Biology

Phylum Aschelminthes Definition, Examples, Characteristics

Aschelminthes are pseudocoelomate. They are bilaterally symmetrical, triploblastic, non-segmented, vermiform, organ-system grade construction that includes full digestive tubes.

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This article writter by MN Editors on November 19, 2021

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Phylum Aschelminthes Definition, Examples, Characteristics
Phylum Aschelminthes Definition, Examples, Characteristics

Phylum Aschelminthes Definition

Aschelminthes are pseudocoelomate. They are bilaterally symmetrical, triploblastic, non-segmented, vermiform, organ-system grade construction that includes full digestive tubes.

Characteristics of Phylum Aschelminthes 

  • They are generally aquatic, free-living or parasitic.
  • These are bilaterally symmetrical and unsegmented worms.
  • The body is slim vermiform, generally worm-like, or flattened.
  • They’re usually tiny and even microscopic. However, they can reach an inch or longer in length.
  • They are triloblastic and pseudocoelomate with organ system grades of body structure.
  • Body wall covered by a syncytial cellulosis epidermis that is covered by the cuticle that is thick and scleroprotein.
  • Cilia are absent, with the exception of the an anterior cilia on rotifers.
  • Muscles are mainly longitudinal fibers.
  • It is straight, complete , with a mouth, straight , non-muscular the intestine, and anus muscular pharynx and highly specialized.
  • The circulatory and respiratory systems aren’t functioning.
  • The excretory system is comprised of a network of canals and protonephridia (in certain) to regulate the regulation of osmoregulation. Cloaca can be found in certain.
  • The system for nerves is very simple and comprises a the circumenteric nerve ring, which has the anterior and posterior longitudinal nerves.
  • The sense organs take shape of pits, papillae bristles and eyespots.
  • They are usually dioecious i.e. both sexes have distinct. Ducts and gonads are either double or single.
  • The process of reproduction is not asexual in these species.
  • Eggs have a chitinous outer shell as well as cleavage determinate, spiral and.
  • The life cycle of these animals is straightforward or complex, but usually without particular larval stage.

Classification of phylum Aschelminthes

The phylum is a heterogeneous collection of animals, which is why it is classified differently by various Zoologists. The classification here is based on and on a modification of L. Hymann (1951) and L. Hymann (1951) however Storer as well as Usinger (1971) are the only ones who have considered the different classification of Aschelminthes as separate phylas in addition to classify Aschelminthes with superphylum.

Class 1. Nematoda (Gr., nema=thread+ eidos= form)

  • Terrestrial or aquatic, free-living or parasitic roundworm.
  • The body is elongated, cylindrical and unsegmented.
  • Body wall with a thick cuticle cellulose or syncytial epidermis and long-distance muscles with four band.
  • There is no cilia, there is no respiratory or circulatory system.
  • The digestive system is completed by muscles in the pharynx, and
  • The glandular organs’ excretory system or canals, or both.
  • Nervous system, including the circumenteric ring, the posterior and anterior nerves.
  • Sense organs simple.
  • Males with penial-spicules. smaller than females.
  • There are two or three gonads. Male genital ducts go to the female genital duct with an opening of its own.
  • Fertilization
  • The development process is typically directly. There is no asexual reproduction or regeneration.
  • Examples: Ascaris, Necator, Wuchereria, Trichinella.

Order 1. Enploidea

  • Not ringed cuticle, typically cuticular bristles.
  • Anterior side with six labial papillae.
  • 10-12 bristles in two or three circles.
  • Esophagus is divided into two parts: anterior and posterior glandular.
  • Cephalic amphids with cyathiform slits.
  • Examples: Enoplus, Anticoma, Synonchus.

Order 2. Dorylaimoidea

  • Soft cuticle with no bristles.
  • Anterior end has two circles of papillae that are six and ten each.
  • Buccal cavity equipped with a protruding spear.
  • The back part of the pharynx is enlarged.
  • Cyathiform amphids.
  • Examples: Dorylamius, Tylencholaimus, Actinolaimus.

