Alien spiders: First record of Loxosceles gaucho Gertsch, 1967 (Araneae: Sicariidae) in the Amazon region, Brazil

Abstract

We present the first record for Loxosceles gaucho Gertsch, 1967 in the Amazonian region of Brazil. Four males, fifteen females and forty-nine immatures were collected in different places in Manaus, Amazonas, Brazil. This is the third species of Loxosceles reported in the Amazon region along with L. amazonica Gertsch, 1967, and L. similis Moenkhaus, 1898. This is the first record of an invasive species of a venomous animal in the state of Amazonas, Brazil, which is noteworthy due to its synanthropic habit, which increases the risk to the local population.

Key-Words
Manaus; Aranha marrom; Brown recluse spider; Venomous species

INTRODUCTION

Loxosceles Heinecken & Lowe, 1832 is a cosmopolite genus of spiders that are commonly known as “violin spiders”, “recluse spiders” or “brown recluse spiders” in North America (Valdez-Mondragón et al., 2018). In Brazil, Loxosceles spiders are better known as “aranhas-marrons” (brown spiders, in Portuguese) and are distributed through the whole country (Table 1).

Table 1
Species of Loxosceles recorded for Brazil. Data based exclusively on taxonomic papers included in the World Spider Catalog, version 20.5. 2019.

Species	Distribution
Loxosceles adelaida Gertsch, 1967	¹Rio de Janeiro and ¹São Paulo
Loxosceles amazonica Gertsch, 1967	¹,³Amazonas, ²Pará, ²Tocantins, ²Bahia, ²Ceará, ²Maranhão, ²Paraiba, ²Pernambuco, ²Piaui, ⁴Rio Grande do Norte and ²Mato Grosso
Loxosceles anomala (Mello-Leitão, 1917)	⁸Minas Gerais
Loxosceles cardosoi Bertani, von Schimonsky & Gallão, 2018	⁵Bahia
Loxosceles carinhanha Bertani, von Schimonsky & Gallão, 2018	⁵Bahia
Loxosceles chapadensis Bertani, Fukushima & Nagahama, 2010	⁵Bahia
Loxosceles ericsoni Bertani, von Schimonsky & Gallão, 2018	⁵Minas Gerais
Loxosceles gaucho Gertsch, 1967	¹São Paulo, ¹,⁹Paraná, ¹Rio Grande do Sul and Amazonas*
Loxosceles hirsuta Mello-Leitão, 1931	⁶Paraná and ⁶Rio Grande do Sul
Loxosceles immodesta (Mello-Leitão, 1917),	⁸São Paulo
Loxosceles intermedia Mello-Leitão, 1934	⁷São Paulo, ¹,⁷Rio de Janeiro, ⁹Paraná and Distrito Federal
Loxosceles karstica Bertani, von Schimonsky & Gallão, 2018	⁵Bahia and ⁵Minas Gerais
Loxosceles laeta (Nicolet, 1849)	¹Rio Grande do Sul, ¹Santa Catarina, ⁹Paraná, ¹São Paulo, ¹Minas Gerais and ¹⁰Rio de Janeiro
Loxosceles muriciensis Fukushima, de Andrade & Bertani, 2017	⁴Alagoas
Loxosceles niedeguidonae Gonçalves-de-Andrade, Bertani, Nagahama & Barbosa, 2012	¹¹Piaui
Loxosceles puortoi Martins, Knysak & Bertani, 2002	¹²Tocantins
Loxosceles similis (Moenkhaus 1898),	¹Pará, ¹São Paulo and ¹Minas Gerais
Loxosceles troglobia Souza & Ferreira, 2018	¹³Bahia
Loxosceles willianilsoni Fukushima, de Andrade & Bertani, 2017	⁴Rio Grande do Norte

• ¹Gertsch, 1967; ²Silveira, 2015; ³et al.,; ⁴et al.,; ⁵et al.,; ⁶Mello-Leitão, 1931; ⁷Mello-Leitão, 1934; ⁸Mello-Leitão, 1917; ⁹Marques-da-Silva & Fischer, 2005; ¹⁰Silveira, 2009; ¹¹et al.,; ¹²et al.,; ¹³Souza & Ferreira, 2018.

