In arachnids, the abdomen is the second of two body regions. How many body regions do arachnids have?

In arachnids, the abdomen is the second of two body regions. How many body regions do arachnids have?

• A. Two
• B. Three
• C. Four
• D. Five

Answer: (A)

Arachnids have two main body regions: the front region called the prosoma (also known as the cephalothorax), which bears the eyes and legs, and the rear region called the opisthosoma (the abdomen). Since the abdomen is the second of these two regions, the total number of body regions is two. This fused front region contrasts with insects, which have three distinct regions (head, thorax, abdomen) because their head and thorax remain separate. So, the body plan of arachnids includes two regions in total.

Arachnids have two main body regions: the front region called the prosoma (also known as the cephalothorax), which bears the eyes and legs, and the rear region called the opisthosoma (the abdomen). Since the abdomen is the second of these two regions, the total number of body regions is two. This fused front region contrasts with insects, which have three distinct regions (head, thorax, abdomen) because their head and thorax remain separate. So, the body plan of arachnids includes two regions in total.