Analyses of mating process in intact WT zebrafish pairs. (A) A schematic illustration showing the entire process of mating. The male fish is shown in grey. The expanded panel represents processes from quivering to spawning. In hooking, one pectoral fin of the male is positioned under the female belly (arrow head). Arrows in illustrations represent directions of fish movements. (B) Photographs from a video showing the process from freezing to spawning. The male fish is behind the female in the initial frame. Released eggs are encircled with a white line in the last frame. Arrows indicate temporal sequence. (C) Photographs of freezing (upper) and hooking behavior (lower). In freezing, the female bends her body in S-shape in response to quivering. In hooking, the male holds the female using the female dorsal fin as an anchor for its contorted trunk. (D) Representative time course displaying the number of mating events (left) and eggs released (right) in 1 min during a 60 min pairing session. (E) Total egg numbers were divided by the numbers of spawning in a single pairing session (n = 10 pairs). Dots represent values of individual pairs. A box represents the accumulated data. (F, G) The number of fertilized eggs and fertilization rate were plotted against the total number of eggs. The number of fertilized eggs strongly correlated with the total egg number (r = 0.81, p = 0.0047). Fertilization rate was independent from the total egg number. Regression lines are shown in (D), (F) and (G).
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