A new species of Loxosceles Heineken & Lowe (Araneae, Sicariidae), with updated distribution records and biogeographical comments for the species from Mexico, including a new record of Loxoscelesrufescens (Dufour)

Violins we see, species we don't… Species delimitation of the spider genus Loxosceles Heineken & Lowe (Araneae: Sicariidae) from North America using morphological and molecular evidence

In modern systematics, different sources of evidence are commonly used for the discovery, identification, and delimitation of species, especially when morphology fails to delineate between species or in underestimated species complexes or cryptic species. In this study, morphological data and two DNA barcoding markers-cytochrome c oxidase subunit I (COI) and internal transcribed spacer 2 (ITS2)-were used to delimit species in the spider genus Loxosceles from North America. The molecular species delimitation analyses were carried out using three different methods under the corrected p-distance Neighbor-Joining (NJ) criteria: 1) Assemble Species by Automatic Partitioning (ASAP), 2) General Mixed Yule Coalescent model (GMYC), and 3) Bayesian Poisson Tree Processes (bPTP). The analyses incorporated 192 terminals corresponding to 43 putative species of Loxosceles, of which 15 are newly recognized herein, as putative new species, based on morphology and congruence between molecular methods with COI. The average intraspecific genetic distance (p-distance) was <2%, whereas the average interspecific genetic distance was 15.6%. The GMYC and bPTP molecular methods recovered 65-79 and 69 species respectively, overestimating the diversity in comparison with morphology, whereas the ASAP method delimited 60 species. The morphology of primary sexual structures (males palps and female seminal receptacles) was congruent with most of the molecular methods mainly with COI, showing that they are robust characters for identification at the species level. For species delimitation COI was more informative than ITS2. The diversity of Loxosceles species is still underestimated for North America, particularly in Mexico which holds the highest diversity of this genus worldwide.

IL, Duran CFD, Cammayo MFKM, Alviola MS, Mercado SMQ, Osio CAL, Eusebio OL, Lucañas CC, Barrion AT. Integrative taxonomy reveals first record of Loxoscelesrufescens (Dufour, 1820) (Araneae, Sicariidae) in the Philippines

Background

The spider family Sicariidae Keyserling, 1880 represented by the synanthropic Mediterranean recluse spider, Loxoscelesrufescens (Dufour, 1820), is reported in the Philippines for the first time, based on morphological and molecular data. The introduced spider was observed in a small cave (Kamantigue Cave) in Lobo, Batangas Province. Considering the medical importance of this spider, the proximity of its habitat to human habitation and tourist sites poses a potential public health concern.

New information

This study reports on the first record of the family Sicariidae in the Philippines and the fourth recorded occurrence of L.rufescens in Southeast Asia.

Comparative treatment with hyperbaric oxygen therapy in a model of systemic loxoscelism in rats

Objectives

Spiders of the Loxosceles genus, known as violin spiders, produce venom with dermonecrotic and systemic effects, as it is a species widely distributed in the world, its study represents a high medical relevance. Systemic loxoscelism, which occurs in 1 in 5 cases and is the most frequent in children, can be fatal, so the study of effective therapy is of great relevance. In the present study, we compared different therapeutic options to mitigate the systemic effects of Loxosceles boneti venom in a model in which prepubertal rats were used.

Materials and Methods

A model of systemic intoxication by L. boneti venom was provoked in male Wistar rats. Study groups were formed: healthy control, with venom and untreated control, treatment with N-acetylcysteine, and/or hyperbaric oxygenation therapy. Subsequently, pathological analysis of the kidney and lung was performed. The oxidant-antioxidant response was evaluated, and molecular analysis of the COX-1 and COX-2 enzymes was performed.

Results

Regenerative changes were observed at the cellular level in both treatments, being more noticeable in the hyperbaric oxygen therapy (HBO) group. The anti-oxidant response was outstanding in the same group.

Conclusion

Both treatments offer considerable benefits, however; further studies are needed to provide adequate therapeutics.

Clinical aspects, diagnosis and management of Loxosceles spider envenomation: literature and case review

The genus Loxosceles comprises 140 species widely distributed around the world. These spiders are nocturnal, sedentary and remarkably nonaggressive, although they cause accidents in humans with wide degrees of severity, generating signs and symptoms that define the clinical condition known as loxoscelism. Its local signs and symptoms were first reported in 1872, and over the years, a large medical literature has been accumulated; unfortunately, it is not always trustworthy. Assessing the reliability of such information, we reviewed 120 case reports of loxoscelism published in 84 articles over the past 20 years. This search allowed us to gather information on the clinical aspects, diagnosis and treatment of loxoscelism, showing that the severity of these accidents has multiple degrees and that it is influenced by many factors. Thus, coupled with epidemiological and species occurrence information, this study can be a useful tool for the clinical practice of loxoscelism. It may support and provide a multidisciplinary view that should be taken into consideration when establishing the therapeutic approach in cases of Loxosceles envenomation.

Under an integrative taxonomic approach: the description of a new species of the genus Loxosceles (Araneae, Sicariidae) from Mexico City

A new species of the spider genus Loxosceles Heineken & Lowe, 1832, Loxosceles tenochtitlan Valdez-Mondragón & Navarro-Rodríguez, sp. nov., is described based on adult male and female specimens from the states of Mexico City, Estado de Mexico and Tlaxcala. Integrative taxonomy including traditional morphology, geometric and lineal morphology, and molecules (DNA barcodes of cytochrome c oxidase subunit 1 (CO1) and internal transcribed spacer 2 (ITS2)), were used as evidence to delimit the new species. Four methods were used for molecular analyses and species delimitation: 1) corrected p-distances under neighbor joining (NJ), 2) automatic barcode gap discovery (ABGD), 3) general mixed yule coalescent model (GMYC), and 4) poisson tree processes (bPTP). All molecular methods, traditional, geometric and lineal morphology were consistent in delimiting and recognizing the new species. Loxosceles tenochtitlan sp. nov. is closely related to L. misteca based on molecular data. Although both species are morphologically similar, the average p-distance from CO1 data was 13.8% and 4.2% for ITS2 data. The molecular species delimitation methods recovered well-supported monophyletic clusters for samples of L. tenochtitlan sp. nov. from Mexico City + Tlaxcala and for samples of L. misteca from Guerrero. Loxosceles tenochtitlan sp. nov. is considered a unique species for three reasons: (1) it can be distinguished by morphological characters (genitalic and somatic); (2) the four different molecular species delimitation methods were congruent to separate both species; and (3) there is variation in leg I length of males between both species, with the males of L. misteca having longer legs than males of L. tenochtitlan sp. nov., also morphometrically, the shape of tibiae of the palp between males of both species is different.