Morphology of Earthworm Questions in English

(N/A) $\Rightarrow$ Earthworm is a reddish-brown terrestrial invertebrate.
$\Rightarrow$ It inhabits the upper layer of moist soil.
$\Rightarrow$ During the daytime,they live in burrows made by boring and swallowing the soil.
$\Rightarrow$ In gardens,they can be traced by their faecal deposits known as worm castings.
$\Rightarrow$ The common Indian earthworms are $Pheretima$ and $Lumbricus$.
$\Rightarrow$ The earthworm is a coelomate animal belonging to the phylum $Annelida$.
$\Rightarrow$ Earthworms have a long,cylindrical body.
$\Rightarrow$ The body is divided into $100-120$ short segments. Its length is approximately $15 \ cm$.
$\Rightarrow$ The dorsal surface of the body is marked by a dark median mid-dorsal line (dorsal blood vessel) along the longitudinal axis.
$\Rightarrow$ The anterior end consists of the mouth and the prostomium.
$\Rightarrow$ The prostomium is a lobe which serves as a covering for the mouth and as a wedge to force open cracks in the soil.
$\Rightarrow$ The first body segment is called the peristomium.
$\Rightarrow$ The body has no specific head. The mouth is semilunar in shape,and the anus is at the posterior end.
$\Rightarrow$ In a mature worm,segments $14-16$ are covered by a prominent dark band of glandular tissue called the clitellum.
$\Rightarrow$ The body is divisible into three regions: preclitellar,clitellar,and postclitellar segments.
$\Rightarrow$ The ventral surface is distinguished by the presence of genital openings.
$\Rightarrow$ Four pairs of spermathecal apertures are situated on the ventro-lateral sides of the intersegmental grooves,i.e.,between segments $5-9$.
$\Rightarrow$ $A$ single female genital pore is present in the mid-ventral line of the $14^{th}$ segment.
$\Rightarrow$ $A$ pair of male genital pores are present on the ventrolateral sides of the $18^{th}$ segment.
$\Rightarrow$ Genital papillae are located on the ventrolateral sides in the $17^{th}$ and $19^{th}$ segments.
$\Rightarrow$ Numerous minute pores called nephridiopores open on the surface of the body.
$\Rightarrow$ In each body segment,except the first,last,and clitellum,there are rows of $S$-shaped setae,embedded in epidermal pits.
$\Rightarrow$ Setae are helpful in obtaining a grip in the soil and play an important role in locomotion.

(A) The body of an earthworm $(Pheretima \, posthuma)$ can be distinguished into dorsal and ventral surfaces based on specific morphological features:
$1$. The dorsal surface is characterized by the presence of a dark median mid-dorsal line, which represents the dorsal blood vessel visible through the skin.
$2$. The ventral surface is characterized by the presence of genital openings, such as the female genital pore, male genital pores, and genital papillae, which are absent on the dorsal side.
Therefore, option $A$ is the correct answer.

(D) In earthworms,each body segment (except the first,the last,and the clitellar segment) bears a ring of tiny,curved,chitinous structures known as setae. Setae play an important role in locomotion and copulation.

(B) In the ventral view of the earthworm $(Pheretima \ posthuma)$,the spermathecal pores are located in the intersegmental grooves of segments $5/6, 6/7, 7/8$,and $8/9$.
$P$ points to the spermathecal pores.
The female genital pore is a single median pore located on the $14^{th}$ segment.
The male genital pores are a pair of ventro-lateral pores located on the $18^{th}$ segment.
In the provided diagram,$Q$ represents the female genital pore located on the $14^{th}$ segment.
Therefore,$P$ represents spermathecal pores and $Q$ represents the female genital pore.

(C) The image shows the anterior end of an earthworm,specifically highlighting the intersegmental grooves (labeled as $P$).
In earthworms,the body is divided into segments called metameres.
The intersegmental grooves are present between all segments except the first and last segments,and the clitellar region ($14^{th}-16^{th}$ segments).
Therefore,the correct option is $C$.