Early life-history processes in benthic octopus: Relationships between temperature, feeding, food conversion, and growth in juvenile Octopus pallidus

Abstract

Initial growth in cephalopods is exponential, making early life-history critical in determining growth trajectories. Few captive studies have however examined the early life-history of cephalopods in fluctuating temperatures as would be encountered in the wild. This study investigates the relationship between early growth and the significant factors affecting growth, namely food intake, food conversion and fluctuating environmental temperatures. Pale octopus ( Octopus pallidus) hatchlings were reared in captivity under either a warming or cooling temperature regime. Individual variations and periodicity in feeding rates ( F r), food conversion rates ( C r), growth rates ( G r), and the relationship between these variables and temperature were examined weekly. Food conversion rates were variable between individuals but also within individual octopus, which exhibited large fluctuations in C r over time, exceeding 100% d − 1 in one instance. Although individual F r, C r and G r displayed fluctuations over time, there was no evidence of periodicity for any of the variables. Changes in temperature were not significantly correlated to changes in F r, C r or G r. Feeding rate did not appear to influence growth rate or food conversion rate. Food conversion rate was negatively correlated to feeding rate in the same week, and positively correlated to growth rate. Short periods of low or no food consumption were common and the high values obtained for food conversion rate for some individuals suggest that octopus can grow substantially with little or no food intake. Individual variability observed in octopus growth may be dependent on the growth mechanism involved, specifically a fine balance between the continuous hyperplasic and hypertrophic growth found in cephalopods.