What Kind of Annelid Has Setae to Aid in Locomotion 103 Section Review
In this article we volition hash out about Hirudinaria Granulosa:- one. Habit and Habitat of Hirudinaria Granulosa ii. External Features of Hirudinaria Granulosa 3. Trunk Wall 4. Locomotion five. Digestive System 6. Coelom 7. Hemocoelomic System viii. Respiratory Arrangement 9. Excretory Arrangement 10. Nervous System 11. Sense Organs 12. Reproductive Organisation xiii. Copulation and Fecundation and Others.
Contents:
- Habit and Habitat of Hirudinaria Granulosa
- External Features of Hirudinaria Granulosa
- Body Wall of Hirudinaria Granulosa
- Locomotion of Hirudinaria Granulosa
- Digestive Organization of Hirudinaria Granulosa
- Coelom in Hirudinaria Granulosa
- Hemocoelomic System of Hirudinaria Granulosa
- Respiratory System of Hirudinaria Granulosa
- Excretory System of Hirudinaria Granulosa
- Nervous System of Hirudinaria Granulosa
- Sense Organs of Hirudinaria Granulosa
- Reproductive Arrangement of Hirudinaria Granulosa
- Copulation and Fertilisation of Hirudinaria Granulosa
i. Habit and Habitat of Hirudinaria Granulosa :
Hirudinaria granulosa is a common Indian leech constitute in freshwater tanks, ponds, lakes, swamps, and slow streams. Information technology prefers shallow water and remains concealed nether weeds, logs and stones. It is sanguivorous (blood-sucking) sucking the blood of fishes and frogs, ands also of cattle or homo beings when they enter the swimming.
Leeches show a great diversity in their habits and habitat. Some species are marine, some are freshwater, while others are terrestrial. Though many species are blood-suckers (ectoparasitic) yet a large number are not ectoparasitic but are predatory and feed on worms, snails and insect larvae.
2. External Features of Hirudinaria Granulosa :
(i) Shape and Size:
The body of Hirudinaria is soft, vermiform, elongated, bilaterally symmetrical and metamerically segmented.
In a state of extension the body is dorsoventrally flattened and appears near strap-shaped simply in a land of wrinkle, the trunk becomes more or less cylindrical. The body is broadest near the posterior end, while narrowest near the anterior terminate. It has great power of wrinkle and expansion. A full grown specimen may achieve the length of xxx to 35 cm.
(ii) Colouration:
The trunk is beautifully coloured with characteristic markings. The dorsal surface is generally olive-greenish and the ventral surface is orange-yellow or orange-ruby-red and the 2 sides bear distinct stripes of orangish or xanthous and black. On the dorsal side is a median longitudinal blackness stripe.
(three) Partitioning:
The body of leech is divided metamerically into segments or somite'south merely metamerism is much reduced and the number of segments, dissimilar other annelids, is fixed in leeches, they always have 33 segments or somite'south.
In case of leech the external segmentation does non correspond with the internal segmentation. But the original partitioning is obscured by secondary external annulation. Each segment is cleaved up externally past grooves into rings called annuli.
The first and second segments have one annulus each, the 3rd has 2 annuli, segments 4th to 6th take three annuli each, segments seventh to twenty-second are wide having five annuli each, segments twenty-third to twenty-6th have two annuli each, segments twenty-seventh to thirty-third have 1 annulus each, they class the posterior sucker.
Withal, segments with less than 5 annuli are referred to as incomplete, while those with five annuli are called complete segments. Each annulus of a segment is divided into small rectangular areas by longitudinal wrinkles. Each such area has a sort of papilla-like construction bearing sensory organ chosen annular receptor; there are 18 such receptors both on the dorsal and ventral surfaces of each annulus.
As well these, the commencement annulus of each segment bears larger sensory organs called sensillae or segmental receptors; these are four pairs on the dorsal side and three on the ventral side. Due to this the commencement annulus of each segment is chosen sensory annulus.
(4) Suckers:
Each end of the torso of leech bears a hollow muscular organ, the sucker. The anterior sucker or cephalic or oral sucker is formed by the fusion of the prostomium with a few somite'south of anterior region. It is oval in outline and is placed on the ventral surface of anterior end. Information technology too possesses a ventrally directed cup-like hollow construction, the pre-oral chamber, which leads into the mouth.
