The Structure Of The Hermaphroditic Proglottid: Distinctive Features

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The Structure Of The Hermaphroditic Proglottid: Distinctive Features
The Structure Of The Hermaphroditic Proglottid: Distinctive Features
Video: The Structure Of The Hermaphroditic Proglottid: Distinctive Features
Video: PHY103 - Distinctive Features I 2023, February
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The proglottid is represented by separate segments. There are a large number of them. Together with the head, the segments form a body that belongs to the tapeworms. Separate segments are usually called metameres.

Content

  • 1 Education
  • 2 Structure of segments
  • 3 Features of the morphology of proglottids

    • 3.1 Detailed description
    • 3.2 Male reproductive apparatus
    • 3.3 The mature form of the metamer
  • 4 Proglottid difference

Education

A striking representative of tapeworms is tapeworm. Metameres are formed throughout the life cycle of the parasite. This happens near the head. Each subsequent head is slightly larger in size, which distinguishes the latter from the previous one.

The latter are sharply limited from each other. Old proglottids are found at the end of the parasite's body. They can be separated from tapeworms singly or in groups. Each segment has the ability to reproduce independently of the other, since it has both male and female genital organs.

This fact puzzles many biologists. Therefore, it was decided to study them in more detail. Some scientists suggest that proglottids can be considered as separate organisms. In their opinion, the tapeworm is a whole colony of proglottids.

The first segment from the head has a separate digestive system. It is independent of the entire tapeworm. Each subsequent segment is different from the previous one. Gradually, the metameres are stripped of all organs and converted into a container for storing eggs.

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Segment structure

In nature, it is customary for the structure of proglottids to be different. Depending on this, they are distinguished:

  • strobili kraspedotny;
  • akraspedotny type.

The first type involves the imposition of a segment on an adjacent one. Accordingly, the second ability to overlap is deprived. Each segment, as mentioned above, has a digestive system and male and female genital organs. In addition, they also have an excretory system. During the separation of a mature proglottid from a tapeworm, it contains not only eggs, but also embryos.

Features of the morphology of proglottids

Upon reaching puberty, the length of the segment ranges from 3 to 5 mm. The head has suction cups and one proboscis. There are hooks on it, which are evenly distributed in two rows. The neck is short and almost invisible.

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The shape of the proglottid is rectangular, but more expanded, so it looks like a square. On one side and on the other side of the body, there are thin tubes that are responsible for the release of processed substances. They communicate with the transverse canal at the back of each segment. Because of this structure, the excretory system resembles a staircase.

Detailed description

The location of the ovary is the posterior part of the segment. It is formed by narrow branches of brown, dark purple and red shades. In turn, the tubes are collected in lobes. Two of them are larger and move to the sides. The dimensions of the third are smaller, and the lobe is directed forward.

Under the lobes that form the ovary, there is an ootype - a body similar to a circle. The vagina leaves him. It is thin in structure and is located parallel to the ejaculatory canal. Opens into a sex bag.

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Near the ootype in the posterior part of the segment, the vitelline is located, which looks like a thin stretched mesh. A thin pale pink or purple tube is stretched between it and the anterior wall of the proglottid. This is the womb. It has a characteristic branched type, is closed and can store up to 5000 eggs.

Male reproductive apparatus

It looks a little different. Represents the formation of vesicular testes. Their color may vary. From red to purple or dark brown.

The ejaculatory canal is formed by the accumulation of vas deferens. It is almost impossible to notice them. The channel through which the fertilization fluid moves is like a thick spiral. Location - across the segment. Opens into a ledge that represents a genital bag.

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Each strobila has 3 to 4 proglottids. The penultimate one is hermaphrodite. The last segment is a mature proglottid

The mature form of the metamer

The structure has some differences. It resembles a rectangle in shape, as it is elongated in length. If you compare with the hermaphrodite, they immediately note that it is much larger. Like the penultimate one, it has tubes on the sides that remove the processed substances in the process of life.

On one side there is a genital bag. Most of the central space is occupied by the uterus of a mature proglottid. It is characterized by strong branching. There are 7 to 12 branches. It is red, purple or brown.

A mature proglottid cannot be in the same place. It comes off the end of the strobe. The next metamer will soon take her place. Mature segments do not come off one by one. As a rule, no more than 6 pieces leave the strobila at once.

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The tapeworm soon becomes sexually mature. Like most parasites, it has a hermaphroditic reproductive system. This is their main danger to living organisms. Since they do not require another sexually mature individual for reproduction.

Difference Proglottids

The hermaphroditic proglottid has a different structure. This is influenced by the type of tapeworm. Features:

  1. Bovine tapeworm hermaphroditic proglottid is larger than pork tapeworm. The sizes do not differ much, but an experienced scientist will pay attention to this and correctly determine the type of segment.
  2. The internal structure is the same.
  3. The ovary of the bovine tapeworm consists of two lobes. The absence of a third, additional lobe, indicates that a pork tapeworm is in front of a person.
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The hermaphroditic proglottid of bovine and pork tapeworms practically do not differ in anything, with the exception of one detail, which is the segment. Despite the absence of an additional lobe, the parasite continues to multiply. This feature was formed during evolution and continues to remain in this form to this day.

Scientists have long studied the structure of the hermaphroditic proglottid. But they still do not stop researching the parasites. These little creatures not only have an interesting segment structure, but also an amazing life cycle. They are absolutely unique in their kind and unlike other living beings.

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