Other copepods Gannies are large sea birds: some are up to two meters in wingspan, but weigh relatively little, 1.5-3.5 kilograms. Like pelicans, they have air cushions under their skin. Northern white boobies, three species or subspecies, breed on islands and

Crustaceans

Crustaceans Aquatic arthropods with gill breathing, the shell of which is formed by chitin soaked in limestone, are crustaceans. It is known that crabs live just as well in the air, on the seashore, as in the water. The crab, being an amphibian, is nevertheless deprived

Crustaceans

Crustaceans

CRUSTACEANS

CRUSTACEANS

copepod frogs

copepods

copepods

And interstitial fauna are less common in plankton. The structure and lifestyle of free-living representatives of copepods are mainly considered below.

There is the World Society of Copepodologists. World Association of Copepodologists), which publishes the newsletter " Monoculus copepod newsletter».

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  The body of copepods is divided into three tagmas: head - cephalosome (in copepodology it is sometimes called cephalothorax, cephalothorax), chest (thorax) and abdomen (abdomen). At the same time, many copepodologists call the telson (anal lobe) the last abdominal (anal) segment.

  The body of copepods can "fold" in half, curving in the sagittal plane. At the same time, the boundary between the functionally anterior part of the body (prosoma) and the functionally posterior part (urosoma) in cyclopoids and harpacticids passes between the segments of the thorax, which bear the fourth and fifth pairs of legs. These groups are united under the name "Podoplea" - "foot-belly". In kalanoids, the border between the prosoma and urosoma passes behind the segment bearing the fifth pair of legs, therefore they are called "Gymnoplea" - "blue-bellied". This character, which correlates well with other structural features, is given a high taxonomic weight, and Podoplea And Gymnoplea are considered as taxonomic categories (in modern classifications of copepods - as superorders).

  Head and its appendages

  The head bears the first one-branched antennae (antennales, mustaches), the second two-branched antennae (antennae), mandibles, first maxillae (maxillae), second maxillae (maxillae) and maxillipedes (mandibles) - appendages of the first thoracic segment fused with the head. In representatives of most families of harpacticids and in some representatives of other orders, the next segment of the chest, which carries swimming limbs, merges with the head, which can be greatly modified in this case.

  On the head, between the mandibles, there is a mouth opening, covered in front by a large upper lip, and behind by a small lower lip. On the front edge of the head there is a downward outgrowth - the rostrum, sometimes detached.

  Antennae I (antennales) are always single-branched. The number of their segments varies among representatives different units. So, harpacticids usually have 5-8 segments (up to 14 in males); most kalanoids have 21-27 segments; cyclopoids have 9 to 23 segments. In typical representatives, the relative length of the antennules differs: in kalanoids they are approximately equal to the body, in cyclopoids they are equal to the cephalothorax, and in harpacticids they are noticeably shorter than the cephalothorax. Antennae I are involved in locomotion and also carry sensilla.

  Antennae II are usually two-branched (in many cyclopoids they are single-branched), they are involved in creating water currents for swimming and feeding.

  The mandible is subdivided into a coxa, which forms a chewing outgrowth (gnathobase) with teeth and setae, and a palp, which initially consists of a basis, exo-, and endopod. Often the branches, and sometimes the base of the palp, are reduced. So, in many Cyclopes, only three setae extend from the mandible, which are considered to be the rudiment of the palp.

  On the chewing teeth of the mandibles of many marine copepods there are "crowns" made of silicon oxide, which help them to chew through the strong houses of diatoms.

  Breast and its appendages

  On the four segments of the chest following the mandibular segment, there are biramous swimming limbs - flattened legs that serve as the main engines when swimming, for the presence of which the detachment got its name. The swimming limb consists of a two-segmented protopodite, the basal (proximal) segment of which is called the coxa, and the distal one is the basis, and two branches extending from the basis (sometimes it is believed that the protopodite includes another segment - the precox, which is weakly separated from the body). The outer (exopodite) and inner (endopodite) branches each consist of 2-4 segments and bear long setae covered with long thin outgrowths (setulae) and shorter spines.

  On the last segment of the chest is the fifth pair of pectoral legs, which usually do not participate in swimming and are greatly reduced or modified in many groups. In males of most families of kalanoids, they are sharply asymmetric. The endopodites of both legs are often rudimentary, the exopodite of one of the legs serves to transfer the spermatophore to the female's spermatheca during mating, and the larger exopodite of the other limb bears a long claw-like curved spine, which is involved in holding the female. The structure and armament of the fifth pair of legs for cyclopoids and kalanoids is the most important taxonomic feature.

