We thank the Washington University Zebrafish Shared Resource for animal care. This research was supported by the NIH (R01 NS113915 to M.H.M.).

<ol>
	<li>Becker, C. G., Becker, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neuronal+regeneration+from+ependymo-radial+glial+cells:+cook,+little+pot,+cook.">Neuronal regeneration from ependymo-radial glial cells: cook, little pot, cook.</a> Developmental Cell. 32 (4), 516-527 (2015).</li><li>Mokalled, M. H., Poss, K. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+regeneration+toolkit.">A regeneration toolkit.</a> Developmental Cell. 47 (3), 267-280 (2018).</li><li>Orger, M. B., de Polavieja, G. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Zebrafish+behavior:+opportunities+and+challenges.">Zebrafish behavior: opportunities and challenges.</a> Annual Review of Neuroscience. 40, 125-147 (2017).</li><li>Becker, C. G., Becker, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Adult+zebrafish+as+a+model+for+successful+central+nervous+system+regeneration.">Adult zebrafish as a model for successful central nervous system regeneration.</a> Restorative Neurology and Neuroscience. 26 (2-3), 71-80 (2008).</li><li>Gurevich, D. B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Asymmetric+division+of+clonal+muscle+stem+cells+coordinates+muscle+regeneration+in+vivo.">Asymmetric division of clonal muscle stem cells coordinates muscle regeneration in vivo.</a> Science. 353 (6295), (2016).</li><li>Mokalled, M. H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Injury-induced+ctgfa+directs+glial+bridging+and+spinal+cord+regeneration+in+zebrafish.">Injury-induced ctgfa directs glial bridging and spinal cord regeneration in zebrafish.</a> Science. 354 (6312), 630-634 (2016).</li><li>Kizil, C., Kaslin, J., Kroehne, V., Brand, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Adult+neurogenesis+and+brain+regeneration+in+zebrafish.">Adult neurogenesis and brain regeneration in zebrafish.</a> Developmental Neurobiology. 72 (3), 429-461 (2012).</li><li>Wolman, M. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+genome-wide+screen+identifies+PAPP-AA-mediated+IGFR+signaling+as+a+novel+regulator+of+habituation+learning.">A genome-wide screen identifies PAPP-AA-mediated IGFR signaling as a novel regulator of habituation learning.</a> Neuron. 85 (6), 1200-1211 (2015).</li><li>Granato, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Genes+controlling+and+mediating+locomotion+behavior+of+the+zebrafish+embryo+and+larva.">Genes controlling and mediating locomotion behavior of the zebrafish embryo and larva.</a> Development. 123, 399-413 (1996).</li><li>Brockerhoff, S. E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+behavioral+screen+for+isolating+zebrafish+mutants+with+visual+system+defects.">A behavioral screen for isolating zebrafish mutants with visual system defects.</a> Proceedings of the National Academy of Sciences of the United States of America. 92 (23), 10545-10549 (1995).</li><li>Moens, C. B., Yan, Y. L., Appel, B., Force, A. G., Kimmel, C. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Valentino:+a+zebrafish+gene+required+for+normal+hindbrain+segmentation.">Valentino: a zebrafish gene required for normal hindbrain segmentation.</a> Development. 122 (12), 3981-3990 (1996).</li><li>Cavone, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+unique+macrophage+subpopulation+signals+directly+to+progenitor+cells+to+promote+regenerative+neurogenesis+in+the+zebrafish+spinal+cord.">A unique macrophage subpopulation signals directly to progenitor cells to promote regenerative neurogenesis in the zebrafish spinal cord.</a> Developmental Cell. 56 (11), 1617-1630 (2021).</li><li>Reimer, M. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Motor+neuron+regeneration+in+adult+zebrafish.">Motor neuron regeneration in adult zebrafish.</a> Journal of Neuroscience. 28 (34), 8510-8516 (2008).</li><li>Klatt Shaw, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Localized+EMT+reprograms+glial+progenitors+to+promote+spinal+cord+repair.">Localized EMT reprograms glial progenitors to promote spinal cord repair.</a> Developmental Cell. 56 (5), 613-626 (2021).</li><li>Ahmed, R. U., Alam, M., Zheng, Y. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Experimental+spinal+cord+injury+and+behavioral+tests+in+laboratory+rats.">Experimental spinal cord injury and behavioral tests in laboratory rats.</a> Heliyon. 5 (3), 01324 (2019).</li><li>Pajoohesh-Ganji, A., Byrnes, K. R., Fatemi, G., Faden, A. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+combined+scoring+method+to+assess+behavioral+recovery+after+mouse+spinal+cord+injury.">A combined scoring method to assess behavioral recovery after mouse spinal cord injury.</a> Neuroscience Research. 67 (2), 117-125 (2010).</li><li>Basso, D. M., Beattie, M. S., Bresnahan, J. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+sensitive+and+reliable+locomotor+rating+scale+for+open+field+testing+in+rats.">A sensitive and reliable locomotor rating scale for open field testing in rats.</a> Journal of Neurotrauma. 12 (1), 1-21 (1995).</li><li>Scheff, S. W., Saucier, D. A., Cain, M. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+statistical+method+for+analyzing+rating+scale+data:+the+BBB+locomotor+score.">A statistical method for analyzing rating scale data: the BBB locomotor score.</a> Journal of Neurotrauma. 19 (10), 1251-1260 (2002).</li><li>Li, Q., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Differential+behavioral+responses+of+zebrafish+larvae+to+yohimbine+treatment.">Differential behavioral responses of zebrafish larvae to yohimbine treatment.</a> Psychopharmacology (Berl). 232 (1), 197-208 (2015).</li><li>Wakamatsu, Y., Ogino, K., Hirata, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Swimming+capability+of+zebrafish+is+governed+by+water+temperature,+caudal+fin+length+and+genetic+background.">Swimming capability of zebrafish is governed by water temperature, caudal fin length and genetic background.</a> Scientific Reports. 9 (1), 16307 (2019).</li><li>Ahmed, O., Seguin, D., Gerlai, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+automated+predator+avoidance+task+in+zebrafish.">An automated predator avoidance task in zebrafish.</a> Behavioral Brain Research. 216 (1), 166-171 (2011).</li><li>Conradsen, C., McGuigan, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sexually+dimorphic+morphology+and+swimming+performance+relationships+in+wild-type+zebrafish+Danio+rerio.">Sexually dimorphic morphology and swimming performance relationships in wild-type zebrafish Danio rerio.</a> Journal of Fish Biology. 87 (5), 1219-1233 (2015).</li><li>Leris, I., Sfakianakis, D. G., Kentouri, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Are+zebrafish+Danio+rerio+males+better+swimmers+than+females.">Are zebrafish Danio rerio males better swimmers than females.</a> Journal of Fish Biology. 83 (5), 1381-1386 (2013).</li></ol>

