Anatomy of the Eye | Kellogg Eye Center

• Choroid
  Layer containing blood vessels that lines the back of the eye and is located between the retina (the inner light-sensitive layer) and the sclera (the outer white eye wall).  
• Ciliary Body
  Structure containing muscle and is located behind the iris, which focuses the lens.
• Cornea
  The clear front window of the eye which transmits and focuses (i.e., sharpness or clarity) light into the eye. Corrective laser surgery reshapes the cornea, changing the focus.
• Fovea
  The center of the macula which provides the sharp vision.
• Iris
  The colored part of the eye which helps regulate the amount of light entering the eye. When there is bright light, the iris closes the pupil to let in less light. And when there is low light, the iris opens up the pupil to let in more light.
• Lens
  Focuses light rays onto the retina. The lens is transparent, and can be replaced if necessary. Our lens deteriorates as we age, resulting in the need for reading glasses. Intraocular lenses are used to replace lenses clouded by cataracts.
• Macula
  The area in the retina that contains special light-sensitive cells. In the macula these light-sensitive cells allow us to see fine details clearly in the center of our visual field. The deterioration of the macula is a common condition as we get older (age related macular degeneration or ARMD).
• Optic Nerve
  A bundle of more than a million nerve fibers carrying visual messages from the retina to the brain. (In order to see, we must have light and our eyes must be connected to the brain.) Your brain actually controls what you see, since it combines images. The retina sees images upside down but the brain turns images right side up. This reversal of the images that we see is much like a mirror in a camera. Glaucoma is one of the most common eye conditions related to optic nerve damage.
• Pupil
  The dark center opening in the middle of the iris. The pupil changes size to adjust for the amount of light available (smaller for bright light and larger for low light). This opening and closing of light into the eye is much like the aperture in most 35 mm cameras which lets in more or less light depending upon the conditions.
• Retina
  The nerve layer lining the back of the eye. The retina senses light and creates electrical impulses that are sent through the optic nerve to the brain.
• Sclera
  The white outer coat of the eye, surrounding the iris.
• Vitreous Humor
  The, clear, gelatinous substance filling the central cavity of the eye.

The five senses include sight, sound, taste, hearing and touch. Sight, like the other senses is closely related to other parts of our anatomy. The eye is connected to the brain and dependent upon the brain to interpret what we see.

How we see depends upon the transfer of light. Light passes through the front of the eye (cornea) to the lens. The cornea and the lens help to focus the light rays onto the back of the eye (retina). The cells in the retina absorb and convert the light to electrochemical impulses which are transferred along the optic nerve and then to the brain.

The eye works much the same as a camera. The shutter of a camera can close or open depending upon the amount of light needed to expose the film in the back of the camera. The eye, like the camera shutter, operates in the same way. The iris and the pupil control how much light to let into the back of the eye. When it is very dark, our pupils are very large, letting in more light. The lens of a camera is able to focus on objects far away and up close with the help of mirrors and other mechanical devices. The lens of the eye helps us to focus but sometimes needs some additional help in order to focus clearly. Glasses, contact lenses, and artificial lenses all help us to see more clearly.  

8.5: The Eye – Biology LibreTexts

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Vision is the special sense of sight that is based on the transduction of light stimuli received through the eyes. The eyes are located within either orbit in the skull. The bony orbits surround the eyeballs, protecting them and anchoring the soft tissues of the eye (Figure 8.13). The eyelids, with lashes at their leading edges, help to protect the eye from abrasions by blocking particles that may land on the surface of the eye. The inner surface of each lid is a thin membrane known as the palpebral conjunctiva. The conjunctiva extends over the white areas of the eye (the sclera), connecting the eyelids to the eyeball. Tears are produced by the lacrimal gland, located beneath the lateral edges of the nose. Tears produced by this gland flow through the lacrimal duct to the medial corner of the eye, where the tears flow over the conjunctiva, washing away foreign particles.

Figure 8.13. The Eye in the Orbit

The eye is located within the orbit and surrounded by soft tissues that protect and support its function. The orbit is surrounded by cranial bones of the skull.

