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Octopus minor is widely distributed along the northern coast of China. To date, there is little information on the prey selection process of this species. To understand this process, several experiments were carried out. Three types of bivalves, namely, Ruditapes philippinarum, Mactra chinensis, and Mytilus galloprovincialis, were used to observe the prey selection of O. minor and to analyze the potential causes of prey selection from three aspects: prey profitability, adductor muscle tension and handling time. Under single-prey conditions, we found that the average (±SD) predation rates of O. minor on R. philippinarum, M. chinensis, and M. galloprovincialis were 1.73±0.50, 1.27±0.42, and 0.8±0.2/d, respectively. Under different prey combinations, octopods actively selected one type of prey over the other(s), and the order of prey preference was R. philippinarum, followed by M. chinensis and lastly M. galloprovincialis. Furthermore, the shells of the consumed prey showed that O. minor only consumed bivalves by pulling them apart since there was no evidence of drill holes on the shells. The prey selection of O. minor was related to the prey profitability and handling time; O. minor appeared to select preys with a higher profitability and a shorter handling time. However, the difficulty in opening the bivalve was not consistent with the prey preference of the octopods. These results suggest that O. minor prefers to consume R. philippinarum possibly due to a high profitability and a short handling time that supports the optimum Foraging Theory. [ABSTRACT FROM AUTHOR]

We report on the effects of previous foraging experience on prey-selection by the bivalve feeding polychaete Halla okudai, including whether there was evidence of frequency-dependent predation. Three separate batches of H.okudai were maintained for 30 days on clams, mussels, or oysters, before being offered a choice among these three prey. Initially individuals from all three treatments consumed more clams than mussels, and no oysters. As the number of clams was depleted the polychaetes shifted their diet to include a greater proportion of mussels, but even after 20 days oysters were only eaten by polychaetes that had been previously acclimated to them. Nevertheless, polychaetes from each treatment inspected significantly more of the prey species to which they had initially been acclimated, suggesting that previous experience may increase the likelihood of certain prey being detected. When individuals of H.okudai were repeatedly offered the same prey species, handling time did not decrease (and therefore prey profitability did not increase) with experience, which may be because H.okudai paralyses its prey with toxic mucus. Since repeated experience of the same prey species gives no advantage in terms of reduced handling time, we suggest this may be why this species does not show frequency-dependent prey-selection. [ABSTRACT FROM AUTHOR]