Psilocybin reduces heroin seeking behavior and modulates inflammatory gene expression in the nucleus accumbens and prefrontal cortex of male rats.

Preclinical and human studies indicate psilocybin may reduce perseverant maladaptive behaviors, including nicotine and alcohol seeking. Such studies in the opioid field are lacking, though opioids are involved in more >50% of overdose deaths. Psilocybin is an agonist at the serotonin 2A receptor (5-HT 2A R), a well-documented target for modulation of drug seeking, and evidence suggests 5-HT 2A R agonists may dampen motivation for opioids. We sought to investigate the therapeutic efficacy of psilocybin in mediating cessation of opioid use and maintenance of long-lasting abstinence from opioid seeking behavior in a rat model of heroin self-administration (SA). Psilocybin or 5-HT 2A R antagonists ketanserin and volinanserin were administered systemically to rats prior to SA of 0.075 mg/kg/infusion of heroin, or relapse following forced abstinence. Psilocybin did not alter heroin taking, but a single exposure to 3.0 mg/kg psilocybin 4-24 hours prior to a relapse test blunted cue-induced heroin seeking. Conversely, 5-HT 2A R antagonists exacerbated heroin relapse. To begin to elucidate mechanisms of psilocybin, drug-naïve rats received psilocybin and/or ketanserin, and tissue was collected from the prefrontal cortex (PFC), a region critical for drug seeking and responsive to psilocybin, 24 hours later for RNA-sequencing. 3.0 mg/kg psilocybin regulated ∼2-fold more genes in the PFC than 1.0 mg/kg, including genes involved in the cytoskeleton and cytokine signaling. Ketanserin blocked >90% of psilocybin-regulated genes, including the IL-17a cytokine receptor, Il17ra . Psychedelic compounds have reported anti-inflammatory properties, and therefore we performed a gene expression array to measure chemokine/cytokine molecules in the PFC of animals that displayed psilocybin-mediated inhibition of heroin seeking. Psilocybin regulated 4 genes, including Il17a , and a subset of genes correlated with relapse behavior. Selective inhibition of PFC IL-17a was sufficient to reduce heroin relapse. We conclude that psilocybin reduces heroin relapse and highlight IL-17a signaling as a potential downstream pathway of psilocybin that also reduces heroin seeking.

Morphine-Driven m6A Epitranscriptomic Neuroadaptations in Primary Cortical Cultures.

Opioid overdose is the leading cause of accidental death in the United States and remains a major public health concern, despite significant resources aimed at combating opioid misuse. Neurobiological research to elucidate molecular and cellular consequences of opioid exposure is required to define avenues to explore for reversal of opioid-induced neuroadaptations. Opioids impart well-documented regulation of the transcriptome and epigenetic modifications in the brain, but opioid-induced epitranscriptomic posttranscriptional regulation of RNA is vastly understudied. N6-methyladenosine (m6A) RNA methylation is significantly enriched in the brain and involved in learning, memory, and reward. m6A modifications have not been studied in opioid use disorder, despite being the most common RNA modification. We detected significant regulation of m6A-modifying enzymes in rat primary cortical cultures following morphine treatment, including AlkB Homolog 5 (Alkbh5). The m6a demethylase ALKBH5 functions as an m6A eraser, removing m6A modifications from mRNA. We hypothesized that chronic opioid treatment regulates m6A modifications through modulation of Alkbh5 and profiled m6A modifications in primary cortical cultures following chronic morphine treatment and Alkbh5 knock-down. We observed differential regulation of m6A modifications for a common set of transcripts following morphine or Alkbh5 knock-down, and the two treatments elicited concordant m6A epitranscriptomic profiles, suggesting that a subset of morphine-driven m6A modifications may be mediated through downregulation of Alkbh5 in cortical cultures. Gene Ontology terms of commonly regulated transcripts included serotonin secretion, synapse disassembly, neuron remodeling, and immune response. Thus, we conclude that morphine can drive epitranscriptomic changes, a subset of which may occur in an Alkbh5-dependent manner.

Orbitofrontal intronic circular RNA from Nrxn3 mediates reward learning and motivation for reward.