Movement of the eye within the orbit is accomplished by the contraction of six extraocular muscles that originate from the bones of the orbit and insert into the surface of the eyeball (Figure 8.14). Four of the muscles are arranged at the cardinal points around the eye and are named for those locations. They are the superior rectus, medial rectus, inferior rectus, and lateral rectus. When each of these muscles contract, the eye to moves toward the contracting muscle. For example, when the superior rectus contracts, the eye rotates to look up. The superior oblique originates at the posterior orbit, near the origin of the four rectus muscles. However, the tendon of the oblique muscles threads through a pulley-like piece of cartilage known as the trochlea. The tendon inserts obliquely into the superior surface of the eye. The angle of the tendon through the trochlea means that contraction of the superior oblique rotates the eye medially. The inferior oblique muscle originates from the floor of the orbit and inserts into the inferolateral surface of the eye. When it contracts, it laterally rotates the eye, in opposition to the superior oblique. Rotation of the eye by the two oblique muscles is necessary because the eye is not perfectly aligned on the sagittal plane. When the eye looks up or down, the eye must also rotate slightly to compensate for the superior rectus pulling at approximately a 20-degree angle, rather than straight up. The same is true for the inferior rectus, which is compensated by contraction of the inferior oblique. A seventh muscle in the orbit is the levator palpebrae superioris, which is responsible for elevating and retracting the upper eyelid, a movement that usually occurs in concert with elevation of the eye by the superior rectus (see Figure 8.13). The extraocular muscles are innervated by three cranial nerves. The lateral rectus, which causes abduction of the eye, is innervated by the abducens nerve. The superior oblique is innervated by the trochlear nerve. All of the other muscles are innervated by the oculomotor nerve, as is the levator palpebrae superioris. The motor nuclei of these cranial nerves connect to the brain stem, which coordinates eye movements.

Figure 8.14. Extraocular Muscles

The extraocular muscles move the eye within the orbit.

The eye itself is a hollow sphere composed of three layers of tissue. The outermost layer is the fibrous tunic, which includes the white sclera and clear cornea. The sclera accounts for five sixths of the surface of the eye, most of which is not visible, though humans are unique compared with many other species in having so much of the “white of the eye” visible (Figure 8.15). The transparent cornea covers the anterior tip of the eye and allows light to enter the eye. The middle layer of the eye is the vascular tunic, which is mostly composed of the choroid, ciliary body, and iris. The choroid is a layer of highly vascularized connective tissue that provides a blood supply to the eyeball. The choroid is posterior to the ciliary body, a muscular structure that is attached to the lens by zonule fibers. These two structures bend the lens, allowing it to focus light on the back of the eye. Overlaying the ciliary body, and visible in the anterior eye, is the iris—the colored part of the eye. The iris is a smooth muscle that opens or closes the pupil, which is the hole at the center of the eye that allows light to enter. The iris constricts the pupil in response to bright light and dilates the pupil in response to dim light. The innermost layer of the eye is the neural tunic, or retina, which contains the nervous tissue responsible for photoreception. The eye is also divided into two cavities: the anterior cavity and the posterior cavity. The anterior cavity is the space between the cornea and lens, including the iris and ciliary body. It is filled with a watery fluid called the aqueous humor. The posterior cavity is the space behind the lens that extends to the posterior side of the interior eyeball, where the retina is located. The posterior cavity is filled with a more viscous fluid called the vitreous humor. The retina is composed of several layers and contains specialized cells for the initial processing of visual stimuli. The photoreceptors (rods and cones) change their membrane potential when stimulated by light energy. The change in membrane potential alters the amount of neurotransmitter that the photoreceptor cells release onto bipolar cells in the outer synaptic layer. It is the bipolar cell in the retina that connects a photoreceptor to a retinal ganglion cell (RGC) in the inner synaptic layer. There, amacrine cells additionally contribute to retinal processing before an action potential is produced by the RGC. The axons of RGCs, which lie at the innermost layer of the retina, collect at the optic disc and leave the eye as the optic nerve (see Figure 8. 15). Because these axons pass through the retina, there are no photoreceptors at the very back of the eye, where the optic nerve begins. This creates a “blind spot” in the retina, and a corresponding blind spot in our visual field.

Figure 8.15. Structure of the Eye

The sphere of the eye can be divided into anterior and posterior chambers. The wall of the eye is composed of three layers: the fibrous tunic, vascular tunic, and neural tunic. Within the neural tunic is the retina, with three layers of cells and two synaptic layers in between. The center of the retina has a small indentation known as the fovea.