The authors have no conflicts of interest.

Adult zebrafish are a popular vertebrate system for modeling human diseases and studying mechanisms of tissue regeneration. CRISPR/Cas9 genome editing has revolutionized reverse genetic studies for modeling disease in zebrafish; however, large-scale genetics in adult zebrafish has been hindered by biological and technical challenges, including the unavailability of adult zebrafish tissues to high-throughput phenotyping. Given the complex anatomy of adult zebrafish, prolonged histological processing is required to obtain and analyze tissue architecture. The swim endurance and swim behavior assays described in this study can be used to pre-screen for neural, muscular, or skeletal phenotypes at a medium throughput before histology. Moreover, as studies of tissue regeneration aim to improve functional tissue repair, the protocols described in this study will be widely applicable, if not essential, for studies of neural, muscular, and skeletal regeneration research.
Functional locomotion assays have been integral to our understanding of neural development and regeneration. Standard locomotor assays are widely available in vertebrate species, including rats, mice, and larval zebrafish. Mouse and rat model systems have behavioral and functional locomotion assays such as the BMS16 and BBB17,18, respectively. Similarly, a host of protocols have been described to measure locomotion, startle response, and behavior in larval zebrafish. These protocols are efficient to reveal behavioral differences among experimental groups in light and dark environments, predator evasion, and activity19,20,21. Here, we describe quantifiable, reproducible methods to measure functional recovery after spinal cord injury in adult zebrafish.
Note that this study presents several limitations. First, behavioral studies are highly dependent on genetic and environmental factors. To control for genetic variability, we used siblings to control for age, sex, and the genetic background across experimental groups22,23. To control for environmental factors, we made sure experiments are performed at the same time of the day, under controlled temperature and lighting conditions20. Second, while the swim behavior assay is less sensitive to biased analysis, the researcher running the swim endurance assay determines when a fish reaches exhaustion and proceeds to remove exhausted fish from the swim tunnel chamber without interrupting the rest of the fish cohort. Thus, our swim endurance experiments were performed by a single researcher who is blinded to experimental conditions. It is particularly important to avoid researcher-to-researcher variability for longitudinal studies of experimental groups over time. Finally, collisions between fish can complicate the tracking analysis in swim behavior assays. We thus recommend performing swim behavior assays for groups of five or fewer fish to minimize the chances of collisions between fish.
In consideration of critical steps, we note that injured fish can be fragile especially in the early days after injury. We thus recommend handling fish with extreme care. For swim endurance assays, collecting fish with the PVC tube as quickly as possible, either head or tail first, reduces the chance of secondary injuries during the collection process. For swim behavior assays, the flush pump can occasionally create waves, distorting the movies and causing analysis errors. In this case, the flush pump can be briefly turned off. However, we do not recommend turning off the flush pump for extended times to ensure water is constantly circulating between the swim tunnel chamber and the buffer tank. Monitoring movie recording allows for immediate termination and restarting of the movie if a frame has been dropped or a fish strays from the recording area. In additional considerations, while performing the tracking analysis, if the R code gives an error during file processing, the most likely problem is in the naming of the files. The program is made to function under a very specific naming strategy: Timepoint_Group_Subgroup_Stock number_Anything else (for example, 0_A_1_00001_WildtypeGroupA.avi). This naming allows for multiple time points, groups, and subgroups to be plotted and aligned together. Finally, while checkpoints have been built into the analysis script to ensure proper tracking, it is important to carefully check the analysis output. The program will automatically ask whether the fish number is correct, and prompt movies for re-analysis if the fish number is incorrect. Straight-line artifacts may appear in the Average Y position plot, indicating that an extra object has been recognized as a fish. In this instance, the best course of action is to carefully watch the movie to exclude extra artifacts that tend to appear at a higher flow speed.