Order 3. Mermithoidea

  • Nematodes that are smooth, filiform, parasites in the invertebrates (mainly insects) during the early stages of free-living, as an adult in water or soil.
  • Organs of the head sense reduced to papillae. Usually six.
  • A long Pharynx that is blind.
  • Blind intestine that has been transformed to a food storage organ.
  • Cyathiform amphids or amphids with reduced levels.
  • Examples: Mermis, Paramermis, Aproctonema.

Order 4. Chromadoroidea

  • The cuticle is smooth or ringed.
  • Usually, the cuticle is heavily decorated with knobs, bristles, punctuation.
  • Pharynx with an anterior bulb.
  • Amphids are spirals or can be derived from spirals.
  • Examples: Paracytholamius, Paracanthonchus.

Order 5. Araeolaimoidea

  • A smooth cuticle, occasionally bristles.
  • Labial papillae that are present.
  • Anterior edge with four bristles that are cephalic.
  • Loop-like amphids or spirals.
  • Examples: Plectus, Wilsonema, Odontophora.

Order 6. Monhysteroidea

  • Cuticles that are smooth or lightly ringed usually with bristles.
  • Anterior end has 6, 7 and 8 bristles.
  • Circular amphids.
  • Examples: Cylindrolaimus, Siphonolaimus.

Order 7. Desmoscalecoidea

  • Cuticle that is heavily ringed, and prominent bristles all over or within a limited zone.
  • Anterior end is adorned with four bristles.
  • Crescentic amphids.
  • Marine nematodes.
  • Examples: Desmoscolex, Tricoma, Greeffiella.

Order 8. Rhabditoidea or Anguilluloidea

  • The parasite or free-living
  • The cuticle’s smooth or ringed cuticle.
  • Pharynx with posterior bulb , often with swelling that is anterior to the nerve ring.
  • No caudal glands.
  • Small pockets of amphids.
  • Examples: Rhabditis, Diploscapter, Diplogaster.

Order 9. Rhabdiasoidea

  • Nematodes that are smooth and have a distinct Pharyngeal bulb.
  • Hermaphroditesare also involved in pathogenesis.
  • Animals with parasitic stages.
  • Free-living stages could change into males or females.
  • Examples: Rhabdias, Entomelas.

Order 10. Oxyuroidea

  • Valvulated pharynx, with posterior bulb.
  • Females with long, pointed tail; the terminal part of the female system are often very muscularized.
  • Male with one or two equal spikes.
  • In general, there are caudal alae form the cuticular brusa.
  • Examples: Oxyuris or Enterobius.

Order 11. Ascaroidea

  • The mouth is surrounded by three prominent lips.
  • Pharynx with no posterior bulb, or as at present, it’s not valved.
  • Pharynx, intestine or both, often together with caeca.
  • There is no buccal capsule.
  • Female tail that is blunt Male without caudal alae , and has two similar or almost similar spicules.
  • Examples: Ascaris.

Order 12. Strongyloidea

  • Lips without noticeable lips, typically with a leaf crown.
  • Pharynx sans bulb.
  • Females typically have an ovijector.
  • Male with copulatory brusa , supported by muscular rays. Most commonly 13 in total.
  • Examples: Strongylus, Necator, Ancylostoma.

Order 13. Spiruroidea

  • The mouth usually has two the lateral lips, but sometimes there are smaller ones of 4 or 6.
  • Pharynx with no bulb. It is anteriorly muscled in the posterior glandular.
  • Males with no brays; spikes that are different and unrelated.
  • Examples: Oxyspirura, Rictularia, Thelazia.

Order 14. Dracunculoidea

  • With no distinct lips or buccal capsules with cuticularized buccal caps.
  • Pharynx sans bulb, anteriorly muscled as well as posteriorly glandular.
  • The vulva isn’t functional normally located near or behind the middle of the body.
  • Males with identical filiform spicules, brusa seeking.
  • Examples: Dracunculus, Philometra, Micropleura.