Note that the photoreceptors in the retina (rods and cones) are located behind the axons, RGCs, bipolar cells, and retinal blood vessels. A significant amount of light is absorbed by these structures before the light reaches the photoreceptor cells. However, at the exact center of the retina is a small area known as the fovea. At the fovea, the retina lacks the supporting cells and blood vessels, and only contains photoreceptors. Therefore, visual acuity, or the sharpness of vision, is greatest at the fovea. This is because the fovea is where the least amount of incoming light is absorbed by other retinal structures (see Figure 8.15). As one moves in either direction from this central point of the retina, visual acuity drops significantly. In addition, each photoreceptor cell of the fovea is connected to a single RGC. Therefore, this RGC does not have to integrate inputs from multiple photoreceptors, which reduces the accuracy of visual transduction. Toward the edges of the retina, several photoreceptors converge on RGCs (through the bipolar cells) up to a ratio of 50 to 1. The difference in visual acuity between the fovea and peripheral retina is easily evidenced by looking directly at a word in the middle of this paragraph. The visual stimulus in the middle of the field of view falls on the fovea and is in the sharpest focus. Without moving your eyes off that word, notice that words at the beginning or end of the paragraph are not in focus. The images in your peripheral vision are focused by the peripheral retina, and have vague, blurry edges and words that are not as clearly identified. As a result, a large part of the neural function of the eyes is concerned with moving the eyes and head so that important visual stimuli are centered on the fovea. Light falling on the retina causes chemical changes to pigment molecules in the photoreceptors, ultimately leading to a change in the activity of the RGCs. Photoreceptor cells have two parts, the inner segment and the outer segment (Figure 8.16). The inner segment contains the nucleus and other common organelles of a cell, whereas the outer segment is a specialized region in which photoreception takes place. There are two types of photoreceptors—rods and cones—which differ in the shape of their outer segment. The rod-shaped outer segments of the rod photoreceptor contain a stack of membrane-bound discs that contain the photosensitive pigment rhodopsin. The cone-shaped outer segments of the cone photoreceptor contain their photosensitive pigments in infoldings of the cell membrane. There are three cone photopigments, called opsins, which are each sensitive to a particular wavelength of light. The wavelength of visible light determines its color. The pigments in human eyes are specialized in perceiving three different primary colors: red, green, and blue.

Figure 8.16. Photoreceptor

(a) All photoreceptors have inner segments containing the nucleus and other important organelles and outer segments with membrane arrays containing the photosensitive opsin molecules. Rod outer segments are long columnar shapes with stacks of membrane-bound discs that contain the rhodopsin pigment. Cone outer segments are short, tapered shapes with folds of membrane in place of the discs in the rods. (b) Tissue of the retina shows a dense layer of nuclei of the rods and cones. LM × 800. (Micrograph provided by the Regents of University of Michigan Medical School © 2012)

At the molecular level, visual stimuli cause changes in the photopigment molecule that lead to changes in membrane potential of the photoreceptor cell. A single unit of light is called a photon, which is described in physics as a packet of energy with properties of both a particle and a wave. The energy of a photon is represented by its wavelength, with each wavelength of visible light corresponding to a particular color. Visible light is electromagnetic radiation with a wavelength between 380 and 720 nm. Longer wavelengths of less than 380 nm fall into the infrared range, whereas shorter wavelengths of more than 720 nm fall into the ultraviolet range. Light with a wavelength of 380 nm is blue whereas light with a wavelength of 720 nm is dark red. All other colors fall between red and blue at various points along the wavelength scale. Opsin pigments are actually transmembrane proteins that contain a cofactor known as retinal. Retinal is a hydrocarbon molecule related to vitamin A. When a photon hits retinal, the long hydrocarbon chain of the molecule is biochemically altered. Specifically, photons cause some of the double-bonded carbons within the chain to switch from a cis to a trans conformation. This process is called photoisomerization. Before interacting with a photon, retinal’s flexible double-bonded carbons are in the cis conformation. This molecule is referred to as 11-cis-retinal. A photon interacting with the molecule causes the flexible double-bonded carbons to change to the trans– conformation, forming all-trans-retinal, which has a straight hydrocarbon chain (Figure 8.17). The shape change of retinal in the photoreceptors initiates visual transduction in the retina. Activation of retinal and the opsin proteins result in activation of a G protein. The G protein changes the membrane potential of the photoreceptor cell, which then releases less neurotransmitter into the outer synaptic layer of the retina. Until the retinal molecule is changed back to the 11-cis-retinal shape, the opsin cannot respond to light energy, which is called bleaching. When a large group of photopigments is bleached, the retina will send information as if opposing visual information is being perceived. After a bright flash of light, afterimages are usually seen in negative. The photoisomerization is reversed by a series of enzymatic changes so that the retinal responds to more light energy.

