Lower and higher crustaceans: characteristic differences. Crustaceans in nature Ecological niches in lower crustaceans

lower crustaceans

Subclass Gillpods

The most primitive These small crustaceans have leaf-shaped legs and are used equally for locomotion and respiration. They also create a current of water that brings food particles to the mouth. Their eggs easily tolerate desiccation and wait in the soil for the new rainy season. Artemia is interesting among the branchiopods: it can live in salt lakes with a salt concentration of up to 300 g / l, and dies in fresh water after 2-3 days.

Subclass Maxillopods (maxillopods)

Representatives of the order of barnacles are amazing: sea acorns and sea ducks. These sea crayfish have moved to a sedentary lifestyle in houses made of calcareous plates. The larva is a typical nauplius, sinks to the bottom and is attached by antennules. The antennae and the entire anterior part of the head turn into an attachment organ (a long fleshy stalk in sea ducks, or a flat wide sole in sea acorns), antennae and compound eyes atrophy, pectoral legs stretch into long two-branched "antennae" that drive food to the mouth.

Crustaceans (Ass. F. D. MORDUKHAI-BOLTOVSKOY)

Lower crustaceans (Entomostraca)

The lower crustaceans have an inconsistent number of body segments, usually an indistinctly delimited abdomen that never bears limbs. In fresh and generally inland water bodies of the Rostov region. lower crustaceans are represented by four orders: branchiopods (Branchiopoda), cladocera (Cladocera), copepods (Copepoda) and shellfish (Ostracoda). These are in most cases small, sometimes microscopic animals that live exclusively in water.

1. Branchiopods (Branchiopoda)- these are relatively large crustaceans with a clearly dissected body with a large number of leaf-shaped, equipped with gill appendages, swimming legs (from 10 to 40). They inhabit very shallow temporary reservoirs and puddles, which usually dry up in summer. In the reservoirs of the floodplain Don, formed during the spring flood, you can often find the most interesting representative of these crustaceans - shield - Lepidurus apus. This is an extremely peculiar type of animal up to 4-5 cm, covered on the dorsal side with a greenish armor covering the entire body, with the exception of the posterior abdomen, equipped with two long tail filaments (Fig. 1). Along with Lepidurus, Rpus, very close to it, is found, differing from the first in the absence of a plate between the tail filaments.

Most of the reservoirs in which these crayfish live completely dry up by the middle of summer. However, shields reappear in them next spring, as they lay the so-called "resting" or "winter" eggs, not only equipped with a dense shell that allows them to endure drying and freezing of the reservoir without harm, but even, apparently, needing complete drying. for further development.

In the same temporary reservoirs, there are also other representatives of the described detachment, devoid of armor - gills. Gill legs have an elongated body with a thin tail (abdomen) and 10-20 pairs of long legs bearing gills; the head is separated from the body and equipped with stalked eyes and large curved antennae ("antennas"). Branchinella spinosa was found among the branchiopods in the reservoirs of the Don floodplain. In the salt lakes of the Many-chey basin, another branchiopod, artemia (flrtemia salina v. principalis, Fig. 2), is common. Artemia is a well-known inhabitant of salt water bodies, remarkable in that it cannot exist in fresh water bodies, and in salt water it feels great even at such a concentration of salts at which all other animals die. In this case, Artemia can develop in large quantities. In some saline reservoirs of the Manych Valley, the entire mass of water, devoid of any animals, is filled with floating remains of the leaf-shaped legs of Artemia.

In addition to the scutes and branchiopods, among the branchiopods there is also a group of forms equipped with a bivalve shell, similar to mollusk shells, but usually very thin and transparent. In floodplain lakes and swampy reservoirs one can often find these small (rarely more than 1a/a cm) crustaceans that swim quickly with the help of numerous (10-30 pairs) legs.

In the Rostov region species of Leptestheria, Caenestheria, and Cyzicus were found from this group.

