A checklist of the scorpions of Ecuador (Arachnida: Scorpiones), with notes on the distribution and medical significance of some species

Ecuador harbors one of the most diverse Neotropical scorpion faunas, hereby updated to 47 species contained within eight genera and five families, which inhabits the “Costa” (n = 17), “Sierra” (n = 34), “Oriente” (n = 16) and “Insular” (n = 2) biogeographical regions, corresponding to the western coastal, Andean, Amazonian, and the Galápagos archipelago regions, respectively. The genus Tityus Koch, in the family Buthidae, responsible for severe/fatal accidents elsewhere in northern South America and the Amazonia, is represented in Ecuador by 16 species, including T. asthenes, which has caused fatalities in Colombia and Panama, and now in the Ecuadorian provinces of Morona Santiago and Sucumbíos. Underestimation of the medical significance of scorpion envenoming in Ecuador arises from the fact that Centruroides margaritatus (Gervais) (family Buthidae) and Teuthraustes atramentarius Simon (family Chactidae), whose venoms show low toxicity towards vertebrates, frequently envenom humans in the highly populated Guayas and Pichincha provinces. This work also updates the local scorpion faunal endemicity (74.5 %) and its geographical distribution, and reviews available medical/biochemical information on each species in the light of the increasing problem of scorpionism in the country. A proposal is hereby put forward to classify the Ecuadorian scorpions based on their potential medical importance.


Introduction
Ecuador, despite its small size (only 250,000 km 2 or 1.5 % of South America), ranks 17 th among the nations of the world in biodiversity [1,2]. This is attributable to, among other factors, the confluence of several biogeographic regions: Chocó and Tumbez (encompassing the "Costa" region), northern and south-central Andes (Sierra" region), the northern and southwestern Amazon (Oriente" region) and the insular region of Galápagos (Fig. 2). Ecuador harbors one of the richest arachnid faunas of the Neotropics [3]; specifically, its scorpion fauna ranks high amongst South American countries in terms of diversity, with 12.70 species per 100,000 km 2 [4].
Pioneering work by Eugéne Simon, Reginald I. Pocock, Alfredo Borelli, Karl Kraepelin, and Cândido de Mello-Leitão initiated the cataloguing of Ecuadorian scorpions [5][6][7][8][9][10][11][12][13]. Although less known, the work of the Ecuadorian taxonomist Francisco Campos [14,15], together with Behr-Castillo and Correa [16], also contributed to the knowledge of local scorpions, particularly in the province of Guayas. The work of Wilson R. Lourenço has allowed recognition of Ecuador as part of a region exhibiting the highest alpha-diversity for scorpions in the world, also encompassing Southern Colombia, the Northeast region of Peru, and the Upper Amazon region of Brazil [17].
Particularly, the genera Tityus C. L. Koch (in the family Buthidae) and Teuthraustes Simon (in the family Chactidae) show a high concentration of species in Ecuador [18,19]. A center of endemism in Ecuador for Teuthraustes has been proposed based on its extreme local diversity [20]. Despite such diversity, little is known about the toxicity of local scorpions, particularly within the speciose genus Tityus, which contains all medically important species in South America, and exhibits a phylogenetic divergence paralleled by functional, structural, and immunological differences among their toxins [21,22].
Mostly dating from records obtained at the turn of the 19 th century and from the 1900-1920 period, type localities for a number of Ecuadorian species are obscure. An example of this situation shown recently is the chactid Chactas rubrolineatus Simon, described by Eugène Simon from Rio Içá in 1880, which was wrongly assigned to Ecuador by Mello-Leitão [10] when in fact its location lies in Brazil [23].
The goal of this work is therefore to update the list of species and review the literature on scorpion Ecuadorian fauna from geographical and toxicological standpoints whenever the information is available. This idea arises, on one hand, from the increasing clinical relevance of some species in the country, with several fatal and severe infant cases reported from the provinces of Sucumbíos and Morona Santiago in 2012-2014 ( [24]; Dr. Jorge Blanco, Fundación Herpetológica Gustavo Orcés, personal communication). Comprehension of the basis underlying the extreme diversity of the Ecuadorian scorpion fauna, particularly in the case of those species toxic to humans, necessarily relies on the correct assignment of collection localities.
Here follows a list of the taxa currently recognized to inhabit Ecuador, including comments on their distribution and type localities, after confronting published collection sites with contemporary geographical names. We used various search engines for placing type localities (Google Earth, GeoNames). Taxa are organized in alphabetical order. Figure 1 summarizes the occurrence of individual species per province; the map in Fig. 2 identifies provinces in the contemporary political map of Ecuador. Information on the location of holotypes and syntypes for Ecuadorian species is available from the cited literature [17,[25][26][27][28][29][30][31][32]. We also review the potential medical importance of scorpion genera and species prevalent in Ecuador.

