30 October, 2017

A new species of Physoctonus from southern Amazonia, Brazil

Wilson Lourenco has recently published an article presenting av new species of Physoctonus Mello-Leitao, 1934 (Buthidae) from southern Amazonia, Brazil.

Physoctonus amazonicus Lourenco, 2017

The biogeography of Physoctonus is also discussed.

Further studies on new specimens of the rare genus Physoctonus Mello-Leitão, 1934, lead to the description of a third new species. Until now only Physoctonus debilis (C. L. Koch, 1840) and Physoctonus striatus Esposito et al., 2017, were known from sites located in the caatingas of the north-east region of Brazil. The new species of Physoctonus was collected by the French arachnologist J. Vellard in the Campos do Pará during his field trips back to the 1920/1930, and entrusted to the author in the early 1980s. The populations of P. debilis and P. striatus from north-east Brazil and that of the new species certainly present disrupted distributions. Biogeographical comments on this pattern of distribution are also added.

Lourenco WR. A new species of Physoctonus Mello-Leitão, 1934 from the ‘Campos formations’ of southern Amazonia (Scorpiones, Buthidae). ZooKeys. 2017;711. [Open Access]

Thanks to Venomtech on Twitter for informing me about this article!

Family Buthidae

27 October, 2017

A new vaejovid genus from USA and Mexico

Michael E. Soleglad and co-workers have recently published an article presenting a new genus in the family Vaejovidae from USA and Mexico. Four species have been included in the new genus.

Catalinia Soleglad, Ayrey, Graham & Fet, 2017 (New genus).

Catalinia andreas (Gertsch & Soleglad, 1972) (Previously Pseudouroctonus andreas (Gertsch & Soleglad, 1972)).

Catalinia castanea (Gertsch & Soleglad, 1972) (Raised from subspecies status. Previously Pseudouroctonus minimus castaneus (Gertsch & Soleglad, 1972)).

Catalinia minima (Kraepelin, 1911) (Previously Pseudouroctonus minimus minimus (Kraepelin, 1911)).

Catalinia thompsoni (Gertsch & Soleglad, 1972) (Raised from subspecies status. Previously Pseudouroctonus minimus thompsoni (Gertsch & Soleglad, 1972)).

The habitat and biogeography of the new species is discussed. An identification key is also provided.

Genus Catalinia, gen. nov. (Scorpiones: Vaejovidae) is described from southern California, USA and Baja California, Mexico. The genus is composed of four species formerly placed in Pseudouroctonus: Catalinia minima (Kraepelin, 1911), comb. nov. (type species), C. andreas (Gertsch et Soleglad, 1972), comb. nov., C. castanea (Gertsch et Soleglad, 1972), comb. nov., and C. thompsoni, comb. nov. (Gertsch et Soleglad, 1972). Major diagnostic characters of Catalinia include a carapace with a very weak anterior indentation, a very stout metasoma with little or no tapering from segment I to V, and a mating plug with two partial bases. Evidence is presented suggesting that Catalinia is closely related to the “apacheanus” species group of Pseudouroctonus.

Soleglad ME, Ayrey RF, Graham MR, Fet V. Catalinia, a new scorpion genus from southern California, USA and northern Baja California, Mexico (Scorpiones: Vaejovidae). Euscorpius. 2017(251):1-64. [Open Access]

Family Vaejovidae

06 October, 2017

An update on the medical important scorpions of Mexico

Mexico has a very high diversity of scorpions, but also many medical important species in the genus Centruroides Marx, 1890 (Buthidae). Several of these species have an urban distribution making scorpions a significant health problems in some areas.

Lidia Riano-Umbarila and co-workers have recently published a major study of the medical importance of several Centruroides species based on LD50 tests (a controversial test from a animal welfare and ethics point of view). The article add more knowledge to the list of potential dangerous scorpions species in Mexico (click on the picture to see the species mentioned in this study).

The increment in the number of scorpion envenoming cases in Mexico is mainly associated to the rapid growth of the urban areas, and consequently, to the invasion of natural habitats of these arachnids. On the other hand, there is a great diversity of scorpion species, so it is indispensable to identify those of medical importance, which we now know are many more than the 7-8 previously reported as dangerous to humans. Because different LD50 values have been reported for the venom of the same species, probably due to variations in the experimental conditions used, in this work we determined the LD50 values for the venoms of 13 different species of scorpions using simple but systematic procedures. This information constitutes a referent on the level of toxicity of medically important scorpion species from Mexico and establishes the bases for a more comprehensive assessment of the neutralizing capacity of current and developing antivenoms.

Riano-Umbarila L, Rodriguez-Rodriguez ER, Santibanez-Lopez CE, Guereca L, Uribe-Romero SJ, Gomez-Ramirez IV, et al. Updating knowledge on new medically important scorpion species in Mexico. Toxicon. 2017;138:130-7. [Subscription required for full text]

American "superbat" (Antrozous pallidus) is immune against scorpion venom

The Pallid Bat (Antrozous pallidus). Photo: Courtesy by Connor Long (C)

A few weeks ago an article by  Bradley Hopp and co-workers presented a study of the Pallid Bat (Antrozous pallidus) using the Arizona Bark Scorpion (Centruroides sculpturatus Ewing, 1928) as prey. The Arizona Bark Scorpion is the most venomous scorpion in the US, and the researchers observed that the hunting bats were stung by their prey without any serious symptoms.

Systematic observations and experiments with injections of scorpion venom in the bats confirmed that The Pallid Bat is probably resistant to the venom of the bark scorpion. An altered sodium ion channel function may partly be the mechanism for this resistance.

The pallid bat (Antrozous pallidus), a gleaning bat found in the western United States and Mexico, hunts a wide variety of ground-dwelling prey, including scorpions. Anecdotal evidence suggests that the pallid bat is resistant to scorpion venom, but no systematic study has been performed. Here we show with behavioral measures and direct injection of venom that the pallid bat is resistant to venom of the Arizona bark scorpion, Centruroides sculpturatus. Our results show that the pallid bat is stung multiple times during a hunt without any noticeable effect on behavior. In addition, direct injection of venom at mouse LD50 concentrations (1.5 mg/kg) has no effect on bat behavior. At the highest concentration tested (10 mg/kg), three out of four bats showed no effects. One of the four bats showed a transient effect suggesting that additional studies are required to identify potential regional variation in venom tolerance. Scorpion venom is a cocktail of toxins, some of which activate voltagegated sodium ion channels, causing intense pain. Dorsal root ganglia (DRG) contain nociceptive neurons and are principal targets of scorpion venom toxins. To understand if mutations in specific ion channels contribute to venom resistance, a pallid bat DRG transcriptome was generated. As sodium channels are a major target of scorpion venom, we identified amino acid substitutions present in the pallid bat that may lead to venom resistance. Some of these substitutions are similar to corresponding amino acids in sodium channel isoforms responsible for reduced venom binding activity. The substitution found previously in the grasshopper mouse providing venom resistance to the bark scorpion is not present in the pallid bat, indicating a potentially novel mechanism for venom resistance in the bat that remains to be identified. Taken together, these results indicate that the pallid bat is resistant to venom of the bark scorpion and altered sodium ion channel function may partly underlie such resistance.

Hopp BH, Arvidson RS, Adams ME, Razak KA. Arizona bark scorpion venom resistance in the pallid bat, Antrozous pallidus. PLoS One. 2017;12(8):e0183215. [Open Access]

Thanks to Matt Simon for informing me about this article.