The effect of variability in growth on somatic condition and reproductive status in the southern calamary Sepioteuthis australis

The aim of the present study was to determine how the lifetime growth rates of adult southern calamary Sepioteuthis australis related to somatic and reproductive condition. A hierarchy of biological levels was explored: whole-animal, muscle fibre, and proximal condition. Evidence at all biological levels suggested that allocation of energy given to growth and reproduction was gender-specific. Females may not be allocating the same level of energy to somatic growth due to a greater requirement to re-allocate energy for reproductive growth. There was evidence that faster-growing males were in better somatic and reproductive condition. However, both males and females in better somatic condition were also in better reproductive condition. Fast growth rates by individuals were achieved primarily by muscle fibre growth, rather than production of new fibres. However, mantle muscle instantaneous growth rates (assessed through RNA:protein ratio) decreased as males became larger and more reproductively mature; no association was evident in females. An inverse correlation between gonad size and muscle instantaneous growth rates in females suggested energy was being directed away from somatic growth and towards reproductive growth. There was evidence that lifetime growth rates could predict the reproductive or somatic condition of adult calamary, but this was gender-specific.