Water lilies (Nymphaea) produce the familiar floating foliage known as lily pads. These hardy aquatic plants feature tough, round leaves connected by long stems to thick, carbohydrate-rich rhizomes anchored in the sediment. Lily pads form the base of an extensive food web, providing a substantial food source for a wide range of aquatic and semi-aquatic animals.
Aquatic Invertebrate Herbivores
The most numerous grazers of lily pads are aquatic invertebrates that consume the plant material directly. These herbivores cause characteristic damage to the floating leaves.
Aquatic snails, such as the Great Pond Snail and Ramshorn Snail, frequently graze on the leaves by scraping the soft surface tissue. While many snails prefer algae or decomposing organic matter, pointed-shelled varieties readily feed on live lily pads. This surface feeding weakens the pads, making them susceptible to further damage.
Numerous insect larvae also specialize in consuming lily pad tissue. The water lily beetle (Galerucella nymphaeae), for example, has larvae and adults that chew slit-like holes or graze away the upper layer of the leaf surface. This leaves the pads with a scarred appearance that prematurely ages the foliage.
The larvae of the China mark moth (Elophila nymphaeata) cut oval shapes from the leaves, folding the pieces together to create portable shelters while they feed. Other insect larvae, such as chironomid midges, tunnel between the upper and lower layers of the leaves, creating wavy lines that cause the tissue to rot and fall apart.
Mammalian and Large Reptile Consumers
Larger animals, including mammals and reptiles, cause substantial destruction to entire lily pad plants, often targeting the submerged structures. Beavers and muskrats are major mammalian consumers of water lilies. Muskrats are known to consume the floating leaves, stems, and the thick, starchy rhizomes buried in the mud.
The rhizomes are dense with carbohydrates, providing a high-energy food source for cold-weather survival. Beavers also consume the entire plant, including underground parts, often incorporating the stems and pads into the construction of their lodges and dams. Moose wade into the water to feed on the foliage, while white-tailed deer graze on the floating pads in shallow areas.
Large reptiles, primarily certain species of turtles, are active herbivores that consume lily pads. Turtles feed on the leaves, causing noticeable damage to the floating surface. While usually part of a broader omnivorous diet, their foraging habits can significantly impact the localized lily pad population.
Specialized Fish and Other Aquatic Vertebrates
Certain species of fish consume aquatic vegetation, including lily pads. The Grass Carp (Ctenopharyngodon idella) is a large, herbivorous fish native to Asia, often introduced globally for aquatic weed control. These fish possess specialized throats and teeth designed to grind coarse plant matter.
While grass carp will consume water lilies, they are often not the preferred food source compared to softer, submerged weeds like hydrilla or elodea. The mature leaves and thick, tough stems of water lilies are less palatable. This makes the fish less effective at controlling a dense lily pad infestation than they are at clearing other aquatic plants. They graze on them when other food sources become scarce, consuming the leaves and potentially disturbing the roots.