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Structure of Earthworm
खखख – खखखखखखखख (Pheretima) )
खखखख – खखखखखखखखखख (posthuma) )
(2) खखखख खखखखखख खखखख खखखखखखखखखख (P. posthuma) ) खख खख खख खखखख खखख खख खखखखख
(6) खखखख 13 खखखखखख खख खखखखखखख खख खखखख खखखख खखख खख खखखखखखख (clitellum) खखखख
खख ख खखखखखख खखखख खखखखख खखख खखखखखख (seta) e) खखखख खखख ख
(genita) l pa) pilla) e) खखखख खखख ख
Phylum: Annelida Class: Oligocheata Genus: Pheretima Species: posthuma Common Name: earthworm Habit and Habitat: Earthworm is a burrowing animal usually live inside the soil surface in solitary. It burrows by ingesting soil from the mouth and liberate out from the anus on the soil surface as castings.
It feeds upon the dry or green leaves, dead materials, insect larvae, eggs, etc.
Usually earthworm is widely distributed in fertile or loam soil which burrow at the depth of about 6″ inches.
DIGESTIVE SYSTEM:
It includes Digestive tract or Alimentary canal or Gut.
Fig: Digestive system DIGESTIVE TRACT: It completes from anterior mouth or prostomium up to posterior anus includes buccal cavity pharynx, oesophagus, stomach and intestine. The mouth is highly elastic can protrude out and protrude in surrounded by 1st^ body segment acting as lips called peristomium. Mouth follows short buccal cavity lies within 2nd^ and 3rd^ body segments.Buccal cavity is divisible into upper semi circular dorsal chamber. When this chamber gets extended size of buccal cavity becomes larger. Buccal cavity follows another short phyarynx lies in the 4th,5th, and 6th^ segments of the body marked by pharyngeal mass on the dorsal pharynx. This mass secrete saliva or mucin and proteolytic enzyme. Due to heavy pharyngeal mass, pharynx is also depressed into upper, dorsal and lower ventral chambers separated by horizontal shelve. The wall of the dorsal chamber has ciliated epithillium cells which produces ciliatary current help in the collecton of enzyme. The collected saliva and enzyme 1st^ diffuse into dorsal chamber. So it is also called salivary chamber. Pharynx follows short oesophagus in 7th, 8th segment of the body. In the 8th^ or 8/9th^ segment modifies into hard and oval gizzard surrounded by numerous circular muscles. The internal wall is also covered by hard cuticle layer. The contraction and relaxation of circular muscles easily masticate food and soil. Thus acting as grinding organ. Gizzard follows short simple tube stomach extending from 9th^ upto 14th^ body segments. The internal wall of the stomach also secrete proteolytic enzyme. Stomach follows the longest portion of the alimentary canal intestine extending from 15th^ to last but one segment of the body. It has large diameter and looks brownish in colouration. Structurally and functionally intestine is divisible into three regions;
- Pre-typhlosolar region or digestive region
- Typhlosolar region or Absorption region
- Post- typhlosolar region or solar region At last post-typhlosolar region opens to posterior anus through which release out food waste and soil particles in the form of castings. PHYSIOLOGY OF DIGESTION : The physiology of digestion includes ingestion, digestion,absorption and egestion. If the food is green, first of all take into their burrow then mix with mucins secreted by the skin which makes colourless food after that including other foods with soil ingest through mouth follows buccal cavity and pharynx. Gizzard: In gizzard, completely powdered making more easy. The main significant of ingesting soil is only to produce more friction during breaking down of food. Stomach: In stomach ones more protein is partially digest as in the pharynx.In the pre - typhlosolar region, food is completely digested as follows;Enzymes from the wall of the intestine. a) Enzyme trypase – react upon protein which convert into peptones and finally digest into amino acid. b) Enzyme lipase – react upon fat acid which convert into fatty acid and glycerol. c) Enzyme amylase – react upon carbohydrate convert into sugar and finally into glucose or fuctose. After almost digestion, digested foods including undigested foods soil posses over to tryphlosolar region in which all the digested food molecules are absorbed by typhlosole and circulate through blood vascular system.Remaining portion of food and soil passes over to post typhlosolar region for storage. At last such substances eject out from the anus in the form of castings.
Fig: Different types of Nephridia. REPRODUCTIVE SYSTEM : Earthworm is a hermaphrodite animal because male and female reproductive organs are both found in the single animal even then there is no self fertilization always cross fertilization because of protandrous character. Male reproductive organ:
- Two pairs of testes lies in the 10th^ and 11thsegment.
- Two pairs of seminal vesicles lies in the 11th^ and 12 th segment.
- Two pairs of vasadeferentia ducts 12th^ segment to 18th^ segment.
- Two testis sacs – 10th^ and 11th^ segments.
- Two prostate glands extend from 17th^ to 21st^ or 22nd.