The orbitofrontal cortex (OFC) is a vital component of brain reward circuitry that is important for reward seeking behavior. However, OFC-mediated molecular mechanisms underlying rewarding behavior are understudied. Here, we report the first circular RNA (circRNA) profile associated with appetitive reward and identify regulation of 92 OFC circRNAs by sucrose self-administration. Among these changes, we observed downregulation of circNrxn3, a circRNA originating from neurexin 3 (Nrxn3), a gene involved in synaptogenesis, learning, and memory. Transcriptomic profiling via RNA sequencing and qPCR of the OFC following in vivo knock-down of circNrxn3 revealed differential regulation of genes associated with pathways important for learning and memory and altered splicing of Nrxn3. Furthermore, circNrxn3 knock-down enhanced sucrose self-administration and motivation for sucrose. Using RNA-immunoprecipitation, we report binding of circNrxn3 to the known Nrxn3 splicing factor SAM68. circNrxn3 is the first reported circRNA capable of regulating reward behavior and circNrxn3-mediated interactions with SAM68 may impact subsequent downstream processing of RNAs such as the regulation of gene expression and splicing.

Heroin Regulates Orbitofrontal Circular RNAs.

The number of drug overdose deaths involving opioids continues to rise in the United States. Many patients with opioid use disorder (OUD) that seek treatment still experience relapse. Perseverant opioid seeking behaviors represent a major challenge to treating OUD and additional therapeutic development will require insight into opioid-induced neurobiological adaptations. In this study, we explored the regulation of a novel class of RNAs, circular RNAs (circRNAs), by the addictive opioid heroin in the rat orbitofrontal cortex (OFC), a brain region that mediates behavioral responses to rewarding stimuli. Microarray analysis identified 76 OFC circRNAs significantly regulated in male rats after heroin self-administration. We evaluated the specificity of these findings by measuring heroin-associated circRNA expression in female rats after heroin self-administration and in rats that self-administered sucrose. We identify circGrin2b, circUbe2cp, circAnks1a, circAdcy5 and circSlc24A2 as heroin-responsive circRNAs in the OFC. Linear mRNA levels of heroin-associated circRNAs were unchanged except for Grin2b and Adcy5. An integrated bioinformatics analysis of regulated circRNAs identified microRNAs predicted to bind heroin-associated circRNAs and downstream targets of circRNA: microRNA sponging. Thus, heroin regulates the expression of OFC RNA splice variants that circularize and may impact cellular processes that contribute to the neurobiological adaptations that arise from chronic heroin exposure.

Asymmetric viability in reciprocal crosses of zebrafish Danio rerio and pearl danio Danio albolineatus.

Interspecies hybrids have long been studied to further understanding of speciation. Reciprocal crosses sometimes have asymmetric viability, a phenomenon termed 'Darwin's corollary to Haldane's rule'. It has been proposed that this asymmetry is caused by Dobzhansky-Muller incompatibilities between nuclear genes and cytoplasmic factors (e.g., maternal transcripts, mitochondrial genome). The molecular basis of this hypothesis has received little empirical investigation, presumably due to the lack of an appropriate model system. We report a case of extreme asymmetry in viability between reciprocal hybrids of zebrafish Danio rerio and pearl danio Danio albolineatus. Hybrids from D. rerio females × D. albolineatus males (n = 4 crosses) were viable, with 83.2 ± 9.6% surviving from fertilization to 5 days post-fertilization (dpf) and 80.1 ± 14.4% surviving from 5 to 21 dpf. Hybrids from D. albolineatus females × D. rerio males (n = 6 crosses) were inviable after embryonic development. These hybrids developed pericardial oedema at 1 dpf and only 37.2 ± 18.0% survived from fertilization to 5 dpf. Of the 595 larvae alive at 5 dpf, only one juvenile with stunted growth survived to 21 dpf. We propose that given the resources available for the D. rerio model system and the strong asymmetry in viability between reciprocal crosses, these hybrids will allow investigation of the molecular basis for Darwin's corollary to Haldane's rule.

The neurobiology of non-coding RNAs and Alzheimer's disease pathogenesis: Pathways, mechanisms and translational opportunities.

