It is not without reason that sea lilies
have received their name: outwardly they are indeed reminiscent of a pennibranched
flower. Their body consists of a cup (central cone) and radial articulated
arms (feelers) with side branches, pinnulae. Sea lilies are the sole recent
echinoderms that have retained the body orientation characteristic of their
echinoderm ancestors: the mouth is turned upwards, and the animal’s dorsal
side is turned to the soil surface. An articulated attachment pedicel with
a cluster of attachment outgrowths—cirruses or, like in stemless, a cluster
of cirruses branches directly from the cup. There may be little teeth or
claws on the cirrus ends, with which the lily securely fastens itself to
Like in all Echinodermata, it, body structure is subordinate to radial five=ray symmetry. It always has five arms; however, they may repeatedly separate to produce from 10 to 200 false arms with numerous side pinnulae, forming a dense catch network. The feelers surrounding the mouth have mucous-ciliary ambulacral grooves, along which food particles captured from water depths are transported to the oral cavity. The latter is situated I the middle of the upper (abdominal) cup surface, to which five ambulacral grooves converge from the arms. The anal opening is also situated alongside on the apex of a special papilla. With regard to feeding habits, sea lilies eat microplankton.
Apart from their external form and orientation of dorsal-abdominal body axis, sea lilies are distinuished from other echinoderms by a slightly simplified ambulacral system: they have neither leg-controlling ampoules, nor madrepore plates.
Stemless lilies can detach from the substrate and move along the sea floor, and even surface by moving their arms.
The plankton larva of sea lilies is called vitellaria.
After metamorphosis, the larva takes a miniature stalk-like semblance of an adult animal. The pedicel disappears in stemless lilies as they become adults.
Six hundred and twenty five lily species are known to exist, most of them inhabiting tropical waters or at great depths. One species occurs in Southern Primorye, (1) Heliometra glacialis (Leach, 1815)
Sea lily (comatulid) cup from top (abdominal side). Ab—ambulacral groove; Aï—anal cone; B—rays; M—mouth; P—pinnulae (according to Roehler).