The posterior sucker or anal sucker is circular in outline and forms the highly muscular disc at the posterior end of the body of leech. It is formed by the fusion of last seven segments. It is much better developed and larger in size than the inductive sucker. Both suckers are directed ventrally, the leech tin firmly grip the substratum by its suckers. The two suckers are primarily meant for adhesion and locomotion.
(v) Clitellum:
During breeding flavour a girdle-like clitellum is formed around segments 9th to eleventh, rest of the year there is no clitellum.
(vi) Eyes:
On the dorsal side are 5 pairs of optics, one pair on each of the beginning and 2nd segments, and ane pair on the first annulus of the segments third, quaternary and fifth.
(vii) External Apertures:
External apertures in the trunk are as follows:
(a) Oral cavity:
It is a narrow triradiate discontinuity situated in the centre of the funnel like pre-oral bedchamber of the anterior sucker.
(b) Anus:
Information technology is a very minor discontinuity situated mid-dorsally on the 20-sixth segment at the root of the posterior sucker.
(c) Nephridiopores:
There are seventeen pairs of nephridiopores lying on the ventral surface of the body, of which one pair lies on the last annulus of each of the segments from sixth to twenty-second.
(d) Male person generative aperture:
It is situated in a groove between the 2d and third annuli of the tenth somite on the mid-ventral line of trunk. A filamentous penis is sometimes seen protruding through this aperture.
(due east) Female generative aperture:
It is usually smaller and less conspicuous than the male discontinuity. It is situated mid-ventrally in a groove between the second and third annuli of the eleventh somite of the body.
Divisions of Body of Hirudinaria:
The body of leech is composed of 33 somite's and is divisible into the post-obit six regions:
one. Cephalic or Head Region:
It is equanimous of the first five segments. It includes the prostomium, anterior sucker, the mouth and the optics; in fact a pair of optics are situated on the dorsal side of first annulus in all the cephalic segments. Therefore, these segments are also referred to as the ocular segments.
Nephridiopores are absent in this region. The first two segments are uniannulate, the tertiary segment is biannulate and fourth and fifth segments are triannulate. The prostomium and the kickoff three segments course the upper lip.
2. Preclitellar Region:
Information technology includes three segments, i.e., Half dozen, Vii, and 8, all bearing nephridiopores. Somite VI is triannulate but the remaining two are completely quinquannulate, i.due east., each with five annuli.
three. Clitellar Region:
It is equanimous of 3 consummate segments, i.e., IX, 10 and XI. There is no permanent clitellum in Hirudinaria but temporary clitellum develops just during breeding season. This region possesses glandular wall. Nephridiopores are too present in this region, the male and female person generative apertures are situated mid-ventrally on the X and Xi segments respectively. The segments of clitellar region are quinquannulate.
iv. Middle Region:
It is the largest region of the trunk and consists of eleven consummate somites (XII to XXII). All the segments of this region are quinquannulate and possess nephridiopores.
5. Caudal Region:
This region is short and consists of four incomplete somites, i.due east., XXIII to XXVI. Segment XXIII is triannulate but the remaining three are biannulate. Segment XXVI bears the anal discontinuity on the dorsal side. There are no nephridiopores.
half dozen. Posterior Sucker:
It is equanimous of seven segments (XXVII to XXXIII) arranged in concentric rings and each represented past a unmarried annulus. These 7 segments are completely fused and their intersegmental furrows are greatly suppressed.
3. Body Wall of Hirudinaria Granulosa :
The body wall consists of five layers, viz., cuticle, epidermis, dermis, muscular layer, and botryoidal tissue.
(i) Cuticle:
The cuticle is the outermost, thin, fragile, transparent, colourless and moderately elastic protective covering. It is thicker slightly on the dorsal surface than on the ventral surface. It is perforated throughout by which epidermal glands open out. It is secreted by the underlying epidermis and is cast off in the form of thin transparent spreads periodically.
(ii) Epidermis:
The epidermis is a unmarried-prison cell layer of hammer-shaped cells, some epidermal cells grade several kinds of unicellular tubular and pear-shaped glands, the gland cells are sunk into the dermis, they secrete mucus which covers the body.