2. Branched mustache, or Cladocera- the overwhelming majority are very small animals with an almost unsegmented body with a small number of swimming legs (no more than 6). The body is dressed in a transparent, thin shell and in front bears a pair of branched antennae - antennas that serve for movement, which occurs abruptly. The head is usually equipped with one large eye, often of a rather complex structure. Cladocera inhabit absolutely all fresh water bodies and are one of the most common groups of crustaceans. The extremely wide distribution of Cladocera is due to a large extent to the presence of "winter" or "resting" eggs, which, due to their negligible size, can be carried over long distances by wind along with dust. Reproduction of Cladocera occurs several, and sometimes many times during the year, and it is remarkable that it can go on for a long time without the participation of males (parthenogenetically), but only ordinary "summer" eggs are formed; with the deterioration of the conditions of existence, males appear, fertilizing females, which then lay "winter" eggs.

Cladocera are one of the main constituents of the plankton of fresh water bodies, and also inhabit the coastal zone and thickets in large numbers. They are an important, and sometimes the main object of food for various commercial and non-commercial "plank-eating" fish (herring, sprat, bleak, etc.) and juveniles of most fish that feed on benthic fauna in their adult state. When dried, Cladocera is an all-purpose food for aquarium fish. This food is called daphnia, although in reality daphnia is only one of the very numerous forms of Cladocera.

In the reservoirs of the Rostov region. Cladocera are as rich and diverse as in all water bodies of temperate and southern latitudes (at least 40 species of them were found in the Don basin). Of the planktonic forms often found in the Don River, the aforementioned daphnia (Daphnia longispina) can be mentioned. This is a transparent crustacean 1-2 long mm, whose shell is equipped with a long needle, and the head bears a pointed helmet (Fig. 3). Even more common than daphnia are its close relatives, Moina and Diaphanosoma, which are distinguished by the absence of a helmet and needle. Bosmina (Bosmina longiros tris), very small (no more than 1/2 mm) a rounded crustacean with a long beak, and Chydorus sphaericus, also completely round, but without a beak. In the thickets of the coastal strip and near the bottom, there are many other, related to the latter, cladocerans from the Chydoridae family.

In the salty reservoirs of the Manychs, the majority of Cladocera, generally adapted to fresh water, cannot exist. Only Moina and Diaphanosoma, the most resistant to salinity, remain, but they multiply in large numbers.

Among Cladocera, the Leptodora kindtii, which lives in the plankton of the Don and in general in large reservoirs, stands out. It is relatively very large - about 1 cm- a crustacean, the elongated body of which is almost free from the shell (covering only the "brood pouch" with eggs) (Fig. 4). Leptodora, unlike most other Cladocera, leads a predatory lifestyle and is distinguished by extraordinary transparency. In a living form, it is almost impossible to distinguish it in water, and only when it is killed with formalin or alcohol, it turns white and becomes clearly visible.

Free-living copepods (Euco-pepoda) have a clearly dissected body, subdivided into a wide cephalothorax, equipped with 4 pairs of biramous swimming legs and a narrow abdomen, ending in a biramous fork with bristles ("furka"). The cephalothorax bears in front one small eye and a pair of very long antennae used for swimming.

Like Cladocera, all copepods are very small, often semi-microscopic forms, extremely widespread in all kinds of water bodies. They also form resting eggs and are part of the plankton, representing an important food item for fish fry and adult planktivorous fish.

The way of life of copepods is similar to the way of life of cladocerans; it should, however, be noted that, in contrast to Cladocera, which breed only after the water has completely warmed up and quickly disappears with cooling, copepods are much more resistant to low temperatures and appear in masses even in very early spring, and many live throughout the winter, under the ice.

The most common representatives of copepods are cyclops belonging to the genus Cyclops (currently this genus is divided into several others). Cyclopes have an oval cephalothorax, an elongated abdomen with long caudal setae, and comparatively short swimming antennae. Females carry eggs in two egg sacs on the sides of the abdomen (Fig. 5). Cyclops - small crustaceans (no more than 2-3 mm in length), found in all water bodies, with the exception of heavily polluted ones, and usually leading a planktonic lifestyle. Among the numerous species of this genus (at least 20 species of Cyclops are known for the Rostov Region), Cyclops strenuus, C. vernalis, and C. oithonoides are more common in the plankton of the Don.

