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1 September 2012 Predaceous Diving Beetle, Dytiscus sharpi sharpi (Coleoptera: Dytiscidae) Larvae Avoid Cannibalism by Recognizing Prey
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Larvae of diving beetles such as the various Dytiscus species (Coleoptera: Dytiscidae) are carnivorous and usually prey on other aquatic animals. Cannibalism among larvae of Dytiscus sharpi sharpi (Wehncke) was observed to begin when they were starved for more than two days under artificial breeding conditions. However, the 2-day starved larvae did not show cannibalism in the presence of intact, motionless, frozen tadpoles, or frozen shrimps. The beetle larvae attacked and captured intact tadpoles faster (15 sec) than other motionless and frozen tadpoles (120 sec), indicating that prey movement was an important factor in stimulating feeding behavior in larvae. Prey density does not have an effect on larval cannibalism. In cases in which preys are present at lower densities than that of larvae, a group of beetle larvae frequently fed on single prey. This feeding behavior, therefore, provides direct evidence of self-other recognition at the species level. Using two traps in one aquarium that allows the larvae to detect only prey smell, one containing tadpoles and another empty, the beetle larvae were attracted to the trap with tadpoles at high frequency, but not to the empty trap. In another experiment, the beetle larvae were not attracted to the trap containing a beetle larva. These results suggest that the larvae of D. sharpi sharpi are capable of recognizing prey scent, which enables the promotion of foraging behavior and the prevention of cannibalism.

© 2012 Zoological Society of Japan
Toshio Inoda "Predaceous Diving Beetle, Dytiscus sharpi sharpi (Coleoptera: Dytiscidae) Larvae Avoid Cannibalism by Recognizing Prey," Zoological Science 29(9), 547-552, (1 September 2012).
Received: 16 March 2012; Accepted: 27 April 2012; Published: 1 September 2012

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