Showing papers in "Comparative Biochemistry and Physiology A-molecular & Integrative Physiology in 2022"

Impact of Hygrophila auriculata supplementary diets on the growth, survival, biochemical and haematological parameters in fingerlings of freshwater fish Cirrhinus mrigala (Hamilton, 1822).

Abstract: The present study investigates the effects of Supplementary diet Hygrophila auriculata on the growth, survival, biochemical and haematological parameters of Cirrhinus mrigala. The seaweed was administered to the fish possessing an initial average weight of 14.063 ± 1.828 g. Fish were fed with supplementary diet H. auriculata exhibited significant difference (P < 0.05) in the growth performance, haematological indices such as RBC count, haematocrit volume, haemoglobin, WBC, MCV, MCH and MCHC concentration in contrast to the control after a period of 8 weeks. Also, there were significant differences in biochemical parameters (P < 0.05), between the fish supplemented with dietary H. auriculata extract and the control group. These findings suggest that the administration of H. auriculata extract has a positive effect on the immunological indices and the immune system activity in Mrigal fish.

Different dietary combinations of high/low starch and fat with or without bile acid supplementation on growth, liver histopathology, gene expression and fatty acid composition of largemouth bass, Micropterus salmoides.

Abstract: High dietary levels of fat and/or starch can lower the growth and cause extensive liver inflammation that is linked to mortalities in largemouth bass, Micropterus salmoides. However, bile acids (BA) may mitigate these adverse effects. In a 2 × 2 × 2 factorial feeding trial, M. salmoides juveniles were fed different combinations of dietary high (HF), low fat (LF), high (HS) or low starch (LS) levels with or without BA supplementations at 1% for 8 weeks. A total of 8 isonitrogenous diets were formulated to include, HF/LS, HF/HS, LF/HS, LF/LS, HF/LS-BA, HF/HS-BA, LF/HS-BA and LF/LS-BA. Survival, growth performance, feeding efficiency, whole-body proximate composition, muscle/liver fatty acid composition, hepatic expression of growth regulator (GH/IGF1 axis), lipid metabolism (fatty acid synthase 'FASN' and cholesterol 7 alpha-hydroxylase 'CYP7A1') and antioxidant capacity (superoxide dismutase 'SOD') genes as well as liver histopathology were assessed. Results showed that among diets without BA, there was no significant effect on growth or feeding efficiency, but when BA was included this led to more variable effects including significantly higher weight gain in the LF/HS-BA group compared to all others fed BA. The HF, HS or their combination led to extensive hepatic inflammation, but BA appeared to partially mitigate this in the LF/HS group (i.e. LF/HS-BA). No abnormal liver histopathology was observed in the LF/LS and LF/LS-BA treatments. Muscle 22:6n-3 was significantly higher in the HF/LS and HF/HS-BA groups compared to those fed the HF/HS or LF/LS diets. Dietary fat had a significant effect on the moisture, crude lipid, and caloric content of M. salmoides. Hepatic expression of IGF-I and CYP7A1 were differentially modulated under different treatments. Overall, these results show that BA can alleviate some liver inflammation caused by high dietary starch; however the LF/LS diets led to a better balance between growth performance and liver health.

Invited review: Thermal effects on oxidative stress in vertebrate ectotherms

Abstract: Human-induced climate change is occurring rapidly. Ectothermic organisms are particularly vulnerable to these temperature changes due to their reliance on environmental temperature. The extent of ectothermic thermal adaptation and plasticity in the literature is well documented; however, the role of oxidative stress in these processes needs more attention. Oxidative stress occurs when reactive oxygen species, generated mainly through aerobic respiration, overwhelm antioxidant defences and damage crucial biomolecules. The effects of oxidative damage include the alteration of life-history traits and reductions in whole-organism fitness. Here we review the literature addressing experimental temperature effects on oxidative stress in vertebrate ectotherms. Acute and acclimation temperature treatments produce distinctly different results and highlight the role of phylogeny and thermal adaptation in shaping oxidative stress responses. Acute treatments on organisms adapted to stable environments generally produced significant oxidative stress responses, whilst organisms adapted to variable conditions exhibited capacity to cope with temperature changes and mitigate oxidative stress. In acclimation treatments, the temperature treatments higher than optimal temperatures tended to produce significantly less oxidative stress than lower temperatures in reptiles, whilst in some eurythermal fish species, no oxidative stress response was observed. These results highlight the importance of phylogeny and adaptation to past environmental conditions for temperature-dependent oxidative stress responses. We conclude with recommendations on experimental procedures to investigate these phenomena with reference to thermal plasticity, adaptation and biogeographic variation that provide the most significant benefits to adaptable populations. These results have potential conservation ramifications as they may shed light on the physiological effects of temperature alterations in some vertebrate ectotherms.

C. elegans as a model organism to study female reproductive health.

Abstract: Female reproductive health has been historically understudied and underfunded. Here, we present the advantages of using a free-living nematode, Caenorhabditis elegans, as an animal system to study fundamental aspects of female reproductive health. C. elegans is a powerful high-throughput model organism that shares key genetic and physiological similarities with humans. In this review, we highlight areas of pressing medical and biological importance in the 21st century within the context of female reproductive health. These include the decline in female reproductive capacity with increasing chronological age, reproductive dysfunction arising from toxic environmental insults, and cancers of the reproductive system. C. elegans has been instrumental in uncovering mechanistic insights underlying these processes, and has been valuable for developing and testing therapeutics to combat them. Adopting a convenient model organism such as C. elegans for studying reproductive health will encourage further research into this field, and broaden opportunities for making advancements into evolutionarily conserved mechanisms that control reproductive function.

