Journal of Comparative Physiology B-Biochemical Systems and Environmental Physiology最新文献

The present study investigated the best photoperiod for culturing pacu (Piaractus mesopotamicus) in recirculation aquaculture systems (RAS) based on its growth performance and hematological and oxidative stress responses. Juveniles (∼ 5 g) were subjected to five treatments (in triplicate): 24 L (light):0D (dark), 15 L: 09D, 12 L:12D, 9 L:15D, and 0 L:24D for 45 days. A total of 225 pacu individuals were randomly distributed among 15 tanks of 210 L (n = 15 per tank). Zootechnical, hematological (glucose, lactate, hematocrit, and hemoglobin), and antioxidant and oxidative stress parameters (glutathione S-transferase (GST), total antioxidant capacity against peroxyl radicals (ACAP), and lipid peroxidation (LPO) were analyzed. The zootechnical parameters (e.g., weight gain, Fulton's condition factor, and specific growth rate) were better and worse with 9 L:15D and 24 L:0D photoperiods, respectively. The hepatosomatic index was higher and lower in the 0 L:24D and 9 L:15D photoperiods. Blood lactate levels and antioxidant and oxidative stress responses were increased in the longest photoperiods (15 L:9D and 24 L:0D). In contrast, the treatments that showed lower oxidative damage (liver, gills, brain, and muscle) were 9 L:15D and 12 L:12D. In conclusion, manipulating artificial light is one way to improve fish growth and health, where the best photoperiod for pacu farming in RAS is 9 L:15D.

There is a link between metabolism and reproduction as metabolic hormones affect hypothalamus-pituitary-testis (HPT) hormonal functions and vice versa. The aim of the present study was to investigate the effects of negative energy balance on the reproductive system in male goldfish exposed to testosterone (T) and 17β-estradiol (E₂). Following 7 days of food deprivation (FD), ANOVA models showed significant FD × sex steroid interactions on sperm quality and circulating sex steroid levels. When FD effects were investigated, 11-ketotestosterone (11-KT) level and sperm motility and velocity decreased in food-deprived goldfish in the control group. In E₂-exposed goldfish, FD decreased sperm production in addition to sperm motility and velocity that coincided with an elevation of circulating E₂ level. However, FD did not significantly impact sex steroids and sperm quality in T-exposed goldfish. ANOVA models showed non-significant FD × sex steroid interactions for HSI, GSI, circulating luteinizing hormone (Lh) level, and metabolic (preproghrelin, goat and nucb2) and reproductive (kiss1, gpr54 and gnrh3) mRNAs. Furthermore, results showed that FD decreased HSI, and increased Lh levels and testicular preproghrelin and goat mRNAs, while sex steroids increased mid-brain nucb2, kiss1 and gpr54 mRNAs. Together, our results suggest that FD-induced inhibition of androgenesis resulted in diminished sperm quality associated with activation of the testicular ghrelinergic system, and negative feedback of 11-KT increased Lh level. The FD-induced testicular metabolic and hormonal system was impacted in goldfish exposed to sex steroids. However, the negative effects of FD on sperm quality were accelerated in E₂-exposed goldfish due to estrogenic activity. This study provides novel information to better understand metabolic-associated reproductive disorders in fish.

Ultradian rhythms of metabolism, body temperature and activity are attenuated or disappear completely during torpor in Djungarian hamsters, for all three ultradian periodicities (URsmall, URmedium and URlarge). URsmall and URmedium disappear during entrance into torpor, whereas URlarge disappear later or continue with a low amplitude. This suggests a tight functional link between torpor and the expression of ultradian rhythms, i.e. torpor is achieved by suppression of metabolic rate as well as silencing of ultradian rhythms. Spontaneous torpor is often initiated after an ultradian burst of activity and metabolic rate, beginning with a period of motionless rest and accompanied by a decrease of metabolic rate and body temperature. To extend previous findings on the potential role of the adrenergic system on torpor induction we analysed the influence of the ß3-adrenergic agonist Mirabegron on torpor in Djungarian hamsters, as compared to the influence of the ß-adrenergic antagonist Propranolol. Hamsters were implanted with 10 day release pellets of Mirabegron (0.06 mg day^-1) or Propranolol (0.3 mg day^-1). Mirabegron transiently supressed and accelerated ultradian rhythms but had no effect on torpor behaviour. Propranolol did not affect torpor behaviour nor the expression of ultradian rhythms with the dosage applied during this study.

