Cephalopod hatchling growth: the effects of initial size and seasonal temperatures
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Temperature is known to have a strong influence on cephalopod growth during the early exponential growth phase. Most captive growth studies have used constant temperature regimes and assumed that populations are composed of identically sized individuals at hatching, overlooking the effects of seasonal temperature variation and individual hatchling size heterogeneity. This study investigated the relative roles of initial hatchling size and simulated natural seasonal temperature regimes on the growth of 64 captive Octopus pallidus over a 4-month period. Initial weights were recorded, and daily food consumption and fortnightly growth monitored. Two temperature treatments were applied replicating local seasonal water temperatures: spring/summer (14–18°C) and summer/autumn (18–14°C). Overall octopuses in the spring/summer treatment grew at a rate of 1.42% bwd−1 (% body weight per day) compared to 1.72% bwd−1 in the summer/autumn treatment. Initial size influenced growth rate in the summer/autumn treatment with smaller octopuses (<0.25 g) growing faster at 1.82% bwd−1 compared to larger octopuses at 1.68% bwd−1. This was opposite to individuals in the spring/summer treatment where smaller octopuses grew slower at 1.29% bwd−1 compared to larger octopuses at 1.60% bwd−1. Initial size influenced subsequent growth, however, this was dependent on feeding rate and appears to be secondary to the effects of temperature.
KeywordsInitial Size Carapace Width Instantaneous Growth Rate Total Feed Cephalopod Species
The authors would like to thank Jessica André, TAFI staff and students for their assistance in the maintenance and set up of the culture system, and Michael and Craig Hardy for catching brood stock. This experiment complied with current Tasmanian and Australian laws and approved by the Animal Ethics Committee of the University of Tasmania under project No. A0008130.
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