Many fishes possess specialized epidermal cells that are ruptured by the teeth of predators, thus reliably indicating the presence of an actively foraging predator. Understanding the evolution of these cells has intrigued evolutionary ecologists because the release of these alarm chemicals is not voluntary. Here, we show that predation pressure does not influence alarm cell production in fishes. Alarm cell production is stimulated by exposure to skin-penetrating pathogens (water moulds: Saprolegnia ferax and Saprolegnia parasitica), skin-penetrating parasites (larval trematodes: Teleorchis sp. and Uvulifer sp.) and correlated with exposure to UV radiation. Suppression of the immune system with environmentally relevant levels of Cd inhibits alarm cell production of fishes challenged with Saprolegnia. These data are the first evidence that alarm substance cells have an immune function against ubiquitous environmental challenges to epidermal integrity. Our results indicate that these specialized cells arose and are maintained by natural selection owing to selfish benefits unrelated to predator-prey interactions. Cell contents released when these cells are damaged in predator attacks have secondarily acquired an ecological role as alarm cues because selection favours receivers to detect and respond adaptively to public information about predation.

Hypoxia is an ever increasing threat to aquatic systems. While fluctuating levels of dissolved oxygen (DO) can be a natural phenomenon, hypoxia caused by eutrophication and organic pollution is now considered to be amongst the most pressing and critical water pollution problems in the world, particularly in densely populated regions. The effects of low DO on fishes are an area of great concern and thriving study. Researchers have examined the effects of low DO on fishes from the cellular to community level. The purpose of the current paper is to review the effects of low DO on complex fish behaviour, community and fish physiology. Our review will also highlight studies in which DO is known to interact with a known contaminant. Throughout the paper we will highlight areas in need of future research such as chronic exposure, interactive effects of DO and contaminants, an increased understanding of how hypoxia affects communities of organisms, and finally a need for an increase in freshwater studies.

Sleep deprivation (SD) can suppress cell proliferation in the hippocampal dentate gyrus of adult male rodents, suggesting that sleep may contribute to hippocampal functions by promoting neurogenesis. However, suppression of cell proliferation in rats by the platform-over-water SD method has been attributed to elevated corticosterone (Cort), a potent inhibitor of cell proliferation and nonspecific correlate of this procedure. We report here results that do not support this conclusion. Intact and adrenalectomized (ADX) male rats were subjected to a 96-h SD using multiple- and single-platform methods. New cells were identified by immunoreactivity for 5-bromo-2'-deoxyuridine (BrdU) or Ki67 and new neurons by immunoreactivity for BrdU and doublecortin. EEG recordings confirmed a 95% deprivation of rapid eye movement (REM) sleep and a 40% decrease of non-REM sleep. Cell proliferation in the dentate gyrus was suppressed by up to 50% in sleep-deprived rats relative to apparatus control or home cage control rats. This effect was also observed in ADX rats receiving continuous low-dose Cort replacement via subcutaneous minipumps but not in ADX rats receiving Cort replacement via drinking water. In these latter rats, Cort intake via water was reduced by 60% during SD; upregulation of cell proliferation by reduced Cort intake may obscure inhibitory effects of sleep loss on cell proliferation. SD had no effect on the percentage of new cells expressing a neuronal phenotype. These results demonstrate that the Cort replacement method is critical for detecting an effect of SD on cell proliferation and support a significant role for sleep in adult neurogenesis.

Circadian rhythms in the Syrian hamster can be markedly phase shifted by 3 h of wheel running or arousal stimulation during their usual daily rest period ("subjective day"). Continuous wheel running is predictive but not necessary for phase shifts of this "nonphotic" type; hamsters aroused by gentle handling without running can also show maximal shifts. By contrast, physical restraint, a standard stress procedure and thus presumably arousing, is ineffective. To resolve this apparent paradox, phase-shifting effects of 3-h sessions of restraint or other stress procedures were assessed. In a preliminary study, phase shifts to arousal by gentle handling were significantly potentiated by the cortisol synthesis inhibitor metyrapone, suggesting that stress-related cortisol release may inhibit phase shifts to arousal. Next, it was confirmed that restraint in the subjective day does not induce phase shifts, but behavioral observations revealed that it also does not sustain arousal. Restraint combined with noxious compressed air blasts did sustain arousal and induced a significant cortisol response compared with arousal by gentle handling but did not induce shifts. Restraint combined with continuous horizontal rotation was also ineffective, as was EEG-validated arousal via confinement to a pedestal over water. However, 3 h of resident-intruder interactions (an intense psychosocial stress) or exposure to an open field (a mild stress) did induce large shifts that were positively correlated with indexes of forward locomotion. The results indicate that large phase shifts associated with arousal in the usual sleep period are neither induced nor prevented by stress per se, but are dependent on the expression of at least low levels of locomotor activity. Sustained arousal alone is not sufficient.

Lake sturgeon are arguably the largest and most unique freshwater fish in North America. Unfortunately their uniqueness includes many characteristics that make them especially vulnerable to anthropogenic impacts including overfishing, habitat fragmentation, and degradation. For approximately 100 years lake sturgeon populations across North America have either been in decline and (or) have experienced a sluggish recovery. While this is partly due to lake sturgeon life history, most researchers agree that habitat fragmentation and degradation are currently the highest risk to the species. Though most lake sturgeon populations are depressed, there are a few exceptions that offer a glimpse into what a stable population or recovery may look like. The following review highlights such instances as well as what is known and more importantly what is not known about this unique species. Specifically, we highlight the need for improved and organized sharing of raw data given the fact that many researchers do not have access to the plethora of information available to others (e.g., otoliths for aging). We examine the varying life history and diet choices of this plastic species offering hypotheses for differences in migration routes and distances as well the differing recovery rates found across their range. We highlight myths about the species providing evidence that they may not be as long lived and fecund as previously thought. We examine the lake sturgeon's current legal status across North America including the efforts of nonprofit groups that have had success in increasing population numbers. Most importantly, we highlight logistical problems faced by researchers and data gaps in the literature that must be filled to increase the odds of a successful recovery. Alongside the data gaps, the recovery of this species is fraught with political and industrial road blocks that are as varied as its current recovery. Subsequently, as is the case with many species, its survival will come down to solid scientific knowledge and the value placed on it by society.Résumé : L'esturgeon de lac constitue sans aucun doute l'unique et plus gros poisson d'eau douce en Amérique du Nord. Malheureusement, son unicité inclut plusieurs caractéristiques le rendant vulnérable aux impacts anthropogènes, incluant la surpêche ainsi que la fragmentation de l'habitat et sa dégradation. Pendant environ 100 ans, les populations d'esturgeon de lac sur l'ensemble de l'Amérique du Nord ont connu un déclin et/ou une lente récupération. Alors que ceci est dû en partie au cycle vital de l'esturgeon, la plupart des recherches s'accordent pour dire que la fragmentation de l'habitat et sa dégradation constituent présentement le plus fort risque pour cette espèce. Bien que la plupart des populations d'esturgeon de lac soient déprimées, il existe quelques exceptions offrant une idée de ce que représente une population stable ou en récupération. Cette revue souligne de tels cas ainsi que ce que l'on connaît au sujet de cette espèce unique. Spécifiquement, les auteu...