Annotated list of Ecuadorian scorpion species
Family Bothriuridae Simon, 1880 Genus ehrenbergii is a highly abundant synanthropic scorpion along the coastline [34]. A 6.7 kDa toxin denominated Be1 has been isolated from the venom of B. (B.) ehrenbergii which produces salivary secretion and spastic paralysis in mice at a dose of 3 mg/kg upon intraperitoneal injection and is lethal after two hours [35]. Be1 only comprises 7 % (w/w) of the total venom protein content, in comparison with the typical 20-30 % content of low-molecular-weight neurotoxins in the venom from Tityus species [36], which probably explains the low lethal dose in mice of B. (B.) ehrenbergii crude venom (subcutaneous injection), which is around 20 mg/kg [34]. According to its molecular mass and physiological effects, Be1 may belong to the sodium channel-active family of scorpion toxins (NaScTx).
It is not known whether other Brachistosternus spp., including those prevalent in Ecuador, are of equally low toxicity to mice, but their medical importance requires evaluation considering the higher sensitivity of humans (five-fold more susceptible than mice) to scorpion venom [37]. As venom of another bothriurid from Australia, Cercophonius squama (Gervais), contains only primitive homologs of NaScTxs (lipolytic-like peptides), South American representatives of the family Bothriuridae (including those inhabiting Ecuador) might have diverged toxinologically from those genera prevalent in Southeast Asia [38]. Cekalovic, 1969:163-168. This species is reported in San Gabriel, "Carcha," which actually corresponds to the province of Carchi, northern Ecuador [39]. In his original description, Cekalovic [25] does not specify the province of origin but provided a map that places the type locality roughly within Carchi. San Gabriel is at an altitude of 2,980 m (0.59318 N, 77.83078 W), well above the arid and semi-arid habitats of species within this genus prevalent in central Peru and northern Chile but related to Andean congenerics from Argentina, Chile, Bolivia, and Peru [40]. B. (B.) pegnai type locality is at the northernmost limit of the genus distribution range [33]. ) ehrenbergii has been reported as present in Ecuador [41], although Ochoa and Ojanguren Affilastro [42] have verified its presence only from northern Chile to central Peru. Lourenço [18] places B. (B.) ehrenbergii Ecuadorian populations in the province of Santa Elena without providing precise locations and thus the species has been assigned to this province (Fig. 1), pending new findings in Ecuador.

Family Buthidae Genus Ananteris
This genus comprises one of the smallest Neotropical buthids, between 15 and 41 mm of total body length in the case of Ecuadorian species. They are clearly recognizable by their densely spotted pigmentation, elongated telson, and pectines without fulcra [41]. No venoms from this genus have ever been analyzed, although toxins from Ananteris spp. are predicted to be ancestral to toxins produced by Tityus spp. given the Gondwanian distribution of Ananteris, since extant species are found both in Africa and Central/ South America [43].  [26].

