How many varieties of worms live next to people today, and each type has its own purpose. Some are harmless, swarming in seaweed and coastal silt. Others are parasitizing and invading the body of humans and animals. The former are food for birds and fish, while the latter themselves eat the tissues of living organisms. It depends on the habitat and the structure of their body cavity.
Helminthology and nematodology are sciences that study worms and their life processes: from egg laying and larvae to the formation of adults. The digestive system of nematodes is complex and varied. And today we will focus on this question: do roundworms have a body cavity, and which one?
Types of worms and the structure of their body cavity
When studying worms, you need to pay attention to other types, so that you have something to compare the class of round ones with and know at least approximately their structure. In the process of clarifying the question of whether there is a body cavity in roundworms, consider briefly the crawling family:
- Flatworms have three cell layers: outer (ectoderm), inner (endoderm) and middle (mesoderm). They generally do not have a body cavity as such, and the internal space is filled with parenchyma, due to which food enters, digests and exits. There is no digestive system, or it is complexly branched without intestines.
- Annelled worms have a coelom (secondary body cavity), in the epithelial layer of which there are partitions that separate the segments. These walls divide the cavity and protect the body from external factors. The digestive system is end-to-end with the initial, intermediate and anal intestines.
- Roundworms have a schisocoel (primary body cavity). Digestive system through, without partitions, with intestines and anal outlet. Most of the worms reproduce by an internal algorithm, and individual individuals are fertilized in parthenogenesis by an independent way.
All inhabitants have one common affiliation - a skin-muscular sac, which brings them closer and classifies them as one genus. Having determined whether roundworms have a body cavity, the types and structure of its structure, let's move on to a detailed study of the individuals in question and their digestive scheme.
Description of the body cavity of roundworms
After getting acquainted with the flat, ring and oval members of the animal world, we will find out more thoroughly about the insides of the last representatives. Primary body cavity of a roundwormalso called a pseudo-goal. She does not have her own epithelial layer, and she looks like a through hole between the muscle mass and the common intestine. All major organs and systems are located in this space. Here is the center of the vital activity of the organism and the entire existence of the nematode. The body cavity of a roundworm performs such necessary functions as:
- support and direction of the form;
- muscle formation;
- development of a rigid layer - the cuticle;
- pressurized fluid transmission;
- food accompaniment;
- development of metabolic processes.
We gave a superficial characterization and confirmed in the answer whether roundworms have a body cavity. Yes, primary lithophysis exists, and we'll talk about it in more detail later.
About roundworms in general
Nemathelminths, or nematodes - this is the name of roundworms. Their body is oblong and corpulent, thin and sharp at the ends. Among them stand out:
- gastric;
- rotifers;
- hairy;
- flyers;
- nematodes.
Most of the worms are parasites, and such individuals settle in animals and humans. These are not very pleasant cohabitants who urgently need to be exterminated with the help of the possibilities of modern medicine. Of these, the following are known:
- human roundworm;
- Trichinella;
- whiplash;
- baby pinworm;
- hookworm.
Deepening into the study, we ask the sources: do roundworms have a body cavity?Yes, there is a primary body cavity - we already understand that this is so. But what is its role not only in the development of a boneless creature, but also in the entry of this pest into the human body?
Gastrotricha (Gastrotricha), or Gastrociliary
Now we know where roundworms have their primary inner citadel. The body cavity in gastrotrichous roundworms is not strongly expressed, and half of its area is occupied by parenchyma cells. The gut of the digestive tract runs through three levels:
- front - massive throat;
- medium - glandular;
- rear - anal passage.
The structure of gastrociliary worms is characterized by turbellarians (protonephridia and zones of the ciliary epithelium, hermaphroditism and parenchymal areas in the body cavity), as well as features present in nemathelminths (three intestinal nodes and the primary body cavity). The excretory system consists of two protonephridia. Gastrotricha are fertilized internally. Individuals reproduce in a form of parthenogenesis.
