The excretory system of an earthworm, like that of many other organisms, plays a crucial role in maintaining the internal balance of fluids and eliminating metabolic waste products. Earthworms are segmented worms belonging to the phylum Annelida, and their excretory system is relatively simple yet effective for their needs.
**Components of the Earthworm Excretory System:**
1. **Nephridia:** The primary excretory organs in earthworms are called nephridia (singular: nephridium). Earthworms have numerous nephridia distributed throughout their body segments. These structures resemble small, coiled tubes or tubules.
**Function of Nephridia:**
- **Filtration:** Nephridia filter the coelomic fluid, which is the fluid filling the body cavity of the earthworm. This fluid contains waste products like metabolic nitrogenous waste (ammonia and urea) and excess water.
- **Reabsorption:** Useful substances such as ions and glucose are reabsorbed from the coelomic fluid back into the bloodstream.
- **Secretion:** Nephridia also actively secrete substances, helping to regulate the composition of the coelomic fluid.
**Excretory Process in Earthworms:**
The excretory process in earthworms can be summarized as follows:
1. **Filtration:** Coelomic fluid enters the nephridium through a ciliated funnel-like structure called the nephrostome.
2. **Tubular Transport:** The fluid then moves through the tubular structure of the nephridium, where filtration, reabsorption, and secretion take place.
3. **Waste Elimination:** The waste products, including ammonia and urea, are transported out of the nephridium and are expelled from the earthworm's body through small openings called nephridiopores on the body surface. These nephridiopores are present on most segments of the earthworm, except the first few anterior segments.
**Adaptations for Terrestrial Life:**
Earthworms have evolved this excretory system as an adaptation to their terrestrial (land-dwelling) lifestyle. The excretion of nitrogenous waste as ammonia and its conversion to less toxic forms like urea is essential for conserving water in terrestrial environments.
**Importance of the Earthworm Excretory System:**
The excretory system of earthworms is vital for maintaining the internal environment of the worm, removing waste products, and regulating the composition of body fluids. This system contributes to the overall health and survival of the earthworm, allowing it to thrive in its habitat.
In summary, the excretory system of earthworms, based on nephridia, plays a critical role in maintaining the internal balance of fluids, eliminating waste products, and adapting to a terrestrial lifestyle. This system is an excellent example of how different organisms have evolved specialized mechanisms to handle excretion and osmoregulation in their unique environments.
1. POWERPOINT PRESENTATION ON
“EARTHWORM"
Presented By:-
Abu Md. Zakariya
Class:-BSC 2nd Sem (Zoology Hons.)
Roll no:- 23
Guided By:-
Dr.Sweety Nath Barbhuiya
Asst. Professor
Department of zoology
4. •The nephridia are the excretory organ of earthworm.
•Nephridia are analogous to kidneys of vertebrates.
•Nephridia are present in all segment except in first 3
segments.
•In earthworm, the nephridia functions for the removal of
excretory wastes both from blood and coelomic fluid.
•There are 3 types of nephridia based on the structure and
location:-
1. Septal nephridia.
2. Integumantary nephridia.
3. Pharyngeal naphridia.
What is Nephridia?
Types of Nephridia
5. SEPTAL NEPHRIDIA
•Septal nephridia are the longest nephridia.
•They are located in both sides of septum in each segment,behind the 15th to 2nd
last segment.
•Each inter-segmental septum possess two rows of septal nephridia numbering
80-100 on each septum.
•Septal nephridia opens into intestine.
Functions:-
Septal nephridia discharge the waste products through canal and ducts
into the lumen of the intestine.
6. INTEGUMANTARY NEPHRIDIA
•These are smallest nephridia.
•These are ‘V’ shaped in structure and are the most numerous types of
nephridia.
•Integumantary nephridia are scattered in the body wall in all segments
except in the first 2 segments and last segments.
•In each segment,there are about 200-250 integumantary nephridia.
•However,in the clitellar segments,the number is 10 times more than in
ordinary segments.
•Hence,clitellar region is also termed as the forest of nephridia.
Functions:-
They discharge nitrogenous metabolic waste products directly outside
from the body through nephridiopores.
7. PHARYNGEAL NEPHRIDIA
•They are found as paired and lie one pair in each of the 4th,5th and 6th
segment.
•They have 3 pair of nephridial canal/duct.
•The duct arise from 6th segment which opens into buccal cavity in 2nd
segment,the ducts of 4th & 5th segments opens into the pharynx in 4th
segment.
•Function:-
They discharge the waste products directly into the buccal cavity and
pharynx from where these are passe outside with undigested food through
the anus.