In the past two decades, advances in sequencing technology and analysis of the human and mouse genome have led to the discovery of many non-protein-coding RNAs (ncRNAs) including: microRNA, small-interfering RNAs, piwi-associated small RNAs, transfer RNA-derived small RNAs, long-non-coding RNAs and circular RNAs. Compared with healthy controls, levels of some ncRNAs are significantly altered in the central nervous system and blood of patients affected by neurodegenerative disorders like Alzheimer's disease (AD). Although the mechanisms are still not fully elucidated, studies have revealed that these highly conserved ncRNAs are important modulators of gene expression, amyloid-ß production, tau phosphorylation, inflammation, synaptic plasticity and neuronal survival, all features considered central to AD pathogenesis. Despite considerable difficulties due to their large heterogeneity, and the complexity of their regulatory pathways, research in this rapidly growing field suggests that ncRNAs hold great potential as biomarkers and therapeutic targets against AD. Herein, we summarize the current knowledge regarding the neurobiology of ncRNA in the context of AD pathophysiology.

Two New Types of Homodiploid Fish and Polyploid Hybrids Derived from the Distant Hybridization of Female Koi Carp and Male Bighead Carp.

Bighead carps  (Hypophthalmichthys nobilis) and silver carps (Hypophthalmichthys molitrix) represent an important component of freshwater ichthiofauna in its native range, though they might become mass propagation in other systems (North America) and the reason of concern for fisheries management. Therefore, understanding their reproductive traits and particularly in the context of hybridization with other cyprinids was of value to explain their rapid propagation as well as potential benefits for aquaculture due to their unique diet, behavior, growth potential, and tolerance to deteriorating environmental conditions in freshwater ecosystems. Distant hybridization is an effective tool to create different ploidy offspring with changed phenotypes and genotypes. In this study, we reported distant hybridization of female koi carp (Cyprinus carpio haematopterus, KOC, 2n = 100) × male bighead carp (Hypophthalmichthys nobilis, BIC, 2n = 48) and the spontaneous occurrence of two new "crucian" carp-like homodiploid fish (2nGCC-L; 2nCCC-L; 2n = 100), a new type of triploid hybrid (3nKB, 3n = 124), and a new type of tetraploid hybrid (4nKB, 4n = 148). The body color of 2nGCC-L and 2nCCC-L were gray and multicolor, respectively. Both phenotypes were similar to the crucian carp (Carassius auratus). The difference was that their heads were rounder than those of the crucian carp and they had higher backs. Compared with the KOC with two pairs of barbels and BIC without barbel, 2nGCC-L, 2nCCC-L, and 4nKB had no barbel, but 3nKB had one pair of barbels. Microsatellite patterns and 5S rDNA sequences confirmed that 2nGCC-L, 2nCCC-L, and 3nKB were of hybrid origin. In regard to feeding, KOC was omnivorous and BIC was a typical filter-feeder. However, the 2nGCC-L, 2nCCC-L, and 3nKB were omnivorous. The formation of four kinds of new offspring is a groundbreaking finding in fish genetic breeding and evolutionary biology.

Bacterial Diversity Analysis and Evaluation Proteins Hydrolysis During the Acid Whey and Fish Waste Fermentation.

The disposal of acid whey (Aw), a by-product from fermented products, is a problem for the dairy industry. The fishery industry faces a similar dilemma, disposing of nearly 50% of fish processed for human consumption. Economically feasible and science-based alternatives are needed to overcome this problem. One possible solution is to add value to the remaining nutrients from these by-products. This study focuses on the breakdown of nutrients in controlled fermentations of Aw, fish waste (F), molasses (M), and a lactic acid bacteria (LAB) strain (Lr). The aim was to assess the dynamic variations in microbial diversity and the biochemical changes that occur during fermentation. Four treatments were compared (AwF, AwFM, AwFLr, and AwFMLr), and the fermentation lasted 14 days at 22.5 °C. Samples were taken every other day. Colorimetric tests for peptide concentrations, pH, and microbial ecology by 16S-v4 rRNA amplicon using Illumina MiSeq were conducted. The results of the microbial ecology showed elevated levels of alpha and beta diversity in the samples at day zero. By day 2 of fermentation, pH dropped, and the availability of a different set of nutrients was reflected in the microbial diversity. The fermentation started to stabilize and was driven by the Firmicutes phylum, which dominated the microbial community by day 14. Moreover, there was a significant increase (3.6 times) in peptides when comparing day 0 with day 14, making this treatment practical and feasible for protein hydrolysis. This study valorizes two nutrient-dense by-products and provides an alternative to the current handling of these materials.