Genus Centruroides
This genus contains three species in Ecuador. Venom from Centruroides margaritatus Gervais, the most common scorpion in the coastal region of Ecuador, is richer in toxins active against potassium channels and also antimicrobial peptides in comparison with the higher content of sodium channel-active toxins typically found in venoms of toxic Centruroides species inhabiting Mexico and the southern United States [46,47], explaining the lower toxicity of C. margaritatus to vertebrates. Lourenço [18] reports this species roughly within the province of Santa Elena but no specific locations are provided. Identity of true Ecuadorian C. gracilis populations is pending since records of this species in South America have been questioned [50].
3. Centruroides margaritatus (Gervais, 1841:281-282). This species (Fig. 3) is by far the most abundant scorpion along the Ecuadorian coast and responsible for the majority of envenoming cases in the metropolitan area of Guayaquil, province of Guayas, the most populated city of Ecuador [14,16,]. It is a large species (65-100 mm), with carapace and tergites dark yellow-brown and metasomal segments I-IV yellow-brown, darker on IV; V and telson dark reddish brown [50].
The type locality of this species is Isla Puná, at the entrance of the Gulf of Guayaquil, currently belonging to the province of Guayas [50]. This species has been reported from the coastal provinces of Los Ríos and Santa Elena, and the "Sierra" province of Loja ( Fig. 1), but no data are available on its presence in the coastal provinces of Esmeraldas and El Oro [50]. The records for the "Sierra" provinces of Pichincha and Chimborazo date from 1901-1907 and have not been confirmed since [51]. This species has been the subject of controversy for more than a century in relation to its real range of distribution as has been frequently misidentified with its allied species, Centruroides gracilis (Latreille), and Centruroides edwardsii (Gervais). The matter was settled by Armas et al. [50] who differentiated C. margaritatus from its congeners based on its geographical distribution in South America and the Caribbean, and morphology (the lower hairiness of its pedipalps, which are more oval in shape, and the presence of only eight rows of denticles in the pedipalp fixed finger) [50].
The difficulties associated with the identification of true populations of C. margaritatus are probably the origin of the conflicting reports of its venom lethality towards vertebrates. Marinkelle and Stahnke [52] reported a median lethal dose (LD50) in mice of 59.9 mg/kg (intraperitoneally) from a C. margaritatus Colombian population, whereas Gómez et al. [53] has reported a lethal titer in mice of 5.19 mg/kg for the same species but from a Costa Rican population. Central American C. margaritatus populations now belong to C. edwardsii [50]. As to the Ecuadorian populations of C. margaritatus, venom from specimens collected in Guayaquil has been shown to decrease significantly the cardiac frequency when injected subcutaneously into rabbits [54]. Campos [14] also reports on severe manifestations on a human adult envenomed by C. margaritatus in Playas, province of Guayas, who experienced vomiting, intense dyspnea, shivering, and numbness of the tongue [14]. Despite these observations, no modern reports have been published on envenoming by C. margaritatus in Ecuador. One recent adult case of C. margaritatus envenoming in Guayaquil presented with paresthesia and erythema at the sting site (Dr. Miguel Delgado, Postgraduate Program in Intensive Care, Universidad Espíritu Santo, Guayaquil, personal communication).

