM) and confocal microscopy, besides immunohistochemical and staining methods.  Venom glands from female adult spiders were dissected, fixed in 4% paraformoladeído for 2h, dehydrated in ethanol, embedded in historesin and cut into 1.5mm sections. These sections were stained with hematoxylin/eosin, Gomori and toluidin blue (light microscopy) or Phalloidin, ConA and Topro-3 (confocal microscopy). For SEM experiments, the fixation was performed in 0.1M cacodylic acid buffer containing 2.5% glutaraldehyde and 4% sucrose for 48h. After post-fixation with osmium tetroxide in 1.6% K3Fe(CN)6, they were dehydrated in 30-100% acetone, critical-point dried and sputter-coated with gold. SDS-PAGE analysis glands and their contents showed individual variability. A comparison between the right and left side glands indicated that, although independent, they have similar total composition. Ultrastructural microscopy studies confirmed the ampoule form of the glands, which is maintained externally by two layers of striated muscle fibers that cross perpendicularly. Between the fibers, small pores were observed suggesting a pathway for ion exchange. Internally, the epithelium is formed by acinos full of intracellular secretory vesicles. The study is in progress to better characterize the structure of these glands and to provide an insight into the mechanisms of venom secretion.

FINANCIAL SUPPORT: FUNED, CPqRR, CNPq, FAPEMIG

Correspondence to: lucianams@funed.mg.gov.br