Epidermal Glands:
Several epidermal glands are establish in the epidermis which are every bit follows:
1. Slime glands:
These are distributed all over the body and secrete a slimy mucus that covers the whole trunk. These glands are either tubular or pear-shaped and sunken deep into the dermis. However, these glands are better developed on the dorsal surface than the ventral surface.
ii. Sucker glands:
These glands are distributed just in the suckers and are amassed. These are pear-shaped in the anterior sucker, while rounded or spherical in the posterior sucker. Their secretion smoothens the surface for locomotion.
3. Prostomial glands:
These are institute distributed only in the prostomium. These are pear- shaped and prevarication in groups. Their secretion forms plugs of the ootheca or egg-instance.
4. Clitellar glands:
These glands are found distributed but in the clitellar segments, i.e., Ix, X and XI. They become active simply during the convenance season and are of two types the chitogenous glands and the albumen glands.
The secretion of chitogenous glands forms the wall of the ootheca, while albumen secreted past albumen glands is filled in the ootheca constituting the nourishment of the developing embryo. The chitogenous glands are situated between the circular and oblique muscles, while albumen glands lie in the longitudinal muscles in groups.
(iii) Dermis:
Beneath the epidermis is a dermis made of connective tissue with musculus fibres, capillaries, fat and pigment cells. The glands prevarication in the dermis just open on the surface.
(iv) Musculature:
The musculature below the dermis has a sparse layer of circular muscles and a thicker layer of longitudinal muscles. The longitudinal muscles are powerfully developed and their fibres converge into the two suckers. Round muscles are arranged concentrically in the suckers. Betwixt the circular and longitudinal muscles leeches have an additional double layer of oblique muscles directed spirally around the torso like a ringlet.
At that place are also dorso-ventral muscles arranged segmentally throughout the body, they run from the dorsal to the ventral side in each segment.
In that location are some radial muscles whose fibres radiate from the alimentary canal to the peel, they take the place of septa. The musculus fibres of leech have a feature structure, each fibre has an outer striated and contractile cortex or myoplasm, and an inner unmodified protoplasm called medulla or sarcoplasm.
(5) Botryoidal Tissue:
The mesenchyme of leeches is a characteristic botryoidal tissue made of pigmented and richly vascularised cells which are large and bundled end to end, the cells incorporate a dark chocolate-brown pigment and have intra-cellular branching capillaries filled with fluid.
The botryoidal tissue is probably excretory, it near completely fills the body cavity. Inside the botryoidal tissue are two types of cells characteristic of leeches, they are fat cells and yellow cells. Fatty cells contain fat droplets and some glycogen, yellow cells are filled with yellow, brownish, or green granules, these cells appear to be excretory.
Functions of Trunk Wall:
The body wall of leech performs the following functions:
ane. Information technology protects the internal delicate organs from mechanical injury.
2. The cuticle and slimy glaze bank check evaporation and help in easy escape from the grip of enemies.
three. It is richly supplied with haemocoelomic capillaries, hence, respiratory in function.
4. It is sensory due to the presence of various types of receptors on information technology.
5. The gland cells nowadays in the wall of prostomial segment secrete plugs of the ootheca.
six. The gland cells in the clitellar segments secrete ootheca and albumen; albumen being the nutrient of the developing embryo.
4. Locomotion of Hirudinaria Granulosa :
The leech has ii types of locomotion, creeping, looping or crawling and swimming.
Creeping or Crawling:
In creeping the suckers are alternately fixed to the substratum and the body contracts and extends.
When the anterior sucker is fixed, a moving ridge of wrinkle takes place in the longitudinal muscles shortening the creature and moving the posterior sucker frontwards, by this the body contracts and is pulled forwards, then the posterior sucker is stock-still and a wave of contraction takes identify in the circular muscles passing dorsum from the inductive stop by which the trunk is lengthened and extended forward.
Pond:
In swimming a great dorso-ventral flattening takes place due to contraction of dorso-ventral muscles and undulatory waves laissez passer in a vertical plane over the body from the anterior to the posterior end due to contraction of longitudinal muscles. The leech is a swift swimmer.
v. Digestive System of Hirudinaria Granulosa:
Digestive arrangement consists of the gastrointestinal tract and digestive glands associated with it.
