Intersexual variations in the venom of the Brazilian 'armed' spider Phoneutria nigriventer (Keyserling, 1891)

Venom from male and female specimens of the medically most important Brazilian Ctenidae spider Phoneutria nigriventer (Keyserling, 1891) has been compared. Males showed a slightly higher venom yield (386 mug) than equal sized females (296 mug), while adult females showed nearly a three times higher venom yield (1079 mug). High-pressure liquid-chromatography analyses revealed differences in the venom composition between males and females. A single peak in HPLC (peak 11) was only detected in venom from females carrying egg-sacs, and sodium dodecyl sulfate-gel electrophoresis showed a series of high molecular weight proteins only in the male venom pool. The median lethal dose (LD50) in mice for female venom was 0.63 mug kg(-1) (95% confidence interval [0.54; 0.71] and 0.61 [0.56; 0.73] mug kg(-1)) for females with egg-sacs, when compared to the male venom which showed a LD50 of 1.57 [1.46; 1.88] mug kg(-1). The venom of both sexes was also tested in insects using a termite bioassay with doses of 2, 3, 4, and 5 mug per termite. No effect was detected for the lowest dose of female venom, whereas all the other venom doses from both sexes caused a decreased paralysis time and death of the termites. Comparing the venom of both sexes, it was observed that female venom provoked a faster reaction than male venom. The results indicate that males and females of P. nigriventer have differing venom composition which lead to different effects in biological assays. (C) 2002 Elsevier Science Ltd. All rights reserved.