Figure 8.17. Retinal Isomers

The retinal molecule has two isomers, (a) one before a photon interacts with it and (b) one that is altered through photoisomerization.

The opsins are sensitive to limited wavelengths of light. Rhodopsin, the photopigment in rods, is most sensitive to light at a wavelength of 498 nm. The three color opsins have peak sensitivities of 564 nm, 534 nm, and 420 nm corresponding roughly to the primary colors of red, green, and blue (Figure 8. 18). The absorbance of rhodopsin in the rods is much more sensitive than in the cone opsins; specifically, rods are sensitive to vision in low light conditions, and cones are sensitive to brighter conditions. In normal sunlight, rhodopsin will be constantly bleached while the cones are active. In a darkened room, there is not enough light to activate cone opsins, and vision is entirely dependent on rods. Rods are so sensitive to light that a single photon can result in an action potential from a rod’s corresponding RGC. The three types of cone opsins, being sensitive to different wavelengths of light, provide us with color vision. By comparing the activity of the three different cones, the brain can extract color information from visual stimuli. For example, a bright blue light that has a wavelength of approximately 450 nm would activate the “red” cones minimally, the “green” cones marginally, and the “blue” cones predominantly. The relative activation of the three different cones is calculated by the brain, which perceives the color as blue. However, cones cannot react to low-intensity light, and rods do not sense the color of light. Therefore, our low-light vision is—in essence—in grayscale. In other words, in a dark room, everything appears as a shade of gray. If you think that you can see colors in the dark, it is most likely because your brain knows what color something is and is relying on that memory.

Figure 8.18. Comparison of Color Sensitivity of Photopigments

Comparing the peak sensitivity and absorbance spectra of the four photopigments suggests that they are most sensitive to particular wavelengths.

Age Related Changes to the Eye

While not true for all people, the changes that occur to the eye as a part of aging generally result in some type of vision problem. These changes are known to include a slight shrinkage of the eye, an increase in the amount of connective tissue present, degeneration of some cells, and reduced blood supply.

The loss of fat and connective tissue surround the eye causes wrinkles in the corners of the eyes and sagging skin around the eye. As muscles around the eye weaken eyelids no longer fully close causing the cornea to become dry, irritated, and inflamed.

Age Related Dysfunctions of the Eye

Presbyopia, also known as farsightedness, is the result of the gradual loss of lens elasticity, a flattening of its shape, and an increase in its density. Presbyopia is so common it affects nearly everyone over the age of 40.

Blindness affects 16% of the population over the age of 75 in one or both eyes. While blindness is not a result of aging the incidence of blindness does increase with age.

Glaucoma is the result of elevated pressure within the eye. The pressure is causes by deficient drainage of fluid from the anterior cavity of the eye. The pressure can squeeze shut blood vessels within the eye causing degeneration of the optic nerve fibers and resulting in blindness.

Diabetic retinopathy is another cause of blindness in the aging population. This condition is a complication of diabetes. In some diabetics contractile cells in the wall of retinal capillaries swell and rupture, weakening the vessels and allowing them to dilate and form small pouches called microaneurysms. As blood travels through the larger damaged capillaries adjacent capillaries carry less blood depriving areas of the eye of blood flow. Blindness may result as the disease progresses.

Cataracts are cloudy lens that block from entering the eye. About 90% of people over the age of 70 are said to have some degree of cataract formation. The lenses are composed of fibers that are continuously growing. As the lenses thicken the fibers condense and interfere with the passage of light. The most effective treatment for cataracts is surgical removal.

Age related macular degeneration is a disease of the macular area of the retina. The disease results in the loss of central vision. While the exact causes of macular degeneration are currently unknown, it is thought that the disease disrupts the blood flow between the retina and subretina.

The retina is largely held in place by pressure. As one ages and the retina no longer tightly fits in place. When this happens the nervous-tissue layer can separate from the pigment layer resulting in a detached retina.

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description of the fish, where it is found, species, how long it lives

The flounder fish is a representative of the “Ray-finned” class and belongs to the “Flounder-like” order. The family consists of 6 dozen different fish, which differ in the characteristic body shape.

Contents

• 1 Flounder fish: description
  • 1.1 Appearance
  • 1.2 Character and lifestyle
  • 1.3 How long does a flounder live
  • 1.4 Sexual dimorph unit
• 2 Flounder species
• 3 Natural habitats
• 4 What flounder eats
• 5 Reproduction and offspring
• 6 Natural enemies
• 7 Population and species status
• 8 Commercial value of flounder 9 0010
• 9 Flounder in cooking
• 10 Useful properties of flounder meat

Flounder fish: description

Due to the fact that this detachment has eyes on the right side, they are also called “Right-side flounders”. It is also known that there are forms of flounder in which the eyes are located on the left side of the head. The symmetrically located ventral fins have a rather narrow base.