Material collected
In peridomiciliary areas in the cities of Portoviejo
This species (Fig. 4f ) was described from a specimen collected in "Pororu," Peru, by Pocock [60], but no contemporary locality with this name exists in this country. It has been suggested that the correct locality is Paruro, in the department of Puno, southern Peru [61], although no modern records of T. (A.) asthenes exist for this region, where Tityus (Tityus) soratensis Kraepelin is the only Tityus species reported thus far [62]. More recent Peruvian records for T. (A.) asthenes are supplied by Teruel [63], from Capahuari, province of Loreto, on the border with Ecuador. T. (A.) asthenes presents a disjointed distribution in Ecuador (cis-and trans-Andean), since it inhabits the western and eastern versants of the Andes range, having been reported from the western province of Esmeraldas and the eastern province of Napo [18].
Considering its abundance in the areas where accidents have taken place, T. (A.) asthenes is probably the species associated with the severe and fatal accidents in children from the provinces of Sucumbíos and Morona Santiago (A.B., unpublished observations). T. (A.) asthenes has been found from Peru to Panama, having produced severe envenoming cases and fatalities in Colombia [64] and Panama [47,65]. T. (A.) asthenes neurotoxins from the Panamanian populations are only weakly recognized by the anti-Tityus (Tityus) serrulatus (Brazil) and anti-Tityus (Atreus) discrepans (Venezuela) antivenoms [66]. A test of the immunological reactivity of venom from Ecuadorian populations of T. (A.) asthenes towards available antivenoms is pending.
2. Tityus (Archaeotityus) bastosi Lourenço, 1984:358-359. This species (Fig. 4 -a) belongs to the subgenus Archaeotityus, which comprises highly pigmented scorpions (formerly in the "Tityus clathratus" morphological group), the smallest (18-40 mm) and most ancient group of species in this genus, in which the subaculear tooth is always rhomboidal.  reported from Landangui (4.20521S, 79.22455 W) (Loja province) and Zaruma (El Oro province) (3.69132S, 79.61174 W). This species (Fig. 4b) also belongs to the "Tityus bolivianus" complex and is a shared species with Peru, where has been collected in the departments of Cajamarca and Cuzco [68]. 6. Tityus (Atreus) forcipula (Gervais, 1844:130) Type material from an unknown locality in Colombia [41]. This species (Fig. 4) [17]. Thus, the species is included on the list of current species from Ecuador (Fig. 2). T. (A.) timendus has been placed in the "Tityus asthenes" species complex in the subgeneus Atreus, but has also been cited as an allied species of T. (A.) pachyurus [77], which is responsible for severe envenomings in Colombia and Panama [47,78]. 16 (Fig. 4). It is the only Tityus species thus far described from Ecuador that belongs to the "Tityus androcottoides" morphological group, which comprises scorpions with ventral keels of metasomal segments II to IV partly or largely fused [28]. Most species within this group produce highly toxic venoms and are accountable for severe/lethal scorpionism, mainly in Venezuela [22]. Kovařík et al. [76] synonymized T. (A.) ythieri to Tityus (Atreus) magnimanus Pocock, based on a genetic and morphological comparison, but the species was later reinstated by Ythier [80] on the basis of a misidentification of the T. (A.) ythieri specimens studied by Kovařík et al. [76].

Family Caraboctonidae Genus Hadruroides
Species of Hadruroides (n = 22) are restricted to Ecuador, Peru, northern Chile, and several offshore islands (including the Galápagos), where they inhabit inter-Andean valleys, Pacific deserts, and dry forest habitats [32,81]. In Ecuador the genus is represented by seven species, recently split into two subgenera by Rossi [32]. The nominal subgenus, Hadruroides, now includes only one species, Hadruroides (Hadruroides) charcasus (Karsch), whereas the subgenus Lourencoides Rossi includes all other known species. The total number of Hadruroides species inhabiting mainland Ecuador is now raised to six [32].
Species in this genus appear to be weakly toxic to vertebrates upon peripheral venom injection, as shown in the case of H. (L.) lunatus (from Lima, Peru) based on the low lethality (LD50 = 22 mg/kg) of its venom when injected intraperitoneally in mice. H. (L.) lunatus venom is, however, highly toxic upon central injection (LD50 = 0.1 mg/kg) [83]. Although Hadruroides venoms are not lethal to mammals, at least peripherally, they probably contain components able to elicit heart muscle disruption in vertebrates.
Serum levels of total creatine kinase (CK) and its isoenzyme MB (CK-MB), two widely accepted markers for heart injury or myocardial infarction, have been found significantly elevated in rats envenomed intraperitoneally with a sublethal dose of H. (L.) lunatus venom (5.8 mg/kg) [83]. Venom from another species, H. (H.) charcasus (Karsch) (from northern Peru), produces in the heart of Bufo spinulosus (Amphibia, Bufonidae) cellular necrosis, leukocyte infiltration, and endothelial lesions without significantly altering the cardiac force or frequency [84]. The actual clinical implications of these results are not yet clear, but these activities are probably due to the presence in venoms from Hadruroides spp. of low-molecular-weight neurotoxins and/or phospholipase components [83].

Family Chactidae Genus Chactas
This exclusively Neotropical genus is distributed from Costa Rica to northern Peru, with Colombia as a possible center of dispersion since most known Chactas species are from this country. A number of species have been described in Venezuela and isolated taxa are reported in Brazil and Peru. Species are also known from Costa Rica, Panama and the Island of Trinidad [29]. There are no species within this genus analyzed from either toxinological or clinical standpoints. The venom from the Neotropical chactid Brotheas amazonicus Lourenço possesses an LD50 in mice (intraperitoneally) of 90 mg/kg, two orders of magnitude above the lethality of venoms from Tityus spp. and twice the lethality of venoms from species in genera Brachistosternus and Hadruroides [57].  [31].

