On the noxious black Amazonian scorpion, Tityus obscurus (Scorpiones, Buthidae): Taxonomic notes, biology, medical importance and envenoming treatment
Section snippets
Taxonomy and systematics
Tityus obscurus Gervais, 1843, also known as the black scorpion or “lacrau” by rural communities in the Brazilian Amazon (Pardal et al., 2003), is one of the largest scorpion species in the Amazon Basin. It has total length of 85–100 mm (Lourenço, 2011). Most adult individuals found in nature have a uniformly black body (Fig. 1), whereas juveniles are yellowish with blackish spots on the body (Fig. 1) (Lourenço, 2002, Seiter and Teruel, 2014). Tityus obscurus also exhibits remarkable sexual
Geographical distribution
Although the Amazon Basin has an extension of more than 6 million km2, the spatial distribution of Tityus obscurus is mainly in tropical forests in countries such as Brazil (BRA) (Eastern Amazon-states of Amapá (AP) and Pará (PA)), French Guiana (FRG), and Suriname (SUR) (Fig. 2) (Lourenço and Leguin, 2008). This scorpion can be found in French Guiana near rivers, such as the Camopi, Aya and Arataye (Ythier, 2018; Lourenço, 1983), Upper Oyapock and Antecume-Pata regions, and areas inhabited by
Natural history
The habitats and microhabitats where T. obscurus lives in the Amazon, as well as its geographical distribution, are poorly known. This species can be found in two ecosystems in the Amazon, terra firme forest areas (Lourenço et al., 2000) and seasonally flooded forest areas known as igapós and várzeas (Martins et al., 2021). Most adult individuals of T. obscurus found in the wild have a uniformly black body (Fig. 3A), which makes them inconspicuous to people in these forests (Fig. 3B).
These
Cytogenetics
From a cytogenetic point of view, T. obscurus has high plasticity of diploid chromosome number (Almeida et al., 2017). A comparative study showed that specimens from Santarém (2°26′35″S 54°42′29″W), Pará, Brazil had an intrapopulation karyotype variation (2n = 11, 12, 13 and 14), whereas in other locations the karyotypes were more stable: Belém (1°26′29.7″S 48°27′50.8″W) 2n = 16; Marajó Island (0°53′59.4″S 49°38′17.5″W) 2n = 13, 14; and Rurópolis (4°05′37.7″S 54°54′38.7″W) 2n = 12 (Almeida et
Reproductive biology
All scorpion species are viviparous and their young emerge through the genital operculum (Polis and Farley, 1980). The embryonic development of the scorpion T. obscurus can last from three to four months (Lourenço et al., 2000). Females of this scorpion with newborns have not yet been recorded in the wild, but in the laboratory (Fig. 3H) (Outeda-Jorge et al., 2009). Tityus obscurus can be born in the months of January, February, May, July (Outeda-Jorge et al., 2009) and December (Fig. 1 red
Venom composition
Most studies of T. obscurus venom are from specimens found in the Brazilian Amazon (Amapá and Pará) (Mourão et al., 2020; Tibery et al., 2019; de Oliveira et al., 2018; Dias et al., 2018; Guerrero-Vargas et al., 2012; Murgia et al., 2004; Batista et al., 2000, 2002a, 2002b, 2004; Grottesi et al., 2003, Simon et al., 2018, Stehling et al., 2012, Veloso-Júnior et al., 2019). However, information is lacking on proteomic characterization of venoms from T. obscurus populations from French Guiana and
Envenoming symptoms
The first records of human envenoming by T. obscurus in the Amazon were recorded in French Guiana (Fig. 4). In this region, an Amerindian child stung by T. obscurus died even under intensive care (Hommel et al., 2000). Clinical and epidemiological studies report that T. obscurus from the Lower Amazon region (2°26′35″S 54°42′29″W), Pará, triggers atypical symptoms including dysarthria, myoclonus, ataxia and fasciculation (Table 1) (Torrez et al., 2015; Pardal et al., 2003). A medical study
Therapeutic itinerary of envenomed victims
A therapeutic itinerary (TI) is a set of processes by which individuals or groups of people choose, evaluate and adhere to a treatment regimen (Demétrio et al., 2020). A person envenomed by a scorpion in a riverside community in the Amazon has a higher risk of presenting serious complications than victims of scorpions in other macro-regions of Brazil (da Silva et al., 2018; Pardal et al., 2014b; Pierini et al., 1996). Fishermen, hunters and farmers who live in areas with difficult access are
Traditional practices against scorpion stings in the Amazon
Human communities in the Amazon typically use plant species against scorpion envenoming before an effective antidote is administered (DeFilipps et al., 2004; Duke and Vasquez, 1994; Prance, 1972). Riverside and indigenous communities that are isolated due to the geography of the forest use traditional knowledge of plants against symptoms of animal envenoming (Table 2) (Grenand et al., 2004; Davis and Yost, 1983). About 55% of scorpion victims in the Lower Amazon (2°26′34″S 54°42′28″W), Pará,
The effectiveness of commercial anti-scorpion serum in the Brazilian Amazon
In Brazil, the antivenom responsible for neutralizing scorpion toxins is composed of antibodies derived from animal plasma immunized against T. serrulatus venom (Fan and Monteiro, 2018). This species is technically selected for being one of the most dangerous in the country (Cupo, 2015). After several cases of T. obscurus envenoming in the Lower Amazon (2°26′35″S 54°42′29″W) and Belém (1°25′16.7″S 48°28′11.5″W), Pará, Brazil, that included symptoms such as myoclonus (Pardal et al., 2014a, 2014b
Potential bottlenecks for the production of a specific antivenom for Amazonian scorpionism
The Brazilian anti-scorpion serum is produced mainly in the region of São Paulo and distributed to different regions of the country (Cristino et al., 2021). The centralization of studies on scorpionism and the experience in treating accidents caused by T. serrulatus has allowed regions such as the Southeast to establish research centers for the production of antidotes (Fan et al., 2015). One of the first steps in planning the production of a specific serum is the proven medical relevance of the
Perspective for development of an anti-scorpion serum for Amazonian scorpionism
The Brazilian antiscorpion serum is distributed free of charge to the Amazonian population, but it was not developed based on antigens from Amazonian scorpion venoms (Monteiro et al., 2016). Because of cerebellar-muscular manifestations, almost all patients (91.4%) with scorpionism symptoms admitted to the emergency room of a reference hospital in the Lower Amazon, Pará, had to receive specific antivenom (antiscorpion or antiarachnid) (Pardal et al., 2003, 2014b). This is an noteworthy
Concluding remarks
Tityus obscurus is an arboreal scorpion and can envenom people mainly during unprotected manual work, such as extracting fruit and wood. Males and females of this scorpion have distinct morphological characteristics, but to minimize the risk of misidentification they must be identified by a taxonomist. From a taxonomic point of view, the enigmatic similarity of T. obscurus with other scorpions of the Atreus subgenus is a pending issue that requires detailed studies to elucidate whether the
Ethical statement
This manuscript has not been published and is not under consideration elsewhere.
Author contribution
JM and KB conceived and designed the study. BA and PP: identified the scorpions. JMG, PP, AL, DC and EA performed data analysis. JM, KB and JMG drafted the manuscript. KB, JM, EA, JMG, RP, PP and BA directed the organization and edited the manuscript. All authors read and approved the final version of the manuscript.
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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