Abstract: Artificial light at night (ALAN) is an increasingly pervasive anthropogenic disturbance factor. ALAN can seriously disrupt physiological systems that follow circadian rhythms, and may be particularly influential early in life, when developmental trajectories are sensitive to stressful conditions. Using great tits (Parus major) as a model species, we experimentally examined how ALAN affects physiological stress in developing nestlings. We used a repeated-measure design to assess effects of ALAN on telomere shortening, body mass, tarsus length and body condition. Telomeres are repetitive nucleotide sequences that protect chromosomes from damage and malfunction. Early-life telomere shortening can be accelerated by environmental stressors, and has been linked to later-life declines in survival and reproduction. We also assayed nitric oxide, as an additional metric of physiological stress, and determined fledging success. Change in body condition between day 8 and 15 differed according to treatment. Nestlings exposed to ALAN displayed a trend towards a decline in condition, whereas control nestlings displayed a trend towards increased condition. This pattern was driven by a greater increase in tarsus length relative to mass in nestlings exposed to ALAN. Nestlings in poorer condition and nestlings that were smaller than their nest mates had shorter telomeres. However, exposure to ALAN was unrelated to telomere shortening, and also had no effect on nitric oxide concentrations or fledging success. Thus, exposure to ALAN may not have led to sufficient stress to induce telomere shortening. Indeed, plasticity in other physiological systems could allow nestlings to maintain telomere length despite moderate stress. Alternatively, the cascade of physiological and behavioral responses associated with light exposure may have no net effect on telomere dynamics.
Keywords: Animals
Abstract: A 3 x 2 factorial arrangement was implemented to determine the performance of 450 Cobb broilers subjected to different feeding regimes with and without lighting programs. The chicks were divided into 3 groups according to the feeding regime (ad libitum, restricted, or intermittent), and each group was reared under one of two lighting programs (100% continuous light or 50% continuous light and 50% flashing light). The results showed that the broilers under the ad libitum and intermittent feeding regimes had superior body weight (BW) and average daily gain (ADG) values and the lowest feed conversion ratio (FCR) at 3 and 6 wk of age. Broilers exposed to flashing light and an intermittent feeding regime had the highest BW and ADG values and the lowest FCR. Birds exposed to intermittent feeding had the highest dressed carcass weight and the lowest heart weight. Broilers reared with flashing light had higher tenderness and juiciness values than the other groups. Broilers subjected to a restricted feeding regime and flashing light had the lowest abdominal fat values of all the groups. Tenderness and juiciness were significantly higher in broilers subjected to the ad libitum feeding regime x flashing light and the intermittent feeding regime x flashing light. Broilers fed an intermittent regime had the lowest spleen %, heterophil, heterophil to lymphocyte (H/L) ratio and body temperature values of all the groups, and broilers reared under the intermittent regime x flashing light had the lowest spleen %, H/L ratio and body temperature values. Non-significant differences in all health aspects (shank length, keel bone length, foot pad burns, breast blisters score, hock discoloration, and mortality) were observed among the experimental groups. In conclusion, intermittent and restricted feeding regimes and a flashing lighting program improved the FCR and did not produce any adverse effects on performance or physiological parameters. The results of this work show that intermittent feeding and flashing lighting programs are more beneficial to broiler management.
Keywords: Animals
Abstract: For many animals, finding a mate can be a difficult task. For males, it often involves actively searching for conspecific females, sometimes over great distances. This mate-searching can be aided through chemical or visual signals or cues produced by sexually receptive females. Here, we investigate the roles of olfaction and vision in mate-searching in a strictly nocturnal net-casting spider, Deinopis spinosa. First, we used an olfactometer assay to determine if mature male D. spinosa respond to conspecific airborne cues. We found that mature males, but not mature females, were attracted to airborne cues of mature female conspecifics. We next investigated the relative importance of olfaction and vision in male mate-searching. While manipulating airflow and light levels in screened enclosures in the laboratory, we tested freely moving mature males for mate-searching success. We found no effect of our airflow treatment on mate-searching success. Light levels, however, affected mate-searching in an unexpected way – males were more likely to locate females in complete darkness when compared to dim-light conditions. Our results suggest that visual cues are not necessary for successful male mate-searching in D. spinosa, but that the visual environment can nonetheless influence male behavior. In summary, we provide evidence suggesting that airborne cues, but not visual cues, are important in D. spinosa male mate-searching efforts, though the source of these chemical airborne cues remains unknown.
Keywords: Animals
Abstract: Artificial lighting at night (ALAN) is a global phenomenon that can be detrimental to organisms at individual and population levels, yet potential consequences for communities and ecosystem functions are less resolved. Riparian systems may be particularly vulnerable to ALAN. We investigated the impacts of ALAN on invertebrate community composition and food web characteristics for linked aquatic-terrestrial ecosystems. We focused on food chain length (FCL), a central property of ecological communities that can influence their structure, function, and stability; and the contribution of aquatically derived energy (i.e., nutritional subsidies originating from stream periphyton). We collected terrestrial arthropods and emergent aquatic insects from a suite of stream and wetland sites in Columbus, Ohio, USA. Stable isotopes of carbon ((13) C) and nitrogen ((15) N) were used to infer FCL and contribution of aquatically derived energy. We found that moderate-to-high levels of ALAN altered invertebrate community composition, favoring primarily predators and detritivores. Impacts of ALAN, however, were very taxon specific as illustrated, for example, by the negative impact of ALAN on the abundance of orb-web spiders belonging to the families Tetragnathidae and Araneidae: key invertebrate riparian predators. Most notably, we observed decreases in both invertebrate FCL and reliance on aquatically derived energy under ALAN (although aquatic energetic contributions appeared to increase again at higher levels of ALAN), in addition to shifts in the timing of reciprocal nutritional subsidies. Our study demonstrates that ALAN can alter the flows of energy between aquatic and terrestrial systems, thereby representing an environmental perturbation that can cross ecosystem boundaries. Given projections for global increases in ALAN, both in terms of coverage and intensity, these results have broad implications for stream ecosystem structure and function.
Abstract: Land-based, closed containment salmon aquaculture involves rearing salmon from smolt to adult in recirculating aquaculture systems (RAS). Unlike in open-net pen aquaculture, rearing conditions can be specified in RAS in order to optimize growth and physiological stress tolerance. The environmental conditions that yield optimal stress tolerance in salmon are, however, unknown. To address this knowledge gap, we reared Atlantic (Salmo salar) and coho (Oncorhynchus kisutch) salmon in 7 separate RASs for 400days post-smoltification under 2 photoperiods (24:0 or 12:12, light:dark) and 4 salinities (2.5, 5, 10 or 30ppt.) and assessed the effects of these conditions on thermal tolerance. We found that over the first 120days post-smoltification, rearing coho under a 24:0 photoperiod resulted in a ~2 degrees C lower critical thermal maxima (CTmax) than in coho reared under a 12:12 photoperiod. This photoperiod effect did not persist at 200 and 400days, which was coincident with an overall decrease in CTmax in coho. Finally, Atlantic salmon had a higher CTmax (~28 degrees C) compared to coho (~26 degrees C) at 400days post-smoltification. Overall, these findings are important for the future implications of RAS and for the aquaculture industry to help identify physiologically sensitive time stages.
Keywords: Animals