All varieties of flounder are characterized by common data, such as:

• The presence of a flat body.
• Elongated dorsal and anal fins with many rays.
• Asymmetrical head.
• Closely spaced, bulging eyes that can function independently.
• Lateral line that runs between the eyes.
• Oblique mouth and fairly sharp teeth.
• Fairly short tail.
• The opposite flank is distinguished by a light coloration and strong, rough skin.

Flounder eggs differ in that they do not have a fat drop, so they are in suspension in the water column, where the process of development of future offspring takes place. Five species of flounder prefer spawning in the near-bottom area.

An interesting moment! The ability to mimic this family allows them to skillfully disguise, regardless of the complexity of the background color. At the same time, the Kambalovye are not inferior in their camouflage capabilities even to a chameleon.

Appearance

All varieties of flounder prefer to lead a benthic lifestyle at considerable depths. Their characteristic distinguishing feature is the presence of a thin, oval or diamond-shaped body, as if flattened from the sides.

River flounder (Platichthys flesus) is a term used to describe Star, Black Sea (Kalkan) and Polar flounders.

• Star flounder differs in that it is characterized by a left-sided arrangement of eyes. At the same time, the fish has a dark, greenish or brown body color, with wide black stripes on the fins and studded star-shaped plates. This is characteristic of the side where the eyes are located. The fish grows up to 60 cm in length and can weigh up to 4 kilograms.
• Black Sea Kalkan . Represents a left-handed flounder. On a round body, you can see a lot of bumpy spikes that are randomly scattered throughout the body on the left side. The main body color is brown-olive. The flounder grows in length more than one meter, gaining weight up to 20 kilograms.
• Arctic flounder . It is a cold-resistant representative of a large family. It has an elongated oval body. The body color is monophonic and made in dark brown tones, while the color of the fins has a brown tint.

Varieties of sea flounder thrive in salt water, in addition, they differ in that they have a wide scatter of data regarding their size, body shape, fin color, and eye position.

• Common flounder has a brown-green main color with reddish or orange spots. Adult specimens can weigh all 7 kilograms and grow up to 1 meter in length. The species has excellent opportunities in terms of mimicry.
• The white-bellied southern and northern flounders represent bottom-dwelling marine fish. They can grow up to half a meter in length. A characteristic feature of this species is the presence of a bifurcated lateral line, an arcuate shape. The lower part of the body of the fish has a milky color, and the upper part is brown or wheat-brown.
• Yellowfin flounder is a cold-loving species. The body is rounded, covered with scales with tiny spines. The fins are distinguished by a yellow-golden hue. Adult specimens grow up to 0.5 meters in length and weigh no more than 1 kilogram.
• Halibut . The variety is represented by 5 species. Some of them have a length of 4.5 meters and a weight of 350 kilograms. The arrow-toothed halibut is considered the smallest representative, the length of which is not more than 0.8 meters and weighs about 8 kilograms.

The name Far Eastern flounder is applied to individual subspecies representing the so-called flatfish.

This fish came off Picasso’s canvas – Tropical flounder botus

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Character and lifestyle

These fish prefer to lead an isolated bottom lifestyle, while they can very skillfully disguise themselves depending on the nature of the surrounding landscape. They spend most of their lives in a supine position either on the surface of the ground or in the thickness of the ground, burrowing into it almost completely, with the exception of the eyes, which are always on the surface. This type of life activity allows the fish not only to reliably hide from their enemies, but also to get food for themselves, attacking their prey from a kind of ambush.

At first glance, this fish seems to be slow and clumsy, because it is mainly seen moving slowly in the water column, at a considerable distance from the bottom. In fact, flounder, if necessary, can demonstrate their skills, instantly gaining decent speed.

In case of danger, the fish makes an instant leap forward several meters due to a very powerful jet of water, which is formed by the gill cover. This jet literally “shoots” into the bottom area. As a result, a cloud of turbidity is formed, which gradually settles to the bottom. During this time, the fish manages to grab its prey or get away from the predator.

How long does a flounder live

A flounder can live, if favorable conditions are created for this, for at least 30 years. Being in the natural environment, the flounder rarely lives to such a venerable age, since the bulk falls into industrial fishing nets.