Invited review: Thermal effects on oxidative stress in vertebrate ectotherms

Abstract: Human-induced climate change is occurring rapidly. Ectothermic organisms are particularly vulnerable to these temperature changes due to their reliance on environmental temperature. The extent of ectothermic thermal adaptation and plasticity in the literature is well documented; however, the role of oxidative stress in these processes needs more attention. Oxidative stress occurs when reactive oxygen species, generated mainly through aerobic respiration, overwhelm antioxidant defences and damage crucial biomolecules. The effects of oxidative damage include the alteration of life-history traits and reductions in whole-organism fitness. Here we review the literature addressing experimental temperature effects on oxidative stress in vertebrate ectotherms. Acute and acclimation temperature treatments produce distinctly different results and highlight the role of phylogeny and thermal adaptation in shaping oxidative stress responses. Acute treatments on organisms adapted to stable environments generally produced significant oxidative stress responses, whilst organisms adapted to variable conditions exhibited capacity to cope with temperature changes and mitigate oxidative stress. In acclimation treatments, the temperature treatments higher than optimal temperatures tended to produce significantly less oxidative stress than lower temperatures in reptiles, whilst in some eurythermal fish species, no oxidative stress response was observed. These results highlight the importance of phylogeny and adaptation to past environmental conditions for temperature-dependent oxidative stress responses. We conclude with recommendations on experimental procedures to investigate these phenomena with reference to thermal plasticity, adaptation and biogeographic variation that provide the most significant benefits to adaptable populations. These results have potential conservation ramifications as they may shed light on the physiological effects of temperature alterations in some vertebrate ectotherms.

Acute critical thermal maximum does not predict chronic incremental thermal maximum in Atlantic salmon (Salmo salar)

Abstract: Atlantic salmon is an important aquaculture species farmed in ocean net-pens and therefore subjected to changing environmental conditions, including rising temperatures. This creates a need for research on the thermal tolerance of this species for the future of sustainable aquaculture. We investigated the thermal tolerance of individually tagged Atlantic salmon post-smolts subjected sequentially to two common high-temperature challenges: critical thermal maximum (CTmax) followed by incremental thermal maximum (ITmax). Our goals were (1) to determine whether CTmax can predict ITmax for individual fish, and (2) to examine connections between various body size (mass, length, condition factor), cardiac (absolute and relative ventricle mass) and blood (hematocrit) metrics and thermal tolerance. We found no relationship between CTmax and ITmax. This is of concern because CTmax, which is a quick and easy test, is often used to predict upper lethal limits in fish despite not using real-world rates of temperature increase and not using death as the experimental endpoint (unlike ITmax). Also, some metrics which correlated in one direction with CTmax had the opposite correlation with ITmax. For instance, smaller fish or fish with smaller ventricles had a higher CTmax but a lower ITmax than larger fish or fish with larger ventricles. Taken together, these results highlight the need to take care when using acute thermal tolerance tests to predict real-world responses to rising temperatures.

Dietary lipid levels affected antioxidative status, inflammation response, apoptosis and microbial community in the intestine of juvenile turbot (Scophthalmus maximus L.)

Abstract: A nine-week feeding trial was conducted to comprehensively investigate the effects of different levels of dietary lipid on intestinal physiology of juvenile turbot. Three diets with different lipid levels (8%, 12% and 16%) were formulated, which were designated as the low-lipid group (LL), medium-lipid group (ML) and high-lipid group (HL), respectively. Each diet was fed to six replicate tanks, and each tank was stocked with 35 fish. The results revealed that medium dietary lipid (12%) increased the activities of intestinal digestive enzymes and brush border enzymes. Excessive dietary lipid (16%) decreased the intestinal antioxidative enzyme levels and increased the lipid peroxidation pressure. In addition, HL stimulated the occurrence of intestinal inflammation and significantly up-regulated the mRNA expression level of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), interferon-γ (IFN-γ) and transforming growth factor-β (TGF-β). Dietary LL and HL induced the apoptosis of intestinal epithelial cells. Sequencing of bacterial 16 s rRNA V4 region indicated that the abundance and diversity of intestinal microflora in fish fed with medium lipid diet (12%) were significantly higher than those in other groups, indicating the intestinal microflora ecology in group ML was more balanced. MetaStat analysis indicated that both low- and high-lipid diets significantly reduced the relative abundance of intestinal beneficial bacteria. In conclusion, results of this study demonstrated the sensitivity of intestinal health and microbiota to dietary lipid levels. From the perspective of microecological balance, medium dietary lipid (12%) was more conducive to maintaining the intestinal microflora stability of turbot.

Dietary lipid levels affected antioxidative status, inflammation response, apoptosis and microbial community in the intestine of juvenile turbot (Scophthalmus maximus L.)