Adult zebrafish are eminently used to investigate mechanisms of neuromuscular and musculoskeletal development and disease modeling1,2,3. Zebrafish are capable of efficient, spontaneous repair of multiple tissues, including the brain, spinal cord, and skeletal muscle4,5,6,7. The remarkable capacity to regenerate neuromuscular tissues and model diseases is attracting a growing scientific community into adult zebrafish research1,2,3. However, while assays of locomotion and swim behavior are available and standardized for larval zebrafish, there is a growing need to develop analogous protocols in adult fish8,9,10,11. The goal of this study is to describe protocols to quantify swim endurance and swim behavior in adult zebrafish. We present these protocols in the context of spinal cord regeneration research. However, the behavioral protocols described here are equally applicable to studies of neural and muscle regeneration, neuromuscular and musculoskeletal development, as well as neuromuscular and musculoskeletal disease modeling.
Zebrafish reverse paralysis within 8 weeks of complete spinal cord transection. Unlike poorly regenerative mammals, zebrafish display pro-regenerative immune, neuronal, and glial injury responses that are required for functional spinal cord repair12,13,14. An ultimate readout of functional spinal cord repair is the ability of the lesioned tissue to regain its function after injury. A suite of standardized methods to assess functional regeneration in rodents include locomotor, motor, sensory, and sensorimotor tests15,16,17. Widely used tests in mouse spinal cord injury include the locomotor Basso Mouse Scale (BMS), forelimb motor tests, tactile sensory tests, and grid walking sensorimotor tests15,17. In contrast with mammalian or larval zebrafish systems, behavioral tests in adult zebrafish are less developed, yet much needed to accommodate the growing needs of the tissue regeneration and disease modeling communities.
Complete spinal cord transections result in complete paralysis caudal to the injury site. Shortly after the injury, paralyzed animals are less active and avoid swimming as much as possible. To compensate for lost swim capacity, paralyzed animals display short, frequent bursts by overusing their pectoral fins, which lie rostral to the lesion. This compensatory swim strategy results in rapid exhaustion and lower swim capacity. As the zebrafish spinal cord regenerates, animals regain a smooth oscillatory swim function caudal to the lesion, allowing for increased swim endurance and improved swim behavior parameters. Here, we describe methods to quantify zebrafish swim endurance at increasing water current velocities and swim behavior at low current velocities.

<table><tbody><tr><td>AutoSwim software</td><td>Loligo Systems</td><td>MI10000</td><td>Optional - for Automatic control of current velocity</td></tr><tr><td>Customized lid</td><td>Loligo Systems</td><td>MI10001</td><td>This customized lid is used for swim endurance</td></tr><tr><td>DAQ-BT</td><td>Loligo Systems</td><td>SW10600</td><td>Optional - for Automatic control of current velocity</td></tr><tr><td>Eheim pump</td><td>Loligo Systems</td><td>PU10160</td><td>20 L/min. This pump is placed in theflow-through tank.</td></tr><tr><td>Fiji</td><td>Fiji</td><td>Freely available through Image J (Fiji)</td><td>Specific script available at https://github.com/MokalledLab/SwimBehavior</td></tr><tr><td>Flowtherm</td><td>Loligo Systems</td><td>AC10000</td><td>Handheld digital flow meter - for calibration</td></tr><tr><td>High Speed Camera</td><td>Loligo Systems</td><td>VE10380</td><td>USB 3.0 color video camera (4MP)</td></tr><tr><td>IR light panel</td><td>Loligo Systems</td><td>VE10775</td><td>450 x 210 mm, placed under the swim tunnel&amp;nbsp; chamber</td></tr><tr><td>Monofocal lens</td><td>Loligo Systems</td><td>VE10388</td><td>25mm manual lens</td></tr><tr><td>PVC Tubing</td><td>VWR</td><td>60985-534</td><td>5/16 x 7/16&quot;&amp;nbsp; Wall thickness: 1/16&quot;</td></tr><tr><td>R Studio</td><td>R Studio</td><td>Freely available. Version 3.6 with extra packages.</td><td>Specific script available at https://github.com/MokalledLab/SwimBehavior</td></tr><tr><td>Swim tunnel respirometer</td><td>Loligo Systems</td><td>SW10060</td><td>5L (120V/60Hz). The system includes the swim chamber, motor, manual control of water current velocity, 1 pump placed inside the chamber, standard swim tunnel lid for swim behavior, and modified swim tunnel lid for calibration</td></tr><tr><td>uEye Cockpit</td><td>IDS</td><td>Freely available software to control camera parameters</td><td>Alternative cameras and accompanying softwares could be used</td></tr><tr><td>Vane wheel flow probe</td><td>Loligo Systems</td><td>AC10002</td><td>Digital flow probe - for calibration</td></tr></tbody></table>