Alimentary canal of Hirudinaria :
The alimentary canal of leech is a directly tube extending throughout the length of the torso from the oral fissure to the anus. Leech is sanguivorous (claret-sucking) in habit, therefore, the gastrointestinal tract is very much suited for its blood sucking habit as the nigh portion of the alimentary culvert serves to shop un-coagulated blood, while simply a small portion serves for its digestion and absorption.
The gastrointestinal tract consists of the stomodaeum (lined with ectodermal epithelium and covered by cuticle), the mesenteron (lined with endodermal epithelium and no cuticle covering) and the proctodaeum (lined with ectodermal epithelium and covered by cuticle).
1. Stomodaeum:
It consists of preoral chamber, buccal cavity and pharynx.
(i) Pre-oral Chamber:
It is a cup-shaped depression on the ventral side of the anterior sucker. At the base of the pre-oral sleeping accommodation lies the tri-radiate mouth guarded past the velum, which forms an almost complete partition betwixt the pre-oral chamber in front and the buccal crenel behind. The prostomium and the first four segments of the body course the roof of the pre-oral chamber, while the round rim of the sucker forms its outer purlieus.
(ii) Buccal Crenel:
The triradiate oral fissure leads into very short chamber, the buccal cavity. In the mucous membrane of buccal cavity are embedded three crescentic jaws, one mid-dorsal and the other two are ventro-lateral in position.
Each jaw is a laterally compressed absorber, covered with a fine cuticle which is thickened at the free edge to grade a dentigerous ridge bearing a row of infinitesimal teeth (denticles). Every bit these teeth form a single series on each jaw, the jaw is termed as monostichodont.
The median jaw bears 103 to 128 teeth, while the lateral jaws bear 85 to 115 teeth each. On both the sides of a jaw are small button-shaped salivary papillae, each bearing a number of openings of salivary glands. The number of papillae is 42 to 45 on each side of,a jaw. However, the jaws are moved in such a fashion that they brand a Y-shaped wound on the torso of its victim through which claret is sucked.
(iii) Throat:
The buccal crenel leads into thick-walled muscular pharynx, which is an oval sac running from the fifth to the eighth segment.
The lumen of the pharynx varies in outline in different regions. The muscles of the pharynx are round and radial which join the pharyngeal wall to the body wall; radial muscles dilate the pharynx producing a pump-similar action for sucking blood. Large masses of unicellular pyriform salivary glands surround the pharynx, their ducts open between the teeth of jaws.
The secretion of salivary glands contains a substance called hirudin or anticoagulin which prevents the coagulation of claret of the host when the leech is sucking.
ii. Mesenteron:
The mesenteron consists of oesophagus, crop, tummy and intestine.
(i) Oesophagus:
Information technology is a short narrow tube, through which the pharynx leads into the crop. The lumen of oesophagus is very narrow and its epithelial lining is produced into numerous folds.
(ii) Ingather:
The ingather is the largest region of the alimentary culvert extending from the ninth to the eighteenth segment. Information technology has ten thin-walled chambers, ane in each segment and they are connected with ane another past more than or less circular apertures surrounded past sphincters. Each chamber consists of a pocket-sized anterior and a broad posterior function which is produced into a pair of lateral outgrowths, the caeca.
The chambers and the caeca go on gradually increasing in size towards the posterior side. The concluding chamber of the crop is the largest and its caeca are prolonged backwards upwards to the twenty-second segment. The crop and its caeca are greatly extensible and used for storing blood, one cropful of blood lasts for several months and digested slowly.
(3) Stomach:
It is a small heart-shaped structure lying in the nineteenth segment. The opening of ingather into the stomach is narrow having sphincter muscles which regulate the menstruation of food. The stomach has both secretory and absorbent epithelial cells and its inner lining is produced into numerous transverse folds which anastomose with ane another.
(iv) Intestine:
The stomach leads into the intestine which is not clearly differentiated externally from the stomach. The intestine is a sparse-walled, straight and narrow tube extending from the nineteenth to xx-second segment. Its inner lining is thrown into numerous longitudinal and transverse folds resembling the screw villi to increase the absorbent surface.