- Two common ducts or copulatory organics pseudopenis in 18th^ segments.
- Two male genital opening in 18th^ segments.
- Two pairs of accessory glands each pair in 17thand 19th^ segments. Female reproductive organ :
- One pair of ovary lies in 13th^ segments.
- Two oviducts in 13/14 segments
- Single female genital opening in 14th^ segment.
- Four pairs of spermathecae, each pair in 6th, 7th, 8th^ and 9th^ segment.
- Two pairs of spermaducal funnels in 11th^ and 12thsegments. Male reproductive organ : Testes each pair lies in the 10 th^ and 11 th^ segments. Manufacture spermatozoa by the process of spermatogenesis. Spermatozoa swims actively in the testis fluid present in the testis sac of 10th^ and 11 th^ segments. The 10 thtestis deposits its spermatozoa in 11th^ seminal vesicles. 11thtestes deposits its spermatozoa in 12th^ seminal vesicles. These seminal vesicles provide nourishment till maturity. After the maturation, a spermatozoon again swims back in the testis fluid. Later collect by two pairs of spermaducal funnel of 10th^ and 11thsegments. Spermaducal funnels follows 2 pairs of vasa deferentia duts extending from 12 th^ to 18thsegments. These ducts carry away and restore spermatozoa in the respective prostate glands.
There are two prostate glands looks colourless, leaf life, almost flat extending from 17 th^ to 20 th^ or 21 stsegment. Prostate gland provides nourishment till copulation. Vasa deferentia ducts and internal prostate ducts or copulatory organ or pseudo penis which opens through male opening of the 18thsegment. Beside these male organs also possess two pairs of accessory glands. Each pair is 17 th^ and 19thsegment serve as adhesive organs because their secretion help during copulation. Female reproductive organ: Primary sex ovary is locate in 13th^ septum possess finger like projections containing different stages of eggs. Eggs within the ovary develop by oogenesis process. At maturation wall of the ovary rupture release eggs in the body cavity which are collect by 1 pair of oviducal funnel of 13 th^ segment. It follows oviduct in 13 th, 14th^ segments and opens commonly in the 14th^ segments as female genital opening. There are four pairs of spermathecae, each pair lies in the 6th, 7th, 8th^ and 9th^ segments. Each spermathecae has larger sac ampulla for nourishment and small sac diverticulum which restore sperms collected at the time of copulation. Spermatica although related with the collection of sperm even then kept in the female reproductive organs because of receiver bag.
Cocoon formation: After copulation, earthworm moves into their own burrows. In the burrow, glanular cells of the clitellum become very active whose secretion form a tight sac around the clitellum called clitellar sac. After that earthworm’s body withdraws backward. As a result, sac collects eggs from 14 th^ opening and sperms from spermathecal openings, at last comes out of the anterior region in barrel shape called cocoon. Fig: Process of Cocoon formation Fertilization: Fertilization is external although takes place inside the cocoon which converts into zygote. After few hours, zygote undergoes cleavage give directly young ones. Therefore, the development is direct. NERVOUS SYSTEM :
Fig: T.s nerve cord of Pherithima Nervous system is annulated type, constitute central nervous system, peripheral nervous system and autonomic nervous system. 1.Central Nervous System : Central nervous system related with cerebral ganglia or brain in the 3 rdsegment and ventral nerve cord extending from 5thsegment to 2nd^ last. Minute colorless brain locate just above the buccal cavity in 3 rd^ segment connect with the ventral nerve code by circum pharyngeal connectives. Thus form a ring called nerve ring or circum pharyngeal ring. At the lateral sides of the ring in 4th^ segment present sub pharyngeal ganglia and from 5th^ segment to 2nd^ last present segmental ganglia.
2. Peripheral Nervous System: It is related with nerve fibrous of the ganglia.It includes nerve fibers or nerve, which arises from central nervous system.
- From cerebral ganglia, 8-10 nerves arise and supply to prostomium, buccal chamber, and pharynx.
- From circumpharyngeal connectives, two pairs of nerves arise and supply to 1st^ and 2nd^ segment.
- From subpharyangeal ganglia, three pairs of nerve arise and supply to 2nd, 3rd^ and 4th^ segment.
- From each segmental ganglion, three pairs of nerves arise and supply to respective segment. 3.Autonomic Nervous System : It is primitive form because of lower invertebrate animal. Function:
- Reception of stimuli.
- Conduction of stimuli.
- Conversion of stimuli into messages.
- Conduction of messages towards affective region. Economic importance Beneficial aspects
- It makes the burrow in soil. This is useful for plants and they can grow easily.
- They can be used as food. -They are used as medicines to cure stone in bladder, jaundice etc.
- They can be used as baits for fishing.
- There are used in laboratory for research. Harmful aspects
- They can damage plants in garden.
