Adaptive metabolic responses in a thermostabilized environment: Transgenerational trade-off implications from tropical tilapia.

Relatively warm environments caused by global warming enhance the productivity of aquaculture activities in tropical/subtropical regions; however, the intermittent cold stress (ICS) caused by negative Arctic Oscillation can still result in major economic losses. In contrast to endotherms, ectothermic fishes experience ambient temperature as an abiotic factor that is central to performance and survival. Therefore, the occurrence of extreme temperatures caused by climate change has ignited a surge of scientific interest from ecologists, economists and physiologists. In this study, we test the transgenerational effects of rearing cold-experienced (CE) and cold-naïve (CN) strains of tropical tilapia. Our results show that compared to CN tilapia, the CE strain preferentially converts carbohydrates into lipids in liver at a regular temperature of 27 °C. Besides, at a low temperature of 22 °C, the CE strain exhibits a broader aerobic scope than CN fish, and their metabolite profile suggests a metabolic shift towards the utilization of glutamate derivatives. Therefore, in response to thermal perturbations, this transgenerational metabolic adjustment provides evidence into the adaptive trade-off mechanisms in tropical fish. Nevertheless, global warming may result in less thermal variation each year, and the stabilized ambient temperature may cause tropical tilapia to gradually exhibit lower energy deposits in liver. In addition to those habitants in cold and temperate regions, a lack of cold exposure to multiple generations of fish may decrease the native cold-tolerance traits of subtropical/tropical organisms; this notion has not been previously explored in terms of the biological effects under anthropogenic climate change.

Fragile X Mental Retardation-1 Knockout Zebrafish Shows Precocious Development in Social Behavior.

Fragile X syndrome (FXS) is a generally hereditary form of human mental retardation that is caused by triplet repeat expansion (CGG) mutation in fragile X mental retardation 1 (fmr1) gene promoter and that results in the absence of the fragile X mental retardation protein (FMRP) expression. The common symptoms of FXS patients include learning disabilities, anxiety, autistic behaviors, as well as other behavioral abnormalities. Our previous results demonstrated the behavioral abnormalities in fmr1 knockout (KO) zebrafish such as fear memory impairment and autism-like behavior. Here, we studied the functional role of fmr1 gene on the development of social behavior by behavioral experiments, including shoaling behavior, shoaling preference, light/dark test, and novel tank task. Our results demonstrated that precocious development of shoaling behavior is found in fmr1 KO zebrafish without affecting the shoaling preference on conspecific zebrafish. The shoaling behavior appeared after 14 days postfertilization (dpf), and the level of shoaling elevated in fmr1 KO zebrafish. Furthermore, the fmr1 KO zebrafish at 28 dpf expressed higher anxiety level in novel tank task. These results suggest that the change of shoaling behavior in fmr1 KO zebrafish may result from hyperactivity and an increase of anxiety.