Alterations were observed in zebrafish embryos exposed to anise myrtle (A,C) and lemon myrtle (B,D) extract for 96 h. Heatmap showing the cumulative morbidity and phenotypic and behavioural alterations (A,B). Hatching delay occurred at higher concentrations for both plant extracts, with other mild alterations. The proportion of total mortality observed each experimental day at different concentrations (C,D). Colours represent the experimental time in hours (24–96 h). Most of the mortality occurred in the first 24 h, though continued exposure to lemon myrtle showed ongoing mortality continuing by subsequent days.

Morphological alterations were observed in zebrafish embryos exposed to anise (A) and lemon (B) myrtle extract for 96 h and graphed as a percentage of all larvae. The colours represent different concentrations tested (mg/L). Data show the mean ± SD, n = 60. Asterisks indicate statistical significance when compared to a control group (0 mg/L): p < 0.05 (*) and p < 0.001 (***).

Developmental alterations (A,C) and malformations (B,D) were observed in zebrafish larvae exposed at 96 h post-fertilization to different concentrations of anise (A,B) and lemon (C,D) myrtle extract. The alterations observed were pigmentation delay (Pig. D), developmental delay (Dev. D), yolk sac absorption delay (Yolk Sac AD), yolk sac edema (Yolk Sac E), and cardiac edema (Cardiac E). The malformations observed were localized in the head, eyes, spine, and tail. None of the alternations observed in anise myrtle were significantly different from the control 0 mg/L group. In contrast, in Lemon myrtle, there were substantial alterations and malformations at 240 mg/L. The 480 mg/L group only includes very few survivors. Bar colours represent the concentrations tested in mg/L. Data represent the mean ± SD, n = 60. Asterisks indicate statistical significance when comparing the exposed groups with the control groups: p < 0.05 (*) and p < 0.001 (***).