Abstract: A nine-week feeding trial was conducted to comprehensively investigate the effects of different levels of dietary lipid on intestinal physiology of juvenile turbot. Three diets with different lipid levels (8%, 12% and 16%) were formulated, which were designated as the low-lipid group (LL), medium-lipid group (ML) and high-lipid group (HL), respectively. Each diet was fed to six replicate tanks, and each tank was stocked with 35 fish. The results revealed that medium dietary lipid (12%) increased the activities of intestinal digestive enzymes and brush border enzymes. Excessive dietary lipid (16%) decreased the intestinal antioxidative enzyme levels and increased the lipid peroxidation pressure. In addition, HL stimulated the occurrence of intestinal inflammation and significantly up-regulated the mRNA expression level of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), interferon-γ (IFN-γ) and transforming growth factor-β (TGF-β). Dietary LL and HL induced the apoptosis of intestinal epithelial cells. Sequencing of bacterial 16 s rRNA V4 region indicated that the abundance and diversity of intestinal microflora in fish fed with medium lipid diet (12%) were significantly higher than those in other groups, indicating the intestinal microflora ecology in group ML was more balanced. MetaStat analysis indicated that both low- and high-lipid diets significantly reduced the relative abundance of intestinal beneficial bacteria. In conclusion, results of this study demonstrated the sensitivity of intestinal health and microbiota to dietary lipid levels. From the perspective of microecological balance, medium dietary lipid (12%) was more conducive to maintaining the intestinal microflora stability of turbot.

Ionic currents underlying different patterns of electrical activity in working cardiac myocytes of mammals and non-mammalian vertebrates.

Abstract: The orderly contraction of the vertebrate heart is determined by generation and propagation of cardiac action potentials (APs). APs are generated by the integrated activity of time- and voltage-dependent ionic channels which carry inward Na+ and Ca2+ currents, and outward K+ currents. This review compares atrial and ventricular APs and underlying ion currents between different taxa of vertebrates. We have collected literature data and attempted to find common electrophysiological features for two or more vertebrate groups, show differences between taxa and cardiac chambers, and indicate gaps in the existing data. Although electrical excitability of the heart in all vertebrates is based on the same superfamily of channels, there is a vast variability of AP waveforms between atrial and ventricular myocytes, between different species of the same vertebrate class and between endothermic and ectothermic animals. The wide variability of AP shapes is related to species-specific differences in animal size, heart rate, stage of ontogenetic development, excitation-contraction coupling, temperature and oxygen availability. Some of the differences between taxa are related to evolutionary development of genomes, which appear e.g. in the expression of different Na+ and K+ channel orthologues in cardiomyocytes of vertebrates. There is a wonderful variability of AP shapes and underlying ion currents with which electrical excitability of vertebrate heart can be generated depending on the intrinsic and extrinsic conditions of animal body. This multitude of ionic mechanisms provides excellent material for studying how the function of the vertebrate heart can adapt or acclimate to prevailing physiological and environmental conditions.

Identification and functional analysis of the doublesex gene in the mud crab Scylla paramamosain

Abstract: Doublesex (Dsx) is a crucial member of the Dmrt gene family and plays a vital role in sex determination and differentiation among the animal kingdom. In the present study, a doublesex (designated as Spdsx) gene was identified and characterized for the first time in the mud crab, Scylla paramamosain. The Spdsx cDNA contains an 801 bp open reading frame (ORF) encoding 266 amino acids with a conserved DM domain. Meanwhile, to elucidate the conservation of Dsx, its orthologus were identified in several crustacean species as well. In addition, the expression pattern of Spdsx in various adult tissues and during embryo development was analyzed with qRT-PCR technology. Finally, the roles of Spdsx might play in the testis, androgenic gland, and ovary were analyzed by RNAi technology. The main results are as follows: (1) the Spdsx gene widely existed in analyzed crustacean species, and the multiple sequences alignment result indicated the conservation of Dsx was low except for the DM domain; (2) only one dsx gene was identified in analyzed crab and lobster, while 2 dsx genes (dsx-1 and dsx-2) were identified in shrimps; (3) the Spdsx gene was widely expressed in analyzed tissues, and the expression level in androgenic gland was obviously higher than that in other tissues. Interestingly, the expression level of Spdsx in the ovary was significantly higher than that in testis (p < 0.05); (4) The expression pattern of Spdsx during embryo development was divided into two groups: remained stable from blastula stage to 5 pairs of appendages stage; after 5 pairs of appendages stage, the expression level increased and remained stable from 7 pairs of appendages stage to hatching stage; (5) After the silencing of Spdsx, the expression level of marker genes in testis, ovary, and androgenic gland significantly changed, among which the expression level of vtg and vtgR in ovary down-regulated, the dmrt-like and dmrt-1a (exclusively expressed in testis) in testis up-regulated and the IAG in androgenic gland down-regulated. All the results above demonstrated that the Spdsx play crucial roles in regulating the reproduction system development of mud crab.

Photoperiodic modulation of ovarian metabolic, survival, proliferation and gap junction markers in adult golden hamster, Mesocricetus auratus.

Abstract: Female reproductive physiology is greatly dependent on tight regulation of metabolic and survival factors. Photoperiod regulates female reproductive rhythms but very less information exists explaining whether photoperiod could modulate thyroid hormone homeostasis, metabolic/energy parameters along with survival, proliferation and gap junction proteins in the ovary of a long-day breeder, Mesocricetus auratus. Adult female hamsters were exposed to different photoperiodic regimes i.e., critical photoperiod (CP; 12.5L:11.5D), short photoperiod (SP; 8L:16D) and long photoperiod (LP; 16L:8D) for 12 weeks. LP upregulated thyroidal and gonadal activity as apparent by histoarchitecture, thyroid hormone profile [triiodothyronine (T3), thyroxin (T4) and thyroid stimulating hormone (TSH)], luteinizing hormone (LH), follicle stimulating hormone (FSH), estradiol (E2) and progesterone (P4) levels when compared with SP exposed hamsters. Further, LP increased thyroid hormone receptor-α/deiodinase-2 (TRα/Dio-2), estrogen receptor-α (ERα)/aromatase and insulin receptor/glucose transporter-4 (IR/GLUT-4) expressions in ovary. Interestingly, ovarian sirtuin-1 (SIRT-1) expression was also upregulated under LP condition along with cell proliferation (proliferating cell nuclear antigen or PCNA), survival (B cell lymphoma-2 or Bcl-2) and gap junction (connexin-43) markers when compared to SP exposed hamsters. We also noted elevated levels of circulatory leptin, insulin along with melatonin and its receptor (MT-1) in ovary under SP condition. Thus, we suggest that photoperiod plays a vital role in regulation of thyroid and reproductive hormone homeostasis along with key metabolic and survival markers in the ovary of adult golden hamsters, M. auratus providing further insight into the regulation of female reproductive seasonality in a long-day breeder.

