Inducible Resistance to Pyrethroid Insecticide is Lacking in Adult Aedes aegypti Mosquitoes

Mosquitoes have evolved increased resistance to pyrethroid insecticides including permethrin, and studying their metabolic mechanisms of resistance is the window to human counteraction. If early exposure to insecticides can upregulate certain detoxification genes, this creates lower rates of mortality in a single mosquito’s lifetime. Yellow fever mosquitoes (Aedes aegypti) were exposed to a sublethal dosage of permethrin and mortality rates at a later LC50 dose exposure were recorded. Mortality rates of induced mosquitoes were not lower than the mortality rates of unexposed (control) mosquito groups. If early exposure did not increase mortality, either evidence for inducible same-generational resistance remains to be seen in Aedes aegypti, or other factors were responsible for under-stimulating inducible resistance that were not acknowledged in the experimental design. The experiment may be replicated with adjusted test intervals to find the exact interval at which the upregulated proteins are still active and can confer resistance

Predation and Crypsis in the Evolution of Electric Signaling in Weakly Electric Fishes

Eavesdropping by electroreceptive predators poses a conflict for weakly electric fish, which depend on their Electric Organ Discharge (EOD) signals both for navigation and communication in the dark. The EODs that allow weakly electric fish to electrolocate and communicate in the dark may attract electroreceptive predators such as catfishes and Electric Eels. These predators share with their prey the synapomorphy of passive electric sense supported by ampullary electroreceptors that are highly sensitive to low-frequency electric fields. Any low-frequency spectral components of the EOD make weakly electric fish conspicuous and vulnerable to attack from electroreceptive predators. Accordingly, most weakly electric fish shift spectral energy upwards or cloak low-frequency energy with compensatory masking signals. Subadults and females in particular emit virtually no low-frequency energy in their EODs, whereas courting males include a significant low-frequency component, which likely attracts females, but makes the signals conspicuous to predators. Males of species that coexist with the most predators tend to produce the least low-frequency signal energy, expressing sexual dimorphism in their signals in less risky ways. In these respects, electric signals follow the classic responses to opposing forces of natural and sexual selection, as exemplified in the visual signals of guppies and the acoustic signals of Túngara frogs. Unique to electric fish is that the electric signal modifications that help elude detection by electroreceptive predators are additions to the basal signal rather than losses of attractive components. These enhancements that enable crypsis are energetically costly, but have also provided the evolutionary substrates for subsequent sexual selection and species identity characters

Differential serotonergic modulation of two types of aggression in weakly electric fish

Agonistic aggression has provided an excellent framework to study how conserved circuits and neurochemical mediators control species-specific and context-dependent behavior. The principal inhibitory control upon aggression is serotonin (5-HT) dependent, and the activation of 5-HT1A receptors is involved in its action. To address whether the serotonergic system differentially regulates different types of aggression, we used two species of weakly electric fish: the solitary Gymnotus omarorum and the gregarious Brachyhypopomus gauderio, which display distinctive types of aggression as part of each species\u27 natural behavioral repertoire. We found that in the reproduction-related aggression displayed by B. gauderio after conflict resolution, the serotonergic activity follows the classic pattern in which subordinates exhibit higher 5-HT levels than controls. After the territorial aggression displayed by G. omarorum, however, both dominants and subordinates show lower 5-HT levels than controls, indicating a different response of the serotonergic system. Further, we found interspecific differences in basal serotonin turnover and in the dynamic profile of the changes in 5-HT levels from pre-contest to post-contest. Finally, we found the expected reduction of aggression and outcome shift in the territorial aggression of G. omarorum after 8-OH-DPAT (5-HT1A receptor agonist) administration, but no effect in the reproduction-related aggression of B. gauderio. Our results demonstrate the differential participation of the serotonergic system in the modulation of two types of aggression that we speculate may be a general strategy of the neuroendocrine control of aggression across vertebrates

Bostonia

Founded in 1900, Bostonia magazine is Boston University's main alumni publication, which covers alumni and student life, as well as university activities, events, and programs

Skeeter Feeder

3D printed blood-feeder for mosquitoes and other hematophagous arthropod