Feeding behavior and oxygen consumption of Octopus ocellatus preying on the short-neck clam Ruditapes philippinarum

Abstract

We examined the feeding behavior and energy consumption of Octopus ocellatus preying on short-neck clams under experimental conditions. Observed feeding patterns of individual octopuses of 7.0–52.1 g in wet weight were classified as “pulling”, “pulling–drilling–pulling” or variations of pulling and drilling. Octopuses used pulling for clams with shell lengths (SL) of 0.9–2.9 cm and a combination of pulling and drilling for clams with SL of 0.8–3.6 cm. Pulling alone resulted in a mean time for opening a clam (handling time) of 3.1 min and energy consumption of 8.0 μgO 2 g − 1 . Pulling plus drilling involved longer handling times. Prior to drilling, octopuses showed one of two pulling strategies, “low-energy pulling” or “high-energy pulling”. The latter was more similar to the type of pulling behavior seen when drilling was not used. The high-energy strategy resulted in a mean handling time of 55.4 min and an energy cost of 78.9 μgO 2 g − 1 . Low-energy pulling plus drilling resulted in a shorter handling time (29.5 min) and a lower energy cost (26.4 μgO 2 g − 1 ). We calculated the profitability (yield of energy gain per unit handling time) and energy efficiency (yield of energy gain per unit energy cost) of these feeding strategies. Pulling alone was the most efficient method in terms of profitability, whereas low-energy pulling plus drilling was the most efficient in terms of energy expenditure for young octopuses eating clams.