assessment of swim endurance and swim behavior in adult zebrafish

Due to their renowned regenerative capacity, adult zebrafish are a premier vertebrate model to interrogate mechanisms of innate spinal cord regeneration. Following complete transection of their spinal cord, zebrafish extend glial and axonal bridges across severed tissue, regenerate neurons proximal to the lesion, and regain their swim capacities within 8 weeks of injury. Recovery of swim function is thus a central readout for functional spinal cord repair. Here, we describe a set of behavioral assays to quantify zebrafish motor capacity inside an enclosed swim tunnel. The goal of these methods is to provide quantifiable measurements of swim endurance and swim behavior in adult zebrafish. For swim endurance, zebrafish are subjected to a constantly increasing water current velocity until exhaustion, and time at exhaustion is reported. For swim behavior assessment, zebrafish are subjected to low current velocities and swim videos are captured with a dorsal view of the fish. Percent activity, burst frequency, and time spent against the water current provide quantifiable readouts of swim behavior. We quantified swim endurance and swim behavior in wild-type zebrafish before injury and after spinal cord transection. We found that zebrafish lose swim function after spinal cord transection and gradually regain that capacity between 2 and 6 weeks post-injury. The methods described in this study could be applied to neurobehavioral, musculoskeletal, skeletal muscle regeneration, and neural regeneration studies in adult zebrafish.