Many species in the genus can cause severe envenoming of humans, which is known as loxoscelism (Swanson & Vetter, 2006). The venom of Loxosceles causes an intense inflammatory process around the site of the bite along with vasoconstriction, edema, hemorrhage and focal necrosis, therefore the clinical picture may be cutaneous or cutaneous-visceral (Barbaro & Cardoso, 2003). In Brazil, Loxosceles intermediaMello-Leitão, 1934, Loxosceles laeta (Nicolet, 1849) and Loxosceles gauchoGertsch, 1967 are the main species responsible for in-house bites on humans (Cardoso et al., 2003). There is a single species recorded In Amazonas, Brazil, Loxosceles amazonica Gertsch, 1967 (Gertsch, 1967; Almeida et al., 2017).

Loxosceles gaucho is an endemic species from south and southwest of Brazil, being its type locality known for São Paulo (Gertsch, 1967). The female of this species is easily identifiable by the presence of a transverse and sclerotized plate firmly holding the seminal receptacles in genitalia of female (Figs. 2B-C), while males are easily identified by having the palpal femur 4 times longer than wide and by the embolus thick at base, forming sinuous curve (Figs. 1B-C) (Gertsch, 1967). The distribution of the species is currently known only for the states of São Paulo, Minas Gerais, Rio Grande do Sul and Paraná (Gertsch, 1967; Fischer, 1994). The purpose of this work is to record for the first time L. gaucho in northern Brazil (Amazonas, Manaus), to report a checklist of the known Brazilian species of Loxosceles and to present an identification key to the known Loxosceles species of Amazonas, Brazil.

MATERIAL AND METHODS

The specimens were captured in the period from 2016 to 2018 in two popular farmers market, one located at the central region of the Manaus city, at Manaus Moderna farmers market (03°08′28.20″S, 60°01′19.35″W) and the other at the eastern part of the city, at the Coroado farmers market (03°05′00.37″S, 59°58′49.18″W). The spiders were located in cardboard boxes and in debris next to the farmers market and were manually collected. Egg sacs and immatures were also collected at the Coroado farmers market.

Specimens were deposited in the Invertebrate Zoology Collection at Instituto Nacional de Pesquisas da Amazônia (INPA). Specimen identification was made using Gertsch (1967). The left male palp was illustrated in prolateral view and female spermathecae were illustrated in prolateral and retrolateral view. Digital images were taken using a stereomicroscope Leica M205A equipped with a camera (Leica DMC4500), the illustrations were made in an Adobe Photoshop CC 2017 and the distribution map was created using SimpleMappr (Shorthouse, 2010).

Material examined (4 ♂ and 15 ♀): 2 ♂ and 2 ♀, BRAZIL, Amazonas, Manaus, Centro, (03°08′28.20″S, 60°01′19.35″W) 26.viii.2016, M.Q. Almeida leg.; 2 ♂ and 3 ♀, 49 juveniles, BRAZIL, Amazonas, Manaus, Coroado, (03°05′00.37″S, 59°58′49.18″W), 09.vi.2018, M.Q. Almeida leg.; 9 ♀ and 52 specimens prelarva state, BRAZIL, Amazonas, Manaus, Coroado, (3°8′28.20″S, 60°1′19.35″W), 09.vi.2018, M.Q. Almeida leg.; 1 ♀ BRAZIL, Amazonas, Manaus, Coroado, (03°08′28.20″S, 60°01′19.35″W), 09.vi.2018, M.Q. Almeida leg. The specimens will be deposited in the Invertebrate Collection of the Instituto Nacional de Pesquisas da Amazônia (INPA), Manaus, Amazonas, Brazil.

RESULTS

A total of 68 specimens of L. gaucho were collected, four males (Fig. 1), fifteen females (Figs. 2, 3A) and forty-nine juveniles. Egg sacs were found with 52 specimens in prelarva state (Figs. 3B-E). This is the second record of a Loxosceles species to state of Amazonas, Brazil, as previously, only L. amazonica was registered. These two species can be distinguishable by the identification key below.