Microplastics ingestion induces plasticity in digestive morphology in larvae of Xenopus laevis.

Abstract: Global changes in temperature, predator introductions, and pollution might challenge animals by altering food conditions. A fast-growing source of environmental pollution are microplastics. If ingested with the natural food source, microplastics act as artificial fibers that reduce food quality by decreasing nutrient and energy density with possible ramifications for growth and development. Animals might cope with altered food conditions with digestive plasticity. We examined experimentally whether larvae of the African clawed frog (Xenopus laevis) exhibit digestive morphology plasticity (i.e., gut length, mass, and diameter) in response to microplastics ingestion. As natural systems contain non-digestible particles similar in size and shape to microplastics, we included cellulose as a natural fiber control group. Gut length and mass increased in response to microplastics and cellulose ingestion indicating that both types of fibers induced digestive plasticity. Body mass and body condition were similar across experimental groups, indicating that larvae fully compensated for low nutrient and energy density by developing longer intestines. The ability of a species to respond plastically to environmental variation, as X. laevis responded, indicates that this species might have the potential to cope with new conditions during global change, although it is uncertain whether this potential may be reduced in a multi-stressor environment.

Protein sources influence both apparent digestibility and gastrointestinal evacuation rate in juvenile slipper lobster (Thenus australiensis).

Abstract: Apparent digestibility and gastrointestinal evacuation rate were measured to assess the potential of five commercially available protein sources for their inclusion in feeds for juvenile slipper lobster, Thenus australiensis. Protein sources tested were fishmeal, krill meal, lupin meal, soybean meal and squid by-product meal. Apparent digestibility of crude protein ranged from 79.6% to 95.3%, with fishmeal protein significantly less digestible than lupin meal, squid by-product meal and soybean meal. Gastrointestinal evacuation rate was estimated from marker replacement, where yttrium oxide replaced ytterbium oxide. Faeces were collected every 3 h for 48 h, and a kinetic model was used to calculate the rate and time for the second marker to replace the first marker. Gastrointestinal evacuation (≥ 95%) was completed between 4 and 6 h with no significant differences among protein sources. Faeces consisted of both markers in equal parts 2.7 to 5.0 h after the feed switch, with lupin meal reaching the midpoint significantly faster than squid by-product meal and reference feed. The present study is the first in crustaceans to examine the relationship between apparent digestibility and gastrointestinal evacuation, showing more digestible protein sources had slower evacuation rates. The combined approach provides deeper insight into crustaceans' digestive physiology and helps understand their ability to digest specific ingredients. Further research is recommended to understand protein requirements in a broader context to verify highly digestible protein sources meet all nutritional requirements.

Protein sources influence both apparent digestibility and gastrointestinal evacuation rate in juvenile slipper lobster (Thenus australiensis)

Abstract: Apparent digestibility and gastrointestinal evacuation rate were measured to assess the potential of five commercially available protein sources for their inclusion in feeds for juvenile slipper lobster, Thenus australiensis. Protein sources tested were fishmeal, krill meal, lupin meal, soybean meal and squid by-product meal. Apparent digestibility of crude protein ranged from 79.6% to 95.3%, with fishmeal protein significantly less digestible than lupin meal, squid by-product meal and soybean meal. Gastrointestinal evacuation rate was estimated from marker replacement, where yttrium oxide replaced ytterbium oxide. Faeces were collected every 3 h for 48 h, and a kinetic model was used to calculate the rate and time for the second marker to replace the first marker. Gastrointestinal evacuation (≥ 95%) was completed between 4 and 6 h with no significant differences among protein sources. Faeces consisted of both markers in equal parts 2.7 to 5.0 h after the feed switch, with lupin meal reaching the midpoint significantly faster than squid by-product meal and reference feed. The present study is the first in crustaceans to examine the relationship between apparent digestibility and gastrointestinal evacuation, showing more digestible protein sources had slower evacuation rates. The combined approach provides deeper insight into crustaceans' digestive physiology and helps understand their ability to digest specific ingredients. Further research is recommended to understand protein requirements in a broader context to verify highly digestible protein sources meet all nutritional requirements.

What to do with low O2: Redox adaptations in vertebrates native to hypoxic environments.

