Horizontal gene transfer underlies the painful stings of asp caterpillars (Lepidoptera: Megalopygidae).

Larvae of the genus Megalopyge (Lepidoptera: Zygaenoidea: Megalopygidae), known as asp or puss caterpillars, produce defensive venoms that cause severe pain. Here, we present the anatomy, chemistry, and mode of action of the venom systems of caterpillars of two megalopygid species, the Southern flannel moth Megalopyge opercularis and the black-waved flannel moth Megalopyge crispata. We show that megalopygid venom is produced in secretory cells that lie beneath the cuticle and are connected to the venom spines by canals. Megalopygid venoms consist of large aerolysin-like pore-forming toxins, which we have named megalysins, and a small number of peptides. The venom system differs markedly from those of previously studied venomous zygaenoids of the family Limacodidae, suggestive of an independent origin. Megalopygid venom potently activates mammalian sensory neurons via membrane permeabilization and induces sustained spontaneous pain behavior and paw swelling in mice. These bioactivities are ablated by treatment with heat, organic solvents, or proteases, indicating that they are mediated by larger proteins such as the megalysins. We show that the megalysins were recruited as venom toxins in the Megalopygidae following horizontal transfer of genes from bacteria to the ancestors of ditrysian Lepidoptera. Megalopygids have recruited aerolysin-like proteins as venom toxins convergently with centipedes, cnidarians, and fish. This study highlights the role of horizontal gene transfer in venom evolution.

Production, composition, and mode of action of the painful defensive venom produced by a limacodid caterpillar, Doratifera vulnerans.

Venoms have evolved independently several times in Lepidoptera. Limacodidae is a family with worldwide distribution, many of which are venomous in the larval stage, but the composition and mode of action of their venom is unknown. Here, we use imaging technologies, transcriptomics, proteomics, and functional assays to provide a holistic picture of the venom system of a limacodid caterpillar, Doratifera vulnerans Contrary to dogma that defensive venoms are simple in composition, D. vulnerans produces a complex venom containing 151 proteinaceous toxins spanning 59 families, most of which are peptides <10 kDa. Three of the most abundant families of venom peptides (vulnericins) are 1) analogs of the adipokinetic hormone/corazonin-related neuropeptide, some of which are picomolar agonists of the endogenous insect receptor; 2) linear cationic peptides derived from cecropin, an insect innate immune peptide that kills bacteria and parasites by disrupting cell membranes; and 3) disulfide-rich knottins similar to those that dominate spider venoms. Using venom fractionation and a suite of synthetic venom peptides, we demonstrate that the cecropin-like peptides are responsible for the dominant pain effect observed in mammalian in vitro and in vivo nociception assays and therefore are likely to cause pain after natural envenomations by D. vulnerans Our data reveal convergent molecular evolution between limacodids, hymenopterans, and arachnids and demonstrate that lepidopteran venoms are an untapped source of novel bioactive peptides.

Structure and bioactivity of an insecticidal trans-defensin from assassin bug venom.

Disulfide-rich peptides such as defensins play diverse roles in immunity and ion channel modulation, as well as constituting the bioactive components of many animal venoms. We investigated the structure and bioactivity of U-RDTX-Pp19, a peptide previously discovered in venom of the assassin bug Pristhesancus plagipennis. Recombinant Pp19 (rPp19) was found to possess insecticidal activity when injected into Drosophila melanogaster. A bioinformatic search revealed that domains homologous to Pp19 are produced by assassin bugs and diverse other arthropods. rPp19 co-eluted with native Pp19 isolated from P. plagipennis, which we found is more abundant in hemolymph than venom. We solved the three-dimensional structure of rPp19 using 2D 1H NMR spectroscopy, finding that it adopts a disulfide-stabilized structure highly similar to known trans-defensins, with the same cystine connectivity as human α-defensin (I-VI, II-IV, and III-V). The structure of Pp19 is unique among reported structures of arthropod peptides.

Pediatric Toxicoepidemiology of Tramadol Intoxication in Iran: A 5-year Cross-Sectional Study.

OBJECTIVE: We aimed to find the toxicoepidemiological indicators of tramadol poisoning in children and also the relationship of these indicators (such as demographic characteristics, and referral time) with the final therapeutic outcome. METHODS: In this cross-sectional study with retrospective data collection, we included the records for all the patients under 18 that have been admitted due to tramadol poisoning between 2010 and 2015 to Noor and Ali-Asghar (PBUH) University hospital which serves as the referral medical center for acute poisonings management in the central part of Iran and is located in Isfahan. Demographic characteristics, ingested dose, dosage forms, clinical manifestations, coingested drugs, and the outcome of treatment for all pediatric patients were documented and descriptively analyzed. FINDINGS: Demographic and clinical data of a total of 189 patients including 101 male (53.4%) with a mean age of 16.66 ± 2.64 years were abstracted and included in this study. The average time between tramadol ingestion and hospital admission was 3.39 ± 3.23 h. Mean duration of hospitalization was 12.3 ± 10.7 h. In all cases, the route of drug exposure was oral, and the most common form of drug dosage form was 100 mg tablets (n = 122) proceeded by 200 mg tablets (n = 32). The mean estimated dose of ingested tramadol was 1126 ± 1061 mg (median, 900 range, 50-7000 mg). 43.9% of the poisoned patients were high school students, and 23.3% had a high school diploma. Intentional intoxications were reported in 93.1% cases and 42.9% had coingestions. Activated charcoal (87.3%), gastric lavage (59.3%), oxygen therapy with mask (46.6%), naloxone (11.6%), anticonvulsants (13.2%), and intubation and ventilation (5.3%) were done as first-line therapeutic measures. CONCLUSION: Our results suggest that the trend of acute tramadol poisoning among children is decreasing, mostly accidental in adolescents and commonly intentional among young children. Proper education to improve emotional intelligence for young adults and to keep drugs out of reach of the children and safer packaging is recommended to reduce tramadol poisoning incidence in the pediatric population.