3. Proctodaeum:
Proctodaeum consists of rectum simply.
(i) Rectum:
The intestine opens into a short, thin-walled somewhat ciliated rectum running from the twenty-second to twenty-sixth segment. The rectum opens by a dorsal anus in the xx- 6th segment above the posterior sucker.
Histology of Gastrointestinal tract:
Histologically, the wall of alimentary canal is fabricated of a layer of columnar epithelium resting on a basement membrane layer which is followed by the layer of connective tissue. The epithelial layer of stomodaeum and proctodaeum is lined by cuticle; it is ciliated in the proctodaeum and provided with goblet cells in the crop.
The connective tissue contains circular muscle fibres and haemocoelomic capillaries, it contains circular and longitudinal muscle fibres in the preoral chamber and in the pharynx it contains all the musculus fibres, i.eastward., circular, longitudinal and radial.
Digestive Glands of Hirudinaria Granulosa:
These include the salivary glands and some other isolated gland cells plant in the mucous membrane of the gut wall.
A. Salivary Glands:
These are unicellular, pyriform, glandular mass of cells situated effectually and behind the pharynx.
Each glandular prison cell has elongated fine ductule which finally enters the jaws to open in raised salivary papillae. The secretion of these glands contains an anticoagulant substance called hirudin; hirudin prevents coagulation of claret and so that the leech can suck blood effectively and for longer elapsing to fill up its crop and caeca.
B. Gland Cells:
These are in the form of goblet cells, establish scattered throughout the lining of crop. These secrete mucus in the ingather.
Food, Feeding and Digestion of Hirudinaria :
Since, leech is sanguivorous in addiction, hence, it feeds on blood of cattle visiting the water source where information technology lives. In feeding the leech applies its oral sucker to the skin of its victim, the jaws move towards and away from each other, they painlessly puncture the peel, pump-similar action of the pharynx sucks in big quantities of blood to fill the crop, secretion of hirudin prevents coagulation of blood.
In the crop, the blood is haemolysed in which corpuscles flare-up, haemoglobin gets dissolved in the plasma and the blood becomes dark red; this blood passes slowly through the sphincter discontinuity into the stomach where it turns light-green and is digested, just the haemoglobin of ingested blood is absorbed straight past the cells of the stomach, it is the globin of ingested blood which is mainly used every bit food.
Notwithstanding, the process of digestion is very wearisome; a cropful of blood takes 10 to fourteen months for complete digestion.
Abderhalden and Heise (1909) establish a peptolytic ferment which hydrolyses proteins in an alkaline medium. Nonetheless, digestion has been reported to occur entirely by gut bacteria in Hirudo (Busing et al, 1953).
Absorption and Egestion in Hirudinaria :
Absorption of digested food takes place in intestine and tum. The undigested food, if any, is stored temporarily in rectum and egestion occurs through the anus.
vi. Coelom in Hirudinaria Granulosa :
The perivisceral coelom of general annelids has been lost in leeches, it is invaded and almost obliterated past botryoidal tissue, what is left is reduced to 4 intercommunicating haemocoelomic channels, their branches and some coelomic sinuses.
The haemocoelomic channels are dorsal and ventral channels with thin walls, and 2 lateral channels which accept caused muscular walls secondarily. All four longitudinal channels are lined with coelomic epithelium.
The haemocoelomic channels take many branches, the most prominent are those of the ventral aqueduct which class baglike swellings enclosing ciliated organs, these swellings are perinephrostomial ampullae. All channels and their branches incorporate ruby haemocoelomic fluid, considering of this the channels are called haemocoelomic channels and not blood vessels, their fluid is not blood, but coelomic fluid coloured red due to dissolved haemoglobin.
Coelomic sinuses are spaces within testes sacs and ovisacs which enclose the gonads, and around the vasa deferentia. They are lined with coelomic epithelium which gives ascent to gonads, they contain colourless coelomic fluid with no haemoglobin, suggesting the fact that the coelomic sinuses are remnant of original coelom and they separate very early earlier haemoglobin develops in the coelomic fluid.
seven. Haemocoelomic System of Hirudinaria Granulosa:
At that place is no truthful blood vascular arrangement and the coelomic infinite and fluid take been modified to form the circulatory system, it consists of much-reduced coelom containing cherry-red coelomic fluid with haemoglobin in solution and colourless amoeboid corpuscles.
