Sea lilies are marine animals often mistaken for plants due to their graceful, flower-like appearance. Found across the world’s oceans, these ancient creatures use a unique strategy to sustain themselves. This article explains what sea lilies are, how they feed, and their diet.
Understanding Sea Lilies
Sea lilies are marine invertebrates belonging to the class Crinoidea, which also includes feather stars, and are part of the phylum Echinodermata. They are characterized by a central cup-shaped body called a calyx and numerous feathery arms that extend outwards. Many species possess a stalk, which anchors them to the seafloor, though some can detach and move. These animals primarily inhabit deep ocean environments, but some species can also be found in shallower reefs. Their lineage dates back over 480 million years to the Ordovician period, making them one of the oldest living echinoderm groups.
How Sea Lilies Feed
Sea lilies are passive suspension feeders, capturing food particles suspended in the water as currents flow past. Their feathery arms, known as brachials, are specialized for this purpose. Each arm is lined with smaller, feather-like structures called pinnules, which increase the surface area for food collection. Within the ambulacral grooves along their arms, sea lilies possess numerous tube feet.
These tube feet are covered in sticky mucus that traps small, drifting food particles. Tiny hair-like projections called cilia, located within the ambulacral grooves, rhythmically beat to move the mucus-bound food along the grooves. This process, known as ciliary-mucoid feeding, transports the captured particles towards the sea lily’s mouth. Sea lilies often orient their arms into a fan shape, perpendicular to the current, to maximize feeding efficiency.
The Sea Lily Diet
The diet of sea lilies consists primarily of microscopic particles suspended in the water column. Their main food sources include various forms of plankton, such as phytoplankton and zooplankton larvae. This can encompass small crustaceans like copepods and krill, as well as other tiny organisms. Additionally, sea lilies consume organic detritus, which is decaying organic matter.
By consuming these suspended particles, sea lilies play a role in nutrient cycling within their marine ecosystems. Their presence helps regulate the populations of planktonic organisms, contributing to the overall health and balance of the food chain.