Differential influences of (±) anatoxin-a on photolocomotor behavior and gene transcription in larval zebrafish and fathead minnows

Abstract

Background Though anatoxin-a (antx-a) is a globally important cyanobacterial neurotoxin in inland waters, information on sublethal toxicological responses of aquatic organisms is limited. We examined influences of (±) antx-a (11–3490 µg/L) on photolocomotor behavioral responses and gene transcription associated with neurotoxicity, oxidative stress and hepatotoxicity, in two of the most common alternative vertebrate and fish models, Danio rerio (zebrafish) and Pimephales promelas (fathead minnow). We selected environmentally relevant treatment levels from probabilistic exposure distributions, employed standardized experimental designs, and analytically verified treatment levels using isotope-dilution liquid chromatography tandem mass spectrometry. Caffeine was examined as a positive control. Results Caffeine influences on fish behavior responses were similar to previous studies. Following exposure to (±) antx-a, no significant photolocomotor effects were observed during light and dark transitions for either species. Though zebrafish behavioral responses profiles were not significantly affected by (±) antx-a at the environmentally relevant treatment levels examined, fathead minnow stimulatory behavior was significantly reduced in the 145–1960 µg/L treatment levels. In addition, no significant changes in transcription of target genes were observed in zebrafish; however, elavl3 and sod1 were upregulated and gst and cyp3a126 were significantly downregulated in fathead minnows. Conclusion We observed differential influences of (±) antx-a on swimming behavior and gene transcription in two of the most common larval fish models employed for prospective and retrospective assessment of environmental contaminants and water quality conditions. Sublethal responses of fathead minnows were consistently more sensitive than zebrafish to this neurotoxin at the environmentally relevant concentrations examined. Future studies are needed to understand such interspecies differences, the enantioselective toxicity of this compound, molecular initiation events within adverse outcome pathways, and subsequent individual and population risks for this emerging water quality threat.

Effects of 4 testing arena sizes and 11 types of embryo media on sensorimotor behaviors in wild-type andchd7mutant zebrafish larvae

“…These studies typically require small-diameter wells and use locomotor behavior as an output for measuring toxicity. A few studies have reported significant changes in locomotion and activity levels when arena size increased, while exposure concentrations and other variables remained constant 17,27,28,39 . Another study reported significant changes in locomotion and an interaction between well size and the concentration of a neurostimulant 28 .…”

“…A few studies have reported significant changes in locomotion and activity levels when arena size increased, while exposure concentrations and other variables remained constant 17,27,28,39 . Another study reported significant changes in locomotion and an interaction between well size and the concentration of a neurostimulant 28 . In these studies locomotion of larvae was tested in dim light for an extended perior 39 , or in variations of the visuomotor response (VMR) assay in which locomotion is analyzed during repeated cycles of light and dark illumination 17,27 .…”

“…Previous work has demonstrated differences in overall activity levels of larval zebrafish as arena size changes 17,27,28 , but to determine if arena size alters the types of movement performed and/or the location of larvae within the arena, we recorded and measured spontaneous locomotion at 50 frames per second for 18.5 min and analyzed the frequency of swim and turn movements 12,29 , total distance traveled, and thigmotaxis (preference for proximity to the wall) behavior. We found robust differences in total distance traveled as arena size increased (Fig.…”

Advancing statistical treatment of photolocomotor behavioral response study data

“…The most common strategy is to calculate the average of the response variable across the entire domain, regardless of light/dark period [3][4][5]. It is also common for univariate ANOVA to be repeated twice, once for the measurements in the light periods and once for those in the dark periods [6][7][8]. Alternatively, it may be repeated several times for each individual light/dark period itself [9][10][11].…”

Natural toxins: environmental contaminants calling for attention

“…Two studies bring information relevant for hazard assessment of selected cyanobacterial metabolites. Lovin et al [50] observed species-specific responses in two of the most common larval fish models (zebrafish and fathead minnow) after exposure to neurotoxin anatoxina, with more pronounced sublethal effects in fathead minnows at environmentally relevant concentrations. Kubickova et al [51] conducted an extensive review focused on retinoid compounds that can be also produced by cyanobacterial blooms.…”