Intraspecific variation in the Egyptian scorpion Scorpio maurus palmatus venom collected from different biotopes.

The present study was conducted to explore the following hypotheses: (i) do scorpions (Scorpio maurus palmatus) from different biotopes exhibit intraspecific diversity in their venom? (ii) if so, is this variation associated with ecological or genetic factors, geographical distance, and/or multiple interrelated parameters? To address these questions, scorpions were collected from four geographically isolated localities in Egypt. Three of these locations are from mutually isolated pockets in the arid biotope of Southern Sinai (Wadi Sahab, El-Agramia and Rahaba plains). The fourth population was sampled from the semiarid biotope of Western Mediterranean Costal Desert (WMCD). Using reducing gel electrophoresis (SDS-PAGE), we have shown biotope-specific variation in the expression of peptides from scorpions collected from these distinct areas. WMCD sourced venom samples contain higher molecular weight protein components (219, 200, 170, 139, 116 kDa) than Southern Sinai scorpion venom samples. The Southern Sinai venom is characterized by the presence of 11 protein bands (93-0.58 kDa) that are not mirrored in the individual venom samples of WMCD. Bands of 33 and 3.4 kDa were characteristics of all individual venom samples of the scorpion populations. Even within Southern Sinai area, Sahab venom contains five fractions that are not detected in both El-Agramia and Rahaba venom samples. Moreover, male and female venom analysis revealed some sex-related proteomic similarities and differences between scorpion populations. Female venom appears to be more complicated than the male venom. Female venom samples showed bands of 219, 200, 77.5, 55.5, 45, 39, 37, 24 and 16 kDa which were absent in the male venom. The random amplified polymorphic DNA (RAPD) technique was used to estimate the genetic distance between the four scorpion populations. The RAPD data confirmed the genetic diversity at molecular level among the sampled populations. More than 77 RAPD bands (ranging in size from 125 to 15,000 bp) were defined from the four scorpion populations. Of the 77 bands, 57 (76.2%) were polymorphic and 20 were monomorphic among the populations. The similarity coefficient data of venom and DNA were used to construct separate dendrograms, which grouped together the Southern Sinai populations and these were some distance away from the WMCD population. Taken together, we suspect that a combination of local environmental conditions, geographical separation and genetic separation may play a major role in the intraspecific variation of venom of S. m. palmatus.

Neurotoxic and cytotoxic effects of venom from different populations of the Egyptian Scorpio maurus palmatus.

Neurotoxic and cytotoxic effects of venoms from Scorpio maurus palmatus taken from different populations were assessed for geographic based variability in toxicity, and to evaluate their insecticidal potency. Scorpions were collected from four regions. Three locations were mutually isolated pockets in the arid area of Southern Sinai. The fourth sample was collected from a population inhabiting the semi-arid environment of Western Mediterranean Coastal Desert. The neurotoxic (paralytic) effect of the venom from each population was assayed by its ability to induce permanent disability in adult cockroaches within 3h. Venom was applied using microinjection techniques through an intersegmental membrane. Probit analysis was used to calculate the Paralytic Effective Dose (PED(50), ng/100mg). Levels of glutathione, lipid peroxidation, protein carbonyl content and nitric oxide, as well as the activities of superoxide dismutase, catalase and cholinesterase, were measured to assess the cytotoxicity of the venom. The results show that the injected venom from each population induced obvious spasticity, followed by flaccid paralysis. All the tested biochemical parameters, except glutathione content, revealed significant differences in toxicity in venom taken from the different scorpion populations. We conclude that (i) the venom of this scorpion has significant neurotoxic and cytotoxic effects on insect cells, (ii) its efficacy, as assessed by the PED(50) unit, exhibited variation across its geographic range, and (iii) components in the venom may have the potential for being developed into effective and environmentally friendly bioinsecticides.