Functional consequences and population differences in the developmental plasticity of muscle to temperature in Atlantic herring Clupea harengus

The development of the axial muscles was investigated in Atlantic herring Clupea harengus from 2 spring-spawning (Clyde and Blackwater) and 1 autumn-spawning (Manx) populations in 2 successive years. The results indicate significant developmental differences between stocks. Myofibril synthesis and the development of acetylcholinesterase activity at the neuromuscular junctions occurred later with respect to embryonic stage at 5 degreesC than at 8 and 12 degreesC in Clyde herring, with much less pronounced differences between temperatures for the other populations. In a second series of experiments, Clyde herring were incubated at 5 and 12 degreesC until shortly after hatching, and then reared at ambient temperature in triplicate tanks. The 5 degreesC group had a faster growth rate than the 12 degreesC group with respect to effective day-degrees from hatch. However, flexion of the notochord and the development of the dorsal and anal fin ray muscles occurred at shorter body lengths in the 12 than 5 degreesC groups. The maximum escape velocity of larvae during fast-starts was determined using a high-speed video. Over the size range 11.2 to 18.5 mm total length, the adjusted mean maximum velocity was 24% higher in larvae hatched from 12 than 5 degreesC eggs. Cruising swimming behaviour also differed between groups with the 12 degreesC larvae showing reduced yaw relative to the 5 degreesC larvae, indicating a more developmentally advanced sub-carangiform style of locomotion.