Transcriptomic response to soybean meal-based diets as the first formulated feed in juvenile yellow perch (Perca flavescens).

With increasing levels of fish meal (FM) protein in aquafeeds being replaced with soybean meal (SBM) protein, understanding the molecular mechanisms involved in response to alternative diets has become a critical concern. Thus, the goal of this study was to examine transcriptional differences in the intestine of juvenile yellow perch through RNA-sequencing (RNA-seq), after their initial introduction to a formulated diet with 75% SBM protein inclusion for 61 days, compared to those fed a traditional FM-based diet. Transcriptomic analysis revealed a concise set of differentially expressed genes in juveniles fed the SBM-based diet, the majority of which were intrinsic to the cholesterol biosynthesis pathway. Analysis of total body lipid and cholesterol levels were also investigated, with no between-treatment differences detected. Results of this study demonstrate that in response to SBM-based diets, yellow perch juveniles up-regulate the cholesterol biosynthesis pathway in order to maintain homeostasis. These findings suggest that the upregulation of the cholesterol biosynthesis pathway may negatively impact fish growth due to its large energy expenditure, and future studies are warranted.

Effects of homozygosity on sex determination in zebrafish Danio rerio.

Gynogenetic zebrafish Danio rerio were obtained by activating D. rerio oocytes with UV irradiated common carp Cyprinus carpio sperm and then applying one of four different shocks [two (early) meiotic and two (late) mitotic shocks]. Gynogens produced by three of the shocks survived to maturity. All adult gynogens (n = 52) except one were found to be male. There was no difference in growth rate between the biparental controls and gynogens produced through the most effective shock, thereby eliminating growth rate as a possible cause of the skewed sex ratio. Gynogen males had reduced fertility compared to biparental controls, with about half of gynogens being unable to reproduce through natural spawning (all controls reproduced successfully). Gynogen males that did reproduce gave lower fertilization rates compared with controls. This demonstrates the negative effects of increased homozygosity on male reproductive function. Families sired by meiotic gynogen males were more likely to be female biased (33% of families) compared with families sired by biparental control males (11%). In addition to confirming the polygenic nature of sex determination in D. rerio, these observations suggest that recessive or over-dominant male-determining alleles are present in domesticated D. rerio populations.

Why are triploid zebrafish all male?

Adult triploid zebrafish Danio rerio has previously been reported to be all male. This phenomenon has only been reported in one other gonochoristic fish species, the rosy bitterling Rhodeus ocellatus, despite the fact that triploidy is induced in numerous species. To investigate the mechanism responsible, we first produced triploid zebrafish and observed gonad development. Histological sections of juvenile triploid gonads showed that primary growth oocytes were able to develop in the juvenile ovary, but no cortical alveolus or more advanced oocytes were found. All adult triploids examined were male (n = 160). Male triploids were able to induce oviposition by diploid females during natural spawning trials, but fertilization rates were low (1.0 ± 3.1%) compared with diploid male siblings (67.4 ± 16.6%). The embryos produced by triploid sires were aneuploid with a mean ploidy of 2.4 ± 0.1n, demonstrating that triploid males produce aneuploid spermatozoa. After confirming that adult triploids are all male, we produced an additional batch of triploid zebrafish and exposed them (and a group of diploid siblings) to 100 ng/L estradiol (E2) from 5 to 28 dpf. The E2 treated triploids and nontreated triploids were all male. The nontreated diploids were also all male, but the E2 treated diploids were 89% female. This demonstrates that triploidy acts downstream of estrogen synthesis in the sex differentiation pathway to induce male development. Based on this and the observations of juvenile gonad development in triploids, we suggest that triploidy inhibits development of oocytes past the primary growth stage, and this causes female to male sex reversal.