  Abdomen and its appendages

  The abdomen usually consists of 2-4 segments (excluding the telson). On the first segment of the abdomen are paired genital openings. In harpacticids and cyclopoids, it has a rudimentary sixth pair of legs; in kalanoids, it is devoid of limbs. The remaining segments of the abdomen do not bear limbs. On the telson there are two movable appendages - a fork, or furka (furcal branches). These appendages consist of one segment and are not homologous to limbs. The furca bears furcal setae, the length and arrangement of which is an important taxonomic feature.

  sexual dimorphism

  Typically, in females, the first and second abdominal segments fuse to form a large genital segment; no such fusion occurs in males, so males have one more abdominal segment than females.

  Representatives Cyclopoida And Harpacticoida males are usually noticeably smaller than females, have hook-shaped, shortened antennae I, which serve to grasp and hold females during mating.

  Many Calanoida females and males do not differ in size. Males have one modified antenna I, which is called the geniculate antenna. It is expanded in the middle part and is able to "fold in half"; like the Cyclopes, it serves to hold the female during mating.

  In some cases, sexual dimorphism is observed in the structure of almost any pair of limbs and body segments.

  Internal structure

  covers

  Nervous system and sense organs

  The central nervous system consists of the brain and the ventral nerve chain connected to it by the peripharyngeal nerve ring. An unpaired nerve departs from the brain to the naupliar eye and paired nerves to the frontal organ, as well as nerves to the antennules and antennae (the latter from the tritocerebrum). The subesophageal ganglion includes the ganglia of the mandibles, the first and second maxillae. The ganglia of the ventral nerve cord are slightly separated from each other. The entire abdominal nerve chain is located in the cephalothorax, it does not enter the abdomen.

  Nutrition

  Most free-living copepods feed on single-celled or small colonial algae, which they filter out in the water column, as well as benthic diatoms, bacteria, and detritus, which they may pick up or scrape off at the bottom. Many species of kalanoid and cyclopoid are predators that eat other types of crustaceans (juvenile copepods and cladocerans), rotifers, insect larvae of I-II instars (including chironomid larvae and kulicid), etc. The copepodite stages of some freshwater cyclopoids climb into the brood chambers of Daphnia, where eggs are eaten.

  A more detailed study of the "filtration" feeding of copepods with the help of high-speed microfilming revealed that many of them "hunt" for individual cells of algae, which they catch one by one. Algae-eating copepods store food energy in fat droplets found in their tissues, which are often yellowish-orange in color. In polar species, feeding primarily on diatoms, during the period of mass spring “blooming”, the volume of fat reserves can reach half of the body volume.

  Reproduction and development

  Mating is preceded by complex sexual behavior in which both chemoreception and mechanoreception seem to usually play an important role. Female copepods secrete sex pheromones, which are perceived by males with the help of chemosensory bristles (aesthetics) of the first antennae.

  When mating in most Calanoid families, the male first captures the female by the telson or furcal branches with the help of a geniculating antenna, then by the body area located in front of or immediately after the genital segment with the help of the legs of the fifth pair, while the male and female are usually located "head to tail " each other . Mating lasts from several minutes to several days.

  Free-living copepods have spermatophoric fertilization. Large, comparable in size to the size of the animal's abdomen, kalanoid spermatophores are transferred to the genital segment of the female during mating with the help of the left fifth leg of the male; at its end there are "tweezers" that hold the bottle-shaped spermatophore by the narrowed basal part.

  Role in ecosystems

  Copepods play an extremely important role in aquatic ecosystems and throughout the biosphere. Apparently, they have the largest biomass among all groups of aquatic animals and almost certainly occupy the first place in terms of their share in the secondary production of water bodies. As consumers of phytoplankton, copepods are the main consumers of the first order in the seas and fresh waters. Copepods serve as the main food for many other aquatic animals, from cnidarians and ctenophores to baleen whales.

  surface water oceans are now considered the largest sink of carbon dioxide (2 billion tons per year - probably about a third of anthropogenic emissions). In many ways, the absorption of excess carbon dioxide is provided by the vital activity of copepods.

  Many planktonic copepods feed at night in the surface layers of the ocean, and migrate to the depths during the day to avoid being eaten by visual predators. Their corpses, discarded exuvia and fecal pellets sink into deeper layers of water. This (like the breathing of living copepods that digest food at depth) contributes to the movement of biogenic carbon from the upper layers of the water to the bottom sediments. In addition, the formation of fecal pellets during feeding of copepods contributes to the purification of the upper layers of water from mineral suspensions. This increases the transparency of the water and hence the production of phytoplankton.

