How Do Annelids Excrete Waste?
Annelids excrete their nitrogenous waste in the form of ammonia. As ammonia readily diffuses into the water, the majority of this nitrogen is likely to pass through the body wall. Although these capacities are limited, annelid excretory organs are more active in maintaining water and ion balances.
Excretory Organ in Annelids
Nephridia are the excretory organs of annelids as in many invertebrates. Nephridia come in two varieties in annelids. A protonephridium is made up of a tubule that connects to the outside of the body at one end and has a closed bulb at the other. The bulbar end of protonephridia has a tuft of flagella that propels fluid through the tubule. The excretory orifice (opening) of a nephridium is called a nephridiopore.
Excretion in Polychaetes
The majority of polychaetes have metanephridium, a different type of nephridium. A metanephridium has a ciliated open funnel known as a nephrostome. It extends through an anterior septum and into the coelom of a neighbouring segment. A tubule at the other end enters the body through a nephridiopore or, on rare occasions, the intestine. The number of metanephridia per segment is typically one, and the tubules can be heavily coiled, with one section dilated into a bladder. For active ion transport between the blood and the nephridium, a capillary bed is typically connected to a metanephridium tubule.
Chloragogen Cells
Chloragogen cells are yellow cells around the intestine of annelids. They are similar in function to that of a vertebrate liver. The metabolism of amino acids occurs there. Ammonia is converted to urea and amino acids are deaminated by chloragogen tissue. Additionally, it transforms surplus carbohydrates into fat and glycogen, two molecules that store energy.
Functions of Nephridia
- Helps in excreting nitrogenous wastes out of the body.
- Helps in regulating osmotic balance.
- In some cases, they aid in reproduction as they act as gonads.
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