25 July, 2012

Metabolic cost of venom regeneration and venom complexity in Parabuthus transvaalicus

It has previously has been showed that venom use is costly, both in terms of metabolic and ecological costs (Nisani et al, 2007; Nisani, 2008), that some scorpions have two types of venom with different composition (and different "production costs") (Inceoglu et al., 2003) and that Parabuthus transvaalicus Purcell, 1899 (Buthidae) are able to regulate venom use at different levels (Click here for more information).

Zia Nisani and co-workers have now further confirmed the relatively high cost of venom regeneration and also have shown that greater venom complexity can be associated with higher cost of venom production.

We investigated the biochemical profile of regenerated venom of the scorpion Parabuthus transvaalicus in relation to its metabolic cost and toxicity. Using a closed-system respirometer, we compared oxygen consumption between milked and unmilked scorpions to determine the metabolic costs associated with the first 192 h of subsequent venom synthesis. Milked scorpions had a substantially (21%) higher mean metabolic rate than unmilked scorpions, with the largest increases in oxygen consumption occurring at approximately 120 h, 162 h, and 186 h post-milking. Lethality tests in crickets indicated that toxicity of the regenerated venom returned to normal levels within 4 d after milking. However, the chemical profile of the regenerated venom, as evaluated by FPLC and MALDITOF mass spectrometry, suggested that regeneration of different venom components was asynchronous. Some peptides regenerated quickly, particularly those associated with the scorpion’s “prevenom,” whereas others required much or all of this time period for regeneration. This asynchrony could explain the different spikes detected in oxygen consumption of milked scorpions as various peptides and other venom components were resynthesized. These observations confirm the relatively high metabolic cost of venom regeneration and suggest that greater venom complexity can be associated with higher costs of venom production.

Nisani Z, Boskovic DS, Dunbar SG, Kelln W, Hayes WK. Investigating the chemical profile of regenerated scorpion (Parabuthus transvaalicus) venom in relation to metabolic cost and toxicity. Toxicon. 2012;60(3):315-23. [Subscription required for full text]

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