Individuals colonizing new areas at expanding ranges encounter numerous and unpredictable stressors. Exposure to unfamiliar environments suggests that colonists would differ in stress levels from residents living in familiar conditions. Few empirical studies tested this hypothesis and produced mixed results, and the role of stress regulation in colonization remains unclear. Studies relating stress levels to colonization mainly use a geographical analysis comparing established colonist populations with source populations. We used faecal glucocorticoid metabolites (FGMs) to assess both spatial and temporal dynamics of stress levels in an expanding population of midday gerbils (Meriones meridianus). We demonstrated that adult males and females had higher FGM levels in newly emerged colonies, compared with the source population, but differed in the pattern of FGM dynamics post-foundation. In males, FGM levels sharply decreased in the second year after colony establishment. In females, FGM levels did not change with time and remained high despite the decreasing environmental unpredictability, exhibiting among-individual variation. Increased stress levels of colonist males damping with time post-colonization suggest they are flexible in responding to immediate changes in environmental uncertainty. On the contrary, high and stable over generations stress levels uncoupled from the changes in the environmental uncertainty in female colonists imply that they carry a relatively constant phenotype associated with the reactive coping strategy favouring colonization. We link sex differences in consistency and plasticity in stress regulation during colonization to the sex-specific life-history strategies.

It is possible that the reproductive strategy of the short-beaked echidna is related to seasonal changes in fat deposition and energy availability, regulated by seasonal changes in endocrine function. We predicted that circulating leptin levels would be directly proportional to adiposity during most of the year, but that a change in this relationship would occur during the pre-breeding season to allow increased fat deposition. To test this hypothesis, we made use of a captive colony of echidnas to describe and quantify changes in fat distribution and the adipostatic hormone leptin. First we assessed seasonal changes in circulating leptin levels, body mass and adiposity for three male and three female adult echidnas maintained on a standard diet. Second, we explored the relationship between circulating leptin levels and increased caloric intake for an additional five adult female echidnas that were provided with supplemented nutrition. Third we visualised fat distribution in male and female adult echidnas using magnetic resonance imaging (MRI) before and after the breeding season, to determine where fat is deposited in this species. For echidnas maintained on the standard diet, there were no seasonal changes in body mass, body fat or plasma leptin levels. However, female echidnas provided with supplemented nutrition had significantly elevated plasma leptin levels during the breeding season, compared to the pre-and post- breeding periods. MRI showed substantial subcutaneous fat depots extending dorso-laterally from the base of the skull to the base of the tail, in both sexes. Pre-breeding season, both sexes had considerable fat deposition in the pelvic/rump region, whilst the female echidna accumulated most fat in the abdominal region. This study shows that male and female echidnas accumulate body fat in the pelvic/rump and the abdominal regions, respectively and that circulating leptin may promote fattening in female echidnas during the breeding season by means of leptin resistance. However, further research is required to evaluate the precise relationship between seasonal changes in leptin and adiposity.

Djungarian hamsters (Phodopus sungorus) living at constant 15 °C T_a in short photoperiod (8:16 h L:D) showed pronounced ultradian rhythms (URs) of metabolic rate (MR), body temperature (T_b) and locomotor activity. The ultradian patterns differed between individuals and varied over time. The period length of URs for MR, T_b and activity was similar although not identical. Wavelet analysis showed that three different URs are existing in parallel, URs of small amplitude and short duration (URsmall), URs of medium amplitude and medium duration (URmedium) and URs of large amplitude (URlarge), superimposed on each other. URlarge were accompanied by an increase in locomotor activity, whereas URsmall and URmedium were of metabolic origin with lacking or delayed responses of activity. An energetic challenge to cold which raised total energy requirements by about 50% did not accelerate the period length of URs, but extended the amplitude of URsmall and URmedium. URlarge corresponds with the URs of activity, feeding and drinking, sleep and arousal as described in previous studies, which are related to midbrain dopaminergic signalling and hypothalamic ultradian signalling. The cause and control of URmedium and URsmall is unknown. Their periods are similar to periods of central and peripheral endocrine ultradian signalling, suggesting a link with URs of metabolism.

Electrical muscle stimulation (EMS) has been shown to stimulate the production of myokines (i.e., brain-derived neurotrophic factor (BDNF)), but the most effective EMS parameters for myokine production have not been fully elucidated. The purpose of this study was to quantify the optimal EMS frequency for stimulating myokine production. This study included sixteen young adults (male, n = 13, age = 27.3 ± 5.5 years). Participants underwent four EMS interventions (20 min each) with the following conditions: (1) 4 Hz, (2) 20 Hz, (3) 80 Hz, and (4) control (no intervention). Blood samples were obtained before and immediately after EMS. For the control condition, blood samples were taken before and after 20 min of quiet sitting. BDNF and cathepsin-B levels were analyzed in serum. Compared to preintervention levels, stimulation at 20 Hz resulted in significantly greater postintervention cathepsin-B and BDNF levels (p < 0.01). On the other hand, the control condition did not result in a significant change between pre- and posttreatment. Furthermore, stimulation at 20 Hz caused significantly larger increases in cathepsin-B and BDNF levels than stimulation at 4-80 Hz or the control condition (p < 0.05). In conclusion, stimulation at 20 Hz effectively causes a robust cathepsin-B and BDNF response. Based on these results, we suggest a new strategy for rehabilitation of people with neurological disorders.