Sexual dimorphism

Male flounders can be distinguished from females in several ways. First, they are smaller in size and weight, and secondly, they have a greater distance between the eyes. In addition, they have longer rays of the pectoral and dorsal fins.

Species of flounder

Currently known 60 species of flounder are represented by 23 genera:

• The genus of spiny flounder includes Spiny flounder and Nadezhny flounder.
• The genus of arrow-toothed halibut is represented by the Asian arrow-toothed halibut and the American arrow-toothed halibut.
• The genus of sharp-headed flounder includes Gerzenstein’s flounder and sharp-headed flounder.
• The Warty flounder genus consists of a single species called the Warty flounder.
• The Eopsetta genus is represented by the Far East flounder (Grigoriev’s flounder) and Jordan’s flounder.
• The genus “Long flounder” consists of such species as the Red flounder and the Far Eastern long flounder (Steller’s smallmouth).
• The halibut flounder genus consists of such species as Japanese halibut flounder (Japanese flounder-ruff), Northern halibut flounder, Flounder-ruff and Bering Sea halibut flounder.
• The genus “Halibut” (whitebark halibut) consists of the Atlantic halibut and the Pacific halibut.
• The genus of two-colored flounder and two-lined flounder is represented by such species as white-bellied flounder and northern two-lined flounder.
• The genus Limandy includes several more species and is represented by the yellowfin flounder, yellowtail flounder, Ershovatka, Long-snouted estuary and Sakhalin flounder.
• The genus “Polar flounder” is represented by one species – the Naked flounder.
• Genus “Oregon flounders”.
• The genus “Smallmouth flounder” is represented by several species, including the small-headed flounder and the Pacific smallmouth.
• The genus “River flounder” is also represented by several species, including the Starry flounder.
• The genus “Sea flounder” includes several species, including the species Yellow sea flounder.
• The genus Hardhead flounder includes the species Horned flounder.
• Genus of spotted flounders.
• The winter flounder genus includes species such as the Yellowstripe flounder, the Schrenk flounder and the Japanese flounder.

Attention should be paid to the genus Dexists and Embassichts, which includes the Deep Sea Embassicht, as well as the genus Isopsets, Veraspets, Tanakiuses, Psalmodiscuses, Parophrises and Black Halibuts.

Interesting to know! Halibuts are considered the largest representatives of the family that live in the waters of the Pacific and Atlantic oceans. Halibuts live for about half a century, inhabiting great depths.

Natural habitats

Some species have a preference for the northern latitudes of the Pacific depths, with many of them found in the Sea of ​​Japan, Bering, Okhotsk and Chukchi Seas. For freshwater forms, characteristic habitats are lagoons, lower reaches of rivers and bays. For some species, distribution within the northern latitudes of the Atlantic, as well as within the waters of the Black, Baltic and Mediterranean seas, is considered characteristic. Some species feel great not only in the marine environment, but also in the lower reaches of such rivers as the Southern Bug, Dnieper and Dniester. Due to the fact that the Sea of ​​Azov has recently become too salty, and the inflowing rivers have become noticeably shallow, the Black Sea flounder Kalkan preferred to migrate to the mouth of the Don River. Cold-resistant species, as a rule, live in arctic latitudes, occurring in the waters of the Kara, Barents, White, Bering and Okhotsk seas. At the same time, they swim in such rivers as the Yenisei, Ob, Kare, Tugura, where they prefer places with soft silty soils.

Marine varieties of flounder inhabit weakly and strongly saline waters, living at depths up to 200 meters inclusive. Many of the species are considered valuable commercial fish, while they are found in the waters of the Eastern Atlantic, as well as in such seas as the Mediterranean, Barents, White and Baltic Seas. The southern white-bellied flounder is characterized by distribution in the waters of the Sea of ​​Japan, and some northern subspecies are limited to the waters of the Okhotsk, Kamchatka and Bering Seas.

An interesting moment! Flatfish are distinguished by rich species diversity and great biological flexibility, which allowed them to spread throughout the territories located along the entire Eurasian continent, as well as in the waters of inland seas.

Yellowfin flounder is widespread in the waters of the Sea of ​​Japan, the Sea of ​​Okhotsk and the Bering Sea. Large populations of this species are distributed within Sakhalin and the western waters of Kamchatka, where they live at depths up to 80 meters, preferring the near-bottom area. For halibut fish, characteristic habitats are the waters of the Arctic Ocean and the Pacific Ocean, including the waters of the Barents Sea, the Bering Sea, the Sea of ​​Okhotsk and the Sea of ​​Japan.

