Sea lily - description, features and interesting facts. Fossil "Sea lily" - Ludovit

sea ​​lilies, or crinoids (lat. Crinoidea), - one of the classes of echinoderms. About 700 species are known in the world, 5 species in Russia.

Biology

Bottom-dwelling animals with a body in the form of a cup, in the center of which there is a mouth, and a corolla of branching rays (arms) extends upward. An attachment stalk up to 1 m long extends down from the calyx in stalked crinoids, growing to the ground and bearing lateral appendages ( cirri); in stemless ones there are only mobile cirri. At the ends of the cirri there may be teeth, or “claws,” with which stemless lilies are attached to the ground.

Sea lilies are the only echinoderms that have retained the body orientation characteristic of the ancestors of echinoderms: their mouth is turned upward, and their dorsal side is turned towards the surface of the ground.

Like all echinoderms, the body structure of crinoids is subject to pentaradial radial symmetry. There are 5 arms, but they can be repeatedly divided, giving from 10 to 200 “false arms”, equipped with numerous side branches ( kicking). The loose corolla of the sea lily forms a net to trap plankton and detritus. The hands on their inner (oral) side have mucociliary ambulacral grooves leading to the mouth; along them, food particles captured from the water are transferred to the mouth. On the edge of the calyx, on a conical eminence ( papilla) is the anus.

There is an exoskeleton; the endoskeleton of the arms and stalk consists of calcareous segments. Branches of the nervous, ambulacral and reproductive systems extend inside the arms and stalk. Besides external form and the orientation of the dorsal-ventral axis of the body, crinoids differ from other echinoderms in their simplified ambulacral system - there are no ampullae that control the legs, and there is no madrepore plate.

Evolution

Fossil stems of crinoids

Trochites - fossilized segments of the stems of crinoids

Fossil crinoids are known from the Lower Ordovician. They are believed to have evolved from primitive stalked echinoderms of the class Eocrinoidea. They reached their greatest prosperity in the Middle Paleozoic, when there were over 5,000 species, but by the end of the Permian period most of them died out. The subclass Articulata, to which all modern crinoids belong, has been known since the Triassic.

Fossilized remains of crinoids are among the most common fossils. Some limestone strata dating from the Paleozoic and Mesozoic are composed almost entirely of them. Fossil segments of crinoid stems that resemble gears are called trochites.

Lifestyle and nutrition

Stalked crinoids (about 80 species) are sessile and are found at depths from 200 to 9,700 m.

Stemless (about 540 species), most diverse in the shallow waters of tropical seas, often brightly and variegatedly colored. Approximately 65% ​​of stemless crinoids live at depths of less than 200 m. In the tropical Pacific Ocean, up to 50 species can live on one reef. Stemless lilies are able to detach from the substrate, move along the bottom and float up due to the movement of their hands.

All sea lilies are passive filter feeders, filtering out a nutrient suspension from the water: protozoa (diatoms, foraminifera), invertebrate larvae, small crustaceans and detritus.

Reproduction and development

Dioecious; gametes develop in pinnules. Development with a floating larva (doliolaria). The larvae, attaching to the substrate, turn into a miniature stem like an adult lily. In stemless lilies, as they grow in adult form the stem dies.

• Kingdom: Animalia, Zoobiota = Animals (Invertebrates)
• Subkingdom: Eumetazoa = True multicellular animals
• Class: Crinoidea = Sea lilies

Class: Crinoidea = Sea lilies

It is not for nothing that sea lilies got their name from appearance really resemble a pinnately branched flower. Their body consists of a “cup” (central cone) and radially extending segmented “arms” (tentacles) with lateral branches - pinnules. Sea lilies are the only modern echinoderms that have retained the body orientation characteristic of the ancestors of echinodermatids: their mouth is facing upward, and the animal’s dorsal side is facing the surface of the ground. From the calyx in stalked lilies there extends a jointed attachment stalk with a bundle of attachment processes - cirri or, as in stemless lilies, a bundle of cirri extends directly from the calyx. At the ends of the cirri there may be denticles, or “claws,” with which the lily is firmly attached to the substrate.

