the th segment is called the sub-pharyngeal ganglion (Figure. . ). The brain and the sub - pharyngeal ganglia are connected by a pair of circum-pharyngeal connectives.
They run one on each side of the pharynx. Thus a nerve ring is formed around the anterior region of the alimentary canal. The double ventral nerve cord runs backward from the sub - pharyngeal ganglion. The brain along with other nerves in the ring integrates sensory inputs and command muscular responses of the body.
The earthworm’s receptors are stimulated by a group of slender columnar cells connected with nerves. The Photoreceptors (sense of light) are found on the dorsal surface of the body. Gustatory (sense of taste) and olfactory receptors (sense of smell) are found in the buccal cavity . Tactile receptors (sense of touch), chemoreceptors (detect chemical changes) and thermoreceptors (changes in temperature) are present in the prostomium and the body wall.
How do the earthworm’s sense activity in their habitat without eyes, ears or a nose? Excretory System Excretion is the process of elimination of metabolic waste products from the body. In earthworm, excretion is effected by segmentally arranged, minute coiled, paired tubules called nephridia. There are three Figure .
Lampito mauritii – Types of Nephridia 3KDU\QJHDO QHSKULGLD 0LFURQHSKULGLD 0HJDQHSKULGLXP 3KDU\QJHDOQHSKULGLXP 0LFURQHSKULGLXP 0HJDQHSKULGLXP XI Std Biology-Zoology Chapter- types of nephridia; (i) pharyngeal or tufted nephridia – present as paired tufts in the th - th segments (ii) Micronephridia or Integumentary nephridia – attached to the lining of the body wall from the14 th segment to the last which open on the body surface (iii) Meganephridia or septal nephridia – present as pair on both sides of intersegmental septa of the th segment to the last and open into intestine (Figure . ). The meganephridium has an internal funnel like opening called the nephrostome, which is fully ciliated . The nephrostome is in the preceding segment and the rest of the tube is in the succeeding segment.
This tube consists of three distinct divisions, the ciliated, the glandular and the muscular region. The waste