  These small crustaceans, which aquarists feed to fish, are the main and most numerous representatives of aquatic metazoans. In addition, copepods are one of the main links in the food chain, the state of which ultimately affects our health. Their abundance and species diversity constitute an important part of the planet's biosphere. The biology and life features of copepod mini-crustaceans will be discussed in this article.

  Free-living crustaceans are one of the most important components of zooplankton in salt and fresh waters. They make up the vast majority of the food base of most fish and some marine mammals, which is called the generalizing word "krill". The usual food chain of the seas and oceans looks something like this: marine phytoplankton - copepods - herring - dolphin.

  

  small crustaceans

  Sizes of copepods range from 1 to 30 millimeters. Like all crustaceans, their body consists of three sections - the head, chest and abdomen. Respiration is carried out by the entire surface of the body, there are no gills.

  On the head is the oral apparatus (mandibles), simple eyes and two pairs of antennae:

  • Single-branched antennules are jointed formations that participate in movement and perform the functions of sensory organs.
  • Biramous antennules. Their main function is to provide water flow for swimming and feeding.

  segmental body

  On four segments of the chest are the main swimming legs of the crustacean - flattened and similar to oars, for which these animals got their name. The fifth segment contains modified limbs, which in some representatives of copepods play a role in sexual reproduction.

  The abdomen of 2-4 segments is usually devoid of limbs and ends with paired movable appendages. Most species are characterized by sexual dimorphism, which is expressed in the number of segments of the abdomen, the structure of the limbs and the shape of the antennae.

  

  Growth, development and fitness

  Copepods are small in size and have outgrowths that increase the body area - such features allow these planktonic animals to stay in the water column at no extra cost. This is facilitated by a thin chitinous cover and reserves of fat, which accumulates in special fat drops and often gives color to these crustaceans.

  When a sudden change in body position in the water column is required, they swim with the help of their limbs or make jet jumps by folding their body in half.

  Representatives of almost all types of copepods are dioecious organisms. Despite the outward simplicity, mating in these crustaceans is preceded by complex sexual behavior. In the process of mating, the male transfers a spermatophore (special bag) to the female's abdomen; fertilization of eggs can be both external and internal.

  The larval form (nauplius) emerges from the eggs, which, after several molts, turns into an adult crustacean.

  The strongest

  If you think that the most powerful animals live on land, you are wrong. Recent studies show that small copepods can be considered the strongest. These crustaceans are capable of moving 500 times their size in 1 second. Their small legs develop a power of movement that is 10 times greater than that of other animals.

  As you know, copepods also make jumps. The speed that they develop at the same time is 3-6 km / h. Few? This is comparable to if a person of average height could run at a speed of several thousand kilometers per hour.

  

  The main component of plankton

  About 20-25% of plankton are representatives of this particular group of crustaceans, united in 3 orders:

  Food for aquarium fish

  Cyclops and diatoms are the most famous representatives of these crustaceans, which are fed to aquarium fish. This is a high protein food for fry and adult aquarium inhabitants. At the same time, the nauplii of the Cyclopes are the most nutritious. But do not forget when feeding aquarium fish that cyclops are predators and grow quite quickly. Therefore, from food for fry, they can turn into predators that attack small fish. That is why experienced aquarists do not feed their pets with live food, but freeze it first.

  Depending on what the cyclops ate, crustaceans are red, brown, green, gray. This property of accumulating dyes in your body is also used to give a brighter color. aquarium fish.

  

  Value in nature

  These small crustaceans form a key link in the food chains of marine ecosystems. Modern research shows that the reduction of krill in ocean waters (according to some estimates, it has amounted to 80% since 1976) threatens the existence of not only many species of fish, but also penguins, seals and even whales.

  In addition, copepods, together with other benthic saprophytes, provide water purification from corpses and waste products. Planktonic crustaceans purify water from mineral suspension, contribute to its transparency, and therefore increase the efficiency of plant plankton. And in the end, it is they who participate in the enrichment of the atmosphere with oxygen and the absorption of carbon dioxide from it. This is how small crustaceans are built into a system common to the planet that regulates the climate and the state of the atmosphere.

  Copepods ( Copepoda) is the largest and most diverse group of crustaceans. They currently include more than 14,000 species, 2,300 genera, and 210 families, and this is certainly not the full number of organisms inhabiting the seas and continental waters, transitional zones between water and land, or living in symbiotic relationships with other animals. They are the most numerous multicellular animal group on earth, outnumbering even insects, which include more species but fewer individuals!