Larval rearing of zebrafish at suboptimal temperatures.

Temperature-sensitive mutants have been widely utilized in single-cell and invertebrate model systems, particularly to study the function of essential genes. Few temperature-sensitive mutants have been identified in zebrafish, likely due to the difficulty of raising zebrafish at low temperatures. We describe a novel rearing protocol that allows rapid growth of larval and juvenile zebrafish at 23 °C compared to previous data in the literature. Embryos collected from four breeding pairs were maintained at 28.5 ±â€¯0.5 °C until 5 days post-fertilization (dpf) - the onset of exogenous feeding. Larvae were then divided to six tanks and three tanks were cooled to 23 ±â€¯0.2 °C. Fish were fed a live diet (marine rotifers Brachionus plicatilis and Artemia nauplii) and maintained under a set of environmental parameters shown to increase growth rate: continuous light, low salinity (3ppt), and algal turbidity. Mean total length and weight of fish at 21dpf were 12.7 ±â€¯0.3 mm and 20.5 ±â€¯1.5 mg for the 23 °C treatment and 18.5 ±â€¯0.4 mm and 67.3 ±â€¯3.4 mg for the 28.5 °C control. By 35 dpf, the fish raised at 23 °C had reached a mean length and weight of 18.9 ±â€¯0.7 mm and 76.4 ±â€¯6.7 mg, approximately the size control fish reached at 21 dpf. At 35 dpf, water temperature was raised to 28 °C and fish were reared to maturity (75 dpf) under standard conditions (freshwater, 13 L:11D photoperiod, dry diet, no added algal turbidity). Sex ratio and fertility were assessed and compared between temperature groups. There were no significant differences in sex ratio, fertilization rate, embryo viability at 1 dpf, clutch size, or relative fecundity. This rearing protocol will allow for efficient utilization of temperature-sensitive mutations in the zebrafish model system.

Contested Paradigm in Raising Zebrafish (Danio rerio).

The current body of work on rearing larval/juvenile zebrafish is based on (1) utilization of freshwater and (2) diurnal light/dark cycle, (3) provision of live feed at modest density, and (4) culture in high visibility environment. We challenged these rearing approaches by maintaining zebrafish under constant light for 46-48 days (days postfertilization [dpf]), while securing continuous feeding in high turbidity and saline (1.8-2.1 parts per thousand) environment for the experiment's duration, allowing 24 h feeding/growth of fish from first exogenous feeding to maturation. There was no evidence of negative effects on zebrafish larvae behavior, growth, survival, and life cycle duration at constant illumination when food was continuously available. Zebrafish were stocked at high initial density (100 larvae/L) in a static system and fed high densities of rotifers (Brachionus plicatilis) (200-400/mL) from 6 to 12 dpf. Fish density was then reduced by 50% and two diet treatments, live rotifers or brine shrimp (Artemia) nauplii (10/mL), followed. Fish were reared on these two diets until first maturation. Performance of adult zebrafish fed live rotifer followed by Artemia nauplii diet was the highest recorded in the literature after 42 dpf, 250 ± 29 (males) and 430 ± 5 mg (females). Use of these rearing conditions, during the entire life cycle, until reproduction, resulted in the shortest ever recorded generation time (from egg to egg) of 43-45 dpf and fertilization rate (1 dpf) of 80.3%-94%.

The expression of hypoxia-inducible factor-1α gene is not affected by low-oxygen conditions in yellow perch (Perca flavescens) juveniles.

