Ringed Parasitic Worms: Description, Table Of Species

Table of contents:

Ringed Parasitic Worms: Description, Table Of Species
Ringed Parasitic Worms: Description, Table Of Species

Video: Ringed Parasitic Worms: Description, Table Of Species

Отличия серверных жестких дисков от десктопных
Video: Microbiology of Parasites 2023, February
Anonim

Page content

  • Classes of annelids
  • Taxonomy
  • Spread
  • Internal structure

    • Musculature
    • Body cavity
    • Digestive system
    • Excretory system
    • Circulatory system of annelids
    • Respiratory system
    • Nervous system and senses
  • You can defeat parasites!

The annelids (Annelida) are the most highly organized worms with a whole. Their sizes range from a few millimeters to 3 m. The elongated body is divided into segments by inner annular septa; sometimes there are several hundred such segments. Each segment may have lateral outgrowths with primitive limbs - parapodia, armed with bristles.

The musculature consists of several layers of longitudinal and circular muscles. Breathing is carried out by the skin; excretory organs - paired nephridia, located segmentally. The nervous system consists of a "brain" formed by paired ganglia and the abdominal nerve cord.

What to do in such a situation? To get started, we recommend reading this article. This article details the methods of dealing with parasites. We also recommend contacting a specialist. Read the article >>>

The closed circulatory system consists of the abdominal and dorsal vessels, connected in each segment by small annular vessels. Several of the thickest vessels in the front of the body have thick muscular walls and act as "hearts". In each segment, the blood vessels branch out, forming a dense capillary network.

Some annelids are hermaphrodites, while others differ in males and females. Development is direct or with metamorphosis. There is also asexual reproduction (budding).

What are annelid parasitic worms
What are annelid parasitic worms
Image
Image

Classes of annelids

Ringed worms are divided into 3 classes: polychaetae, few-bristled worms and leeches.

Polychaeta (Polychaeta) have primitive limbs (parapodia) with numerous bristles on each segment. Branched appendages - gills, with the help of which gas exchange is carried out - are often associated with bilobed parapodia. On a clearly isolated head there are eyes (in some species even capable of accommodation), tactile antennae and organs of balance (statocysts). Some species are capable of luminescence.

Representatives of this class are inhabitants of the seabed (found at a depth of up to 10 km), where they swim, crawl on the ground or burrow into silt, but some can also be found in freshwater lakes. Many worms build pipes of various shapes from grains of sand, which never leave. From 6 to 10 thousand species. Many worms are predators, others feed on detritus, there are practically no parasites among them. Polychaete worms (for example, nereis) serve as food for many fish. Some worms (palolo) are consumed by humans.

Small bristles (Oligochaeta) - mainly soil worms. Among them, there are both giant earthworms up to 2.5 m long and dwarf forms. All segments, except for the oral one, have bristle setae. Parapodia are not expressed, the head is slightly separated. The thin cuticle is constantly moisturized by secreted mucus; gas exchange is carried out through the cuticle by diffusion.

Small bristle worms are mainly hermaphrodites with cross fertilization; the genitals are scattered over several body segments. The complex structure of these organs is an adaptation to the terrestrial lifestyle. Parthenogenesis is known in some species. There is no metamorphosis; from the cocoons formed in the process of copulation, a dozen young worms emerge in a few weeks.

Leeches (Hirudinea) have a flattened body, usually colored brown or green. There are suckers on the front and back ends of the body. Body length from 0.2 to 15 cm. Tentacles, parapodia and, as a rule, no setae. The musculature is well developed. The secondary body cavity is reduced. Breathing is cutaneous, some have gills. Most leeches have 1–5 pairs of eyes.

The lifespan of leeches is several years. They are all hermaphrodites. Eggs are laid in cocoons, there is no larval stage. Most leeches suck blood from various animals, including humans. Leeches pierce the skin with a proboscis or denticles on the jaws, and a special substance - hirudin - prevents blood from clotting. Sucking blood from a single victim can take months. In the intestines, blood does not deteriorate for a very long time: leeches can live without food for even two years. Some leeches are predators that swallow their prey entirely.

Leeches live in fresh water bodies, they are also found in the seas and soil. Leeches serve as food for fish. The medicinal leech is used by humans for medicinal purposes. 400-500 species.