Like all echinoderms, the body structure is subject to radial pentaradial symmetry. There are always 5 hands, but they can be repeatedly divided, giving from 10 to 200 “false hands” with numerous side pinnules, forming a thick trapping “net”. The tentacles surrounding the mouth have mucociliated ambulacral grooves, through which food particles captured from the water column are transported to the mouth opening. The oral opening is located in the middle of the upper (“ventral”) surface of the calyx and 5 ambulacral grooves from the “hands” converge to it. Nearby is the anus, located at the top of a special papilla. By the nature of their feeding, sea lilies are sestonophages.

In addition to the external shape and orientation of the dorsal-ventral axis of the body, crinoids differ from other echinoderms in a somewhat simplified ambulacral system - they do not have ampullae that control the “legs” and a madrepore plate.

Stemless lilies are able to detach from the substrate and move along the bottom and even float up due to the movement of their “hands”.

The planktonic larva of crinoids is called vitellaria.

After metamorphosis (“transformation”), the larva turns into a miniature stalked likeness of an adult animal. In stemless lilies, the stem disappears as it grows into an adult form.

There are 625 known species of lilies, most of which live in tropical waters or on great depths. One species lives in Southern Primorye - (1) Heliometra glacialis (Leach, 1815).

Order Comatulida This order includes all 560 species of stemless crinoids. Comatulids lead a free lifestyle; they swim or crawl, keeping their mouth surface always upward. If any comatulid is turned over with its mouth towards the substrate, it quickly takes the correct position again. Most comatulids constantly break away from the support and swim for some time, gracefully raising and lowering one or the other rays. When swimming, multi-rayed individuals alternately use different sections of the rays, and all their arms take part in the movement. Comatulids move at a speed of approximately 5 m/min, making about 100 strokes of their rays, but are able to swim only a short distance. Their swimming is pulsating in nature, that is, they swim with stops, as they quickly get tired and rest for some time. It is believed that comatulids swim no more than 3 m at a time. After resting, they swim again until they find a suitable place to attach.

Comatulids are attached to the substrate with the help of cirri, the number, appearance, length and character of which are highly dependent on the habitat. various types. For example, comatulids living on soft silts have long, thin, almost straight cirri, capable of covering large areas of soil and providing good “anchoring”. On the contrary, crinoids living on hard soils are equipped with short, strongly curved cirri, firmly grasping stones or other hard objects. Cirri do not take part in the movement of most comatulids. Only a few comatulids are indifferent to light, such as Tropiometra carinata. A significant part of the species prefers to live in shaded places and avoids direct sunlight. If the stone is turned toward the light with the side to which the comatulids are attached, they quickly move to the shaded part of it.

In species that care for their offspring, the number of eggs produced is sharply reduced. For example, in the Antarctic species Notocrinus virilis from the family Notocrinidae, only two or three embryos at the same stage of development are often found in the brood pouches. Fertilized eggs enter the brood pouches through a break in the wall between the ovary and the brood pouch. However, the method of fertilization of eggs in these sea lilies is still not clear. Representatives of other families of comatulids also show similar care for their offspring.

No wonder sea ​​lily got its name. In appearance, it really resembles a pinnately branched flower. There are 625 known species of lilies, most of which live in tropical waters or at great depths. The body of the sea lily consists of a “cup” and radially extending segmented “arms” with lateral branches - pinnules.
- the only modern echinoderms that have retained the body orientation characteristic of the ancestors of echinodermatids: their mouth is turned upward, and the animal’s dorsal side is turned to the surface of the ground. From the calyx of the stalked sea lily there extends a jointed attachment stalk with a bundle of attachment processes - cirri or, as in stemless crinoids, a bundle of cirri extends directly from the calyx. At the ends of the cirri there may be teeth, or “claws,” with which the lily is firmly attached to the ground.
Like all echinoderms, the body structure is subject to radial pentaradial symmetry. There are always 5 hands, but they can be repeatedly divided, giving from 10 to 200 “false hands” with numerous side pinnules, forming a thick trapping “net”. The tentacles surrounding the mouth have mucociliated ambulacral grooves, through which food particles captured from the water column are transported to the mouth opening. The oral opening is located in the middle of the upper (“ventral”) surface of the calyx and 5 ambulacral grooves from the “hands” converge to it. Nearby is the anus, located at the top of a special papilla.

