Laboratory growth, feeding, oxygen consumption and ammonia excretion of Octopus ocellatus

Hatchlings from eggs spawned by a female Octopus ocellatus were reared individually in closed seawater systems to make precise analyses of their daily amount of feeding, growth, oxygen consumption and ammonia excretion over the life span at 20°C and 25°C. Octopuses were fed with live hermit crabs. After about 120 d of rearing, hatchlings of about 0.11 g grew to 16.1 ± 7.4 g at 20°C and 18.6 ± 13.1 g at 25°C, respectively. Mean instantaneous growth rates in weight for the first 25 d were higher at 25°C, 8.3 ± 2.3%, than 20°C, 5.6 ± 2.5%, and both rates declined to about 1.0% after 100 d. Mean feeding rate at 20 d post-hatching was 30% of body weight per day and declining to less than 7% after 100 d. Feeding rate at 25°C was significantly higher than that of 20°C during the first 50 d. Oxygen consumption rates for individuals increased with increasing wet weight, and were slightly higher at 25°C than those at 20°C for animals less than about 3 g in wet weight. Growth rate, feeding level and oxygen consumption rate were sensitive to temperature in the early life period during the first 50 d. Without copulation two females spawned unfertilized eggs at 135 d after hatching (14.17 g) at 20°C and 152 d (7.68 g) at 25°C, respectively. The life span of O. ocellatus was estimated to be 6 mo to 1 yr depending on geographic location.