The spider-like arachnids known as Opiliones (also known as “harvestmen” or “daddy-long-legs”), are a species often handled by humans. They are the subject of an urban legend which not only claims that harvestmen are venomous, but are in fact more venomous than any of the spiders but are incapable of biting humans due to their lack of penetration. This is untrue on several counts. None of the known species have venom glands or chelicerae bearing fangs, instead having smaller, pincer-like chelicerae that cannot usually penetrate human skin.In addition, incidents of opiliones biting people are rare, and no reported bites by these species have had any lasting effects.
spider venom
Spider venom: enhancement of venom efficacy mediated by different synergistic strategies in Cupiennius saleiBesides the power of the chelicerae, synergistic interactions between different components in the venom of Cupiennius salei ensure the hunting success of this spider. The main components of the venom were tested alone or in combination according to their physiological venom concentrations in Drosophila bioassays.
The high K+ ion content of the venom synergistically increases the insecticidal activity of the neurotoxins CSTX-1, CSTX-9 and CSTX-13 by 20% but does not influence the insecticidal effectiveness of the antimicrobially and cytolytically acting cupiennin 1a. Histamine only enhances the activity of the main neurotoxin CSTX-1. An important role in the envenomation process is exhibited by cupiennin 1a, which increases the insecticidal activity of the above-mentioned neurotoxins by up to 65%. Additionally, the highly synergistic effect of the enhancer CSTX-13 on CSTX-1, provoked in non-toxic physiological concentrations, could be verified for CSTX-9, but not for cupiennin 1a. CSTX-1 and CSTX-9 show positive interactions only when both are injected in toxic non-physiological concentrations.
Introduction
Spider venoms are complex mixtures of components used to paralyse prey items and defend against predators. Rapid paralysis results from the modifications of various ion channel targets by low molecular mass compounds, neurotoxic peptides and proteins. However, much less is known about the interactions of venom components within a prey organism (Adams, 2004; Kuhn-Nentwig et al., 2004).
The Central American spider Cupiennius salei (Keyserling 1877) uses its venom as economically as possible. The amount of venom injected varies depending on size, activity, defense behaviour and venom sensitivity of a prey item (Malli et al., 1999; Wigger et al., 2002; Wullschleger and Nentwig, 2002). This optimal venom
dosage is continued on the biochemical level through positive interactions among various venom components (Kuhn-Nentwig et al., 1998; Wullschleger et al., 2004). In C. salei venom, proteins with molecular masses above 10 kDa have been identified. Additionally, disulfide-rich neurotoxins, highly cationic peptides with molecular masses between 3-10 kDa, and low molecular mass compounds, such as ions, biogenic amines, polyamines and neurotransmitters, are present (Kuhn-Nentwig et al., 2004).To date, toxicological information and sequence data for the neurotoxins CSTX-1 and CSTX-9, and the neurotoxic two-chain enhancer peptide CSTX-13 have been reported (Kuhn-Nentwig et al., 2004; Wullschleger et al., 2004).
These highly cationic, α-helical, cysteine-free peptides may play a dual role in the venom: protection of the venomous apparatus against microbial invaders and, after venom injection into prey, an enhancement of the paralytic effect of the neurotoxins (Kuhn-Nentwig, 2003). Insecticidal activities of similar cytolytically acting peptides have also been reported for the spider Lycosa carolinensis (Yan and Adams, 1998) and the ant Pachycondyla goeldii (Orivel et al., 2001). Beyond these insecticidal activities, additional synergistic interactions with neurotoxins have been demonstrated for the spiders Oxyopes kitabensis (Corzo et al., 2002) and C. salei (Kuhn-Nentwig et al., 2004).
spider venom
The term “daddy-long-legs” also can refer to the similar-looking cellar spider. This species (a true spider) can bite humans, but its venom is not known to have any effects beyond mild discomfort at the site of the bite
spider venom
