Earthworm Flashcards
Where are earthworms found?
They are found everywhere ( Cosmopolitan)
Write the systematic position of Earthworm.
Kingdom - Animalia
Phylum - Annelida
Class - Oligochaeta
Genus - Pheretima
Species - P. postuma
Class 1: Polychaeta
“poly - many
chaete - hair”
- Marine forms
- Presence of parapodia with setae
- Clitellum is absent
- Unisexual
Eg : Neris
Class 2 : Oligochaeta
“ oligos - few
chaete - hair “
- Terrestrial and freshwater forms
- Presence of setae, no parapodia
- Clitellum is present for entire life
- Hermaphrodite
- Development is direct
Eg : Pheretima postuma
Class 3 : Hirudinea
“hirudo - leech “
1.Ectoparasite, occurring in fresh and marine water.
2. Presence of sucker, lack of parapodia or setae.
3. Clitellum develops during breeding season.
4. Development is direct.
Eg : Hirudinea
Class 4: Archiannelida
“archi - first”
- Exclusively marine forms
- Presence of tentacles, no setae or parapodia
- Clitellum is absent
- Unsexual or hermaphrodite
- Development is indirect
Eg : Polygordius
Habitat :
- Cosmopolitan
- Lives in top soil of earth making borrows in soft and moist areas, rich in humus.
- Moves with contraction and expansion of their muscular body and chitinous setae.
- Nocturnal, lives in borrow during daytime and comes out at night time for feeding.
- Hermaphrodite
- Undigested food comes out as castings
- There is no self fertilization due to protandrous condition i.e. male gametes ripe earlier than female.
- Earthworm has power of regeneration i.e. if it is cut into two pieces, the upper portion regenerated but the lower portion dies.
What is the shape of Pheretima postuma?
Long, narrow, cylindrical and bilaterally symmetrical body. Anterior is pointer but posterior is somewhat blunt.
What is the size of Pheretima postuma?
15cm in length and 3 to 5 mm in diameter. The thickest part lies a little below the anterior end.
What is the color of Pheretima postuma?
-Dark brown in color
- Dorsal side of the body is darker than the ventral side
- The shiny dark brown color is due to deposition of special pigment in skin called porphyrin.
- Porphyrin is derived from the chlorophyll present in the food of earthworm.
- It prevents the organism from the harmful effect of light.
How can dorsal and ventral side of earthworm be distinguished?
- Presence of dorsal blood vessel, forming a dark mid-dorsal line running under the skin from anterior to posterior end of the body.
Segmentation of earthworm?
- 100-120 ring like segments called somites or metameres
- They are separated from each other by intersegmental grooves
- The segments is true one, i.e. the external segmentation corresponds with the internal segmentation of the body, called metameric segmentation.
Peristomium :
- Doesn’t have distinct head, eyes and tentacles
- The first segment is peristomium
- Just anterior to the mouth hangs a small, fleshy sensory lobe known as prostomium. It has sense of touch ( tactile in sense )
What is clitellum?
Clitellum is girdle like thick band of glandular tissue which surrounds 14th, 15th and 16th segments. Secretes mucous to keep it moist, albumen for plastering the burrow wall to minimize the friction and produces cocoon during breeding time, in which fertilization as well as development of young organism takes place.
On the basis of presence and absence of clitellum, the body of earthworm can be divided into how many regions?
On the basis of presence and absence of clitellum, body of earthworm can be divided into 3 regions. They are:
1. Preclitellar region : 1st to 13th segments
2. Clitellar region : 14th 15th and 16th segment
3. Post clitellar region : 17th segment to last segment
