Eliciting conditioned taste aversion in lizards:Live toxic prey are more effective than scent and taste cues alone

Conditioned taste aversion(CTA)is an adaptive learning mechanism whereby a consumer associates the taste of a certain food with symptoms caused by a toxic substance,and thereafter avoids eating that type of food.Recently,wildlife researchers have employed CTA to discourage native fauna from ingesting toxic cane toads(Rhinella marina),a species that is invading tropical Australia.In this paper,we compare the results of 2 sets of CTA trials on large varanid lizards(“goannas,”Varanus panoptes).One set of trials(described in this paper)exposed recently-captured lizards to sausages made from cane toad flesh,laced with a nausea-inducing chemical(lithium chloride)to reinforce the aversion response.The other trials(in a recently-published paper,reviewed herein)exposed free-ranging lizards to live juvenile cane toads.The effectiveness of the training was judged by how long a lizard survived in the wild before it was killed(fatally poisoned)by a cane toad.Both stimuli elicited rapid aversion to live toads,but the CTA response did not enhance survival rates of the sausage-trained goannas after they were released into the wild.In contrast,the goannas exposed to live juvenile toads exhibited higher long-term survival rates than did untrained conspecifics.Our results suggest that although it is relatively easy to elicit short-term aversion to toad cues in goannas,a biologically realistic stimulus(live toads,encountered by free-ranging predators)is most effective at buffering these reptiles from the impact of invasive toxic prey.

B Vitamins Supplementation Can Improve Cognitive Functions and May Relate to the Enhancement of Transketolase Activity in A Rat Model of Cognitive Impairment Associated with High-fat Diets

Objective:To determine whether B vitamin treatment was sufficient to reduce cognitive impairment associated with high-fat diets in rats and to modulate transketolase(TK)expression and activity.Methods:To test this,we separated 50 rats into five groups that were either fed a standard chow diet(controls)or a high-fat diet(experimental groups HO,HI,H2,and H3).HO group animals received no additional dietary supplementation,while H1 group animals were administered 100 mg/kg body weight(BW)thiamine,100 mg/kg BW riboflavin,and 250 mg/kg BW niacin each day,and group H2 animals received daily doses of 100 mg/kg BW pyridoxine,100 mg/kg BW cobalamin,and 5 mg/kg BW folate.Animals in the H3 group received the B vitamin regimens administered to both H1 and H2 each day.Results:Over time,group HO exhibited greater increases in BW and fat mass relative to other groups.When spatial and memory capabilities in these animals were evaluated via conditioned taste aversion(CTA)and Morris Water Maze(MWM),we found B vitamin treatment was associated with significant improvements relative to untreated HO controls.Similarly,B vitamin supplementation was associated with elevated TK expression in erythrocytes and hypothalamus of treated animals relative to those in HO(P<0.05).Conclusion:Together,these findings suggest B vitamin can modulate hypothalamic TK activity to reduce the severity of cognitive deficits in a rat model of obesity.As such,B vitamin supplementation may be a beneficial method for reducing cognitive dysfunction in clinical settings associated with high-fat diets.