Scorpion morphology has changed little over the last four hundred million years. In the other hand, they naturally developed venom glands as a special weapon used in prey and defense. Tityus stigmurus belongs to the Buthidae family, widely distributed around the world and comprising all the species considered of medical interest . In Brazil, scorpions from the genus Tityus are responsible for most reported envenomation accidents, primarily Tityus serrulatus, Tityus stigmurus and Tityus bahiensis. T. stigmurus is the main causal agent of scorpionism in the Northeast; its envenomation is often characterized by local symptoms, such as: pain (94.4%), hyposthesia (30%), edema (17.8%), erythema (17.8%) and paresthesia (15.6%) . Nishikawa  reported that T. stigmurus venom is the most toxic (DL50 = 0.773mg/kg) when compared to T. serrulatus and T. bahiensis. Nevertheless, T. serrulatus is the only species that has been significantly studied.
In addition to their clinical relevance, scorpion venoms are known to contain a very complex mixture of biologically active compounds . Of these, neurotoxins are the most studied and play a key role in the pathogenesis of scorpionism. These toxins are small peptides that interact with several types of ion channels, modifying the electrical activity of excitable cells . The most widely known ion channels recognized by these molecules are Na+ channels , K+ channels , ryanodine sensitive Ca2+ channels , T-type Ca2+ channels [10, 11] and Cl- channels . Their properties make these peptides useful as molecular and pharmacological tools for studying ion channels. Another noteworthy class of molecules present in the venom gland are antimicrobial peptides, which may be involved in ancient innate immunity . There are an estimated 150,000 distinct polypeptides found in the approximately 1500 known scorpion species worldwide , representing a broad scope for drug research and development.
The venoms of T. stigmurus
T. serrulatus and T. bahiensis have similar toxic components and display a high degree of cross reactivity between specific antiserums [15–18]. Earlier studies reported the sequence of some T. stigmurus toxins, homologous to the previously known gama, III-8 and IV-5 toxins from T. serrulatus. These were named Tst-1, Tst-2 and Tst-3, respectively,  and are toxic to mice, recognizing Na-channels through different modes of action [19, 20]. Holaday et al.  purified butantoxin, a K-channel blocker from the three medically important Tityus species mentioned above. Potassium channel toxins were also predicted in Tityus stigmurus venom using a proteomic approach .
Although the scorpion venom repertoire has been extensively investigated by PCR-based methods conducted with cDNA libraries [23–25], this strategy, in addition to cloning, isolation and characterization procedures, is limited by the specificity of the PCR primers used. In recent years, the number of proteomic and transcriptomic analyses performed has increased [26–35], since they are better able to assess venom diversity. Thus, in addition to known venom peptides and proteins, non yet described molecules can also be obtained. Moreover, transcriptomics has the advantage of providing insight into biological processes occurring in venom gland cells.
Previous investigations have used milked scorpion glands to achieve an enriched toxin library [26, 27, 29, 30]; however, only one used a so called “replete” venom gland not actively engaged in regenerating venom . Few scorpion nucleotide sequences are currently deposited in public databases, particularly for the Tityus genus, despite its clinical importance. The present study describes the transcriptomic expression of T. stigmurus scorpion from non-stimulated venom glands, using specimens collected in the urban area of Natal, Brazil.