This organization is spoken of every bit a haemocoelomic organization, and thered coelomic fluid as a haemocoelomic fluid, the channels in which information technology flows are chosen haemocoelomic channels.
The haemocoelomic system consists of 4 longitudinal haemocoelomic channels, their branches, and some networks formed by capillaries. The longitudinal haemocoelomic channels are one dorsal channel, one ventral aqueduct, and two lateral channels.
The haemocoelomic fluid flows from posterior to anterior side in the dorsal and lateral channels, and it flows from the anterior to posterior side in the ventral aqueduct. All four channels are joined to each other in the posterior region. The dorsal and ventral channels are distributing channels, the lateral channels are both distributing and collecting channels.
Longitudinal Channels and their Branches :
1. Dorsal Channel:
The dorsal aqueduct runs mid-dorsally beneath the trunk wall and to a higher place the alimentary canal. It has a thin wall, which is non-contractile being made of connective tissue and coelomic epithelium. In each segment the dorsal channel gives off ii pairs of dorso-laterals taking the haemocoelomic fluid to the dorsal and dorso-lateral regions of trunk wall and several dorsointestinals going to the gastrointestinal tract.
The dorsal aqueduct bifurcates in the twenty-second segment and these two branches join the ventral channel posteriorly. Anteriorly the dorsal channel forms a network in a higher place the comestible canal from the sixth to the first segment. In the dorsal channel there is no valve and haemocoelomic fluid flows backside forward.
2. Ventral Channel:
The ventral channel, similar the dorsal channel, has non-contractile thin wall being made of connective tissue and coelomic epithelium. Information technology lies mid-ventrally below the comestible canal extending from the anterior to the posterior stop. It is broad and encloses the central nervous arrangement within information technology.
Information technology gives off two pairs of branches in each segment, the first branch or cutaneous co-operative divides on each side into ii branches, a ventral branch going to the ventral body wall, and an abdomino-dorsal branch which passes vertically upwards to the dorsal body wall.
The 2nd branch of the ventral channel in commisures of the lateral haemocoelomic channels, each segment is a pair of nephridial branches, each nephridial branch runs outwards and enlarges into a perinephrostomial ampulla which encloses the ciliated organ.
The nephridial branch is found only in eleven segments which contain testes, these branches take the haemocoelomic fluid to nephridia, trunk wall and ciliated organs around which they class bag-similar perinephrostomial ampullae. Like dorsal aqueduct, the ventral channel has no valve only haemocoelomic fluid flows from anterior to posterior side of the trunk.
3. Lateral Channels:
The lateral channels run symmetrically i on each side of the alimentary canal. They are big in diameter and become even larger in the posterior third of the trunk. The lateral channels have contractile muscular walls and they comprise valves which allows the haemocoelomic fluid to catamenia from behind forwards just.
A lateral aqueduct gives out one co-operative and receives two branches in each segment. It gives out a latero-ventral co-operative which bifurcates into an anterior and a posterior co-operative and each joins its fellow of the opposite side mid-ventrally to form a rhomboidal swelling, i.eastward., ventral commissure of laterals in each segment, and then they have the haemocoelomic fluid to the gastrointestinal tract, nephridia and reproductive organs.
Each lateral channel receives a latero-Iateral branch in each segment from the skin and nephridium of its side, and a latero-dorsal branch from the skin and the viscrea; the latero-dorsals of both lateral channels are connected together dorsally above the dorsal channel by dorsal commissure of the laterals.
Thus, the branches of the lateral channels supply the haemocoelomic fluid to the skin, nephridia, reproductive organs, gastrointestinal tract and lower body wall; and they collect the haemocoelomic fluid from all parts, i.eastward., from upper and lower body wall, skin, alimentary canal, nephridia and reproductive organs.
Anteriorly the lateral channels break upwardly into capillaries in fifth segment, and posteriorly they join the ventral channel.
Capillary System of Hirudinaria Granulosa :
The four channels not only communicate with each other but they course capillaries in the skin, muscles and botryoidal tissue. This capillary organization (Fig. 67.18) has iii primary sets, a set of botryoidal capillaries forming a network in the botryoidal tissue.
