Difference Between Biramous and Uniramous Arthropods

The key difference between biramous and uniramous arthropods is that biramous arthropods have limbs with two branches, each having a series of segments attached end to end, while uniramous arthropods have limbs with a single series of segments attached end-to-end.

Phylum Arthropoda belongs to Kingdom Animalia. It is the phylum that consists of the highest number of species and the highest number of individuals, including insects. Arthropods have an exoskeleton, segmented bodies and paired joined appendages. Arthropod’s appendages, especially jointed limbs, can be either biramous or uniramous. There is a series of segments attached end to end in the uniramous limb. In contrast, in biramous limbs, there are two branches, each having a series of segments attached end to end. Insects and myriapods have uniramous legs while crustaceans have biramous legs.

CONTENTS

1. Overview and Key Difference
2. What are Biramous Arthropods
3. What are Uniramous Arthropods
4. Similarities Between Biramous and Uniramous Arthropods
5. Side by Side Comparison – Biramous vs Uniramous Arthropods in Tabular Form
6. Summary

What are Biramous Arthropods?

Biramous limbs are the arthropod limbs/legs that have two branches. In each branch, a series of segments are attached end to end. Crustacean limbs are biramous. Therefore, they have two branches in their legs. They are named as exopod and endopod.

Exopod is the external branch or the ramus. Endopod is the internal branch. In addition, their second antennae are also biramous. Endopod is generally used for walking or modified for grasping, chewing, or reproduction. On the other hand, the exopod is often a flattened gill.

What are Uniramous Arthropods?

Uniramous limbs are not branched. They consist of a series of segments joined end to end without branching. The legs of insects, myriapods and hexapods are uniramous. Therefore, their legs are not branched into two, like in biramous. The nature of uniramous limbs is a shared characteristic. Hence, it is used to group uniramous arthropods into one taxon called uniramia.

Moreover, it is believed that several groups of arthropods evolved uniramous limbs from ancestors with biramous limbs by the loss of exopods.

What are the Similarities Between Biramous and Uniramous Arthropods?

• Biramous and uniramous are two types of arthropod jointed limbs based on the branching or the absence of it.
• Both types of appendages have a series of segments attached end to end.
• These types of limbs are useful for arthropods for walking and other purposes.

What is the Difference Between Biramous and Uniramous Arthropods?

Biramous arthropods are the members of arthropods that have two-branched limbs. On the other hand, uniramous arthropods are the members of arthropods that have unbranched limbs. So, this is the key difference between biramous and uniramous arthropods. Biramous limbs have two branches while uniramous limbs are unbranched. For example, crustaceans have biramous limbs, while insects, myriapods and hexapods have uniramous limbs. Besides, the two branches of biramous limbs are known as exopods and endopods while uniramous limbs do not have two such types.

Below infographic summarizes the difference between biramous and uniramous arthropods.

Summary – Biramous vs Uniramous Arthropods

Arthropods have appendages which are jointed. They can be either biramous or uniramous.  Biramous appendages are branched in two. Each branch consists of a series of segments joined end to end. In contrast, uniramous appendages are not branched. It has a series of segments joined end to end. Generally, crustacean limbs are biramous while insects, myriapods and hexapods limbs are uniramous. Thus, this summarizes the difference between biramous and uniramous.

Reference:

1. “Arthropod Leg.” Wikipedia, Wikimedia Foundation, 15 Nov. 2019, Available here.
2. Carsten, Wolff, et al. “The Clonal Composition of Biramous and Uniramous Arthropod Limbs.” Proceedings of the Royal Society B: Biological Sciences, 5 Feb. 2008, Available here.

Image Courtesy:

1. “Figure 28 04 09” By CNX OpenStax – (CC BY 4.0) via Commons Wikimedia

2. “Scutigera coleoptrata MHNT” By Didier Descouens – Own work (CC BY-SA 4.0) via Commons Wikimedia