Fig. 1

Experimental design. A Chronic stress (CS) protocol lasting 21 days to cover around three waves of spermatogenesis period in zebrafish. CS consisted of a predictable handling source of stress (twice per day) and a main body of unpredictable chronic stress (UCS). Each stressor included in the UCS was applied twice per week. Seven stressors were used in the UCS protocol: (1) cooling: 30 min in a tank at 23 °C; (2) heating: 30 min in a tank at 33 °C; (3) low water level: 2 min in a tank with extreme low water level exposing the dorsal body of the fish to the air; (4) chasing: 8 min of chasing with a net; (5) crowding: 50 min of crowding animals in a 250-mL beaker; (6) tank change: three consecutive relocations of the animals in a new tank after 30 min, and (7) predator: 50 min exposure to a video of the zebrafish predator Archocentrus nigrofasciatus. B Five trials performed to validate CS protocol (trial 1), perform molecular and histological analyses after CS protocol (trial 2), find altered pathways in the gonads after CS (trial 3), evaluate CS protocol at physiological level (trial 4), and analyze the molecular scenario in the derived progenies (trial 5). The fish batch used in each trial is codified by a number for easier interpretation of the experimental design (batch 1; batch 2, batch 3, and batch 4). CASA, computer-assisted sperm analysis