Question

how many types of nephridia occur in pheretima distinguish them ​

Answer 1

Answer:

Types of Nephridia

According to their position in the body, they are of 3 types:

Septal Nephridia/ Typical Nephridia

Pharyngeal Nephridia

Integumentary Nephridia

Septal Nephridia or Typical Nephridia

septal-nephridia

They are well developed and the largest nephridia, and found attached to both sides of each intersegmental septum behind the 15th segment.

Each septum has 40-50 septal nephridia and they are arranged in two rows. So each septum has 80-100 septal nephridia.

It consists of 3 main parts:

a. Nephridiostome: also called Nephrostome.

It is funnel shaped and externally ciliated, opening into the coelomic cavity.

It consists of mouth like opening, which is surrounded by larger upper lip and smaller lower lip.

Upper lip is formed by a large central cell and eight or nine marginal cell, whereas the lower lip is formed of four or five compact cells. The lips have several rows of cilia.

Funnel leads into a short and narrow-ciliated neck, which is continued into the body of the nephridium.

Due to continuous movement of cilia all the nitrogenous substances of the coelomic fluid are absorbed in the nephridium.

b. Body

It is the main tubular part of the nephridia which is coiled around at its axis.

It consists of two parts:

1. Short straight lobe- is one half of the twisted loop.

It is short, straight tube which remains attached to the twisted loop.

2. Long twisted loop with narrow apical lobe.-

The twisted loop consists of proximal and distal limb, which are spirally twisted upon each other.

Proximal limb is attached to neck and terminal duct of the twisted loop, while the distal limb to the straight lobe.

The number of twist varies from 9-13.

c. Terminal duct

It is the end part of the main body.

Only one intracellular canal.

Proximal limb of the body of nephridium ends in a short and narrow duct called terminal duct.

All the terminal ducts of a segment open into septal excretory duct of their side. Septal excretory duct collect the excretory products and transfer them to a pair of supra-intestinal excretory duct.

Nephridial tube

Nephridium consists of a syncytial glandular mass, inside which coiled tubules run that end up in a narrow terminal duct that opens into excretory duct and eventually lead into the intestine through supra intestinal excretory duct. Coiled tubules have four ciliated tract, one in neck, two in body and one in terminal duct. There are four parallel tubules in the straight lobe, 3 in the basal part and two in the apical part of each limb of the twisted loop and a single tubule in each of the neck and terminal duct.

Answer 2

HLO MATE HERE IS UR ANSWER

❤. TYPES OF NEPHRIDIA ❤

❤. PHARYNGEAL NEPHRIDIA ❤

⭐. They are present in 4th ,5th ,6th segments .

⭐. The open into pharynx and buccal cavity (enteronephic) they are closed nephridia because nephuostome is absent.

❤. INTEGUMENTS NEPHRIDIA ❤

⭐. They are present attached inner side of body wall from 3rd segments to the last.

⭐. They open to outside (exonephunic) by nephidiopores.

⭐. They are close type.

❤. SEPTAL NEPHRIDIA ❤

⭐. Attached to both sides of the septa .

⭐. They are open type having nephostome.

⭐. They open into intestine.

⭐. Hence enteronephunic.

⭐. They are present from 15/16 septerm to the last.

⭐. They are distinguished by the location of segments.