By the nature of their feeding, sea lilies are sestonophages.
In addition to the external shape and orientation of the dorsal-ventral axis of the body, the sea lily differs from other echinoderms in a somewhat simplified ambulacral system - it does not have ampullae that control the “legs” and a madrepore plate.
Stemless sea ​​lily is able to move along the bottom and even float up due to the movement of its “hands”. The planktonic larva of crinoids is called vitellaria. After metamorphosis (“transformation”), the larva turns into a miniature stalked likeness of an adult animal. In stemless lilies, the stem disappears as it grows into an adult form.
Latin name crinoidea miller.

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Sea lilies or crinoids (Crinoidea) are bottom-dwelling animals with a predominantly sedentary lifestyle. These are animals belonging to the phylum Echinodermata, and not plants at all, as the name might suggest. Exists from the Ordovician to the present. The body consists of a stem, a calyx and brachioles - arms. Stems and arms are made up of segments various shapes, during the life of the animal they are connected by muscles; in the fossil state they often fall apart. In many species of modern crinoids the stem is reduced.

Filters by power type. Now these are deep-water animals; previously, when there was less pressure from predators, they also lived in shallow water. They experienced maximum prosperity at the end of the Paleozoic. In the Moscow region, crinoids are often found in limestones Carboniferous period. Most often, segments of various shapes and pieces of stems are found, much less often - calyxes. Sometimes you come across whole crinoids in limestone, but such finds are very rare. The diameter of the segments ranges from a few millimeters to 2 centimeters. Stem length – up to 1 meter modern forms and up to 20 meters for fossils.

Crinoids are rarely preserved entirely; this required rapid burial of the body of the lily in sediment, otherwise it would quickly break into individual segments or columns of segments. But these segments and columns are very strong; they are found in abundance not only in limestone, but also in marble. They can be seen in marble and marbled limestone at many Moscow metro stations. The segments, which are essentially calcite crystals, are difficult to dissolve and they resist well the pressure during rock metamorphosis, so crinoids are practically the only type of large fossils preserved in marble.

In the Paleontological Museum there is a huge slab with intact fossilized lilies. It was brought from a quarry in the Myachkovo region. Unfortunately, this quarry has long been abandoned and overgrown, and it is almost impossible to find anything there.

Sea lilies belong to the echinoderms; they, like all echinoderms, have five-ray symmetry. This is clearly visible in the structure of the channel in the center of the stem. Often the channel has the shape five-pointed star or "flower" with five petals. Although, most often the channel is simply round. Sometimes the stem itself has a pentagonal shape, then the lily's segments look like small stars.

The first museum that I was able to visit as part of the paleontological conference Cephalopods: present and past was the world famous Urwelt Museum Hauff located in the German town of Holzmaden. I have already posted some photographs of fossils taken in this museum on Ammonite, but such a museum deserves a separate story. Urwelt Museum Hauff is the largest private paleontological museum in Germany. It grew out of the personal collection of paleontologist and preparator Bernard Gauff (Bernhard ... >>>

The southern slope of the Ternovskaya ridge in the area of ​​Mount Kara-Koba is one of the traditional places for searching for fossils of the Cretaceous period. However, the dense forest cover of the once-cut terraces, and our active search work, gradually reduced the number of new finds. Luck smiled this fall. Miners with powerful equipment appeared at the foot of the mountain, and over the course of several weeks they dug a deep trench with access to the Kara-Koba plateau. During mining operations, hundreds of cubic meters were raised to the surface... >>>

It's full of surprises. Some of them, together with corals and algae, form unique underwater gardens. Sea lilies are bottom animals, and not plants, as it seems at first glance. They belong to the echinoderms.

Where do sea lilies live?

Their class has a fairly extensive distribution area. There are practically no places in the world's oceans where they are not found. There are about 700 species of feather stars. In Russia there are only 5 species of them.

Sea lilies have inhabited all the oceans. Depth doesn't matter to them. They feel equally good everywhere. And yet, the bulk of these animals prefer to settle in warm ocean waters with thickets of coral reefs located at shallow depths (up to 200 meters).

Types of sea lilies

The sea lily class is represented by two varieties of feather stars - stalked and stalkless. All individuals, regardless of their species, are attached to all kinds of objects located under water. Stalked crinoids, having secured their stems to something, remain in this position forever. The area of ​​their life activity is limited by the length of the stalk on which they swing.

Stemless lilies, having lost their support, gained greater freedom of action. They, having detached themselves from the substrate, are able to cover small distances. Animals swim using rays that work like fins. However, each feather-star deprived of a stalk in the process of development does not bypass the attached stalked stage. This feature and the reproduction of crinoids of both species brings them closer to each other.

