Thyroid hormone determines energy efficiency of locomotion in zebrafish (Danio rerio) in a temperature-sensitive manner

Dataset associated with manuscript. Abstract The energetic cost of animal movement has important ecological ramifications because it can comprise a large proportion of energy budgets. Understanding the mechanisms that determine energetic efficiency of locomotion (cost of transport; òCoT) is important to estimate environmentally induced changes in movement patterns and energy allocation. We aimed to determine whether thyroid hormone and differences in morphology underlie individual differences in òCoT in zebrafish (Danio rerio). We found that pharmacologically induced hypothyroidism increased òCoT particularly at cooler temperatures (24oC cf 30oC). Hypothyroid fish also had lower critical swimming speed (Ucrit) and reduced tailbeat amplitudes overall, but increased amplitudes at higher swimming speed. Tailbeat frequencies increased with increasing speed, but hypothyroidism modulated these responses. Fineness ratio and cross-sectional area were unrelated to òCoT. Our data indicate that òCoT is embedded within the broader thyroid regulatory network, which renders efficiency of movement sensitive to environmental temperature changes and endocrine-disrupting pollution.