Salmonids possess a unique respiratory system comprised of three major components: highly pH-sensitive hemoglobins, red blood cell (RBC) intracellular pH (pHi) protection, and a heterogeneous distribution of plasma accessible carbonic anhydrase (paCA), specifically with absence of paCA at the gills. These characteristics are thought to have evolved to enhance oxygen unloading to the tissues while protecting uptake at the gills. Our knowledge of this system is detailed in adults, but little is known about it through development. Developing rainbow trout (Oncorhynchus mykiss) express embryonic RBCs containing hemoglobins that are relatively insensitive to pH; however, availability of gill paCA and RBC pHi protection is unknown. We show that pre-hatch rainbow trout express gill paCA, which is lost in correlation with the emergence of highly pH-sensitive adult hemoglobins and RBC pHi protection. Rainbow trout therefore exhibit a switch in respiratory strategy with hatch. We conclude that gill paCA likely represents an embryonic trait in rainbow trout and is constrained in adults due to their highly pH-sensitive hemoglobins.

Southern Distinct Population Segment (sDPS) green sturgeon spawn solely in one stretch of the Sacramento River in California. Management of this spawning habitat is complicated by cold water temperature requirements for the conservation of winter-run Chinook salmon. This study assessed whether low incubation and rearing temperatures resulted in carryover effects across embryo to early juvenile life stages on scaling relationships in growth and metabolism in northern DPS green sturgeon used as a proxy for sDPS green sturgeon. Fish were incubated and reared at 11 °C and 15 °C, with a subset experiencing a reciprocal temperature transfer post-hatch, to assess recovery from cold incubation or to simulate a cold-water dam release which would chill rearing larvae. Growth and metabolic rate of embryos and larvae were measured to 118 days post hatch. Reciprocal temperature transfers revealed a greater effect of low temperature exposure during larval rearing rather than during egg incubation. While 11 °C eggs hatched at a smaller length, log-transformed length-weight relationships showed that these differences in developmental trajectory dissipated as individuals achieved juvenile morphology. However, considerable size-at-age differences persisted between rearing temperatures, with 15 °C fish requiring 60 days post-hatch to achieve 1 g in mass, whereas 11 °C fish required 120 days to achieve 1 g, resulting in fish of the same age at the completion of the experiment with a ca. 37-fold difference in weight. Consequently, our study suggests that cold rearing temperatures have far more consequential downstream effects than cold embryo incubation temperatures. Growth delays from 11 °C rearing temperatures would greatly increase the period of vulnerability to predation in larval green sturgeon. The scaling relationship between log-transformed whole-body metabolism and mass exhibited a steeper slope and thus an increased oxygen requirement with size in 11 °C reared fish, potentially indicating an energetically unsustainable situation. Understanding how cold temperatures affect green sturgeon ontogeny is necessary to refine our larval recruitment estimations for this threatened species.

Honey bees (Apis mellifera) are one of the most crucial pollinators, providing vital ecosystem services. Their development and functioning depend on essential nutrients and substances found in the environment. While collecting nectar as a vital carbohydrate source, bees routinely encounter low doses of ethanol from yeast fermentation. Yet, the effects of repeated ethanol exposure on bees' survival and physiology remain poorly understood. Here, we investigate the impacts of constant and occasional consumption of food spiked with 1% ethanol on honey bee mortality and alcohol dehydrogenase (ADH) activity. This ethanol concentration might be tentatively judged close to that in natural conditions. We conducted an experiment in which bees were exposed to three types of long-term diets: constant sugar solution (control group that simulated conditions of no access to ethanol), sugar solution spiked with ethanol every third day (that simulated occasional, infrequent exposure to ethanol) and daily ethanol consumption (simulating constant, routine exposure to ethanol). The results revealed that both constant and occasional ethanol consumption increased the mortality of bees, but only after several days. These mortality rates rose with the frequency of ethanol intake. The ADH activity remained similar in bees from all groups. Our findings indicate that exposure of bees to ethanol carries harmful effects that accumulate over time. Further research is needed to pinpoint the exact ethanol doses ingested with food and exposure frequency in bees in natural conditions.