Order 15. Filarioidea

  • A worm that is filiform, but without lips.
  • Small buccal capsules, or basic buccal capsules.
  • The pharynx has a muscular anterior as well as posteriorly glandular.
  • Pharyngeal bulb is absent.
  • Females have a Vulva anterior.
  • Brusa lacking, spicules indistinguishable and different.
  • Examples: Wuchereria, Loa loa.

Order 16. Trichuroidea or Trichinelloidea

  • The body is filiform in the front.
  • Lips and mouth without lips.
  • Slender pharynx.
  • Included in the cirrus the spicule is present only.
  • Examples: Trichinella, Trichuris.

Order 17. Dioctophymoidea

  • Medium to very long-sized.
  • Lips without lips are It is surrounded by 6,12 or papillae.
  • A pharynx with a bulb that is not long.
  • Male who has muscular brusa, but with no Rays.
  • Examples: Dictyophyme, Hystrichis,,

Class 2. Nematomorpha or Gordiacea (Gr., nema=thread+ morphe= shape)

  • Hairworm, which is that is found in freshwater. One genus (Nectonema) marine.
  • The body is thin, long, and circular.
  • Body wall is covered in a large papillae and a thick cuticle.
  • Epidermis cellular, single-layered.
  • In the digestive tract, it is fully developed in the larva, but it degrades in adults who do not feed. Cloaca present.
  • Pseudocoel typically consists of parenchyma.
  • No respiratory, circulatory, or excretory system.
  • Nervous system consisting of an encircenteric nerve ring as well as the midventral cord of nerve.
  • Gonads and gonoducts in a pair. Oviducts also extend into Cloaca.
  • Juveniles are parasites in grasshoppers crickets and other insects.
  • Examples: Gordius, Paragordius, Nectonema.

Order 1. Cordioidea

  • Bristles for swimming are wanted.
  • Pseudocoel is a plethora of parenchyma.
  • Paired gonads.
  • Examples: Paragordius, Gordius

Order 2. Nectonematoidea

  • Bristles for swimming are arranged in two rows.
  • Unfilled pseudocoel.
  • There’s only one way to go.
  • Marine form.
  • Examples: Nectonema.

Class 3. Rotifera (L., rota= wheel + ferre= to bear)

  • Microscopic creatures found in lakes, ponds and streams. Rarely found in oceans, they are known as wheel bearers.
  • The body wall is thickened to stiff plates or lorica the head.
  • Anterior part with corona ciliated (wheel organ) that is used to provide food and for locomotion.
  • Post-anal foot with Toes as well as adhesive glands to attach the foot.
  • The body’s musculature comprises transverse and longitudinal muscle bands as well as strands and.
  • The digestive system that has an organ for grinding, called mastax, which is lined inside with a cuticle that is strong.
  • The excretory system consists of two protonephridia as well as two Protonephridial tubes, which are empty into bladders.
  • The nervous system comprises three major ganglia as well as nerves.
  • Eyespots and antennae of the sensory organs.
  • Males are less slender than females. Parthenogenesis is a common phenomenon.
  • Female oviparous, with no larval stages.
  • Examples: Philodina, Asplanchna, Rotarian.

Order 1. Seisonacea

  • Long neck and body. neck.
  • Corona is tiny.
  • Paired ads.
  • They are found as the result of a combination of crustaceans and commensals.
  • Examples: Seison.

Order 2. Budelloidea

  • Corona usually has two trochal discs.
  • Two pedal glands are more than.
  • Female with germovitellaria in pairs.
  • The swimming or the creeping forms.
  • Examples: Rotaria or Rotifera, Philodina, Mniobia.

Order 3. Monogonontea

  • Sessile or swimming forms.
  • Small males or degenerate.
  • Males usually have one testis.
  • Female posses single germovitellaria.
  • Examples: Mytilina, Limnias.