Genus Teuthraustes
All the species of Teuthraustes so far described (n = 24) have been collected in the Andean mountains of Ecuador, Peru and Colombia, and in the Amazonian highlands of Venezuela and Brazil, with the highest species diversity corresponding to Ecuador. Even though the taxonomic validity of some of these taxa will probably be the subject of further scrutiny, the outstanding concentration of species in Ecuador is realistic [20]. In their transferring of Chactas camposi Mello-Leitão to the genus Teuthraustes, Ochoa and Pinto da Rocha [30] presented a list of the 11 Ecuadorian species thus far reported, together with their provinces of origin. The following account clarifies the origin of some of these species and their geographical distribution.
1. Teuthraustes atramentarius Simon, 1878:400. This species is widespread in the provinces of Cotopaxi, Ibarra, and Pichincha (Fig. 3), and is certainly the most abundant scorpion in the metropolitan area of Quito [88]. Together with C. margaritatus from the coastal region, the abundance of these two species in the most industrialized and populated areas of Ecuador (i.e. Pichincha and Guayas provinces) suggests their responsibility for most scorpion envenomings in these regions. The fact that their venoms are not significantly toxic to vertebrates [52,89] has been taken to indicate that scorpions are not of medical significance in the country, a situation reminiscent of the weakly toxic, widespread Venezuelan species, Rhopalurus laticauda (Thorell) [79]. In fact, T. atramentarius envenoming in humans only produces local symptomatology, resembling a bee sting [90].  [14]. A further search for this species in the provinces of Cañar, Bolívar, Guayas, and Pichincha is pending to determine its true distribution range.
Ecuador" without further details on its location. Borelli´s locality most probably refers to the channel of river Santiago, which originates in Ecuador from the union of two rivers, the Namangoza and the Upano, in the province of Morona Santiago, Ecuadorian Amazonia, where it flows 55 km before reaching the current border with Peru. The collector, Italian zoologist Enrico Festa, commented that the places where he collected in the Valle del Santiago were not far from the Marañón River, now belonging to Peru [90]. Back in the 1890s the area between the two rivers was under the jurisdiction of Ecuador. The species range of distribution includes the Cueva de los Tayos, also in Morona Santiago [44].

5.
Teuthraustes gervaisii (Pocock, 1893:82). Type material from the city of Cuenca, the capital of the Azuay province [41,60]. As in the case of Tityus (T.) ecuadorensis, "Piscobamba" is referenced as the type locality for this species, but instead the river Piscobamba is the probable site of collection in the province of Loja. This species has also been reported from the cities of Loja and Vilcabamba, also in the Loja province, and from Zaruma (3.4128S, 79.3642 W), province of El Oro [18].

Family Troglotayosicidae Genus Troglotayosicus
The genus includes two troglomorphic species (i.e., with morphological adaptations to life in cavernicolous habitats, e.g., the absence of median eyes), one described from Ecuador and a second from the neighbor-