Hypoxia can affect various fish populations, including yellow perch Perca flavescens, which is an economically and ecologically important species in Lake Erie, a freshwater system that often experiences hypoxia in the hypolimnetic part of the lake. Fish, similarly to mammals, possess molecular oxygen sensor-hypoxia-inducible factor-1 (HIF-1), a transcription factor that can affect expression of many downstream genes related to animal growth and locomotion, protein synthesis, as well as ATP and amino acid metabolism. HIF-1 is a heterodimer, which consists of two subunits: oxygen-sensitive and oxygen-insensitive subunits, α and ß, respectively. In this study, we report first on the molecular cloning and sequencing of P. flavescens HIF-1α. The full-length complementary DNA (cDNA) was isolated and submitted to the GenBank with accession number KT783483. It consists of 3529 base pairs (bp) carrying a single open-reading frame that encompasses 2250 bp of the coding region, 247 bp of the 5' untranslated region (UTR), and 1032 bp of the 3' UTR. The "de novo" prediction of the 3D structure of HIF-1α protein, which consists of 749 amino acids, is presented, too. We then utilized One-Step Taqman® real-time RT-PCR technology to monitor changes in HIF-1α messenger RNA (mRNA) copies in response to chronic hypoxic stress. An experiment was conducted using 14-day post-swim-up stage yellow perch larvae with uninflated swim bladders. This experiment included three treatment groups: hypoxia, mid-hypoxia, and normoxia, in four replicates (four tanks per treatment) with the following dissolved oxygen levels: 3, 4, and >7 mg O2/L, respectively. At the end (2 weeks) and in the middle (1 week) of the experiment, fish from each tank were sampled for body measurements and molecular biology analysis. The results showed no differences in survival (∼90%) between treatment groups. Oxygen concentration was lowered to 3.02 ± 0.15 (mean ± SE) mg O2/L with no adverse effect on fish survival. The highest growth rate was observed in the normoxic group. A similar trend was observed with fish body length. The growth rate of fish declined with decreasing water-dissolved oxygen. The number of HIF-1α mRNA copies was not significantly different between hypoxic, mid-hypoxic, and normoxic conditions, and this was true for fish obtained in the middle and at the end of the experiment. Graphical abstract.

Physiological changes and reproductive performance of Sterlet sturgeon Acipenser ruthenus injected with thiamine.

To evaluate the effects of thiamine on physiological changes and spawning performance of Sterlet sturgeon Acipenser ruthenus, 45 farmed female fish (698.6±8.9g) were randomly distributed in 9 tanks (1000L) and fed a diet with 1g/kg of an anti-thiamine drug. This was provided for 5 months prior to spawning. Thiamine hydrochloride was intraperitoneally injected to fish at three different doses: 0 (T0, as control), 5 (T5) and 50 (T50) mg/kg body weight at days 30, 90 and 150 after the experiment started. After five months, the results showed no significant differences in weight gain and hemoglobin level, but hematocrit significantly increased in T5 group. There was no significant difference in glucose-6-phosphate dehydrogenase and estradiol-17ß, but testosterone was significantly increased in the T50 group. Total thiamine concentration in the eggs was significantly higher in T50 than that detected in the control group. Fecundity and larval mortality at 6day post hatch (dph) showed no significant differences among treatments, while the number of eggs per gram was significantly lower in T0 than that observed in T50. Larval weights at 1 (11.6mg) and 6 (23.1mg) dph and larval lengths at 6 (15.6mm) dph were significantly affected by the treatment with the highest level of thiamine injection (T50). Diseases symptoms such as yolk sac deformation, erratic pattern of swimming, and loss of equilibrium were observed at 4 dph in T0 and T5 groups. The overall results revealed that thiamine injection has positive effects on reproductive performance in the sturgeon and the negative impacts of anti-thiamine in the offspring can be reduced by the injection of this vitamin to the broodstock.

Zebrafish embryonic development is induced by carp sperm.

Haploid gynogenetic screens increase the efficiency of forward genetic screens and linkage analysis in fish. Typically, UV-irradiated zebrafish sperm is used to activate zebrafish oocytes for haploid screens. We describe the use of UV-irradiated common carp sperm to activate haploid gynogenetic zebrafish development. Carp × zebrafish hybrids are shown to have a characteristic set of features during embryonic development and exhibit functional development of several tissues (muscle, heart and nervous system). Hybrids become inviable past the embryonic stages. This technique eliminates the possibility of incompletely irradiated zebrafish spermatozoa contaminating haploid progenies. While developing this protocol, one unique zebrafish female was identified which, upon insemination with UV-irradiated carp spermatozoa, repeatedly displayed spontaneous diploidization of the maternal chromosomes in her offspring.