We set up the swim tunnel as described in section 1 of this protocol (Figure 1). We assessed the swim endurance (section 2 of this protocol) as well as swim behavior (sections 3 and 4 of this protocol) of adult zebrafish at baseline and after spinal cord injury (Figure 2).
For establishing baseline motor function, we examined the swim endurance of wild-type zebrafish under increasing water current velocities (Figure 3A). In this assay, wild-type zebrafish swam for 41 min before getting exhausted. Fish were then subjected to complete spinal cord transections as previously described and swim endurance assays were performed6. After anesthetizing zebrafish using MS-222, a small incision is made with fine scissors to transect the spinal cord 4 mm caudal to the brainstem region. A complete transection was confirmed visually. To confirm the loss of swim capacity after spinal cord surgery, injured animals were assessed at 2 or 3 days post-injury (dpi). At this time point, zebrafish are completely paralyzed caudal to the lesion site. Swim endurance was assessed at 2, 4, and 6 weeks post-injury (wpi). At 2 wpi, lesioned fish lost 60% of their swim endurance capacity (Figure 3A). Regenerating fish gradually regained swim endurance at 4 and 6 wpi. These results indicated that wild-type zebrafish are capable of regaining swim endurance capacity after spinal cord injury.
To examine zebrafish swim behavior during spinal cord regeneration, we tracked the swim behavior of wild-type animals at 0 cm/s water current velocity or under constant, low current velocities of 10 and 20 cm/s (Figure 3B). Average tracks of fish position in the swim tunnel chamber were used for visual assessment of swim behavior at low current velocities (Figure 3B). In this assay, uninjured controls swam steadily in the front part of the swim tunnel chamber (closer to the source of water current), which corresponds to an elevated Y position (Figure 3B). In contrast, at 2 wpi, injured fish were not able to maintain steady swim capacity against the current. Consequently, their swim tracks are more irregular with an overall decrease in Y position (Figure 3B). Y position increased at 4 and 6 wpi, indicating that regenerating animals gradually regained their ability to swim in the front of the swim tunnel chamber. To quantify swim behavior parameters, we calculated the percent activity, position in the swim tunnel (Y position), and time swam against the current (Figure 3C-E). Relative to uninjured controls, lesioned animals at 2 wpi were markedly less active (Figure 3C), stalled in the rear quadrant of the swim tunnel (Figure 3D), and lost their ability to swim against low current velocities (Figure 3E). Consistent with their innate ability to achieve functional recovery, lesioned animals gradually normalized swim behavior parameters at 4 and 6 wpi (Figure 3C-E). The swim endurance and swim behavior parameters together offered quantifiable readouts of swim function and functional spinal cord repair in zebrafish.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/63240/63240fig01.jpg" /> 
Figure 1: Swim tunnel set up and customized lids. (A) Representative images of the swim tunnel set up including zoomed top and side views of the swim tunnel chamber. (B) Images of the swim tunnel lids used for the various applications described in this protocol. A standard, fully enclosed swim tunnel lid is used for swim behavior assays (section 3 of this protocol). A modified swim tunnel lid that accommodates a handheld digital flow meter is used for calibration (section 1 of this protocol). A modified swim endurance lid, containing a removable lid at the posterior end of the swim tunnel chamber, allows for the removal of exhausted fish during swim endurance testing (section 2 of this protocol). <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/63240/63240fig01large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/63240/63240fig02.jpg" /> 
Figure 2: Experimental pipeline to assay for swim endurance and swim behavior in adult zebrafish. For swim endurance, fish swam against an increasing water current until exhaustion. For swim behavior, swim parameters are assessed in the absence of and at low current velocities. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/63240/63240fig02large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/63240/63240fig03.jpg" /> 
Figure 3: Functional recovery in wild-type zebrafish after spinal cord injury. (A) Motor function determined by swim endurance assays for wild-type zebrafish at baseline and 2, 4, and 6 wpi. Dots denote individual animals from two independent experiments. (B) Swim behavior assays tracked wild-type zebrafish under low water current velocities. The average Y position is shown at each time point throughout tracking (0 cm/s for 5 min, 10 cm/s for 5 min, and 20 cm/s for 5 min). (C-E) Percent activity (C), average Y position in the tunnel (D), and time swam against the flow (E) were quantified at 20 cm/s. For all quantifications, two independent experiments are shown. n = 30 in the pre-injury condition; n = 23 at 2 wpi, n = 20 at 4 wpi, n = 18 at 6 wpi. One-way ANOVA was used for statistical analyses. Error bars represent the Standard Error of the Mean (SEM). *P &#60; 0.05; **P &#60; 0.01; ***P &#60; 0.001; ****P &#60; 0.0001. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/63240/63240fig03large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
Supplementary File 1: <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/63240/Burris et al_Supplementary File 1.docx" target="_blank">Please click here to download this File.</a>

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Assessment of Swim Endurance and Swim Behavior in Adult Zebrafish

Capable of functional recovery after spinal cord injury, adult zebrafish is a premier model system to elucidate innate mechanisms of neural regeneration. Here, we describe swim endurance and swim behavior assays as functional readouts of spinal cord regeneration.

Due to their renowned regenerative capacity, adult zebrafish are a premier vertebrate model to interrogate mechanisms of innate spinal cord regeneration. ...

assessment-of-swim-endurance-and-swim-behavior-in-adult-zebrafish

Nanyang Technological University

Research

JoVE Journal

Neuroscience

3.1K Views.  Washington University School of Medicine. Capable of functional recovery after spinal cord injury, adult zebrafish is a premier model system to elucidate innate mechanisms of neural regeneration. Here, we describe swim endurance and swim behavior assays as functional readouts of spinal cord regeneration.

Video: Assessment of Swim Endurance and Swim Behavior in Adult Zebrafish

Using Touch-evoked Response and Locomotion Assays to Assess Muscle Performance and Function in Zebrafish

Zebrafish muscle development is highly conserved with mammalian systems making them an excellent model to study muscle function and disease. Many myopathies affecting skeletal muscle function can be quickly and easily assessed in zebrafish over the first few days of embryogenesis. By 24 hr post-fertilization (hpf), wildtype zebrafish spontaneously contract their tail muscles and by 48 hpf, zebrafish exhibit controlled swimming behaviors. Reduction in the frequency of, or other alterations in, these movements may indicate a skeletal muscle dysfunction. To analyze swimming behavior and assess muscle performance in early zebrafish development, we utilize both touch-evoked escape response and locomotion assays.
Touch-evoked escape response assays can be used to assess muscle performance during short burst movements resulting from contraction of fast-twitch muscle fibers. In response to an external stimulus, which in this case is a tap on the head, wildtype zebrafish at 2 days post-fertilization (dpf) typically exhibit a powerful burst swim, accompanied by sharp turns. Our method quantifies skeletal muscle function by measuring the maximum acceleration during a burst swimming motion, the acceleration being directly proportional to the force produced by muscle contraction.
In contrast, locomotion assays during early zebrafish larval development are used to assess muscle performance during sustained periods of muscle activity. Using a tracking system to monitor swimming behavior, we obtain an automated calculation of the frequency of activity and distance in 6-day old zebrafish, reflective of their skeletal muscle function. Measurements of swimming performance are valuable for phenotypic assessment of disease models and high-throughput screening of mutations or chemical treatments affecting skeletal muscle function.