Concluding remarks
Surrounded by areas where scorpion stings are frequent and usually inflicted by noxious species, such as southern Colombia and the Brazilian Amazonia, there was a need to update the list of the scorpion fauna from Ecuador, and establish their geographic distribution and potential medical significance in light of recent accidents in children, some of them fatal [93,56]. As noted before, insufficient efforts have been made, particularly in the case of the genus Tityus, to correlate human incidents and the precise geographical distribution of the species involved [94]. Preparation of a risk map for scorpionism in Ecuador and the possible manufacturing of a scorpion antivenom effective in the country would be facilitated by establishing such a correlation. This work updates the number of Ecuadorian scorpion species to 47 and clarifies their distribution by biogeographic area and political provinces upon a thorough revision of individual collection localities based on contemporary records, summarized in Fig. 1. Such clarification should be helpful in future re-collections of specimens. This work also raises the number of endemic taxa to 35 (74.5 % of endemism), a rate comparable to that of Colombia (75.6 %) and only surpassed in northern South America by Venezuela (91.3 %) [79,95]. For instance, Ecuador has been recognized as the probable center of dispersion for the scorpion genus Teuthraustes, in the family Chactidae, with half of the described species (n = 12) being endemic to the country [20]. Such dynamic speciation of Ecuadorian scorpions has been attributed to an evolutionary mode involving genetic drift in small founder populations, as the plant genera Gasteranthus (Gesneriaceae) and Anthurium (Araceae), with 25 and 50 %, respectively, of their world total species endemic to the environs of Ecuador [17,[96][97][98].
The incidence of scorpion stings in endemic areas is the result, among other factors, of the distribution areas of noxious species, their local abundance and ecology. The most speciose scorpion genera in Ecuador are Tityus (16 spp.), Teuthraustes (12 spp.), and Hadruroides (7 spp.), followed by Ananteris (3 spp.), Brachistosternus (2 spp.) and Centruroides (2 spp.), notwithstanding differences in their relative abundance among the biogeographical areas of "Costa," "Sierra" and "Oriente" (Fig. 2). Scorpions in the genus Hadruroides are very abundant along the hyperxerophitic coastal areas (in provinces of El Oro, Guayas, and Santa Elena) and can be found under stones and dry manure [14]. There are no reports on the abundance of Ecuadorian Brachistosternus spp. but they are common in dunes of the Peruvian central and northern coast and should present a similar ecology in Ecuador, at least in the case of B. (B.) ehrenbergii [34]. Species in the genus Teuthraustes in Ecuador are mostly forest-dwelling taxa, native to the inter-Andean valleys, and are not hazardous to humans as shown in the case of T. atramentarius, a synanthropic, abundant species in the area of Quito, province of Pichincha [88,89]. As stated above, C. margaritatus is the most common species found in domiciliary environments along the Ecuadorian coast and in populated areas such as Guayaquil and Milagro (province of Guayas), Babahoyo and Quevedo (province of Los Ríos), Portoviejo, Manta, and Chone (province of Manabí). Ananteris spp. are mostly sylvatic species. Specimens of Tityus spp. are abundant in domiciliary and peridomiciliary habitats of rural communities located in tropical and subtropical rain forest areas of Sucumbíos and Morona Santiago ("Oriente" area) and also in the province of Esmeraldas ("Costa" area), where they have been responsible for severe and lethal cases of scorpionism.
Traditionally, scorpions were not considered dangerous in Ecuador and their sting was supposedly fiercer if specimens from the coastal areas were involved, based on the notion that species from drier places produce venoms with higher toxicity [99]. Regardless of the species, envenoming manifestations in humans, which were claimed to be predominantly local, were reported to resemble those derived from wasp or bee stings [99]. Such an assumption, which has prevailed in modern times, is a consequence of the low toxicity towards vertebrates of the venoms produced by C. margaritatus and T. atramentarius, which are the most common urban species in the country. It is clear from the above account that noxious scorpion species inhabit Ecuador and are capable of producing significant morbidity and pediatric mortality.
According to the species involved, their areas of distribution and the available knowledge of the venom action and composition of allied taxa, as presented in this annotated checklist, we propose a classification of the Ecuadorian scorpion fauna as follows: 1. Species in genera Hadruroides, which are mainly coastal (Fig. 4), would produce severe accidents only if envenoming occurs by a central pathway. Local manifestations such as intense pain, edema and ulceration are expected [100]. Venoms of Hadruroides spp. contain cytotoxic components that may produce heart muscle disruption. Sting by Brachistosternus spp., also a coastal species in Ecuador [with the exception of B. (B.) pegnai, restricted to Carchi], and recognized by their generally clear and yellowish coloration, produces intense pain in humans without further complications, although some venoms contain neurotoxins that can produce autonomic effects [35].

Species in genera Centruroides and Teuthraustes
inhabiting Ecuador, particularly C. margaritatus and T. atramentarius (Fig. 3) appear not to produce venoms significantly toxic to humans. For instance, envenoming by the C. margaritatus population inhabiting the surroundings of Cali, Colombia -