Rearing American bullfrog tadpoles in different tank colors: Effect on metamorphosis, performance, and biochemistry responses

Abstract

This study examined the influence of tank color on the performance, time to metamorphosis, skin pigmentation, and biochemistry parameters of American bullfrog tadpoles and froglets. Six hundred tadpoles (0.94 ± 0.11 g) were selected (Gosner stage – 25) and distributed in a completely randomized design in 15 tanks of 40 L (1 tadpole L−1) in a recirculating aquaculture system, five repetitions of each color (blue, black, and white). Biometrics were performed every 14 days in all experimental units, and when the tadpoles at metamorphic climax and following complete transformation. Animals were weighed, measured, and photographed to evaluate the growth performance, uniformity, and skin pigmentation analyses. At the conclusion of metamorphosis, twenty-four animals randomly selected per treatment were euthanized. Twelve of them were macerated to performed of the whole-body biochemistry analysis, and the other twelve were dissected to obtain the biological indexes. The tadpoles raised in blue, and black tanks reached the metamorphosis climax and transitioned into froglets more rapidly (P < 0.05) than animals held in white tanks. However, tadpoles at metamorphic climax reared in black tanks had prolonged time to complete the metamorphosis (P < 0.05). The tadpoles raised in blue background had the higher values for final body weight throughout the experiment (P < 0.05). The tadpoles raised at blue and black tanks had the higher values for body weight gain, body length, body length gain, protein efficiency ratio, specific growth rate and lower feed conversion ratio throughout the experiment (P < 0.05). The pre- and pro-metamorphic uniformity of tadpoles was affected by the color of the tank, with the white treatment having lower uniformity at the 14, 42, 56, 70 and 98 days of the experiment (P < 0.05). In addition, tadpoles on metamorphic climax and froglets raised on black, and blue tanks had darker color of skin compared with the animals raised in white tanks, with animals raised in black tanks showing darker skin tones (P < 0.05). However, neither the growth, and uniformity of tadpoles on metamorphic climax and froglets, nor the biological indexes and whole-body biochemistry of froglets were affected by tank color (P > 0.05). Therefore, considering the homogeneity in growth, and time to metamorphosis, blue colored tanks represent best choice for reared of American bullfrog tadpoles.