Intersexual variations in the pharmacological properties of Coremiocnemis tropix (Araneae, Theraphosidae) spider venom.

This study aimed to determine the biochemical, insecticidal and neurotoxic properties of venom from both sexes of the Australian spider Coremiocnemis tropix (Araneae, Theraphosidae). Insecticidal properties were tested in crickets, while in vitro neurotoxicity was determined in an avian skeletal muscle preparation. Some intersexual differences in venom composition were identified by rp-HPLC and by LC-MS, but the majority of components were found in venoms of both sexes. Injecting the venom into crickets revealed that venom from male specimens was slightly more potent, while female venom induced more prominent effects in the chick biventer cervicis nerve-muscle preparation. The results from the chick assay suggest the presence of at least two vertebrate-active neurotoxins. A pre-synaptic neurotoxin may explain the reversible inhibition of muscle twitches and the unaffected response to nicotinic agonists at medium concentrations of female and medium to high concentrations of male venom. In addition, the presence of a neurotoxin that blocks post-synaptic nicotinic receptors might explain the irreversible inhibition of muscle twitches and the reduced response to nicotinic agonists at high concentrations (5-10 microg/ml) of venom from female specimens only.