Alarm response of hatchlings of the apple snail, Pomacea canaliculata (Gastropoda: Ampullariidae), to aqueous extracts of other individuals

We examined how hatchlings of the freshwater snail, Pomacea canaliculata, responded to aqueous extracts of conspecific hatchlings. Three, 3-day-old hatchlings were macerated in deionized water (1 mg hatchling per 1 ml water). When 0.5 ml of the aqueous extract was added to a test tube containing 10 hatchlings of the same age and 50 ml of water, the hatchlings in the water began to crawl out of the water within 5 min. The proportion of hatchlings that crawled out of the water approached 0.6–0.9 after 1 h, but gradually decreased to 0.4 after 24 h. The relatedness between the live and the macerated hatchlings had no significant influence on the response. Hatchlings of egg masses obtained either in the laboratory or in the wild responded similarly to aqueous extracts of hatchlings from either egg mass. This suggests that the conditions under which the egg masses were incubated or the conditions that their parents had experienced had no effect on the hatchlings’ response. When compared with experiments reported on other aquatic animals, we consider the behavior of the hatchlings to be an alarm response of escaping from predators.