BackgroundExcept for the northern region, where the Amazonian black scorpion, T. obscurus, represents the predominant and most medically relevant scorpion species, Tityus serrulatus, the Brazilian yellow scorpion, is widely distributed throughout Brazil, causing most envenoming and fatalities due to scorpion sting. In order to evaluate and compare the diversity of venom components of Tityus obscurus and T. serrulatus, we performed a transcriptomic investigation of the telsons (venom glands) corroborated by a shotgun proteomic analysis of the venom from the two species.ResultsThe putative venom components represented 11.4% and 16.7% of the total gene expression for T. obscurus and T. serrulatus, respectively. Transcriptome and proteome data revealed high abundance of metalloproteinases sequences followed by sodium and potassium channel toxins, making the toxin core of the venom. The phylogenetic analysis of metalloproteinases from T. obscurus and T. serrulatus suggested an intraspecific gene expansion, as we previously observed for T. bahiensis, indicating that this enzyme may be under evolutionary pressure for diversification. We also identified several putative venom components such as anionic peptides, antimicrobial peptides, bradykinin-potentiating peptide, cysteine rich protein, serine proteinases, cathepsins, angiotensin-converting enzyme, endothelin-converting enzyme and chymotrypsin like protein, proteinases inhibitors, phospholipases and hyaluronidases.ConclusionThe present work shows that the venom composition of these two allopatric species of Tityus are considerably similar in terms of the major classes of proteins produced and secreted, although their individual toxin sequences are considerably divergent. These differences at amino acid level may reflect in different epitopes for the same protein classes in each species, explaining the basis for the poor recognition of T. obscurus venom by the antiserum raised against other species.

There are a great number of studies about Brazilian scorpions. However, little is known about the venom of scorpions of northern Brazil, mainly about Tityus obscurus, which is responsible for the most number of accidents in the Amazon. Thus, this study aimed to evaluate some pharmacological effects of T. obscurus venom in rats and mice. In rats, the venom (10 mg/kg i.p.) caused hemorrhagic patches in the lung parenchyma but did not lead to pulmonary edema. There was a decrease in general activity, observed in the activity box after venom injection. The venom did not induce changes in the occurrence and intensity of experimentally induced convulsions, nor did it cause hippocampal neuronal loss. In mice, the LD obtained was 3.13 mg/kg (i.p.). Different doses of the venom (0.2; 1; 5; 10; 15 μg/30 μL per hind paw) induced edematogenic and moderate nociceptive activity in mice. The Tiyus serrulatus venom used as comparison caused more intense symptomatology in mice. Comparing to the venom of other Tityus scorpions of medical importance, that have convulsant and intense nociceptive effects and cause lung edema, as described in the literature, we can conclude that the venom of T. obscurus probably has different characteristics.

The Serra de Piquiatuba is situated in the area of the 8th Battalion of Engineering and Construction-8° BEC, located at km 8 of the Santarém-Cuiabá highway, in the municipality of Santarém, Pará, Brazil. This region is characterized by a hot and humid climate with rainfall exceeding 1900 mm p.a. In this study, we present a species list of scorpions from the Serra de Piquiatuba, based on data collected from September to November 2010. Five species were recorded, all common in the Amazon, belonging to the families Buthidae and Chactidae. The observed diversity patterns are discussed considering other scorpion inventories carried out in Brazil and possible sampling biases. The present study raises methodological questions to be further addressed in scorpion community ecology studies.