Rotatoria (Rotatoria)
The body cavity of rotifer roundworms is highly structured. The digestive system of this species contains:
- mouth and throat;
- mastax - chewing stomach;
- medium intestine;
- posterior short intestine;
- anal passage.
The stomach contains a cuticular anvil - jaws with two hammers. The midgut contains two glandsfor digestion. Two protonephridia work in the excretory system, the channels of which are connected with the bladder and the anus. Rotifers deposit seeds through an oviduct attached to a tail gut called the cloaca. For the full life development of the main types of rotatoria, the mixing of parthenogenetic and sexual generations is necessary. Rotifers have great vitality, they are able to form cysts to wait out adverse conditions and resettlement.
Hairies (Nematomorpha)
If you wonder if hairy roundworms have a body cavity, you can say with confidence: yes. Although she is a little different and different from her colleagues. In general structure, they are similar in hypodermis and smooth muscles. But the intestines are almost or completely reshaped. Adult nematomorpha worms practically do not feed. There is also no excretory system. Only the nervous system contains the peripharyngeal ring and the neuro-abdominal trunk attached to it. But the females of this species breed very intensively, laying more than a million eggs into the water through the hindgut.
Acanthocephala
Do roundworms have a body cavity? Immediately I want to note the developed schizocele. This parasite has a powerful structure for sticking to the donor organism:
- proboscis with hooks;
- proboscis retractor, or muscular cord;
- cervical;
- metasome –trunk area;
- thick hypodermis;
- longitudinal and circular muscles;
- pseudocuticle.
There is no digestive scheme. The excretory organs also include a pair of protonephridia. The nervous system has two trunks from the sides and ganglia of the head. The genital area consists of two oviducts and the uterus, vagina and ducts. The giant acanthocephalans macrocanthorhynchus hirudinaceus grow preferably in the intestines of piglets, where they enter with the soil and where they reach their maturity. Some individuals stretch 25 centimeters in length.
Nematoda (Nematoda)
Getting acquainted with the most extensive class - nematodes, we have almost come to know whether roundworms have a body cavity? Oh sure. And nematoda is no exception to the rule. They have a pronounced internal system that lacks a mesodermal lining and is filled with fluid. It also has a digestive branch:
- oral cavity and pharynx;
- esophagus;
- midgut;
- hindgut;
- anal passage.
In the excretory secretion there is a hypodermis, consisting of one or two cells, also called neck glands. Excretory canals and four phagocytic cells pass in the anterior part of the body. The organs of touch (papillae) and chemical perception (amphids) are poorly developed. The female reproductive circuit has two oviducts, the same number of ovaries, and one pair of uterus.
In conclusion about roundworms and more
As we seethe primary cavity in the family of round crawlers is diverse and even somewhat similar to the organs of other inhabitants of the fauna. But worms are worms for that, not only to be a food chain, but also to remain pests for animals and people. Keep in mind that these small invertebrates can destroy the body in a few months of being in it. This applies not only to round pests, but also to flat, ribbon and ring parasites. These are such unexpected, but dangerous stickies, like:
- Flukes - hepatic fasciola (Fasciola hepatica), cat fluke (Opisthorchis felineus), lanceolate fluke (Dicrocoelium lanceatum).
- Tapeworms - tapeworms (Cyclophyllidea), Pseudophyllidea (Pseudophyllidea).
And it doesn't matter whether predators have a body cavity or not, you need to take all measures to combat them and strictly follow the instructions so as not to become infected with larvae. Their entry into the human body occurs through water and raw or poorly processed meat of livestock. And if something bad has already happened, then you should not hesitate: it is important to undergo intensive therapy against the invader. Today, this is done quickly and painlessly by specialized methods.
Let's summarize the reasoning about whether roundworms have a body cavity. Yes or no? Now all doubts disappear by themselves - such a space is a must. It may differ in some criteria, but this is not so important. All such parasites are arranged in almost the same way. And we, people, need to study such an interesting side of the animalpeace.