What flounder eats

These fish go hunting either at dusk, or at night, or in the morning. Flounder is considered a predatory fish, so its diet is represented by animal food objects. At a young age, individuals feed on benthos, amphipods, various worms, larvae, crustaceans and caviar. As they mature, the flounder moves on to larger worms, brittle stars, echinoderms, as well as small fish, many invertebrates and crustaceans. Shrimps and medium-sized capelin are especially popular with representatives of this family.

Due to the peculiarities of the body structure, which is associated with the lateral position of the head, this fish easily gets various mollusks from the thickness of the sea or river bottom. At the same time, it should be noted that the jaws of the flounder are strong and powerful, so the fish can easily deal even with crab shells. Due to the fact that the family feeds on food objects with a high content of proteins, the fish is of great value.

Reproduction and offspring

Spawning periods largely depend on habitat conditions, which is associated with periods of spring, warming of the water column, etc. As a rule, many species spawn between the first decade of February and the month of May, although there are some exceptions.

Large rhombus (turbo) prefers to spawn in the waters of the Baltic and North Seas, starting from April and including August. As for the polar flounder, the process of its spawning takes place in the water column covered with ice, and the period occupies a segment from December to January inclusive.

Depending on the species, the ability to reproduce occurs after a minimum of 3 years of life. Many species are characterized by a high degree of fertility, so the number of eggs in a clutch can range from several hundred thousand to several million pieces. As a rule, the period of development of eggs takes a couple of weeks no more. To spawn, the flounder chooses places with sufficient depth and a sandy bottom.

An important point! The flounder fry born into the world have the usual body shape, like for a fish, since they are characterized by symmetrically developed sides, since the eyes are located classically, on both sides of the head. Flounder fry eat zooplankton and other small food items.

Some species prefer areas up to 50 meters deep, which is due to the excellent buoyancy of the eggs, as well as the absence of the need to attach them to any base.

Giant turbot fish underwater. Giant halibut/flounder underwater.

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Natural enemies

Thanks to its abilities, the flounder fish changes its body color depending on the nature of the color of the bottom of the reservoir. This allows the fish to be unnoticed by many predators. This does not mean at all that the fish is completely devoid of natural enemies. The most dangerous for her are halibut, eel and man. The fish has quite tasty, delicious meat, therefore it is caught in large quantities in all areas of the oceans.

Population and species status

At the moment there are many problems associated with daily fishing for many valuable fish species. The main problem is associated with overfishing of easily accessible and, especially, small species. This problem has deep roots and is related to multi-species fisheries. Unfortunately, we have not yet been able to solve it. The total number of flounder depends on many natural factors, so experts note some cyclicality, characteristic of both the conditions of decline and the conditions of increase in the population.

Such factors include the constant negative impact of a person associated with his life, including the fact that a person exerts enormous pressure as a result of commercial, uncontrolled fishing. As an example, we can take the Arnoglos Mediterranean flounder and the Kessler flounder, which are on the verge of extinction, so their total number is extremely small.

Commercial value of flounder

Flounder belongs to the category of valuable commercial fish. It is caught in large volumes in the Black and Baltic Seas, and flounder kalkan and turbot flounder – in the waters of the Mediterranean Sea. In the caught fish, the body color is slightly greenish in color, while the meat is white. Regardless of the method of preparation, all flounder dishes are easily absorbed by the human body. Often the meat of this fish is used as a preparation of dietary dishes.

Flounder in cooking

Flounder meat is rich in proteins, while the amount of fat is negligible, which makes it possible to include the meat of this fish in the diet. The energy value of fresh fish is at the level of 90 kcal per 100 grams of meat, and boiled flounder – 103 kcal per 100 g of product. The largest number of calories in fried fish is about 223 kcal, so fried flounder is not suitable as a dietary dish, since there is a high probability of gaining extra pounds.

Flounder meat is quite tasty, but if cooked incorrectly, you can get a dish with a specific smell. To prevent this from happening, you need to remove the skin from the flounder, cut off the head and get rid of the insides.

Useful properties of flounder meat

This fish has a huge potential for useful characteristics, therefore it is an indispensable product for preparing dietary dishes. A large amount of protein, which is easily absorbed by the human body and which is so necessary for human life, is only a small fraction of the positive qualities. Its meat contains a sufficient amount of omega-3 fatty acids, which allow the body to fight malignant tumors. In addition to fatty acids, meat is rich in phosphorus, nicotinic and pantothenic acids, riboflavin, thiamine, pyridoxine and various salts. Fish also contains a whole complex of vitamins of group “B”, as well as vitamins “D”, “E” and “A”, the effect of which on the human body is purely positive.