Abstract: Reactive oxygen species (ROS) are important cellular signalling molecules but sudden changes in redox balance can be deleterious to cells and lethal to the whole organism. ROS production is inherently linked to environmental oxygen availability and many species live in variable oxygen environments that can range in both severity and duration of hypoxic exposure. Given the importance of redox homeostasis to cell and animal viability, it is not surprising that early studies in species adapted to various hypoxic niches have revealed diverse strategies to limit or mitigate deleterious ROS changes. Although research in this area is in its infancy, patterns are beginning to emerge in the suites of adaptations to different hypoxic environments. This review focuses on redox adaptations (i.e., modifications of ROS production and scavenging, and mitigation of oxidative damage) in hypoxia-tolerant vertebrates across a range of hypoxic environments. In general, evidence suggests that animals adapted to chronic lifelong hypoxia are in homeostasis, and do not encounter major oxidative challenges in their homeostatic environment, whereas animals exposed to seasonal chronic anoxia or hypoxia rapidly downregulate redox balance to match a hypometabolic state and employ robust scavenging pathways during seasonal reoxygenation. Conversely, animals adapted to intermittent hypoxia exposure face the greatest degree of ROS imbalance and likely exhibit enhanced ROS-mitigation strategies. Although some progress has been made, research in this field is patchy and further elucidation of mechanisms that are protective against environmental redox challenges is imperative for a more holistic understanding of how animals survive hypoxic environments.

Melatonin and cortisol as components of the cutaneous stress response system in fish: Response to oxidative stress.

Abstract: The skin being a passive biological barrier that defends the organism against harmful external factors is also a site of action of the system responding to stress. It appears that melatonin (Mel) and its biologically active metabolite AFMK (N1-acetyl-N2-formyl-5-methoxykynuramine), both known as effective antioxidants, together with cortisol, set up a local (cutaneous) stress response system (CSRS) of fish, similar to that of mammals. Herein we comment on recent studies on CSRS in fish and show the response of three-spined stickleback skin to oxidative stress induced by potassium dichromate. Our study indicates that exposure of the three-spined stickleback to K2Cr2O7 affects Mel and cortisol levels and pigment dispersion in melanophores in the skin. In our opinion, an increased concentration of Mel and cortisol in the skin may be the strategy to cope with oxidative stress, where both components act locally to prevent damage caused by active oxygen molecules. Furthermore, the pigment dispersion may be a valuable, easy-to-observe mark of oxidative stress, useful in the evaluation of fish welfare.

Physiological effects of capture and short-term captivity in an invasive snake species, the Burmese python (Python bivittatus) in Florida.

Abstract: It is important to evaluate the role of captivity as a potential stressor. An understanding of stress responses to capture and transition to captivity may inform the limitations of laboratory studies on wild animals, aid in understanding the consequences of introducing animals into captive environments, and help predict which species may be successful invasives. We investigated physiological effects of captivity by comparing at-capture blood variables in wild Burmese pythons (Python bivittatus) in Florida to pythons recently brought into captivity (1-109 days). We conducted an acute restraint test by collecting samples at baseline (immediately at handling) and one hour post-restraint across wild field-sampled (n = 19) and recently-captive (n = 33) pythons to evaluate fluctuations in plasma corticosterone, bacterial killing ability, antibody response, leukogram, and serpentovirus infection. We observed higher baseline plasma corticosterone and monocytes in recently captive compared to wild snakes, which both subsided in snakes held for a longer time in captivity, and a mild decrease in lymphocytes in the middle of the captivity period. Functional immunity and viral infection were not affected by captivity, and pythons maintained restraint-induced responses in corticosterone, heterophil to lymphocyte ratio, and monocyte counts throughout captivity. Prevalence for serpentovirus was 50%, though infection status was related to sampling date rather than captivity, indicating that viral infection may be seasonal. The history of Burmese python as a common captive animal for research and pet trade, as well as its general resilience to effects of capture and short-term captivity, may contribute to its invasion success in Florida.

Postprandial nitrogen and acid-base regulation in the seawater acclimated green crab, Carcinus maenas.

Abstract: The effects of feeding (meal of 3% of body mass) on acid-base and nitrogen homeostasis were investigated in the seawater acclimated green shore crab, Carcinus maenas. Feeding did not change gastric fluid pH (~pH 6); however, feeding was associated with a respiratory acidosis. Hemolymph HCO3- did not increase during this acidosis, although titratable and net acid efflux changed from an uptake to an excretion. Feeding affected the crabs' nitrogen homeostasis causing a substantial increase in hemolymph ammonia and urea concentrations after six hours. At this point, hemolymph urea accounted for ~1/3 of nitrogenous waste accumulated within the hemolymph, suggesting a potential role in ammonia detoxification. The postprandial increase in hemolymph ammonia coincided with an 18-fold increase in ammonia excretion rates that accounted for the majority of net acid excreted by the crabs. Urea excretion rates did not increase after feeding; however, branchial urease activity increased, implying that the gills may possess a mechanism to form excretable ammonia through the catabolism of urea. Our results demonstrate that despite an acidic gastric compartment, C. maenas does not experience a postprandial alkaline tide and that any feeding related acid-base challenges are primarily derived from metabolic acid production. Our findings also indicate that unlike the bicarbonate buffering acid-base compensatory response induced by hypercapnia and emersion, acid-base challenges upon feeding are compensated through changes in the excretion of acid equivalents, mainly in the form of ammonia.

