Lourenço Journal of Venomous Animals and Toxins including Tropical Diseases (2016) 22:1 DOI 10.1186/s40409-016-0075-6 REVIEW Open Access Scorpion incidents, misidentification cases and possible implications for the final interpretation of results Wilson R. Lourenço Abstract The aim of this contribution is to bring general information on the classification and in particular on the specific identification of scorpion species dangerous to humans. Several generic groups are taken into consideration, but the Neotropical genus Tityus C. L. Koch, 1836 is used as a major example. The content of this paper is mostly addressed to non-specialists whose research embraces scorpions in several fields such as venom toxins and public health. Although efforts have been made in the last 20 years to create better links between ‘true scorpion experts’ and non-specialists who use scorpions in their research, such exchanges had never led to a consensus among those different branches of biological and medical research. Consequently, many cases of species misidentification and even more serious errors concerning scorpion classification/identification are often present in the specialized literature. In conclusion, it is suggested here that the frequent cases of misidentification observed in several reports may induce mistakes in the final interpretation of results, leading only to more inefficacity in the treatment of problems caused by infamous scorpion species. Keywords: Scorpion, Dangerous species, Misidentification, Biased results, Buthidae, Tityus Background responsible for serious or lethal incidents. It is true, Scorpions are a rather depauperate group within the class however, that the interest on scorpion research in Arachnida with approximately 2,100 known species. They many distinct biological fields was generated by the can be classified among the most ancestral arthropods fact that a number of species possess venoms with po- both in origin and body morphology. They first appeared tent toxins, capable of killing humans. Most deadly as aquatic organisms during the Silurian (approximately species belong to the family Buthidae; though, species 450 million years ago – MYA) and underwent rather small belonging to two other families, Scorpionidae and morphological changes since [1]. Their apparent conserva- Hemiscorpiidae, also threaten humans. tive form led some authors to define them as ‘living The group first appeared as aquatic organisms. In fossils’. However, scorpions most certainly developed their evolutionary history, scorpions almost certainly major biochemical, physiological, behavioral and eco- evolved from Eurypterida (‘water scorpions’) since both logical adaptations that have combined to ensure their groups share several common morphological features. continued success over the past 450 million years. Marine and amphibious scorpions most certainly per- Even if for natural history experts scorpions can be sisted well into the Carboniferous (359–299 MYA) and considered fascinating animals, the interest shown by some species probably reached the Permian (299–251 people in general is only connected with their negative MYA) and Triassic (251-200MYA) periods [2, 3]. The reputation of ‘killers of men’. Nevertheless, only a limited first unequivocally terrestrial (air-breathing) scorpion number of species, probably less than 50, are actually most certainly appeared on land during the late Devonian (416–359 MYA) or early Carboniferous [1, 4]. For a Correspondence: [email protected] precise description of scorpion evolutionary history and Muséum National d’Histoire Naturelle, Sorbonne Universités, Institut de toxin evolution, readers can refer to Lourenço [5]. Systématique, Evolution, Biodiversité (ISYEB), UMR7205-CNRS, MNHN, UPMC, EPHE, CP 53, 57 rue Cuvier, 75005 Paris, France © 2016 The Author(s). Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated. Lourenço Journal of Venomous Animals and Toxins including Tropical Diseases (2016) 22:1 Page 2 of 25 From the beginning of scorpion studies in the late Collection at night with the use of a portable 18th century and during almost 150 years, researchers ultraviolet light. Because of the presence of focused primarily on descriptive taxonomy, general riboflavins in their exocuticles, scorpions become anatomy and very rudimentary biogeography, followed fluorescent under ultraviolet light (Fig. 1) and can by medical research on venom biochemistry. Since the be easily found [12]. This method is most efficient 1970s, however, basic research on scorpions expanded in open areas such as deserts and savannas; however, greatly to encompass behavior, physiology, ecology it can also be used in rainforests. Generally, results are evolutionary and reproductive biology. Moreover, a better in the absence of moonlight. This technique large amount of all the research was based on toxin should be used with prudence, since snakes are not studies and public health problems caused by danger- fluorescent and can represent a danger in dark nights. ous species. New approaches were attempted in this Methods of extraction, such as Berlese, Winkler and last field of research with the use of more precise Kempson may also be successfully employed to methods based on a better knowledge of life history obtain very small species, or juveniles, that inhabit strategies of these organisms [6–9]. organic soil [13]. These diminutive species, in In the general mass of recent publications devoted to general with less than 1.5 cm in total length, venoms, toxins and public health problems, it is yet generally escape from the collection if the other possible to observe major gaps between the most up-to- already described methods are used. date information on scorpion identification/classification produced by true scorpion experts and the information Scorpions are often rather rare and the population diffused by researchers who use these organisms in their densities of many species are low. For this reason, it is own research, but are not aware of their precise classifica- usually recommended that specimens should be brought tion. For this reason, it is suggested here that the frequent alive into the laboratory for study. They can be main- cases of misidentification observed in many reports may tained in boxes with saturated cotton wool in a dish. induce important mistakes in the final interpretation of The bottom of the box must be covered with a layer of results, which can only lead to more inefficacy in the treat- soil of about 2–3 cm in depth, preferably from the ment of problems caused by dangerous scorpion species. In this article, I attempt to explain and elucidate a number of common problems with clarity, accuracy and unambigu- ous communication, hopping that in this way the matter may be accessible to a broad audience. How to approach the identification of scorpions Techniques for collection As already outlined in some of my previous publica- tions, techniques for collecting and sampling are very important to estimate the composition of the scorpion fauna of a given region [10, 11]. Once the sampling is carried out, the identification process may be attempted by the study of some precise characters. There are four main techniques for the collection of scorpions: Overturning stones, rocks and logs beneath which many species can be found. This method, although the most widely used, is time and energy consuming, and the results obtained are generally poor. Pitfall traps may be placed in the soil, when fieldwork is expected to last at least for several days, and preferably for some weeks, in the same site. Results obtained by this method can be very satisfactory if the site chosen contains a large population of scorpions. This method is most successful during dry season, but the traps should be Fig. 1 Tityus brazilae Lourenço & Eickstedt, 1984; female from Brazil under UV light (copyright by Tiago Porto, reproduced with permission) checked daily if adequate results are to be obtained. Lourenço Journal of Venomous Animals and Toxins including Tropical Diseases (2016) 22:1 Page 3 of 25 region where the scorpion was collected. Food such as Old World genera spiders or insects (but not ants) should be offered once Family Buthidae C. L. Koch, 1837 a week. In many cases, reproduction takes place, The genus Buthus Leach, 1815 thereby providing additional material for study. Once The genus Buthus can be considered as the ‘founder’ of specimens have died they should be preserved in 75 % the family Buthidae (Figs. 2, 3, and 4). After its creation alcohol [14]. by Leach [15], many if not most true buthid scorpions were accommodate in this genus, and this situation persisted over most of the 19th century and even during Taxonomic study and identification a large part of the 20th century. Before the creation of The taxonomy of scorpions presents difficulties compar- Buthus, most scorpions were simply placed in the original able with those encountered in most other groups of genus Scorpio Linnaeus, 1758. Nevertheless,