Classes of annelids
Classes of annelids
Image
Image

Taxonomy

To date, experts refer to the annelid type from 16 to 22 thousand modern animal species. There is no single approved classification of rings. The Soviet zoologist V.N. Beklemishev proposed a classification based on the division of all representatives of annelids into two superclasses: non-girdle, which includes polychaetes and echiurids, and girdle, including oligochaetes and leeches.

Below is the classification from the World Register of Marine Species website.

Class * Subclass Infraclass Squad
Polychaeta worms, or polychaetes (lat.Polychaeta)
  • Amphinomida
  • Eunicida
  • Phyllodocida
Polychaeta incertae sedis (disputed species)
Sedentaria Canalipalpata
  • Sabellida
  • Spionida
  • Terebellida
Scolecida
  • Capitell> Opheliida
  • Orbiniida
  • Questida
  • Scolecidaformia
Palpata
  • Polygordiida
  • Protodrilida
Errantia (sometimes called Aciculata)
  • Amphinomida
  • Eunicida
  • Phyllodocida
Class belt (Clitellata) Leeches (Hirudinea) Acanthobdellidea
  • Jaw or proboscis leeches (Arhynchobdellida)
  • Proboscis leeches (Rhynchobdellida)

Small bristle worms (Oligochaeta)

  • Capilloventrida
  • Crassiclitellata
  • Enchytraeida
  • Haplotaxida (this includes the order Earthworms)
  • Lumbriculida
  • Oligochaeta incertae SEDIS (species undefined)
  • Echiura incertae sedis (disputed species)
  • Unreviewed
  • Class Polychaetes (Polychaetes). Representatives of the class have connected lateral appendages (parapodia) bearing chitinous setae; the name of the group is determined by the presence of a large number of bristles per segment. Head with or without appendages. In most cases, dioecious; gametes are discharged directly into the water, where fertilization and development takes place; freely floating and are called trochophores. Sometimes they reproduce by budding or fragmentation. The class has more than 6,000 species, which are divided into free-living and sessile forms.
  • Class Belt (Clitellata). Representatives of the class have little or no setae on their bodies. There are no parapodia. They are characterized by the presence of a unique reproductive organ - a girdle, which is formed from the remains of a cocoon and performs a protective function for fertilized eggs. The class has about 10,000 members.

    • Subclass Small- bristled (Oligochaetes). They live primarily in fresh water. They have bristles arising directly from the walls of the body, due to the small number of which (as a rule, 4 on each segment), the subclass is called low-bristled. As a rule, they do not have appendages on the body. Hermaphrodites. Direct development, no larval stage. There are about 3250 species.
    • Leech subclass. They inhabit mainly freshwater bodies of water, but there are also terrestrial and marine forms. There is a small suction cup at the front end of the body and a large suction cup at the rear end. The fixed number of body segments is 33. The body cavity is filled with connective tissue. Hermaphrodites. Fertilized eggs are deposited in a cocoon. Direct development, no larval stage. There are about 300 species of representatives.

    Echiura class. It is a small group of only about 170 known species, all of which are exclusively marine. The echiuridae annelids were recently attributed after DNA examinations, and earlier it was a separate type. The reason is that their body is different - it does not have segmentation like ringed ones. In some sources, Echiurids are considered not as a separate class, but as a subclass of Polychaetes.

Classes of annelids
Classes of annelids
Image
Image

Spread

Annelids, depending on the species, live on land, in fresh and salt water.

Polychaete worms, as a rule, live in seawater (with the exception of some species that can also be found in freshwater bodies). They are food for fish, crayfish, as well as birds and mammals.

Small-bristle worms, to a subclass of which the earthworm belongs, live in soil fertilized with humus or freshwater bodies.

Leeches are found mostly in the aquatic environment and lead a semi-parasitic lifestyle. Echiuridae are common only in marine waters.

Internal structure

Musculature

The muscular sac is located under the epithelium. It consists of the external annular and internal longitudinal muscles. Longitudinal musculature in the form of a continuous layer or divided into ribbons.

Leeches have a layer of diagonal muscles, which are located between the annular and longitudinal. The dorsal abdominal muscles are well developed in leeches. In wandering polychaetes, flexors and extensors of the parapodia are developed - derivatives of the annular muscles. The annular musculature of oligochaetes is more developed in the anterior eight segments, which is associated with the lifestyle.

