Environmental tolerance of invasive golden apple snails (Pomacea canaliculata (Lamarck, 1822)) and Thai native apple snails (Pila scutata, (Mousson, 1848))

The success of aquatic invasive species such as golden apple snails may be due to the fact that they are very adaptive and can live in wide range of environmental conditions. In contrast, native fauna such as Thai apple snails, which are less locally adaptive than exotic species, are gradually disappearing from their native ecosystems. This study investigated the environmental conditions in a habitat of golden apple snails (Pomacea canaliculata) and compared them with that of Thai native snails (Pila scutata). We also determined degrees of tolerance and growth rates between P. canaliculata and P. scutata raised in water of different qualities. The results revealed that in natural habitats of P. canaliculata, the water quality (dissolved oxygen (DO) 2.37 +/- 0.04 mg l(-1), (biological oxygen demand (BOD5) 10.40 +/- 0.18 mg l(-1)) was much poorer than that of P. scutata (DO 8.03 +/- 0.01 mg l(-1), BOD5 0.83 +/- 0.01 mg l(-1)). Furthermore, when the two types of snails were raised in water of different qualities in the laboratory (clean (DO7.79 +/- 0.03 mg l(-1), BOD5 1.15 +/- 0.01 mg l(-1)), moderately deteriorated (DO2.30 +/- 0.07 mg l(-1), BOD5 12.08 +/- 9.80 mg l(-1)) and deteriorated)DO 1.61 +/- 0.03 mg l(-1), BOD5 16.75 +/- 6.51 mg l(-1)), P. canaliculata consumed larger quantities of food than P. scutata. We observed no statistically significant difference between the growth rates of P. canaliculata and P. scutata in clean water. In contrast, in moderately deteriorated and deteriorated water, growth rates of P. canaliculata were significantly higher than those of P. scutata, thus implying that deteriorated water negatively influenced P. scutata whilst having no adverse effects on P. canaliculata. In addition, in deteriorated water, while P. canaliculata survived throughout the eight weeks of the experiment, all P. scutata had died by the end of week five. Our results show that P. canaliculata was more tolerant to different environmental conditions than P. scutata, therefore, making them a very successful invader.