Zebrafish are an excellent model to study muscle function and disease. During early embryogenesis zebrafish begin regular muscle contractions producing rhythmic swimming behavior, which is altered when the muscle is disrupted. Here we describe a touch-evoked response and locomotion assay to examine swimming performance as a measure of muscle function.

Zebrafish muscle development is highly conserved with mammalian systems making them an excellent model to study muscle function and disease. Many ...

Developmental Biology

Behavioral Approaches to Studying Innate Stress in Zebrafish

Responding appropriately to stressful stimuli is essential for survival of an organism. Extensive research has been done on a wide spectrum of stress-related diseases and psychiatric disorders, yet further studies into the genetic and neuronal regulation of stress are still required to develop better therapeutics. The zebrafish provides a powerful genetic model to investigate the neural underpinnings of stress, as there exists a large collection of mutant and transgenic lines. Moreover, pharmacology can easily be applied to zebrafish, as most drugs can be added directly to water. We describe here the use of the 'novel tank test' as a method to study innate stress responses in zebrafish, and demonstrate how potential anxiolytic drugs can be validated using the assay. The method can easily be coupled with zebrafish lines harboring genetic mutations, or those in which transgenic approaches for manipulating precise neural circuits are used. The assay can also be used in other fish models. Together, the described protocol should facilitate the adoption of this simple assay to other laboratories.

This manuscript describes a simple method to measure stress behaviorally in adult zebrafish. The approach takes advantage of the innate tendency that zebrafish prefer the bottom half of a tank when in a stressful state. We also describe methods for coupling the assay with pharmacology.

Responding appropriately to stressful stimuli is essential for survival of an organism. Extensive research has been done on a wide spectrum of ...

Behavior

The Three-Chamber Choice Behavioral Task using Zebrafish as a Model System

Neurodegenerative diseases are age-dependent, debilitating, and incurable. Recent reports have also correlated hyperglycemia with changes in memory and/or cognitive impairment. We have modified and developed a three-chamber choice cognitive task similar to that used with rodents for use with hyperglycemic zebrafish. The testing chamber consists of a centrally located starting chamber and two choice compartments on either side, with a shoal of conspecifics used as the reward. We provide data showing that once acquired, zebrafish remember the task at least 8 weeks later. Our data indicate that zebrafish respond robustly to this reward, and we have identified cognitive deficits in hyperglycemic fish after 4 weeks of treatment. This behavioral assay may also be applicable to other studies related to cognition and memory.

We present a behavioral chamber designed to assess cognitive performance. We provide data showing that once acquired, zebrafish remember the task 8 weeks later. We also show that hyperglycemic zebrafish have altered cognitive performance, indicating that this paradigm is applicable to studies assessing cognition and memory.

Neurodegenerative diseases are age-dependent, debilitating, and incurable. Recent reports have also correlated hyperglycemia with changes in memory and/or ...

High-Frequency Ultrasound Echocardiography to Assess Zebrafish Cardiac Function

The zebrafish (Danio rerio) has become a very popular model organism in cardiovascular research, including human cardiac diseases, largely due to its embryonic transparency, genetic tractability, and amenity to rapid, high-throughput studies. However, the loss of transparency limits heart function analysis at the adult stage, which complicates modeling of age-related heart conditions. To overcome such limitations, high-frequency ultrasound echocardiography in zebrafish is emerging as a viable option. Here, we present a detailed protocol to assess cardiac function in adult zebrafish by non-invasive echocardiography using high-frequency ultrasound. The method allows visualization and analysis of zebrafish heart dimension and quantification of important functional parameters, including heart rate, stroke volume, cardiac output, and ejection fraction. In this method, the fish are anesthetized and kept underwater and can be recovered after the procedure. Although high-frequency ultrasound is an expensive technology, the same imaging platform can be used for different species (e.g., murine and zebrafish) by adapting different transducers. Zebrafish echocardiography is a robust method for cardiac phenotyping, useful in the validation and characterization of disease models, particularly late-onset diseases; drug screens; and studies of heart injury, recovery, and regenerative capacity.

We describe a protocol to assess heart morphology and function in adult zebrafish using high-frequency echocardiography. The method allows visualization of the heart and subsequent quantification of functional parameters, such as heart rate (HR), cardiac output (CO), fractional area change (FAC), ejection fraction (EF), and blood inflow and outflow velocities.