The Effect of Hypoxia and Hyperoxia on Growth and Expression of Hypoxia-Related Genes and Proteins in Spotted Gar Lepisosteus oculatus Larvae and Juveniles.

We studied the molecular responses to different water oxygen levels in gills and swim bladder of spotted gar (Lepisosteus oculatus), a bimodal breather. Fish at swim-up stage were exposed for 71 days to normoxic, hypoxic, and hyperoxic water conditions. Then, all aquaria were switched to normoxic conditions for recovery until the end of the experiment (120 days). Fish were sampled at the beginning of the experiment, and then at 71 days of exposure and at 8 days of recovery. We first cloned three hypoxia-related genes, hypoxia-inducible factor 2α (HIF-2α), Na(+) /H(+) exchanger 1 (NHE-1), and NHE-3, and uploaded their cDNA sequences in the GeneBank database. We then used One Step Taqman® real-time PCR to quantify the mRNA copies of target genes in gills and swim bladder of fish exposed to different water O2 levels. We also determined the protein expression of HIF-2α and neuronal nitric oxide synthase (nNOS) in the swim bladder by using confocal immunofluorescence. Hypoxic stress for 71 days significantly increased the mRNA copies of HIF-2α and NHE-1 in gills and swim bladder, whereas normoxic recovery for 8 days decreased the HIF-2α mRNA copies to control values in both tissues. We did not found significant changes in mRNA copies of the NHE-3 gene in either gills or swim bladder in response to hypoxia and hyperoxia. Unlike in normoxic swim bladder, double immunohistochemical staining in hypoxic and hyperoxic swim bladder using nNOS/HIF-2α showed extensive bundles of HIF-2α-positive nerve fibers in the trabecular musculature associated with a few varicose nNOS immunoreactive nerve terminals.

Growth and body composition of Midas (Amphilophus citrinellus) and Nile tilapia (Oreochromis niloticus) reared in duoculture / Crecimiento y composición de Midas (Amphilophus citrinellus) y tilapia del Nilo (Oreochromis niloticus) mantenidos en duocultivo / Crescimento e composição dos peixes Midas (Amphilosus citrinellus) e Tilápia-do-Nilo (Oreochromis niloticus) mantidas em duocultivo

Background: cichlids are of economical importance either as food (Nile tilapia) or as ornamental fish (Midas) and both exhibit territorialism and aggressive feeding behavior depending on availability of food and space. Objective: to evaluate the growth rates and behavioral changes of Nile tilapia and Midas kept in mono or polyculture. Methods: Midas and tilapia were maintained in a semi-closed rearing system. Initial weight was 0.83 and 0.81 g for Nile tilapia and Midas, respectively. Four treatments with different fish proportions were used. Midas and tilapia were distributed in 12 glass aquaria with three replicates (n = 30 fish per tank). Treatment ratios between Midas and tilapia were 1:0, 1:1, 2:1 and 0:1, respectively. Fish were fed a commercial diet (40% protein, 12% lipids) for six weeks at 5% weight ratio. Feed offer was adjusted weekly. Observations of behavioral traits were recorded throughout the trial to determine social and feeding conduct. Body composition of fish was assessed at the end of the experiment. Results: Midas modified their feeding behavior and their weight gain increased (3.9 ± 0.3 g) in the 2:1 group. The 0:1 group exhibited the lowest growth rate throughout the experiment (2.9 ± 0.3 g). Midas did not affect Tilapia growth (5.8 ± 0.4 g) across treatments. Interspecies aggressiveness was less evident when reared in monoculture (groups 1:0 y 0:1). Intra and interspecies attacks were higher in the 1:1 and 2:1 groups. Proximate body composition indicated higher lipid levels in Midas across treatments in comparison to tilapia. Conclusions: duoculture benefits growth of juvenile Midas when present at 25-30% of total stocking density with Nile tilapia.