Figure 1
Loxosceles gaucho (male). (A) habitus; (B) palp, retrolateral view; (C) palp, prolateral view. Scale bars: A, 3 mm; B-C, 2 mm.

Figure 2
Loxocesles gaucho (female). (A) habitus; (B) spermathecae, ventral view; (C) epigynum, dorsal view. Scale bars: A, 3 mm; B-C, 2 mm.

Figure 3
Loxocesles gaucho. (A) (female), live specimen; (B) eggsacs; (C) immatures live specimens; (D) specimens in prelarva state; (E) specimen in prelarva state, detail.

Key to the Loxosceles species in Amazonas state, Brazil (Modified from Gertsch, 1967 )

Males

1. Palpal tarsus as wide as palpal tibia. Apex of embolus forming a sinuous curve (Figs. 1B-C) Loxosceles gaucho Gertsch

- Palpal tarsus thinner than palpal tibia. Apex of embolus with a mild curvature (Figs. 4B-C) Loxosceles amazonica Gertsch

Figure 4
Loxosceles amazonica. (A) (Female), live specimen. (B) palp, retrolateral view; (C) palp, prolateral view. (D) spermathecae, ventral view.

Females

1. Spermathecae with a transverse and sclerotized plate and absence of globular lobes at apex (Fig. 2C)Loxosceles gaucho Gertsch

- Spermathecae lacking a sclerotized plate and presence of a group of small globular lobes at apex (Fig. 4D) Loxosceles amazonica Gertsch

Of the five Brazilian regions, the North and the Central-West have the lesser number of species of Loxosceles recorded (3 species in each of these regions) whereas the Northeast has the most species recorded (11 species) (Table 1).

DISCUSSION

The introduction of non-native species can cause serious risks to local biodiversity and some species has the potential to cause envenomation of humans, such as spiders and scorpions (Mack et al., 2000; Silveira, 2009; Duncan et al., 2010; Bertani et al., 2018a).

Most probably, L. gaucho was accidentally introduced in the city of Manaus alongside the trade of fruits, vegetables and other goods from the Southeast region to the North region of the country, since these spiders were collected in farmers’ market in the city (Fig. 5). This species seems to be well adapted to the region’s climate and already has established populations, since egg sacs were collected (Fig. 3B) and also a large number of immatures were collected in one of the localities (Fig. 3C). Those spiders adapt themselves very well in the urban environment due to its various types of shelters (boxes, holes, debris), high availability of alimentary resources and the scarcity of natural predators.

Figure 5
Map showing records of L. gaucho in Brazil. It is indicated in brown the Brazilian states with records in literature: São Paulo and Minas Gerais (Gertsch, 1967; Cardoso et al., 2003), Paraná and Rio Grande do Sul (Gertsch, 1967; Fischer, 1994). In yellow the new record in the state of Amazonas, Manaus city.

Duncan et al. (2010) reported that a female specimen of Loxosceles was identified by Brignoli (1976) as L. gaucho in Tunisia, which has somatic and spermathecae morphology indistinguishable from Brazilian L. gaucho. The formerly mentioned authors discuss that the Tunisian specimen is a representative of another population of L. gaucho that has dispersed across the Atlantic through human trade activities. This idea is supported by the fact that the Tunisian L. gaucho was found near Sfax, the major port and commercial hub in the Mediterranean and a likely place to have introduced species. The city of Manaus is also a city with a large portuary activity although fluvial and the introduction of L. gaucho in Manaus may have been due to this way.

This is the first record of accidental introduction of a venomous animal in the state of Amazonas (Fig. 5). Finally, we hope than beside alert the Public Health Agencies, this led to the discussion of preventive measures to reduce the potential damage to human health and the necessity of having measures to control the identified focus for this species in Manaus.

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• Published with the financial support of the "Programa de Apoio às Publicações Científicas Periódicas da USP"

Edited by

Edited by: Carlos José Einicker Lamas

Publication Dates

• Publication in this collection
  28 Nov 2019
• Date of issue
  2019

History

• Received
  24 Apr 2019
• Accepted
  14 Oct 2019