An Invader's Peculiar Trophic Behavior: Diel Fluctuations and Environmental Drivers

Area of Science:

• Ecology
• Invasive Species Biology
• Malacology

Background:

• The invasive apple snail (Pomacea canaliculata) significantly impacts aquatic vegetation and crops through grazing.
• This snail exhibits unique feeding behavior, including pedal surface collecting using a pedal funnel to gather food from the water surface.

Purpose of the Study:

• To investigate the diel fluctuations of pedal surface collecting behavior in Pomacea canaliculata.
• To evaluate the influence of environmental factors like water temperature, velocity, and photoperiod on this feeding strategy.

Main Methods:

• Conducted four whole-day field observations in a stream to record diel patterns of pedal funnel use.
• Performed laboratory experiments to assess the effects of water temperature, velocity, and photoperiod on pedal funnel formation.
• Ruled out an endogenous rhythm by observing behavior under constant artificial light.

Main Results:

• Pedal funnel frequency was lowest during daylight and highest after sunset, correlating with general activity patterns.
• Pedal funnels formed across the active temperature range, with peak rates at 30°C, but temperature did not affect food captured.
• Pedal funnels were absent at water velocities above 0.12 m·s⁻¹, but stable below this threshold. Behavior was scarce under constant light.

Conclusions:

• Pedal surface collecting in Pomacea canaliculata is primarily a nocturnal behavior, likely a strategy to evade visual predators.
• Environmental factors, particularly light and water velocity, significantly influence this feeding behavior.
• Understanding pedal surface collecting may offer insights into the ecological impact of invasive snails and potential control strategies using molluscicides.