  New phylogeny Copepoda(Huys & Boshall 1991):

  1. PLATYCOPIOIDA;
  2. CALANOYDA;
  3. MORMONILLOIDA,
  4. HARPACTICOIDA;
  5. POECILOSTOMATOIDA;
  6. SIPHONOSTOMATOIDA;
  7. MONSTRILLOIDA;
  8. MISOPHRIOIDA;
  9. CYCLOPOIDA;
  10. GELYELLOIDA

  Copepoda- mobile, frisky and large organisms. With the help of antennae and pectoral legs, striking them like oars, they "fly" in the water column. Their body is spindle-shaped with a clear division into two parts: the cephalothorax and the abdomen, which ends with a furka resembling a fork. An unpaired eye is located on the head, for which one of their families bears the name of the Cyclopes - after the mythical one-eyed giants. Most copepods are predators that attack small animals. But there are also herbivorous forms - Calanids (Calanoida), which have a larger cephalothorax and a shortened abdomen. Their anterior antennae are very long (sometimes more than the length of the body) and serve as the main organ of locomotion. They feed mainly on algae.

  Some species of cladocerans are characterized by cyclomorphosis. Many species are found only in the period of open water, laying eggs for the winter - ephippia, from which in the spring, when the water temperature becomes acceptable, juveniles appear. They also use this during their life in water bodies that dry up: they are in the form of an embryo in the epippia until it rains.

  Zooplankton lives in all water bodies. In stagnant waters, the zooplankton community - zooplanktonocenosis - is richer both in terms of the number of species and abundance. Cladocerans, as a rule, do not tolerate the current well, therefore they prefer lakes, ponds, puddles, reservoirs, but rotifers better withstand dizzying pirouettes in the flow of water, therefore, in rivers, springs, plankton consists mainly of them.

  Zooplankton and benthos are the main communities of invertebrates that ensure the normal functioning of aquatic ecosystems, their self-purification, which are the food base for many fish species. Zooplankton usually consists of three systematic groups of invertebrates: rotifers (Rotatoria, class), cladocerans (Cladocera, detachment), copepods (Copepoda, detachment). The same taxa of invertebrates are also present in the benthos, but due to the specifics of the generally accepted selection of benthic samples, as a rule, rotifers are not taken into account in benthic communities. Most species of crustaceans live both in the water column, being an integral part of zooplankton, and at the bottom of reservoirs, in benthos. So the majority of kalanoids (Calanoida, Copepoda) throughout their life, except for the stage of resting eggs, lead a planktonic lifestyle; cyclops (Cyclopida, Copepoda) also inhabit the water column and are a component of microzoobenthos; harpacticides (Harpacticoida, Copepoda) are considered exclusively benthic animals, but are quite common in plankton. Therefore, speaking about the biodiversity of zooplankton organisms and their knowledge, we mean the diversity and knowledge of planktonic and benthic rotifers, cladocerans and copepods.

  Zooplankton is of particular importance in lake ecosystems, where its abundance and biomass reach significant values. In rivers, communities of planktonic invertebrates are formed in deep-water sections of the channel with a slow current, in kuryas, and floodplain reservoirs. On stretches and rifts where there is no zooplankton as such, planktonic invertebrates are found in drift and benthos.

  Currently, an indicator of the diversity of the zooplankton fauna of the region is the presence of 318 established species and forms, of which 164 species and forms of rotifers belonging to 23 families; 76 - cladocerans belonging to 8 families and 78 - copepods. Among the species of copepods, there are 32 species and forms of the suborder Cyclopidae of one family, 17 species and forms of harpacticidae belonging to two families, and 29 species and forms of harpacticides belonging to 5 families.

  The most diverse in the entire region are rotifers of the genus Brachionus, Keratella, Nothoica, Synchaeta, Polyarthra; from cladocerans - chidorids, from copepods - cyclopids and harpacticides.

  Plankton(from Greek. planktos- wandering), a set of organisms that inhabit the water column of continental and marine reservoirs and are not able to resist the transfer by currents. The composition of plankton includes both plants - phytoplankton (including bacterioplankton), and animals - zooplankton . Plankton is opposed to the population of the bottom - benthos and actively swimming animals - nekton . Unlike the latter, plankton organisms are not capable of independent movement or their mobility is limited. In fresh waters, lake plankton is distinguished - limnoplankton and river - potamoplankton .