Antecedentes: los cíclidos son peces de importancia económica, ya sea como alimento (tilapia del Nilo) o para ornato (Midas), ambos exhiben territorialismo y comportamientos alimenticios agresivos, dependiendo del alimento y espacio disponible. Objetivo: evaluar diferencias en tasas de crecimiento ya sea en mono o duocultivo debido a cambios específicos en comportamiento. Métodos: treinta peces por tanque de tilapia del Nilo y Midas, con un peso inicial de 0,83 y 0,81 g respectivamente, fueron mantenidos en un sistema semicerrado con 12 acuarios y distribuidos en cuatro tratamientos, con tres replicas cada uno, en las siguientes relaciones: 1:0, 1:1, 2:1 y 0:1 tilapias:Midas. Los peces fueron alimentados por 6 semanas al 5% de la biomasa con una dieta comercial 40% de proteína y 12% lípidos y fue reajustado semanalmente. Se estableció la conducta social y de alimentación para cada especie. Finalizando el experimento, se analizaron los valores proximales corporales por tratamiento. Resultados: los Midas modificaron su conducta alimenticia y mostraron una mayor ganancia en peso en la presencia de tilapia en el grupo 2:1 (3,9 ± 0,3 g). El grupo 0:1 mostró la talla más pequeña (2,9 ± 0,3 g). Las tilapias no modificaron su crecimiento (5,8 ± 0,4 g) en ningún tratamiento. La agresividad interespecífica es menos evidente en los peces mantenidos en monocultivo (tratamientos 1:0 y 0:1); incrementándose en los grupos 1:1 y 2:1. Se observó una mayor acumulación de lípidos totales en los Midas en comparación a las tilapias. Conclusiones: el duocultivo de juveniles de Midas con tilapia del Nilo a un total del 25-30% de la densidad total de siembra mejora su crecimiento.

Antecedentes: os ciclídeos são peixes de importância econômica, seja como alimento (tilápia-do-Nilo) ou para ornamentação (Midas), ambos exibem territorialidade e comportamentos alimentares agressivos, atribuídos ao alimento e espaço disponível. Objetivo: avaliar as diferenças em taxas de crescimento quando foram mantidos em mono e policultivo, devido às mudanças específicas em seu comportamento. Métodos: trinta peixes por tanque de tilápia-do-Nilo e Midas, com peso inicial de 0,83 e 0,81 g respectivamente, foram mantidos em um sistema semifechado com 12 aquários e distribuídos em quatro tratamentos, com três repetições cada, nas densidades: 1:0, 1:1; 2:1 e 0:1 tilápias:Midas. Os peixes foram alimentados durante 6 semanas à 5% da biomassa com uma dieta comercial composta de: 40% de proteína e 12% de lipídios e foi reajustada semanalmente. Foi estabelecida a conduta social e de alimentação para cada espécie. Ao final do teste, foram analisados os valores de composição corporal proximal por tratamento. Resultados: os Midas modificaram sua conduta alimentar e mostraram maior ganho de peso na presença de tilápia no grupo 2:1 (3,9 ± 0,3 g). O grupo 0:1 apresentou o menor peso (2,9 ± 0,3 g). As tilápias não modificaram seu crescimento (5,8 ± 0,1 g) em nenhum tratamento. A agressividade interespecífica foi menos evidente para os peixes mantidos em monocultivo (tratamentos 1:0 e 0:1); e incrementou-se nos grupos 1:1 e 2:1. Foi observado um maior acúmulo de lipídios totais nos Midas em comparação às tilápias. Conclusões: o policultivo oferece um crescimento benéfico para Midas juvenis quando estão presentes com tilápia do Nilo em 25-30% do total do cultivo.

Short winters threaten temperate fish populations.

Although climate warming is expected to benefit temperate ectotherms by lengthening the summer growing season, declines in reproductive success following short, warm winters may counter such positive effects. Here we present long-term (1973-2010) field patterns for Lake Erie yellow perch, Perca flavescens, which show that failed annual recruitment events followed short, warm winters. Subsequent laboratory experimentation and field investigations revealed how reduced reproductive success following short, warm winters underlie these observed field patterns. Following short winters, females spawn at warmer temperatures and produce smaller eggs that both hatch at lower rates and produce smaller larvae than females exposed to long winters. Our research suggests that continued climate warming can lead to unanticipated, negative effects on temperate fish populations.