The zebrafish (Danio rerio) has become a very popular model organism in cardiovascular research, including human cardiac diseases, largely due to its ...

Modeling Fetal Alcohol Spectrum Disorders in Zebrafish to Characterize the Impact of an Adverse Embryonic Environment on Adult Social Behavior

Fetal alcohol spectrum disorders (FASD) describe all alcohol-induced birth defects. Birth defects such as growth deficiencies, craniofacial, behavioral, and cognitive abnormalities are associated with FASD. Social difficulties are common behavioral abnormalities associated with FASD and often result in serious health issues. Animal models are critical to understanding the mechanisms responsible for ethanol-induced social defects. Zebrafish are social vertebrates that produce externally fertilized transparent eggs; these characteristics provide researchers with a precise yet simple procedure for creating the FASD phenotype and an innate behavior that can be leveraged to model the social deficits associated with FASD. Thus, zebrafish are ideal for characterizing the social deficits of FASD. The goal of the current protocol is to provide the user with a simple behavioral assay that can be used to characterize the consequences of a negative environment early during development and the effects it can have on social behavior in adulthood. The protocol can be used to characterize the effect mutations or teratogens have on adult social behavior. The protocol outlined here demonstrates how to characterize the social behavior of individual fish during a 20-min social assay. Furthermore, the data obtained using the current protocol provides evidence that the protocol can be used to characterize the effects of embryonic ethanol-induced social defects in adult zebrafish.

The goal of the current protocol is to outline the steps necessary to establish and use a social preference assay for adult zebrafish and demonstrate that it can be used to characterize ethanol-induced social defects.

Fetal alcohol spectrum disorders (FASD) describe all alcohol-induced birth defects. Birth defects such as growth deficiencies, craniofacial, behavioral, ...

Swimming Performance Assessment in Fishes

Swimming performance tests of fish have been integral to studies of muscle energetics, swimming mechanics, gas exchange, cardiac physiology, disease, pollution, hypoxia and temperature. This paper describes a flexible protocol to assess fish swimming performance using equipment in which water velocity can be controlled. The protocol involves one to several stepped increases in flow speed that are intended to cause fish to fatigue. Step speeds and their duration can be set to capture swimming abilities of different physiological and ecological relevance. Most frequently step size is set to determine critical swimming velocity (Ucrit), which is intended to capture maximum sustained swimming ability. Traditionally this test has consisted of approximately ten steps each of 20 min duration. However, steps of shorter duration (e.g. 1 min) are increasingly being utilized to capture acceleration ability or burst swimming performance. Regardless of step size, swimming tests can be repeated over time to gauge individual variation and recovery ability. Endpoints related to swimming such as measures of metabolic rate, fin use, ventilation rate, and of behavior, such as the distance between schooling fish, are often included before, during and after swimming tests. Given the diversity of fish species, the number of unexplored research questions, and the importance of many species to global ecology and economic health, studies of fish swimming performance will remain popular and invaluable for the foreseeable future.

The lives of the majority of fish are predicated on swimming. This protocol describes techniques for capturing a range of swimming modes available to individual and schooling fish, and includes metrics associated with swimming physiology and behaviour.

Swimming performance tests of fish have been integral to studies of muscle energetics, swimming mechanics, gas exchange, cardiac physiology, disease, ...

Biology

Behavioral Test Battery to Assess Neurotoxic Effects in Adult Zebrafish

Neurotoxicity Assessment in Adult Danio rerio using a Battery of Behavioral Tests in a Single Tank

The presence of neuropathological effects proved to be, for many years, the main endpoint for assessing the neurotoxicity of a chemical substance. However, in the last 50 years, the effects of chemicals on the behavior of model species have been actively investigated. Progressively, behavioral endpoints were incorporated into neurotoxicological screening protocols, and these functional outcomes are now routinely used to identify and determine the potential neurotoxicity of chemicals. Behavioral assays in adult zebrafish provide a standardized and reliable means to study a wide range of behaviors, including anxiety, social interaction, learning, memory, and addiction. Behavioral assays in adult zebrafish typically involve placing the fish in an experimental arena and recording and analyzing their behavior using video tracking software. Fish can be exposed to various stimuli, and their behavior can be quantified using a variety of metrics. The novel tank test is one of the most accepted and widely used tests to study anxiety-like behavior in fish. The shoaling and social preference tests are useful in studying the social behavior of zebrafish. This assay is particularly interesting since the behavior of the entire shoal is studied. These assays have proven to be highly reproducible and sensitive to pharmacological and genetic manipulations, making them valuable tools for studying the neural circuits and molecular mechanisms underlying behavior. Additionally, these assays can be used in drug screening to identify compounds that may be potential modulators of behavior.
We will show in this work how to apply behavioral tools in fish neurotoxicology, analyzing the effect of methamphetamine, a recreational drug, and glyphosate, an environmental pollutant. The results demonstrate the significant contribution of behavioral assays in adult zebrafish to the understanding of the neurotoxicological effects of environmental pollutants and drugs, in addition to providing insights into the molecular mechanisms that may alter neuronal function.