Hypoxia- and hyperoxia-related gene expression dynamics during developmental critical windows of the tropical gar Atractosteus tropicus

Abstract: Aquatic hypoxia is both a naturally-occurring and anthropogenically-generated event. Fish species have evolved different adaptations to cope with hypoxic environments, including gill modifications and air breathing. However, little is known about the molecular mechanisms involved in the respiration of embryonic and larval fishes during critical windows of development. We assessed expression of the genes hif-1α, fih-1, nhe1, epo, gr and il8 using the developing tropical gar as a piscine model during three developmental periods (fertilization to hatch, 1 to 6 days post hatch (dph) and 7 to 12 dph) when exposed to normoxia (~7.43 mg/L DO), hypoxia (~2.5 mg/L DO) or hyperoxia (~9.15 mg/L DO). All genes had higher expression when fish were exposed to either hypoxia or hyperoxia during the first two developmental periods. However, fish continuously exposed to hypoxia had increased expression of the six genes by hatching and 6 dph, and by 12 dph only hif-1α still had increased expression. The middle developmental period was the most hypoxia-sensitive, coinciding with several changes in physiology and morphology. The oldest larvae were the most resilient to gene expression change, with little variation in expression of the six genes compared. This study is the first to relate the molecular response of an air-breathing fish to oxygen availability to developmental critical windows and contributes to our understanding of some molecular responses of developing fish to changes in oxygen availability.

Effects of environmental factors on the cellular and molecular parameters of the immune system in decapods.

Abstract: Crustaceans and in particular decapods (i.e. shrimp, crabs and lobsters) are a diverse, commercially and ecologically important group of organisms. They are exposed to a range of environmental factors whose abiotic and biotic components are prone to fluctuate beyond their optimum ranges and, in doing so, affect crustaceans' immune system and health. Changes in key environmental factors such as temperature, pH, salinity, dissolved oxygen, ammonia concentrations and pathogens can provoke stress and immune responses due to alterations in immune parameters. The mechanisms through which stressors mediate effects on immune parameters are not fully understood in decapods. Improved knowledge of the environmental factors - above all, their abiotic components - that influence the immune parameters of decapods could help mitigate or constrain their harmful effects that adversely affect the production of decapod crustaceans. The first part of this overview examines current knowledge and information gaps regarding the basic components and functions of the innate immune system of decapods. In the second part, we discuss various mechanisms provoked by environmental factors and categorize cellular and molecular immune responses to each environmental factor with special reference to decapods.

Antioxidant capacity differs across social ranks and with ascension in males of a group-living fish

Abstract: Animals that live in groups often form hierarchies in which an individual's behaviour and physiology varies based on their social rank. Occasionally, a subordinate can ascend into a dominant position and the ascending individual must make rapid behavioural and physiological adjustments to solidify their dominance. These periods of social transition and instability can be stressful and ascending individuals often incur large metabolic costs that could influence their oxidative status. Most previous investigations examining the link between oxidative status and the social environment have done so under stable social conditions and have evaluated oxidative status in a single tissue. Therefore, evaluations of how oxidative status is regulated across multiple tissues during periods of social flux would greatly enhance our understanding of the relationship between oxidative status and the social environment. Here, we assessed how antioxidant capacity in three tissues (brain, gonad, and muscle) varied among dominant, subordinate, and ascending males of the group-living cichlid fish, Neolamprologus pulcher. Antioxidant capacity in the brain and muscle of ascending males was intermediate to that of dominant (highest levels) and subordinate males (lowest levels) and correlated with differences in social and locomotor behaviours, respectively. Gonad antioxidant capacity was lower in ascending males than in dominant males. However, gonad antioxidant capacity was positively correlated with the size of ascending males' gonads suggesting that ascending males may increase gonad antioxidant capacity as they develop their gonads. Overall, our results highlight the widespread physiological consequences of social ascension and emphasize the importance of tissue-specific measures of oxidative status.

Hypoxia- and hyperoxia-related gene expression dynamics during developmental critical windows of the tropical gar Atractosteus tropicus.

Abstract: Aquatic hypoxia is both a naturally-occurring and anthropogenically-generated event. Fish species have evolved different adaptations to cope with hypoxic environments, including gill modifications and air breathing. However, little is known about the molecular mechanisms involved in the respiration of embryonic and larval fishes during critical windows of development. We assessed expression of the genes hif-1α, fih-1, nhe1, epo, gr and il8 using the developing tropical gar as a piscine model during three developmental periods (fertilization to hatch, 1 to 6 days post hatch (dph) and 7 to 12 dph) when exposed to normoxia (~7.43 mg/L DO), hypoxia (~2.5 mg/L DO) or hyperoxia (~9.15 mg/L DO). All genes had higher expression when fish were exposed to either hypoxia or hyperoxia during the first two developmental periods. However, fish continuously exposed to hypoxia had increased expression of the six genes by hatching and 6 dph, and by 12 dph only hif-1α still had increased expression. The middle developmental period was the most hypoxia-sensitive, coinciding with several changes in physiology and morphology. The oldest larvae were the most resilient to gene expression change, with little variation in expression of the six genes compared. This study is the first to relate the molecular response of an air-breathing fish to oxygen availability to developmental critical windows and contributes to our understanding of some molecular responses of developing fish to changes in oxygen availability.

Photoperiodic modulation of ovarian metabolic, survival, proliferation and gap junction markers in adult golden hamster, Mesocricetus auratus

