The effects of high temperature on bone development, mineralization, and skeletal deformities during Colossoma macropomum larval growth

This study evaluated the effects of temperature on bone development, mineralization, and skeletal deformities during Colossoma macropomum larval growth. The thermal range for efficient metabolism for juveniles has been clearly determined (25–32 °C), but the potential effects of increasing rearing temperature above 32 °C during larval development remains unknown. 11,760 C. macropomum larvae at four days post hatching (DPH) were randomly distributed into 6 circular tanks (28 L; three tanks per condition) connected to two RAS, at a density of 70 larvae L −1 . In one RAS, the water temperature was gradually adjusted to 34 °C (33.85 ± 0.93 °C), while maintained at 29 °C (28.77 ± 0.89 °C) in the other system. These experimental conditions were maintained for 30 days. Larvae at 34 °C exhibited greater standard length, wet weight, and higher specific growth rates in early (9 and 14 DPH) and late (29 and 34 DPH) stages, with no significant differences in survival or condition factor. Elevated temperature accelerated ossification in cranial, axial, and fin structures without altering the number vertebral bodies. Skeletal deformities occurred in both groups, but overall incidences of severe deformities were low and not related to temperature. Ceratohyal overgrowth and opercular cavity deformities were highly prevalent in early stages but diminished subsequently. Some caudal fin deformities (mild deformities) were more common at 34 °C. Overall, rearing tambaqui larvae at 34 °C promoted growth and skeletal mineralization without compromising survival rate. Therefore, rearing at 34 °C may accelerate larvae development, potentially reducing the duration of live feeding phase and the associated production costs.