What is the Difference Between Parapodia and Setae

Parapodia and setae are two locomotive organs in the annelids. Parapodia and setae are also protrusions that are extended from the body. They are external structures in the segmented body of the annelids and help in the movement.

The key difference between parapodia and setae is their structure. Parapodia are fleshy outgrowths in the segmented body of annelids, while setae are stiff bristles in the segmented body of annelids.

CONTENTS

1. Overview and Key Difference
2. What are Parapodia  
3. What are Setae
4. Similarities – Parapodia and Setae
5. Parapodia vs Setae in Tabular Form
6. Summary – Parapodia vs Setae
7. FAQ – Parapodia and Setae

What are Parapodia?

Parapodia are the locomotory organs of the annelids. They are found in segmented marine worms such as Nereis virens. Parapodia are highly vascular and found in the lateral side of the trunk segments of the body. They are also fattened flap-like hollow structures and are filled with coelom.

Figure 01: Parapodia

Furthermore, the functions of the parapodia may include assisting in crawling and swimming, facilitating respiration, and serving as a site for the excretory pore called nephridiopore, through which waste is removed from the body.

What are Setae?

Setae are movable bristle like structures that look like hair and are found in the annelids. Setae, especially in invertebrates like earthworms, help to attach to the surface and prevent backsliding during peristaltic motion. Setae of earthworms are largely composed of chitin. They are also classified based on the limb to which they are attached; for example, notosetae are attached to notopodia while neurosetae are attached to neuropodia.

Figure 02: Microview of Setae

Setae are secreted from the distal ends of parapodia. Furthermore, the functions of the setae may include movement, defense, and, in some, filter feeding.

Similarities Between Parapodia and Setae

• Parapodia and setae are two locomotory organs in the annelids.
• Both are two external structures that occur in annelids.
• They are essential in locomotion.
• Both are important in digging.

Difference Between Parapodia and Setae

Definition

1. Parapodia are fleshy outgrowths or paired bristle-bearing appendages in annelids.
2. Setae are stiff, bristle-like structures in annelids that resemble hair.

Found in

1. Parapodia are found in tapeworms.
2. Setae are found in earthworms.

Significance

1. Parapodia are lateral extensions filled with coelom and supported by chitin.
2. Setae are movable bristles composed of chitin secreted from the distal ends of parapodia.

Function

1. Parapodia help in movement, crawling, swimming, and excretion.
2. Setae help in movement, defense, and feeding.

The following table summarizes the difference between parapodia and setae.

Summary – Parapodia vs Setae

Annelids are segmented worms with over 22,000 species, including ragworms, earthworms, and leeches. The locomotion of annelids is achieved by segmented and bristle-like structures. Parapodia and setae are two locomotory organs found in the annelids. Parapodia are fleshy outgrowths or muscular bristle-bearing appendages in the segmented body, while setae are stiff bristles or hair-like structures in the segmented body. This is the key difference between parapodia and setae.

FAQ: Parapodia and Setae

1. Who have parapodia?

• Parapodia is present in animals that come under the class of Polychaeta in the phylum Annelida. These animals include sandworms, tube worms, and clam worms. Parapodia help in their locomotion.

2. What is parapodia and its function?

• Parapodia are fleshy lateral outgrowths from the body of invertebrates such as annelids. One example is Nereis virens. Parapodia help in locomotion, crawling, swimming and respiration.

3. What animals have setae?

• Annelids have setae. Setae are located on paddle-like appendages called parapodia. Annelids also have parapodia. Generally, setae are secreted from the distal ends of parapodia.

4. Do leeches possess setae?

• Leeches do not possess setae. Leeches normally have a small sucker at the anterior end and a large sucker at the posterior end. They also have clitellum in the mid-region of the body.

5. What are the functions of parapodia and setae?

• Parapodia aid in crawling, swimming, respiration, and digging, whereas setae aid in movement, defense, filter feeding, holding on to the surface, and digging.

Reference:

1. “Seta – an Overview.” ScienceDirect Topics.
2. “Parapodium.” Encyclopædia Britannica, Encyclopædia Britannica, inc.

Image Courtesy:

1. “Aphroditiformia–parapodia” By Caladusp – Own work (CC BY-SA 4.0) via Commons Wikimedia

2. “Micro view of CNTs synthetic setae” (CC BY-SA 3.0) via Commons Wikimedia

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