What is the Difference Between Nephridia and Malpighian Tubules

The main difference between nephridia and malpighian tubules is that the nephridia are the excretory organs of worms, producing urine whereas malpighian tubules are the excretory organs of insects, producing uric acid. Furthermore, nephridia occur in the body cavity while Malpighian tubules line the gut. 

Nephridia and malpighian tubules are two types of excretory organs that help in the removal of wastes from the body of different multicellular organisms. They are also involved in osmoregulation. 

Key Areas Covered 

1. What are Nephridia
     – Definition, Types, Structure, Mechanism
2. What are Malpighian Tubules
     – Definition, Structure, Mechanism
3. What are the Similarities Between Nephridia and Malpighian Tubules
     – Outline of Common Features
4. What is the Difference Between Nephridia and Malpighian Tubules
     – Comparison of Key Differences

Key Terms 

Excretory Organs, Malpighian Tubules (MT), Metanephridia, Nephridia, Protonephridia, Worms 

What are Nephridia 

Nephridia are excretory organs of annelids. They are mainly responsible for the removal of wastes from the body cavity to the aquatic exterior. Moreover, there are two main forms of nephridia among worms based on organization. They are protonephridia and metanephridia. Protonephridia are the more primitive form of nephridia found in flatworms, ribbon worms, and rotifers. The most significant feature of protonephridia is that they are scattered among the other cells of the body. In addition, protonephridium consists of a hollow cell called the flame cell. This cell is inside the body cavity, and it opens to the exterior by a duct. Moreover, the body fluid moves into the flame cell and the cilia or flagella inside the cell filters the body fluid to produce urine. 

Figure 1: Flame Cells and Nephridia

Furthermore, metanephridia are a more complex form of nephridia which occurs in segmented worms or annelids. They usually occur in pairs. However, metanephridia are simply a tubule, and they do not contain a flame cell. The cilia lining inside the tubule is responsible for drawing up the body fluid and conduct them to the exterior.  

What are Malpighian Tubules 

Malpighian tubules (MTs) are the excretory organs of insects. They line the gut of insects. Generally, malpighian tubules occur in pairs and number of pairs depends on the species. The convoluted nature of the malpighian tubules increases the surface area. The microvilli lining of these tubules maintains the osmotic balance while aiding reabsorption. Especially, the mechanism by which the malpighian tubules produce urine is the tubular secretion. Therefore, metabolic wastes diffuse into the tubules. Also, malpighian tubules excrete into the alimentary canal of insects. 

Figure 2: Malpighian Tubules in Bees

Similarities Between Nephridia and Malpighian Tubules 

• Nephridia and Malpighian tubules are two types of excretory organs of multicellular animals. 
• They aid in the osmoregulation. 
• Also, the evolution of both nephridia and malpighian tubules encourages tissue specialization to eliminate wastes through a specialized system. 

Difference Between Nephridia and Malpighian Tubules 

Definition 

Nephridia refer to the tubules open to the exterior which act as an organ of excretion or osmoregulation. They typically have ciliated or flagellated cells and absorptive walls. In contrast, malpighian tubules refer to the tubular excretory organs, numbers of which open into the gut in insects and some other arthropods. 

Occurrence 

Moreover, the main difference between nephridia and malpighian tubules is that the nephridia occur in worms while malpighian tubules occur in insects. 

Structure 

Furthermore, their relevant structure is also an important difference between nephridia and malpighian tubules. That is; nephridia consist of flame cells and tubules while malpighian tubules are convoluted.  

Occurrence in the Body 

Another difference between nephridia and malpighian tubules is that the nephridia occur in pairs while malpighian tubules occur as a tuft. 

Mechanism 

There is also a difference between nephridia and malpighian tubules in their mechanism. Nephridia filter body fluid to produce urine while malpighian tubules use a tubular secretion mechanism to produce urine. 

Product 

In addition, nephridia produce urine while malpighian tubules produce uric acid. 

Excrete into

Another difference between nephridia and malpighian tubules is that the nephridia usually excrete into the aquatic exterior while malpighian tubules excrete into a terrestrial exterior. 

Conclusion 

Nephridia are excretory organs of the worms. They produce urine by filtering the body fluids. On the other hand, malpighian tubules are the excretory organs of insects. They produce uric acid by a tubular secretion mechanism. Therefore, the main difference between nephridia and malpighian tubules is their occurrence and mechanism of excretion.

Reference:

1. “Excretion Systems.” Boundless Biology, Lumen Learning, Available Here

Image Courtesy:

1. “Flame Cells of Planaria and Nephridia of Worms” By Openstax College (CC BY 3.0.) via Openstax CNX
2. “Malpighian Tubules of Insects” By Openstax College (CC BY 3.0.) via Openstax CNX