Due to the presence of amino acids in flounder, eating flounder dishes can reduce cholesterol levels in human blood. The presence of iodine in flounder meat allows you to maintain the protective properties of the body at an optimal level.

Not every fish contains aphrodisiacs that increase sexual desire, therefore, flounder differs from many types of fish in this interesting property.

Due to the presence of so many useful components, regular consumption of flounder dishes allows a person to slow down the aging process, making the skin more elastic.

Big flatfish attack fishing lure underwater. HD Large flounder attacks artificial bait.

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How to store Stillavit? | What and how to store

The drug is available as an ophthalmic solution for eye care. A small course of Stillavit can relieve the eyes of the feeling of “dryness”, remove irritation of the cornea and relieve fatigue from prolonged visual stress. Due to the mild action of the components, the drops are also suitable for those people who experience discomfort when wearing contact lenses.

A notable feature of the solution is the absence of aggressive preservatives , which reduces the likelihood of allergic reactions. This increases the level of requirements for the storage of the drug. This circumstance must be taken into account so that the action of the components retains a healing character during the entire period of the “life” of the solution.

Contents:

• Forms
• How to store the drug according to the instructions?
• How to identify a spoiled product?

Forms of release

The agent is produced in Russia by the company “Company Oftalm-Renaissance” (Moscow). The only release form: drops . The solution is contained in vials made of polymeric material, equipped with a stopper-dropper and a screw cap. Bottle volume: 10 ml .

The action is due to the properties of the active ingredients:

1. Sodium hyaluronate at a concentration of 1.60 mg per 1 ml of solution. Polysaccharide of plant origin obtained by biotechnological method. Physiological, present in large quantities in the corneal endothelium.
2. D-panthenol – 10 mg/ml. Vitamin B5, precursor of pantothenic acid.
3. Sodium chondroitin sulfate – 0.50 mg/ml. Physiological polysaccharide; stimulates the synthesis of hyaluronic acid.

Among the auxiliary components of the solution: disodium EDTA (solvent), sodium tetraborate (antiseptic), sodium salts of phosphoric acids (emulsifier), sodium chloride and water.

The solution is produced under aseptic conditions, which ensures its sterility.

The ability of polysaccharide compounds and pantothenic acid to bind a large number of water molecules provides a moisturizing and lubricating effect of drops. The solution has the necessary viscosity and good adhesive properties. When it enters the anterior part of the eye, it forms a kind of tear film there, which persists when blinking and does not blur vision. Vitamin B5 has a powerful reparative effect, which improves the condition of the cornea and conjunctiva of the eye.

The solution is instilled from 2 to 10 times a day in case of “dry eye” syndrome, large visual loads (working on a computer, watching TV) to relieve corneal irritation from dust, bright light, wind and other factors.

The solution can be used while wearing any type of contact lens. Its use speeds up the process of adaptation to lenses for “beginners”. In people who have a long wearing experience, Stillavit reduces discomfort from contact of the lens with the eye. As a result of instillation, the eyes are moistened, the condition of the cornea and the tear film covering it is stabilized, which significantly improves the tolerability of contact means of vision correction.

How to store the drug according to the instructions?

The manufacturer guarantees the safety and effectiveness of the solution only within the specified expiration date and subject to the storage conditions prescribed by him. The necessary information can be found on the packaging of the product, in the instructions and on the bottle itself.

Basic storage requirements for Stillavit solution are given in the table:

Shelf life	Temperature rating	Humidity
2 years; after opening – 1 month	+5 to +25 °C	Up to 80%

The purchased drug should be kept in its original packaging, removing it from there only for the instillation procedure. It is recommended to write down the date of opening of the vial so as not to miss the end of the 30-day expiration date .

Do not store the solution pack in the bathroom – the humidity is too high there. A suitable place for Stillavit can be a cool living room or a medicine compartment on the side of the refrigerator.

An important condition for maintaining the sterility of the solution is hygiene during instillation of . Wash your hands thoroughly with soap before the procedure. This simple action will not only protect your eyes from possible bacteria from your hands, but also protect the solution itself from contamination. During the introduction of drops into the conjunctival sac, the tip of the dropper should not come into contact with either the fingers or the eyelid. After use, the bottle should be tightly closed with a cap.

How to identify a spoiled product?

The drug should be carefully examined at the time of purchase.