Mosquitoes react to fast moving shadows
A recent study published by Geoff Meyerhof through the Neuroscience Research Institute at UC Santa Barbara examines the effects of fast-moving “shadow stimuli” on the mosquito species Aedes aegypti. Mosquitoes serve as vectors to transmit diseases to hundreds of millions of individuals each year. The females are especially interested in hosts as they require this blood to produce viable offspring. They must balance the necessity of landing and feeding on a host with the potential dangers associated with an attack from said host.
Mosquitoes look for a host using cues such as heat or odor in a process known as “host seeking.” While host seeking, they engage in “visual threat avoidance,” which describes when mosquitoes take flight in response to visual danger. In order to further study Aedes aegypti’s reaction to potentially deadly visual threats, in this case fast-moving shadows, researchers set up a cage and apparatus. The scientists measured the rates at which the mosquitoes landed on the “host” surface, which mimicked a human in scent and temperature. Researchers then used a machine to cast a fast moving shadow along the cage while measuring the rate at which mosquitoes abandoned their “host” and took flight. While this stimulus is meant to mimic the swishing of a tail or the slap of a human hand, the experiment was testing purely the visual component.
The results demonstrated that fast moving shadows caused mosquitoes to take flight and abandon the “host.” However, this aversion was momentary, and mosquitoes were quick to return to areas they had recently abandoned. Additionally, females seemed to be more effective at judging and reacting to this stimulus.
Furthermore, by damaging specific proteins in the mosquito’s eye and tracking their response, scientists were able to determine that rhodopsin proteins OP1 and OP2 affect reactions to shadows under dim light conditions. Additionally, the transient receptor potential cation channel, involved in the chemical ion exchange necessary for vision, reduced evasion abilities in bright light. This research illustrates the potential to develop mosquito deterrents for preventing the spread of disease.
Rats choose food over drugs at longer intervals
A recent study focusing on the relationship between food and methamphetamine in rats was led by Marlaina R. Stocco, a postdoctoral researcher in the Department of Psychological & Brain Sciences at UCSB. The study attempts to understand the effects of addictive drugs and their ability to reduce users’ preference for other activities or reinforcement.
In the research design, rats were first trained to press levers, one of which dispensed food and the other which delivered a dose of methamphetamine (meth). This drug is shown over time to lead to “cognitive dysfunction,” relapse and a severe alteration of the neurotransmitter makeup in rats’ brains. Once the rats learned how to use the two levers, experiments were conducted by presenting both levers to the rats and allowing them to choose between the two. Once the rats made a choice and were given the corresponding food or meth, the levers were retracted for an interval of either 20 or 600 seconds. These intervals were repeated for a six hour duration or until the rats pressed a lever 25 times.
The research found that, at the shorter interval, rats were far more likely to continue to choose the meth lever. However, at the longer interval or 600 seconds, the rats seemed to instead prefer the food reinforcement over the meth. The paper speculated that with shorter intervals the rats were more likely to be still intoxicated when prompted to choose again, thus “still experiencing acute behavioral and physiological drug effects, which in turn promotes a bias towards choosing the drug.” Additionally, they predict that longer intervals lead to more scarcity, which might have caused the value of food to increase at a greater rate in comparison to the drug.
This study offers new data and insight into the effects of drugs like methamphetamine on the physiology of organisms and provides further information for treatment plans or medications in the future.
Shark overfishing could be mitigated by retention bans
Leonardo Feitosa and Alicia Caughman, doctoral students at the Bren School of Environmental Science & Management, recently co-authored a paper assessing mortality rates and the effects of conservation efforts in maintaining shark populations. While some sharks are going extinct due to overfishing, 54% of global shark catch is discarded because they were unintentionally caught while fishing for other species. Through evaluation of shark populations by literature reviews and statistical analysis, the researchers estimate that retention bans that require certain species of shark to be released would help to protect some shark populations. These bans are predicted to be more effective in shark species that reproduce more frequently and thus have higher population growth than those with longer life histories and slower growth. If perfect compliance is modeled, 72.3% of species “could have two to five-fold higher incidental catch and still have fishing mortality at MSY (maximum sustainable yield).”
Additionally, when evaluating the rates of mortality of 37 shark species, a retention ban is predicted to allow two-thirds of the populations to be at or below the maximum sustainable yield value. This metric means that the amount of a species caught is low enough to sustain the population.
However, retention bans are not predicted to be completely effective. Even if these conservation efforts are implemented, 18% of species of sharks are still expected to experience overfishing. To help further mitigate overfishing, further education on safe catch and release for the sharks could help decrease mortality rates. While the researchers note that there are areas where the data is not complete, there is hope that increased research and models can help both industries and scientists establish better practices towards keeping endangered shark populations healthy.
A version of this article appeared on p.13 of the Apr. 10, 2025 edition of the Daily Nexus.