Abstract: Female reproductive physiology is greatly dependent on tight regulation of metabolic and survival factors. Photoperiod regulates female reproductive rhythms but very less information exists explaining whether photoperiod could modulate thyroid hormone homeostasis, metabolic/energy parameters along with survival, proliferation and gap junction proteins in the ovary of a long-day breeder, Mesocricetus auratus. Adult female hamsters were exposed to different photoperiodic regimes i.e., critical photoperiod (CP; 12.5L:11.5D), short photoperiod (SP; 8L:16D) and long photoperiod (LP; 16L:8D) for 12 weeks. LP upregulated thyroidal and gonadal activity as apparent by histoarchitecture, thyroid hormone profile [triiodothyronine (T3), thyroxin (T4) and thyroid stimulating hormone (TSH)], luteinizing hormone (LH), follicle stimulating hormone (FSH), estradiol (E2) and progesterone (P4) levels when compared with SP exposed hamsters. Further, LP increased thyroid hormone receptor-α/deiodinase-2 (TRα/Dio-2), estrogen receptor-α (ERα)/aromatase and insulin receptor/glucose transporter-4 (IR/GLUT-4) expressions in ovary. Interestingly, ovarian sirtuin-1 (SIRT-1) expression was also upregulated under LP condition along with cell proliferation (proliferating cell nuclear antigen or PCNA), survival (B cell lymphoma-2 or Bcl-2) and gap junction (connexin-43) markers when compared to SP exposed hamsters. We also noted elevated levels of circulatory leptin, insulin along with melatonin and its receptor (MT-1) in ovary under SP condition. Thus, we suggest that photoperiod plays a vital role in regulation of thyroid and reproductive hormone homeostasis along with key metabolic and survival markers in the ovary of adult golden hamsters, M. auratus providing further insight into the regulation of female reproductive seasonality in a long-day breeder.

Prolonged cortisol elevation alters whole body and tissue metabolism in rainbow trout (Oncorhynchus mykiss).

Abstract: Chronic elevation of circulating cortisol is known to have deleterious effects on fish, but information about the consequences of prolonged cortisol elevation on the metabolism of fish is scarce. To test the effects of chronic cortisol elevation on the aerobic performance of rainbow trout, we examined how two severities of chronically elevated plasma cortisol levels affected the oxygen uptake during rest and after exhaustive exercise using a high (HC) and a medium cortisol (MC) treatment. High cortisol doses significantly affected standard (SMR) and maximum metabolic rates (MMR) compared to control fish. In comparison, the medium cortisol treatment elevated maximum metabolic rates (MMR) but did not significantly influence SMR compared to a sham group (S) and control group (C). The medium cortisol treatment resulted in a significantly increased metabolic scope due to an elevation of MMR, an effect that was abolished in the HC group due to co-occuring elevations in SMR. The elevated SMR of the HC-treated fish could be explained by increased in vitro oxygen uptake rates (MO2) of specific tissues, indicating that the raised basal metabolism was caused, in part, by an increase in oxygen demand of specific tissues. Haematological results indicated an increased reliance on anaerobic metabolic pathways in cortisol-treated fish under resting conditions.

Mitochondrial characteristics of chicken breast muscle affected by wooden breast.

Abstract: The growth rate of broiler chickens has increased by 400% over the past 50 years, and breast yields continue to increase. This has led to an increase in thoracic muscle abnormalities in broilers, with wooden breast becoming a major issue worldwide. The etiology and the mechanism underlying the etiology of wooden breasts have not yet been elucidated; however, it occurs due to oxidative stress. Reactive oxygen species, which cause oxidative stress, are mainly produced in mitochondria. Thus, in this study, we investigated the relationship between the severity of wooden breast in broilers and the characteristics of mitochondria as the source of reactive oxygen species. Sampling of the pectoralis major muscle at the ventral cranial position was conducted in 50-day-old broilers. The severity of wooden breast was classified into three groups based on the muscle fiber roundness and wing-wing contact test, with highest severity in severe wooden breast and lowest severity in normal breast. Nicotinamide adenine dinucleotide tetrazolium reductase staining revealed an increase in darkly stained muscle fibers, indicating high severity of wooden breast. The mitochondria were swollen in severe wooden breast cases, with highest swelling in severe wooden breast and lowest swelling in normal breast. The expression levels of the mitochondrial antioxidant enzyme genes superoxide dismutase 1 and superoxide dismutase 2 were significantly lower in wooden breast-severe tissue than in normal tissue. These results suggest that when the levels of reactive oxygen species in muscle fibers, which should be constant, are increased, mitochondrial homeostasis is not maintained and the damage levels increase in various membranes of the cell, leading to the disruption of normal physiological functions.

Day vs. night variation in the LPS effects on toad's immunity and endocrine mediators.

Abstract: The immune-endocrine interactions following an immune challenge have been demonstrated in amphibians. When considering immune challenges, the immune-endocrine implications can vary with the injection time (day or night), a pattern not explored in amphibians. We investigated the immune response following a lipopolysaccharide - LPS injection, measured as plasma bacterial killing ability - BKA, phagocytosis of blood cells - PP, and neutrophil to lymphocyte ratio - NLR, splenic proinflammatory cytokines mRNA (IL-1β and IL-6), and also endocrine mediators (corticosterone - CORT and melatonin - MEL plasma levels) in Rhinella icterica adult male toads injected at day (10 am) or night (10 pm). LPS induced increases in CORT, NLR, PP, and IL-1β mRNA compared with amphibian phosphate-buffer saline-injected individuals. For plasma CORT, the response was more pronounced during the night. While for the PP and IL-1β mRNA, the effect was more evident during the day. For NLR, the increase happened at both times, day and night, in the LPS-injected toads. Meanwhile, no changes were observed in BKA, IL-6 mRNA, and MEL levels. Overall, our results demonstrated an LPS-induced inflammatory response in R. icterica toads, characterized by higher PP, NLR, and IL-1β mRNA, followed by activation of the hypothalamic-pituitary-interrenal axis (higher CORT levels). The time in which the toads received the LPS injection affected the endocrine and immune mediators. The higher CORT and lower inflammatory response at night suggested a potential functional interaction between CORT and immune reactivity associated with the differences in night vs. day in R. icterica toads. These results highlight the relevance of investigating different injection times and mechanistic pathways to understand LPS-induced immunomodulation in anurans.

