Zebrafish最新文献

Rotifers, Brachionus plicatilis, are a valuable first exogenous feed for zebrafish because they can provide continuous nutrition for growing zebrafish larvae when used in a rotifer-zebrafish polyculture. Typically cultured at high salinities (>10 ppt), B. plicatilis are temporarily immobilized when moved to lower salinities (5 ppt) used for polycultures, decreasing their accessibility and attractiveness to the larvae. The nutritional value of rotifers varies based on their diet, typically live algae, which has limited nutritional value and may pose biosecurity risks. After confirming that rotifers consume and can reproduce when fed an irradiated, processed larval fish diet (PD), they were reared at 5 or 15 ppt, and fed various combinations of an algae mix and/or PD. Population densities and percentages of egg-bearing rotifers were quantified daily until the population density plateaued, and then their nutritional value was assessed. Results indicated that rotifers thrived at both salinities. Those fed PD were successfully maintained at >500 rotifers per mL and contained a greater ω-6/ω-3 fatty acid ratio. Our findings indicate that enriching rotifers with PD raised at 5 ppt can potentially eliminate rotifer immobilization in polyculture, while providing a nutritious, attractive diet for zebrafish larvae and decreasing biosecurity risks.

The river basins of Brazil contain a highly diverse ichthyofauna of remarkable endemism, including several threatened species. Accordingly, Lignobrycon myersi is a fish species distributed only in a few rivers from the state of Bahia, northeastern Brazil. Since this species is classified as Near Threatened and is poorly studied, efforts to understand the genetic structure of populations and putative cryptic forms should help define efficient strategies of management and conservation. Herein, the molecular identification and the population genetic diversity of specimens of L. myersi across their range (Almada, Contas, and Cachoeira river basins) were assessed using mitochondrial markers (16S rDNA and D-Loop, respectively). The inferences based on phylogenetics, genetic distance, and species delimitation methods invariably identified all samples as L. myersi. In addition, sequencing of D-loop fragments revealed significant haplotype diversity and a considerable level of population genetic structure. Despite their geographic isolation, these data suggested that populations from Almada and Contas rivers represent a single evolutionary lineage that could be managed as a whole. In contrast, the population from Cachoeira River was highly differentiated from the others and should be managed separately as a unique and endemic unit, particularly focused on the conservation of native habitats.

The longevity of sperm in teleost such as zebrafish and medaka is short when isolated even in saline-balanced solution at a physiological temperature. In contrast, some internal fertilizers exhibit the long-term storage of sperm, >10 months, in the female reproductive tract. This evidence implies that sperm in teleost possesses the ability to survive for a long time under suitable conditions; however, these conditions are not well understood. In this study, we show that the sperm of zebrafish can survive and maintain fertility in L-15-based storage medium supplemented with bovine serum albumin, fetal bovine serum, glucose, and lactic acid for 28 days at room temperature. The fertilized embryos developed to normal fertile adults. This storage medium was effective in medaka sperm stored for 7 days at room temperature. These results suggest that sperm from external fertilizer zebrafish and medaka has the ability to survive for at least 4 and 1 week, respectively, in the body fluid-like medium at a physiological temperature. This sperm storage method allows researchers to ship sperm by low-cost methods and to investigate key factors for motility and fertile ability in those sperm.

Synthetic cathinones are drugs of abuse substituted for amphetamine-like stimulant drugs such as methamphetamine. In this study, methamphetamine was studied as a prototypical amphetamine-like drug as a first step toward establishing methods to study this entire drug class. The internal concentration of methamphetamine in zebrafish larvae was determined using matrix-matched calibration along with extraction and purification of samples using the quick, easy, cheap, effective, rugged, and safe technique in liquid chromatography-tandem mass spectrometry. Whole-body and head/trunk uptake and elimination in 5-day postfertilization zebrafish larvae were determined. A gradient method was developed using 5 mM ammonium formate with 0.1% formic acid and methanol with 0.1% formic acid as mobile phases, 10 min of total run time, and a 0.3 mL/min flow rate. The limit of quantification was 60 ng/mL, linearity with r² = 0.9991, and recovery values from 92% to 120%. The internal concentration of methamphetamine was quantifiable in whole-body homogenates within 15 min of uptake analysis. The internal concentration increased with time, whereas a biphasic elimination pattern was shown. With increasing length of exposure, a higher accumulation of drugs was found in the head than in the trunk.