Biological description

The name of this class of animals has Greek roots. Crinoidea translates as “lily-like.” Indeed, individuals belonging to this class have bizarre bodies, similar to a lush flower. The resemblance to flowers is enhanced by the colorful body coloring of the feather stars. When you see a beautiful creature in the ocean, you just want to take a photo of it. Sea lilies are a delightful decoration of underwater gardens, created by a brilliant designer - nature itself.

Crinoids have a cup-shaped body with a mouth cavity in the center. Branching rays (arms) and a corolla rise upward from the calyx. In stalked crinoids, a stalk is attached to the bottom of the calyx, growing up to one meter in length. The stalk with supporting lateral appendages (cirrhi) is attached to the ground. Stemless lilies have only movable cirri, the ends of which are equipped with either denticles or “claws”. Thanks to them, stemless individuals cling to the ground.

Featherstars became the only echinoderms that managed to retain the body orientation characteristic of their ancestors. Their dorsal side touches the ground, and the surface that is equipped with the oral cavity is turned upward. The structure of their bodies is based on five-ray radial symmetry. The body is formed by five rays, capable of being dismembered many times and forming 10-200 “false arms”. The rays are equipped with multiple lateral branches (pinnules).

Thanks to the blossoming corolla, a kind of network is formed that traps plankton and detritus. Rays framing inner side, equipped with mucociliary grooves, which are reduced to the oral cavity. The food caught in them moves towards the mouth. The calyx along the edge from the side of the conical eminence is equipped with an anus.

Formation exoskeleton calcareous segments contribute. It is formed by two parts: the endoskeleton of the rays and the stalk. These bottom animals have an ambulacral, nervous and reproductive system (which determines the reproduction of crinoids). Branches of all designated systems penetrate into the cavity of the rays and stalk.

Crinoids differ from their counterparts not only in the directionality characteristic of the dorsal-ventral axial line, which penetrates the bodies of all individuals, but also in their external configurations. The components of the ambulacral system in feather stars are simplified. For example, it did not include ampoules designed to control the legs. Madrepore plates were also not found in individuals.

Reproduction

Let's figure out what kind of reproduction occurs in sea lilies. These echinoderms are dioecious animals. Reproductive products enter those pinnules that are located closer to the calyx. The male, as a rule, is the first to spray sperm from the pinnules, using special holes.

His behavior leads to stimulation of a female that does not have any reproductive ducts. Her kicknules simply burst and eggs fall out of them. Fertilization of the eggs occurs directly in the water, after which they turn into a barrel-shaped doliolaria larva. This is how sea lilies reproduce.

Development of doliolaria

After 2-3 days, doliolaria settles on the ground. Its front tip is fixed on the substrate, any solid objects, and even on similar individuals.

Having lost her eyelashes, she becomes motionless.

The pentacrinus stage is expressed by the fact that a five-ray structure gradually appears on the calyx. The stalk grows, lengthening, rays develop, and the attached disk enlarges. Doliolaria begins to resemble a tiny feather-star swaying on a stem. Its size varies in the range of 0.4-1 cm. Cold arctic waters encourage larvae to develop up to 5 cm in length. Over time, the doliolaria lengthens, differentiates into a stalk and a calyx, where it subsequently forms. This ends the cystoid stage of larval development.

Differences in group development

If the reproduction of crinoids and the development of larvae are absolutely the same, then after the completion of the pentacrinus stage, further maturation proceeds differently in both groups of crinoids. Stem-shaped individuals, confined to one place, acquire new stalk segments. Their lengthening stem becomes like a stack of coins (after all, individual vertebrae are strung on top of each other).

The vertebrae have a movable joint that is provided by muscles. The center of the stem is pierced by a canal where nerves lie and other organs are hidden. Cirri are located in two ways: either along the entire stem or at its base.

The individual acquires an incredible resemblance to a flower, which, in fact, is demonstrated by numerous gorgeous photos. Modern sea lilies have stems different lengths, it is usually limited to 75-90 cm. And in fossil forms, the length of the stems reached 21 meters. The feather stars of antiquity were real giants.

Stemless lilies develop differently. After a month and a half, the calyx, having independently broken off from the stem, begins to float freely. The stalk dies over time.