Prolonged cortisol elevation alters whole body and tissue metabolism in rainbow trout (Oncorhynchus mykiss)

Abstract: Chronic elevation of circulating cortisol is known to have deleterious effects on fish, but information about the consequences of prolonged cortisol elevation on the metabolism of fish is scarce. To test the effects of chronic cortisol elevation on the aerobic performance of rainbow trout, we examined how two severities of chronically elevated plasma cortisol levels affected the oxygen uptake during rest and after exhaustive exercise using a high (HC) and a medium cortisol (MC) treatment. High cortisol doses significantly affected standard (SMR) and maximum metabolic rates (MMR) compared to control fish. In comparison, the medium cortisol treatment elevated maximum metabolic rates (MMR) but did not significantly influence SMR compared to a sham group (S) and control group (C). The medium cortisol treatment resulted in a significantly increased metabolic scope due to an elevation of MMR, an effect that was abolished in the HC group due to co-occuring elevations in SMR. The elevated SMR of the HC-treated fish could be explained by increased in vitro oxygen uptake rates (MO2) of specific tissues, indicating that the raised basal metabolism was caused, in part, by an increase in oxygen demand of specific tissues. Haematological results indicated an increased reliance on anaerobic metabolic pathways in cortisol-treated fish under resting conditions.

The anaplerotic pyruvate carboxylase from white shrimp Litopenaeus vannamei: Gene structure, molecular characterization, protein modelling and expression during hypoxia.

Abstract: Hypoxic zones are spreading worldwide in marine environments affecting many organisms. Shrimp and other marine crustaceans can withstand environmental hypoxia using several strategies, including the regulation of energy producing metabolic pathways. Pyruvate carboxylase (PC) catalyzes the first reaction of gluconeogenesis to produce oxaloacetate from pyruvate. In mammals, PC also participates in lipogenesis, insulin secretion and other processes, but this enzyme has been scarcely studied in marine invertebrates. In this work, we characterized the gene encoding PC in the white shrimp Litopenaeus vannamei, modelled the protein structure and evaluated its gene expression in hepatopancreas during hypoxia, as well as glucose and lactate concentrations. The PC gene codes for a mitochondrial protein and has 21 coding exons and 4 non-coding exons that generate three transcript variants with differences only in the 5'-UTR. Total PC expression is more abundant in hepatopancreas compared to gills or muscle, indicating tissue-specific expression. Under hypoxic conditions of 1.53 mg/L dissolved oxygen, PC expression is maintained in hepatopancreas, indicating its key role even in energy-limited conditions. Finally, both glucose and lactate concentrations were maintained under hypoxia for 24-48 h in hepatopancreas.

Feeding regimes affected the circadian rhythms of pancreatic digestive enzymes and somatic growth in flathead grey mullet (Mugil cephalus) fry

Abstract: The effect of different feeding regimes on the circadian rhythms of pancreatic digestive enzyme activities was evaluated in Mugil cephalus fry weighting 0.34 ± 0.01 g. Feeding regimes (feeding ration = 3% stocked biomass) differed on the number of meals offered per day: one, two and ten meals per day (R1, R2 and R3, respectively). The number of meals per day affected somatic growth; in particular, fry from the R3 group (0.80 ± 0.01 g) grew better than their congeners from R2 (0.70 ± 0.01 g) and R1 (0.63 ± 0.01 g) groups (P < 0.05). Feeding behaviour was modulated by the feeding regime, being the maximal gut fullness values found just after meal distribution in R1 and R2 groups, whereas this trend was not observed when feed was offered continuously during light hours (R3). Fry from R1 and R2 groups showed hyperphagia as they tended to store in their gut as much as possible feed particles to be later digested due to the limited daily meals. This strategy negatively affected feed digestion due to inappropriate enzyme to substrate ratio, changes in digestive enzyme activities and chyme transit times, which ultimately impaired growth performance. Enzyme activities were modulated by the number of meals, the more frequent the meals offered, the lower enzyme activities, supporting the hypothesis that digestive function is adapted to obtain a maximum benefit of the ingested nutrients. Present results showed that feeding grey mullet fry continuously during day light hours optimized feed digestion and promoted fry growth.

Bee year: Basic physiological strategies to cope with seasonality

Abstract: Worker honey bees are subject to biochemical and physiological changes throughout the year. This study aimed to provide the reasons behind these fluctuations. The markers analysed included lipid, carbohydrate, and protein levels in the haemolymph; the activity of digestive enzymes in the midgut; the levels of adipokinetic hormone (AKH) in the bee central nervous system; the levels of vitellogenins in the bee venom and haemolymph; and the levels of melittin in the venom. The levels of all the main nutrients in the haemolymph peaked mostly within the period of maximal bee activity, whereas the activity of digestive enzymes mostly showed a two-peak course. Furthermore, the levels of AKHs fluctuated throughout the year, with modest but significant variations. These data suggest that the role of AKHs in bee energy metabolism is somewhat limited, and that bees rely more on available food and less on body deposits. Interestingly, the non-metabolic characteristics also fluctuated over the year. The vitellogenin peak reached its maximum in the haemolymph in winter, which is probably associated with the immunoprotection of long-lived winter bees. The analysis of bee venom showed the maximal levels of vitellogenin in autumn; however, it is not entirely clear why this is the case. Finally, melittin levels showed strong fluctuations, suggesting that seasonal control was unlikely.