Small nuclear DNA (snDNA) are valuable cytogenetic markers for comparative studies in chromosome evolution because different distribution patterns were found among species. Parodontidae, a Neotropical fish family, is known to have female heterogametic sex chromosome systems in some species. The U2 and U4 snDNA sites have been found to be involved in Z and W chromosome differentiation in Apareiodon sp., Apareiodon affinis, and Parodon hilarii. However, few studies have evaluated snDNA sites as propulsors of chromosome diversification among closely related fish species. In this study, we investigated the distribution of U2 and U4 snDNA clusters in the chromosomes of 10 populations/species belonging to Apareiodon and Parodon, aiming to identify chromosomal homeologies or diversification. In situ localization data revealed a submetacentric pair carrying the U2 snDNA site among the populations/species analyzed. Furthermore, all studied species demonstrated homeology in the location of U4 snDNA cluster in the proximal region of metacentric pair 1, besides an additional signal showing up with a divergence in Apareiodon. Comparative chromosomal mapping of U4 snDNA also helped to reinforce the proposal of the ZZ/ZW₁W₂ sex chromosome system origin in an A. affinis population. According to cytogenetic data, the study corroborates the diversification in Parodontidae paired species with uncertain taxonomy.

The A1 adenosine receptor is the most widely expressed P1 receptor in vertebrates, performing inhibitory tone of the nervous system. Increased levels of adenosine are crucial to promote tissue protection in threatening situations, such as convulsion and hypoxia. Zebrafish is an established model organism for studies on health and disease. In this study, we evaluated the functionality of A₁ adenosine receptor through development of zebrafish (6-7-day-, 3-, 8-, and 24-month-old), assessing: (I) the effects of the agonist N₆-cyclopenthyladenosine (CPA) over locomotor parameters, (II) the anticonvulsant properties of CPA and adenosine per se in the pentylenetetrazol-induced seizure, and (III) the gene expression of adora1b through development. CPA promoted decreased distance traveled in the highest concentrations/doses tested (larvae: 75 to 500 μM; adults: 20 mg.kg^-1), altered mean velocity (larvae: 50-500 μM; adults: 20 mg.kg^-1) and time in the bottom zone of apparatus (adults: decrease in 20 mg.kg^-1). Adenosine increased the latency of the larvae to reach stage II at 5 and 10 μM. CPA anticonvulsant effect against convulsive stage II was reached at 75 μM, although it decreased basal locomotor activity in larvae. For adults, CPA 10 mg.kg^-1 was effective as anticonvulsant without locomotory effects. Adenosine had minor anticonvulsant effects in the concentration tested (larvae: 5 and 10 μM). The level of gene expression of adora1b was stable in brain from adult animals (8- and 24-month-old animals). These results suggest that zebrafish has similar responses to CPA as mammals. To avoid confounding factors, such as locomotor effects, during any brain function investigation using A₁ adenosine receptor as a target, the concentration below 75 μM or below the dose of 20 mg.kg^-1 of CPA is ideal for zebrafish at larval and adult stages, respectively.

We describe the design, fabrication, and applications of a four-well dish for imaging of the trunk of larval zebrafish. The dish facilitates immobilization of anesthetized zebrafish larvae, with their tails gently pushed against a microscope cover glass, enabling longitudinal imaging at 24-72 h postfertilization using high-resolution objective lenses.

It has been demonstrated that glyphosate-based herbicides are toxic to animals. In the present study, reactive oxygen species (ROS) generation, antioxidant capacity against peroxyl radicals (ACAP), and lipid peroxidation (LPO), as well as the activity and expression of the acetylcholinesterase (AChE) enzyme, were evaluated in Danio rerio males exposed to 5 or 10 mg/L of glyphosate for 24 and 96 h. An increase in ACAP in gills after 24 h was observed in the animals exposed to 5 mg/L of glyphosate. A decrease in LPO was observed in brain tissue of animals exposed to 10 mg/L after 24 h, while an increase was observed in muscle after 96 h. No significant alterations were observed in ROS generation. AChE activity was not altered in muscles or brains of animals exposed to either glyphosate concentration for 24 or 96 h. However, gene expression of this enzyme in the brain was reduced after 24 h and was enhanced in both brain and muscle tissues after 96 h. Thus, contrary to previous findings that had attributed the imbalance in the oxidative state of animals exposed to glyphosate-based herbicides to surfactants and other inert compounds, the present study demonstrated that glyphosate per se promotes this same effect in zebrafish males. Although glyphosate concentrations did not alter AChE activity, this study demonstrated for the first time that this molecule affects ache expression in male zebrafish D. rerio.