Energetics of fish larvae, the smallest vertebrates

• Published in: Acta physiologica Scandinavica 1995-07, Vol.154 (3), p.279-290
• Main Author: WIESER, W.
• Format: Article
• Language: English
• Subjects: aerobic and anaerobic energy metabolism; Animals; Biological and medical sciences; compensatory strategies of metabolism; Development. Metamorphosis. Moult. Ageing; Energy Metabolism - physiology; Fishes - metabolism; Fundamental and applied biological sciences. Psychology; growth; Larva - metabolism; metabolic scaling; mitochondrial density and capacity; muscle development; oxygen content; oxygen debt; temperature; Vertebrates: anatomy and physiology, studies on body, several organs or systems
• ISSN: 0001-6772; 1365-201X
• DOI: 10.1111/j.1748-1716.1995.tb09912.x

In this review recent findings on the energetics offish larvae are presented, highlighting some of the physiological problems linked to small body size. The existence of a mass‐independent phase of specific metabolic rate is confirmed but it is pointed out that in young fish ontogenetic transitions of metabolic scaling have so far been documented only for the routine level of activity. Maximum metabolic rate is limited by mitochondrial density in the swimming muscles which scales with a mass exponent of ˜ 0.9. Mitochondrial density in the swimming muscles of a species of fish, from larva to adult, covers about the same range as mitochondrial density in the skeletal muscles of mammals. However, the aerobic capacity (power density) of mitochondria is one order of magnitude lower in fish than in mammals. Energy metabolism in embryos and early larvae of fish is almost entirely aerobic. Anaerobic power in the fast muscle fibres is low after hatching but increases during the transition from larva to Juvenile with a mass exponent greater than one. In hypoxic water fish larvae swim more economically (i.e. their cost of transport is lower) than in normoxic water. If the rate of growth exceeds a critical threshold (about 10% d‐1) fish larvae are capable of increasing the apparent efficiency of growth, probably by reducing the costs of other energy‐consuming functions of maintenance.