Class 4. Gastrotricha (L., gaster= stomach + trichos= hair)

  • Microscopic, freshwater or marine.
  • The body wall is covered with cuticle-bearing cuticle-bearing short and curved dorsal spines.
  • Corona absence of cilia on ventral surface to aid in movement.
  • Posterior side forked and equipped with glands and adhesive tubes to hold attachments.
  • The body musculature comprises six pairs of muscles that run longitudinally.
  • Mouth, surrounded by bristles.
  • The pharynx is triradiate as well as muscular.
  • The excretory system that includes two protonephridia.
  • The nervous system has a two lateral nerves.
  • Dioecious or Monoecious Parthenogenetic females are common.
  • Development direct. Adults and young are alike.
  • Examples: Chaetonotus, Macrodasys.

Order 1. Macrodasyoidea

  • Marine Forms of worms.
  • Many tubes of adhesive.
  • No protonephridia.
  • Examples: Macrodasys.

Order 2. Chaetonotoidea

  • Most freshwater forms are that are found on plants.
  • Adhesive tubes attached to the tail.
  • A pair of prototonephridia.
  • Reproduction via parthenogenesis.
  • Examples: Chaetonotus, Neodesys.

Class 5. Kinorhyncha (Gr., kineo=more + rhynchos= beak)

  • Marine, microscopic, worm-like.
  • Superficial division of the body in 13 and 14 overlaid bands (Zonites).
  • Body surface with a spiny cuticle, however no cilia.
  • Protruding head or mouth cone as well as covered in scalids.
  • A pair of tubes that are adhesive located in the front portion of the surface ventral.
  • Pseudocoel with amoebocytes in the fluid.
  • A nerve ring that has ventral cords and one ganglion per Zonite. Eyespots are present in certain.
  • The digestive system is complete with salivary glands.
  • Gonads form tubular sacs.
  • Penial spicules are common in males.
  • Fertilization internal. Metamorphosis that includes several larval stages.
  • The development involves a number of developmental stages.
  • Examples: Echinoderes, Pycnophyes.

Order 1. Homalorhagida

  • Neck and head are both protruding.
  • Examples: Trachydemus.

Order 2. Cyclorhagida

  • The only head ring on the market is protruding.
  • Examples: Echinoderes.

Aschelminthes Examples

The most common examples of aschelminth include RoundwormThe most common examples of aschelminth are: Roundworm Ascaris lumbricoides Hookwormand Hookworm Ancylostoma the filarial worm Wuchereria, Pinworm- Enterobius vermicularis and whipworm Trichuris trichiura, etc.

 Aschelminthes Diseases

They are believed to cause various illnesses in animals, plants, and humans. A few of these diseases include:

  • Ascariasis: Ascariasis occurs due to Ascaris lumbricoides, a human disease. It is very prevalent in children. It can cause diarrhea, abdominal discomfort and vomiting.
  • Ancylostomiasis: Ancylostomiasis is due to hookworm infestation within the small intestinal tract. It can cause anaemia. Many intestinal worms are responsible for the. They are stuck in the intestinal wall and draw blood, causing anaemia.
  • Filariasis: It’s caused by roundworms. The cause of lymphatic filariasis is due to Wuchereria bancrofti Brugia Timori, and Brugia malayi. It causes the thickening of skin and the tissues under the skin. Loa loa causes subcutaneous filariasis. It is a skin infection that affects the eyes.
  • Enterobiasis: Enterobiasis is caused by pinworms Enterobius vermicularis. It causes itching of the anal area , and can cause sleep discomfort.
  • Other illnesses that can affect the human body are trichinosis, strongyloidiasis and many more.

There are a variety of nematodes that cause a variety of plant diseases, including the root-knot, root lesion, cyst burrowing, etc. They can harm crops in agriculture. Bacillus Thuringiensis (Bt) produces insecticide protein (Cry and Cyt toxicants) and is efficient against nematodes as well.

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