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

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.