title: Venomous Frogs Use Heads as Weapons.
abstract: Venomous animals have toxins associated with delivery mechanisms that can introduce the toxins into another animal. Although most amphibian species produce or sequester noxious or toxic secretions in the granular glands of the skin to use as antipredator mechanisms, amphibians have been considered poisonous rather than venomous because delivery mechanisms are absent. The skin secretions of two Brazilian hylid frogs (Corythomantis greening and Aparasphenodon brunoi) are more toxic than the venoms of deadly venomous Brazilian pitvipers, genus Bothrops; C. greeningi secretion is 2-fold and A. brunoi secretion is 25-fold as lethal as Bothrops venom. Like the venoms of other animals, the skin secretions of these frogs show proteolytic and fibrinolytic activity and have hyaluronidase, which is nontoxic and nonproteolytic but promotes diffusion of toxins. These frogs have well-developed delivery mechanisms, utilizing bony spines on the skull that pierce the skin in areas with concentrations of skin glands. C. greeningi has greater development of head spines and enlarged skin glands producing a greater volume of secretion, while A. brunoi has more lethal venom. C. greeningi and A. brunoi have highly toxic skin secretions and an associated delivery mechanism; they are therefore venomous. Because even tiny amounts of these secretions introduced into a wound caused by the head spines could be dangerous, these frogs are capable of using their skin toxins as venoms against would-be predators.
authors.affiliation: Laboratory of Cell Biology, Instituto Butantan, São Paulo 05503-900, Brazil.
authors.forename: Carlos
authors.initials: C
authors.lastname: Jared
authors.affiliation: Laboratory of Cell Biology, Instituto Butantan, São Paulo 05503-900, Brazil.
authors.forename: Pedro Luiz
authors.initials: PL
authors.lastname: Mailho-Fontana
authors.affiliation: Laboratory of Cell Biology, Instituto Butantan, São Paulo 05503-900, Brazil.
authors.forename: Marta Maria
authors.initials: MM
authors.lastname: Antoniazzi
authors.affiliation: Laboratory of Cell Biology, Instituto Butantan, São Paulo 05503-900, Brazil.
authors.forename: Vanessa Aparecida
authors.initials: VA
authors.lastname: Mendes
authors.affiliation: Laboratory of Cell Biology, Instituto Butantan, São Paulo 05503-900, Brazil.
authors.forename: Katia Cristina
authors.initials: KC
authors.lastname: Barbaro
authors.affiliation: Department of Zoology, Universidade de São Paulo, São Paulo 05422-970, Brazil.
authors.forename: Miguel Trefaut
authors.initials: MT
authors.lastname: Rodrigues
authors.affiliation: Department of Biology, Utah State University, Logan, UT 84322-5305, USA. Electronic address: e.brodie@usu.edu.
authors.forename: Edmund D
authors.initials: ED
authors.lastname: Brodie
mesh_terms: D000374:Aggression; D000664:Amphibian Venoms / Q000494:pharmacology*; D000818:Animals; D001001:Anura / Q000033:anatomy & histology / Q000502:physiology*; D001938:Brazil; D004305:Dose-Response Relationship, Drug; D006257:Head / Q000033:anatomy & histology*; D008297:Male; D051379:Mice; D013045:Species Specificity
chemical_list: D000664:Amphibian Venoms