title: Intersexual variations in the venom of the Brazilian 'armed' spider Phoneutria nigriventer (Keyserling, 1891).
abstract: 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 microg) than equal sized females (296 microg), while adult females showed nearly a three times higher venom yield (1079 microg). 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 (LD(50)) in mice for female venom was 0.63 microg kg(-1) (95% confidence interval [0.54; 0.71] and 0.61 [0.56; 0.73] microg kg(-1)) for females with egg-sacs, when compared to the male venom which showed a LD(50) of 1.57 [1.46; 1.88] microg kg(-1). The venom of both sexes was also tested in insects using a termite bioassay with doses of 2, 3, 4, and 5 microg 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.
mesh_terms: D000818:Animals; D001681:Biological Assay; D002851:Chromatography, High Pressure Liquid; D004305:Dose-Response Relationship, Drug; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D007275:Injections, Intravenous; D020049:Isoptera / Q000187:drug effects; D007928:Lethal Dose 50; D008297:Male; D051379:Mice; D009043:Motor Activity / Q000187:drug effects; D010243:Paralysis / Q000139:chemically induced; D012727:Sex Characteristics; D013111:Spider Venoms / Q000008:administration & dosage / Q000737:chemistry* / Q000633:toxicity*; D013112:Spiders / Q000502:physiology*
chemical_list: D013111:Spider Venoms