Author Spotlight: Assessment of Environmental and Drug-Induced Behavioral Changes in Adult Zebrafish 

Here, we present a comprehensive behavioral test battery, including the novel tank, Shoaling, and social preference tests, to effectively determine the potential neurotoxic effects of chemicals (e.g., methamphetamine and glyphosate) on adult zebrafish using a single tank. This method is relevant to neurotoxicity and environmental research.

The presence of neuropathological effects proved to be, for many years, the main endpoint for assessing the neurotoxicity of a chemical substance. ...

In Vivo Surface Electrocardiography for Adult Zebrafish

The electrocardiogram waveforms of adult zebrafish and those of humans are remarkably similar. These electrocardiogram similarities enhance the value of zebrafish not only as a research model for human cardiac electrophysiology and myopathies but also as a surrogate model in high throughput pharmaceutical screening for potential cardiotoxicities to humans, such as QT prolongation. As such, in vivo electrocardiography for adult zebrafish is an electrical phenotyping tool that is necessary, if not indispensable, for cross-sectional or longitudinal in vivo electrophysiological characterizations. However, too often, the lack of a reliable, practical, and cost-effective recording method remains a major challenge preventing this in vivo diagnostic tool from becoming more readily accessible. Here, we describe a practical, straightforward approach to in vivo electrocardiography for adult zebrafish using a low-maintenance, cost-effective, and comprehensive system that yields consistent, reliable recordings. We illustrate our protocol using healthy adult male zebrafish of 12-18 months of age. We also introduce a rapid real-time interpretation strategy for quality validation to ensure data accuracy and robustness early in the electrocardiogram recording process.

Here, we present a reliable, minimally invasive, and cost-effective method to record and interpret electrocardiograms in live anesthetized adult zebrafish.

The electrocardiogram waveforms of adult zebrafish and those of humans are remarkably similar. These electrocardiogram similarities enhance the value of ...

A Swimming-Induced Zebrafish Exercise Apparatus for Versatile Training Approaches

To comprehensively investigate the effects of exercise on health and disease, animal models play a pivotal role. Zebrafish, a widely utilized vertebrate model organism, offers a unique platform for such studies. This study introduced the development of a cost-effective apparatus tailored for zebrafish exercise studies utilizing readily available materials. The device is founded on the principles of a swim tunnel and encompasses a network of pipes and valves linked to a submersible pump. Water flow is meticulously monitored by a sensor and regulated via valves. To assess the apparatus&#39;s effectiveness, two training protocols were implemented: moderate-intensity continuous training (MICT) and high-intensity interval training (HIIT). Fish were trained collectively, and their swimming performance was assessed through an endurance test. Both training protocols led to improvements in swimming performance following 30 days of training and induced alterations in the molecular response to exercise compared to a sedentary control group. Notably, HIIT demonstrated superior efficiency over MICT. The zebrafish training system proved to be a valuable tool for investigations in exercise physiology and further advances the utility of the zebrafish model in this field.

The exercise apparatus designed for less fortunate fish facilitates the implementation of diverse exercise protocols with varying intensities by manipulating water flow speed, achievable through rheotaxis.

To comprehensively investigate the effects of exercise on health and disease, animal models play a pivotal role. Zebrafish, a widely utilized vertebrate ...

Zebrafish Maintenance and Husbandry

The zebrafish (Danio rerio) is a powerful vertebrate model system for studying development, modeling disease, and screening for novel therapeutics. Due to their small size, large numbers of zebrafish can be housed in the laboratory at low cost. Although zebrafish are relatively easy to maintain, special consideration must be given to both diet and water quality to in order to optimize fish health and reproductive success.
This video will provide an overview of zebrafish husbandry and maintenance in the lab. After a brief review of the natural zebrafish habitat, techniques essential to recreating this environment in the lab will be discussed, including key elements of fish facility water recirculation systems and the preparation of brine shrimp as part of the zebrafish diet. Additionally, the presentation will include information on how specific zebrafish strains are tracked in a laboratory setting, with specific reference to the collection of tail fin samples for DNA extraction and genotyping. Finally, experimental modifications of the zebrafish environment will be discussed as a means to further our understanding of these fish, and in turn, ourselves.

Maintenance and Husbandry of Danio rerio Zebrafish

The zebrafish (Danio rerio) is a powerful vertebrate model system for studying development, modeling disease, and screening for novel therapeutics. Due to ...