The true auklets (Genus Aethia) are small planktivorous seabirds of the Bering Sea and North Pacific. Two species, the crested and whiskered auklets produce volatile citrus-like odorants. We here show that the whiskered auklet odorant is composed predominantly of two odd-numbered aldehydes (heptanal and nonanal) with no detectable unsaturated aldehydes. By comparison the crested auklet odorant is dominated by even-numbered aldehydes, both saturated and monounsaturated, ranging in size from 6 to 12 carbons. This is evidence of species-specific acquisition or biosynthetic pathways. We clarify the chemistry of the crested auklet odorant. We cite evidence that the C-12:1 aldehyde in crested auklets is actually two isomers, (Z)-4-dodecenal and (Z)-6-dodecenal. We also report on experimental evidence that aldehyde constituents kill and repel ectoparasites. Efficacy of the aldehydes may increase when they are combined in a mixture. The repellency of the mixture increases with chemical concentration. This suggests that individuals with higher chemical production are likely to repel ectoparasites more effectively.

The exogenous application of chemical repellents is widespread in birds, but endogenous production is exceedingly rare. We herein report a new class of avian defensive compounds isolated from the feathers and volatile odor of the crested auklet (Aethia cristatella). Mass spectra indicate that n-hexanal, n-octanal, n-decanal, Z-4-decenal and a 12-carbon unsaturated aldehyde comprise the auklet odorant. Octanal and hexanal are also secreted in the repugnant metasternal gland emissions of heteropteran insects and are known to be potent invertebrate repellents. We suggest that the auklet odorant functions as an ectoparasite repellent and a signal of mate quality. This would represent a rare and direct link between vigor, quality and parasite resistance, one of several putative bases for mate selection. This is the first report of defensive compounds produced by a seabird or colonial bird and one of the few examples of chemical defense in a polar or subpolar marine vertebrate.

Praying mantids are models for a wide variety of behavioral, physiological, and ecological studies, and sex pheromones have been assumed to be important components of their biology. However, no mantid pheromone has ever been identified. We collected volatiles emitted by females of the mantid, Sphodromantis lineola, via solid phase microextraction (SPME). Mass spectral analysis revealed the collected volatiles to be a mixture of pentadecanal and tetradecanal. We prepared a synthetic mixture of these compounds, and found that males were both attracted to this mixture and stimulated to exhibit typical precopulatory behavior. We then examined male antennae with scanning electron microscopy, and confirmed the presence of porous antennal sensilla typical of insect pheromone receptors, i.e., that male mantids are equipped with the appropriate morphological apparatus to receive volatile chemical signals. Pheromones, in conjunction with visual and tactile cues, are thus an important feature of the reproductive biology of this, and undoubtedly other species of mantids. In addition to adding a crucial aspect of behavioral biology to our knowledge of this group, identification and synthesis of mantid pheromones may be a first step in attracting and aggregating these generalist predators for use in pest control.

The crested auklet, Aethia cristatella, emits a class of aldehydes shown to be potent invertebrate repellents when used by heteropterans against their predators. Our aim was to determine the efficacy of these aldehydes against mosquitoes in the laboratory. Synthetic analogues of the auklet odorant were strongly repellent to mosquitoes in controlled laboratory trials. Furthermore, the efficacy was similar to previous reports for commercial mosquito repellents. These results, in combination with a previously published study, show that constituents of the aldehyde odorant are broad spectrum in efficacy against ectoparasitic arthropods of birds. Our report is the first empirical evidence for an endogenous mosquito repellent in birds.

The crested auklet, Aethia cristatella, emits a class of aldehydes shown to be potent invertebrate repellents when used by heteropterans against their predators. Our aim was to determine the efÞcacy of these aldehydes against mosquitoes in the laboratory. Synthetic analogues of the auklet odorant were strongly repellent to mosquitoes in controlled laboratory trials. Furthermore, the efÞcacy was similar to previous reports for commercial mosquito repellents. These results, in combination with a previously published study, show that constituents of the aldehyde odorant are broad spectrum in efÞcacy against ectoparasitic arthropods of birds. Our report is the Þrst empirical evidence for an endogenous mosquito repellent in birds.