Along with cyclops, especially in shallow spring water bodies, representatives of the genus Diaptomus (Diaptomus) are often found, differing in somewhat large sizes (up to 5 mm), longer antennae and a cephalothorax and short abdomen. Many of them are red or blue in color. D. salinus and D. (Paradiaptomus) asiatlcus are of interest among the numerous (about 15) species of Diaptomus (in Rostov oblast), which develop in mass quantities in the saline reservoirs of the Manychi. Other copepods (Heterocope, Calanipeda, Eurytemora) are also found in the plankton of the Don.

In the coastal zone and at the bottom of reservoirs live copepods belonging to the Harpacticidae group. These are extremely small crustaceans with a long body and poorly developed swimming antennae, running along the bottom and, due to their scarcity and small size, usually elude observation.

A significant role in the plankton of most water bodies is played by peculiar copepod larvae - nauplii. These are very microscopic animals with three pairs of legs and one red eye, often, especially in spring, inhabiting water in countless quantities. All copepods in their development go through this larval stage, which after a few weeks, through a series of successive molts, turns into an adult form.

Very close to the copepods (but now they stand out in a special order of branchiura - Branchiura) are also "fish or carp lice" (flrgulus). These are small (no more than 1/2 cm) crustaceans with a flat body, two compound eyes and two suckers with which they are attached to the skin of fish. They suck blood from fish, but often separate from their prey and swim freely in the water for some time. One of the species of this genus, Argulus foliaceus, is often found in the Don.

4. Shellfish (Ostracoda). Shellfish are small crustaceans that live in oval bivalve shells. The presence of a shell brings them closer, but they differ from the latter only in smaller sizes (usually no more than 5-7 mm) and an undivided body with only three pairs of legs that serve not for swimming, but for running (Fig. 7). In addition, their lime-impregnated shell is usually very durable and fossilized, making Ostracoda important in paleontology.

Most shellfish live among thickets and at the bottom of various water bodies. Although they do not have special "winter" eggs, their eggs, and often adult crustaceans themselves, are also able to tolerate drying and freezing without harm.

In freshwater bodies, they usually do not breed in mass quantities and can easily go unnoticed by the untrained eye.

In the Rostov region shell crustaceans are almost not studied. Only a few widespread species that inhabit small floodplain lakes and puddles can be noted: Candona, one of the largest forms with a white shell; Cyclocypris, smaller, rounded; Limnicythere - with an elongated shell, equipped with several large swellings.

Crustaceans- These are aquatic arthropods or inhabitants of wet places. Their body sizes vary from a few millimeters to 1 m. They are ubiquitous; lead a free or attached lifestyle. The class includes about 20 thousand species. Only crustaceans are characterized by the presence of two pairs of antennae, biramous limbs, and gill breathing. The class Crustacea combines 5 subclasses. Conventionally, all representatives are divided into lower (daphnia, cyclops) and higher crayfish (lobster, spiny lobster, shrimp, crayfish).

Representative of higher cancers - river crayfish. It lives in fresh water bodies with running water, is nocturnal and is a predator.

Crayfish. External and internal structure:
1 - Antennae, 2 - Claw, 3 - Walking legs, 4 - Caudal fin, 5 - Abdomen, 6 - Cephalothorax, 7 - Head ganglion, 8 - Digestive tube, 9 - Green gland, 10 - Gills, 11 - Heart, 12 - gonad

The body of the cancer is covered with a dense chitinous shell. The fused segments of the head and chest form the cephalothorax. Its front part is elongated and ends with a sharp spike. Two pairs of antennae are located in front of the spine, and two complex (faceted) eyes are located on the sides on movable stalks. Each eye contains up to 3 thousand small eyes. Modified limbs (6 pairs) form the oral apparatus: the first pair is the upper jaws, the second and third are the lower jaws, the next three pairs are the jaws. The thoracic region bears 5 pairs of jointed limbs. The first pair is the organ of attack and defense. It ends with powerful pincers. The remaining 4 pairs are walking limbs. The limbs of the jointed abdomen are used in females for carrying eggs and cubs. The abdomen ends with a caudal fin. When the crayfish swims, it scoops up water with it and moves with its tail end forward. Bundles of striated muscles are attached to the internal protrusions of the chitinous cover.