Body cavity

Secondary or general. The body cavity is lined with coelomic or perinoneal epithelium, which separates the cavity fluid from tissues and organs. Each body segment of polychaetes and oligochaetes has two coelomic sacs. The walls of the sacs on one side adjoin the muscles, forming a somatopleura, on the other side, to the intestines and to each other, a splanchnopleura (intestinal leaf) is formed. Splanchnopleura of the right and left sacs forms the mesentery (mesentery) - a two-layer longitudinal septum. Developed either two or one septum. The walls of the sacs, facing the adjacent segments, form disseminations. Dissensions disappear in some polychaetes. Generally absent from the prostomium and pygidium. In almost all leeches (with the exception of bristle leeches), between the organs of the parenchyma, it is generally preserved in the form of lacunae.

Coelom functions: support, distribution, excretory, and in polychaetes - sexual.

The origin of the coelom. There are 4 known hypotheses: myocoel, gonocoel, enterocoel, and schizocoel.

Digestive system

It is represented by three departments. Digestion is cavity. The pharynx of carnivorous polychaetes is armed with chitinous jaws. In the pharynx of annelids, the ducts of the salivary glands open. The leech glands contain the anticoagulant hirudin. In earthworms, the channels of the calcareous (morrenic) glands flow into the esophagus. In addition to the pharynx and esophagus, goiter and gizzard are part of the anterior intestine of earthworms. The absorption surface of the midgut increases due to outgrowths - diverticulums (leeches, part of polychaetes) or typhlozol (oligochaetes).

Excretory system

Nephridial type. As a rule, each segment has two excretory canals, they begin in one segment, and open at times in the next segment of the body. The organs of excretion of polychaetes are the most diverse. Polychaete worms have the following types of excretory system: protonephridia, metanephridia, nephromyxia, and mixonephridia. Protonephridia are developed in larvae, they begin with terminal clavate cells with a flagellum (solenocytes), then the nephridium canal. Metanephridia begins with a funnel with a nephrostomy, inside

funnels are cilia, followed by a duct and nephropore. Protonephridia and metanephridia are ectodermal in origin. Nephromyxia and myxonephridia represent the fusion of the protonephridium or metanephridium ducts with the coelomoduct - the genital funnel. Whole products of mesodermal origin.

Internal structure
Internal structure
Image
Image

The excretory organs of oligochaetes and leeches are metanephridia. In leeches, their number is significantly less than body segments (in the medicinal leech, 17 pairs), the separation of the funnel from the canal is characteristic. In the excretory canals of nephridia, ammonia is converted into high molecular weight compounds, and water is absorbed as a whole. Ringed worms also have “buds” of accumulation: chloragenous tissue (polychaetes, oligochaetes) and botryoid tissue (leeches). They accumulate guanine, uric acid salts, which are removed from the coelom through nephridia.

Circulatory system of annelids

Most annelids have a closed circulatory system. It is represented by two main vessels (dorsal and abdominal) and a network of capillaries. The movement of blood is carried out due to the contraction of the walls of the dorsal vessel; in oligochaetes, ring hearts also contract. The direction of movement of blood along the dorsal vessel from back to front, abdominal - in the opposite direction. The circulatory system is developed in bristle-bearing and proboscis leeches.

In jaw leeches, there are no vessels; the function of the circulatory system is performed by the lacunar system. The process of functional replacement of one organ with another, different in origin, is called organ substitution. The blood of annelids is often colored red due to the presence of hemoglobin. In primitive polychaetes, the circulatory system is absent.

Respiratory system

Most breathe with the entire surface of the body; some polychaetes and some leeches have gills. Respiratory organs are evaginated. The gills of polychaetes by origin are a modified dorsal antenna of parapodia, leeches are skin outgrowths.

Nervous system and senses

The nervous system includes: paired cerebral (supraopharyngeal) ganglion, connectives, suboesophageal ganglia, and the abdominal nerve cord or ladder-type nervous system. The abdominal trunks are connected by commissures. The evolution of the nervous system proceeded in the direction of the transformation of the ladder-type nervous system into a chain, the immersion of the system into the body cavity. The nerves extending from the central system make up the peripheral system. There is a different degree of development of the supraopharyngeal ganglion, the brain is either monolithic, or there are sections. For leeches, the fusion of the ganglia of the segments that make up the suckers is characteristic.

Senses. Polychaetes: epithelial sensory cells, antennae, nuchal organs, antennae of parapodia, statocysts, organs of vision (glass or bladder eyes). Senses of oligochaetes: light-sensitive cells, some inhabitants of water have eyes, organs of chemical sense, tactile cells. Leeches: goblet organs - chemical sense organs, eyes.

Popular by topic