Question

In Pheretima, septa are absent between which segments?
A) 3/4 and 9/10
B) 4/5 and 8/9
C) 5/6 and 7/8
D) 7/8 and 6/7

Answer 1

Hint: The genus Pheretima consists of earthworms mostly found in soils. Septa is known as division. When an organism’s body is divided into parts, it is said to be a separate body.

Complete answer: Earthworms belong to the phylum Annelida and are known as burrowers. They are mostly seen in rainy seasons in sandy areas. They usually come out of burrows at night time for the search of food. They have dark brown colour due to the presence of porphyrin pigment that protects the body of earthworms from bright light. Their dorsal surface has a blood vessel running along the length of the body and the ventral side of the body has the presence of genital opening. They are elongated, cylindrical, and narrow in shape. They have a bilaterally symmetrical body with tapering ends. Their body is segmented i.e. it is divided into almost 100 to 120 small ring-like segments. It is known as true segmentation, i.e. the division is not just external, but the internal body of the earthworm is also segmented by membranous divisions called septa. Septa can be a wall or anything that can divide anybody into smaller parts. In Pheretima, i.e. earthworms, septa are present all over the body except between the first four segments and between 9 and 10 segments.
Hence, the correct answer is option A.

Note: The segments present on the interior body of the earthworm are done by intersegmental septa or coelosepta. Even though the whole body of the earthworm is segmented, not all segments are alike, i.e. the first and last segments are different compared to the rest of the segments.