Cancer feeds on both living organisms and decaying animal and plant debris. The crushed food enters through the mouth into the pharynx and esophagus, then into the stomach, which has two sections. Chitinous teeth of the chewing section grind food; in the filter stomach, it is filtered and enters the middle intestine. The ducts of a large digestive gland, which performs the functions of the liver and pancreas, also open here. Under the action of its secret, the food slurry is digested. Nutrients are absorbed, and undigested residues through the hindgut and anus are thrown out.

The excretory organs of cancer are a pair of green glands (modified metanephridia) that open at the base of long antennae. Respiratory organs - gills located on the sides of the cephalothorax. They are permeated with blood vessels in which gas exchange occurs - the blood gives off carbon dioxide and is saturated with oxygen. The circulatory system is not closed. It consists of a pentagonal heart located on the dorsal side and vessels extending from it. The blood pigment contains copper, which is why it is blue in color. The nervous system of crayfish resembles the nervous system of annelids. It consists of the supraglottic and subpharyngeal ganglia, united in the circumpharyngeal ring, and the ventral nerve cord. The organs of vision, touch and smell (on the antennae), balance (at the base of the short antennae) are well developed. Cancers are segregated. Reproduction is sexual, development is direct. Eggs are laid in winter; small crayfish hatch from eggs in early summer. Cancer expresses concern for offspring.

Significance of crustaceans. Crustaceans serve as food for aquatic animals and for humans (lobsters, crabs, shrimps, crayfish). They clean the water bodies from carrion. Some representatives of crustaceans cause diseases of fish, settling on their skin or gills, some are intermediate hosts for tapeworms and roundworms.

blue cuban crayfish

Crustaceans live in aquatic or humid environments and are close relatives of insects, spiders, and other arthropods (type Arthropoda). The peculiarity of their evolutionary series is to reduce the number of metameric (identical) segments through their merging with each other and the formation of more complex body fragments. According to this feature and other characteristics, two groups are distinguished: lower and higher crustaceans. So, let's get to know these animals closer.

Lower and higher crustaceans: characteristic differences

The lower crustaceans differ in small, up to microscopic sizes. In addition, they do not have abdominal limbs, but only chest ones. Unlike primitive forms, higher crustaceans are characterized by a constant (6 pieces) number of identical body segments. For simply arranged crustaceans, the number of such formations ranges from 10 to 46. Moreover, their limbs, as a rule, are biramous. While, in some highly developed animals, this feature disappears. So, in crayfish, the thoracic limbs have one branch.

cherry shrimp

Shrimp Lysmata amboinensis and giant moray

The lower crustaceans are characterized by a softer chitinous cover. Some of them (daphnia, in particular) have transparent shells through which the internal structure is visible. The respiratory system in higher crustaceans is represented by gills. More primitive forms breathe the entire surface of their body, while the bloodstream in some may be completely lost. The nervous system of highly developed species with a variety of behavioral reactions has a complicated structure.

Daphnia (lat. Daphnia) - a genus of planktonic crustaceans

These animals are characterized by well-developed external formations that perform the function of balance (statocysts); bristles covering the entire body, increasing sensitivity; organs that capture the chemical components of the environment. Some lower crustaceans do not have a peripharyngeal ring, their brain is more primitive, while in more developed organisms ganglia merge, their structure becomes more complex.

Lobster, he is a lobster (lat. Nephropidae)

Diversity of biological forms of lower and higher crustaceans

Shrimp "Red Crystal"

Higher species of crustaceans, in particular crayfish, crab, lobster, spiny lobster, and shrimp, play a special commercial role for humans. A useful product consisting of planktonic crustaceans Bentheuphausia amblyops, is krill meat. Has the same lifestyle Macrohectopus branickii living in Lake Baikal. Land woodlice living in moist soil are also highly developed representatives.

Cambarellus patzcuarensis is an endemic type of crayfish

Amphipod Parvexa, an endemic crustacean that lives in about. Baikal

Cancer - mantis (lat. Odontodactylus scyllarus), also known as shrimp - mantis

And in more detail with the various species belonging to this class, with lower and higher crustaceans, you will be introduced to the new articles of the online magazine "Underwater World and All Its Secrets":