• Class: Crustacea = Crustaceans, crayfish
• Subclass: Copepoda Milne-Edwards, 1840 = Copepoda
• Order: Cyclopoida Burmeister, 1834 = Copepods
• Genus: Cyclops Muller, 1776 = Cyclops

Order: Cyclopoida Burmeister, 1834 = Copepods

Order of copepods - Cyclopoida - the largest number species are found in fresh waters.

Freshwater cyclops live in all kinds of water bodies, from small puddles to large lakes, and are often found in a very large number of specimens. The main zone of their habitat is the coastal strip with thickets of aquatic plants. At the same time, in many lakes, certain types of cyclops are confined to thickets of certain plants. So, for example, for Lake Valdai in the Ivanovo region, 6 groups of plants with their corresponding groups of cyclops species are described.

Relatively few species can be considered true planktonic animals. Some of them, belonging mainly to the genus Mesocyclops, constantly live in the surface layers of water, others (Cyclops strenuus and other species of the same genus) make regular daily migrations, descending to a considerable depth during the day.



Cyclopes swim a little differently than Calands. Simultaneously waving four pairs of pectoral legs (the fifth pair is reduced), the crustacean makes a sharp jump forward, up or sideways, and then, using the front antennae, can soar in the water for some time. Since the center of gravity of his body is shifted forward, while hovering, his front end tilts and the body can take a vertical position, and the dive slows down. A new swing of the legs allows the cyclops to rise. These swings are lightning fast - they take 1/60th of a second.

Most Cyclopes are predators, but there are also herbivorous species among them. Such common, widespread species as Macrocyclops albidus, M. fuscus, Acanthocyclops viridis and many others swim quickly above the bottom or among thickets in search of prey.

With the help of their antennae, at a very short distance, they sense small oligochaetes and chironomids, which they grab with their front jaws armed with spikes. The hind jaws and mandibles are involved in the transfer of food to the mandibles. The mandibles make quick cutting movements for 3-4 seconds, followed by a minute pause. Cyclops can eat oligochaetes and chironomids larger than themselves. The rate at which victims are eaten depends on their size and the hardness of their coverings. It takes 9 minutes to crush and swallow a 2 mm long bloodworm, and a 3 mm long larva is destroyed within half an hour. The more delicate, though longer (4 mm) oligochaete worm Nais is eaten in just 3.5 minutes.

Herbivorous cyclops, in particular the common Eucyclops macrurus and E. macruroides, feed mainly on green filamentous algae (Scenedesmus, Micractinium), capturing them in much the same way as predatory ones capture worms and bloodworms; in addition, various diatoms, peridiniums, and even blue-green algae are used. Many species can only eat relatively large algae. Mesocyclops leuckarti quickly fills its intestines with Pandorina colonies (colony diameter 50-75 microns) and almost does not swallow small Chlamydomonas at all.

Freshwater cyclones are very widespread. Some species are found almost everywhere. This is facilitated primarily by adaptations to endure unfavorable conditions, in particular, the ability of crustaceans to endure the drying up of water bodies and passively spread through the air in the form of cysts. The skin glands of many cyclops secrete a secret that envelops the body of the crustacean, often along with egg sacs, and forms something like a cocoon. In this form, crustaceans can be subjected to drying and freezing into ice without losing viability. In Kamerer's experiments, the cyclops were quickly eliminated by soaking dry sludge, which had been stored for about 3 years. Therefore, there is nothing surprising in the appearance of cyclops in spring puddles that occur when snow melts, in freshly flooded fish ponds, etc.

The second reason for the wide distribution of many species of cyclops should be considered the resistance of crustaceans, which are in an active state, in relation to the lack of oxygen in the water, its acidic reaction, and many other factors that are unfavorable for other freshwater animals. Cyclops strenuus can live for several days not only in the complete absence of oxygen, but even in the presence of hydrogen sulfide. Some other species also tolerate adverse gas conditions well. Many cyclops exist excellently in water with an acidic reaction, with a high content of humic substances and extreme poverty of salts, for example, in reservoirs associated with upland (sphagnum) bogs.

Nevertheless, species and even genera of Cyclopes are known, limited in their distribution by some specific conditions, in particular temperature and salt conditions. For example, the genus Ochridocyclops lives only in Lake Ohrid in Yugoslavia, the genus Bryocyclops lives in Southeast Asia and equatorial Africa. Close to the latter genus is the exclusively subterranean genus Speocyclops, species of which have been found in caves and groundwater in southern Europe, Transcaucasia, the Crimea, and Japan. These blind small crustaceans are considered to be the remains of a once more widespread heat-loving fauna.