Mosquito repellents in frog skin

Abstract

The search for novel insect repellents has been driven by health concerns over established synthetic compounds such as diethyl-m-toluamide (DEET). Given the diversity of compounds known from frog skin and records of mosquito bite and ectoparasite infestation, the presence of mosquito repellents in frogs seemed plausible. We investigated frog skin secretions to confirm the existence of mosquito repellent properties. Litoria caerulea secretions were assessed for mosquito repellency by topical application on mice. The secretions provided protection against host-seeking Culex annulirostris mosquitoes. Olfactometer tests using aqueous washes of skin secretions from L. caerulea and four other frog species were conducted to determine whether volatile components were responsible for repellency. Volatiles from Litoria rubella and Uperoleia mjobergi secretions were repellent to C. annulirostris, albeit not as repellent as a DEET control. The demonstration of endogenous insect repellents in amphibians is novel, and demonstrates that many aspects of frog chemical ecology remain unexplored.

A common pumiliotoxin from poison frogs exhibits enantioselective toxicity against mosquitoes

“…and͞or Uperoleia mjobergi) kill blow-flies on contact (20) or repel mosquitoes (21). The mosquito repellents emanating from these frogs are believed to be volatile terpenes (21). PTX 251D is moderately volatile; however, our methods do not indicate whether mosquitoes detect it by olfaction.…”

“…In addition to the field tests cited earlier on the responses of ants (5) and spiders (6) to D. pumilio, laboratory studies show that the skin secretions of Australian frogs (Litoria spp. and͞or Uperoleia mjobergi) kill blow-flies on contact (20) or repel mosquitoes (21). The mosquito repellents emanating from these frogs are believed to be volatile terpenes (21).…”

Unraveling host-vector-arbovirus interactions by two-gene high resolution melting mosquito bloodmeal analysis in a Kenyan wildlife-livestock interface

“…This kind of feeding could be opportunistic when both amphibians and mosquitoes localize in swampy habitats. Alternatively, such feeding behavior may be restricted to specific mosquito species as some mosquito repellants have been isolated from frog skin [47], and mosquitoes may possibly benefit from antimicrobial peptides found in amphibian skin [48]. This study clearly demonstrates the improved resolution of HRM-based bloodmeal analysis by using two distinct molecular markers, revealing broad opportunistic host feeding patterns among mosquito vectors in arbovirus endemic regions of Kenya.…”

Fish mucous cocoons: the ‘mosquito nets’ of the sea

“…In contrast to the astonishingly diverse behavioural adaptations [24] and the use of toxic compounds in other animals [27], parrotfish use a physiological adaptation to deter parasites. This involves large highly specialized glands in the gill cavity and/or under the operculum [3], which secrete a structure that not only protects the whole fish but also allows the fish to sleep, a combination of features not known to occur in any other animal.…”

“…This involves large highly specialized glands in the gill cavity and/or under the operculum [3], which secrete a structure that not only protects the whole fish but also allows the fish to sleep, a combination of features not known to occur in any other animal. Physiological adaptations to control ectoparasites and other fouling organisms in animals are relatively rare and tend to involve chemical compounds [27]. Mucous cocoons, in contrast, are more reminiscent of the barriers, such as mosquito nets, constructed by humans to control biting arthropods [28].…”