EARTH WORM
Scientific name: Pheretima posthuma
Lumbricus
EARTH WORM- MORPHOLOGY
Cylindrical body�100 to 120 metamers /segments �Dorsal median blood vessel�Ventral surface has genital pores�Anterior mouth and prostomium-sensory function�First segment -peristomium
Clitellum-14 to16 segments.�preclitellar,clitellar and post clitellar
Spermathecal opening-5 to 9 segments in intersegmental area�Single median female genital pore-14th segment�Male genital pore-18th segment�Nephridiopore�Setae-S shaped locomotory organ.
ANATOMY�Body wall consists of cuticle,circular and longitudinal muscle,coelomic epithelium.
DIGESTIVE SYSTEM
It is straight tube from first to last segment
Mouth-Segment 1
Buccal cavity –segments 1 to 3
Pharynx- segments 4 to 5
Oesophagus- segments 5 to 7
Gizzard –segments 8 to 9
Stomach- segments 9 to 14
Intestine -segments15 to last
Anus- last segment
DIGESTIVE SYSTEM
It is straight tube from first to last segment
Mouth-Segment 1
Buccal cavity –segments 1 to 3
Pharynx- segments 4 to 5
Oesophagus- segments 5 to 7
Gizzard –segments 8 to 9
Stomach- segments 9 to 14
Intestine -segments15 to last
Anus- last segment
Special features:
Special features:
DIGESTIVE SYSTEM
CIRCULATORY SYSTEM
Closed type
Consists of blood vessels, capillaries, heart and
Blood glands.
Main blood vessels:Dorsal vessal,Ventral vessel,lateral esophageal vessel and sub neural vessel
There are four pair of heart in 7th 9th,12th and 13th segment
Blood glands: produces blood cells and hemoglobin
CIRCULATORY SYSTEM
Closed type
Consists of blood vessels, capillaries, heart and
Blood glands.
Main blood vessels:Dorsal vessal,Ventral vessel,lateral esophageal vessel and sub neural vessel
There are four pair of heart in 7th 9th,12th and 13th segment
Blood glands: produces blood cells and hemoglobin
Special features:
EXCRETORY SYSTEM
Nephridia are the organs of excretion
They are three types
Septal nephridia -15th to last segments, open into intestine
Integumentary nephridia:3rd to last segments,opens through body wall.
Pharyngeal nephridia:Three paired tuft on 4th ,5th and 6th segments,opens into alimentary canal
Nephridia regulate volume and composition of body fluids
NERVOUS SYSTEM
NERVOUS SYSTEM consists of a paired ventral nerve cord and segmental ganglia.
Anterior end in 3rd and 4th segment nerve cord bifurcates, encircle pharynx and joins dorsally to form a cerebral ganglia
NERVOUS SYSTEM
NERVOUS SYSTEM consists of a paired ventral nerve cord and segmental ganglia.
Anterior end in 3rd and 4th segment nerve cord bifurcates, encircle pharynx and joins dorsally to form a cerebral ganglia
Sensory organs: at anterior part of body
photoreceptor to detect light intensity
Chemoreceptors
Receptors for detecting vibration
REPRODUCTIVE SYSTEM
Earth worm is hermaphrodite.Reproductive system of earth worm consists of two pairs of testes located
One pair each in segments 10 and 11. Vasa deferentia arising from these testes reach
Up to 18th segment where it joined with seminal vesicles and prostate gland.
There is a pair of ovary in 13th segment and the oviducts from both side joined at median part and opens outside through a common female genital pore.
There are 4 pairs of spermathecae from segments 5 to 9 which temporarily store sperm.
REPRODUCTIVE SYSTEM
During mating ventral side of one worm juxtaposing the other and there is an exchange of packets of sperm called spermatophore which will be stored in spermathecae.
When ovum /egg mature in ovary it is releases along along with sperm in small packets called cocoon which is secreted by
Clitellum. fertilization takes place inside the cocoon and 2 to 20 baby worms comes out after a period of 3 weeks.