This condition of communication with capillaries of botryoidal tissue is unique, information technology may be compared to vertebrates in which the lymphatic system communicates both with the coelom and the blood system. The second part of the capillary system is an intramuscular set of capillaries in the muscles. The third is a prepare of cutaneous capillaries in pare.
Course of Blood Apportionment in Haemocoelomic System of Hirudinaria Granulosa :
Of the 4 longitudinal channels, the fluid in the dorsal and two lateral channels moves from behind forrard, while in the ventral it runs from anterior to posterior stop of the body. The dorsal and ventral are the distributing channels, while the laterals are collecting as well equally distributing channels. All the channels are in directly communication with i another at the posterior stop.
The dorsal channel supplies fluid to the dorsal and dorso-lateral parts of the body wall and the entire alimentary canal, from where it is collected past latero-dorsals, which bear the fluid to the lateral channels.
The ventral channel supplies the fluid to the ventral, ventro-lateral and median dorsal region of the trunk wall, ciliated organs, nephridia and the atrium. From all these parts the fluid is collected past the latero-lateral branches of the lateral channels.
Lateral channels supply the fluid to the nephridia, genital organs, gut and ventral torso wall through the latero-ventrals and is collected back through the latero-lateral and latero-dorsal branches.
8. Respiratory System of Hirudinaria Granulosa:
There are no special respiratory organs in Hirudinaria. In addition to its primary role of a protective roofing, the skin also serves a respiratory role. Information technology is provided with a rich supply of haemocoelomic fluid in an extensive system of capillaries and capillary loops, which penetrate into the spaces between the inner ends of the epidermal cells.
The epidermis acts equally a permeable membrane through which the CO2 of the haemocoelomic fluid in the capillary loops is exchanged for the O2 dissolved in water. Leeches live in water or in damp soil, and, thus, the skin is always kept wet by the surrounding h2o, while the mucus secreted by the epidermal slime glands as well prevents it from drying on exposure to the temper.
9. Excretory Arrangement of Hirudinaria:
The excretory system consists of segmentally bundled seventeen pairs of nephridia lying in segments from sixth to twenty-second.
The outset six pairs of nephridia are situated in the pre-testicular segments (sixth to eleventh), while the remaining 11 pairs are situated in the testicular segments (12th to twenty-second). The nephridia lying in the pre-testicular segments and the testicular segments are termed pre-testicular and testicular nephridia respectively.
Testicular Nephridium:
A typical testicular nephridium (Fig. 67.20) has a horse-shoe-shaped structure.
Beginning with the inner coelomic terminate a typical testicular nephridium consists of six parts, viz.,:
(i) Ciliated organ
(2) Initial lobe
(iii) Apical lobe
(iv) Main lobe
(v) Inner lobe
(vi) Vesicle-duct and the vesicle
(i) Ciliated Organ:
A ciliated organ is completely enclosed within the perinephrostomial ampullae which is a dilation of the haemocoelomic system. A ciliated organ has a central reservoir which is perforated, effectually which are innumerable ciliated funnels. The reservoir is a more or less spongy structure with an outer wall formed of single layer of cells and a key mass consisting of connective tissue cells which industry corpuscles.
Each ciliated funnel is like an ear-lobe, with about one-fourth of its margin incomplete along one side and is covered with outwardly directed cilia on its outer margin and inner surface. The ciliated organ manufactures coelomic amoeboid corpuscles.
Ciliated organs are joined to nephridia in the embryo, but in the adult fauna they accept no connection with nephridia.
This shows that originally the ciliated organ belonged to a nephridium, but in the adult having no connection with the nephridium. It is not excretory merely has become a part of haemocoelomic arrangement for making corpuscles. Ciliated organs stand for to coelomoducts of Polychaeta and non to nephrostomes of nephridia.
(ii) Initial Lobe:
The initial lobe or the testicular lobe is a long and slender cord-similar structure which twines around the apical lobe, and then ends blindly in front end close to the perinephrostomial ampullae and its posterior end joins the main lobe. It consists of a unmarried row of elongated hollow cells placed end to cease having the intracellular culvert which gives off several diverticula in each cell.
(iii) Apical Lobe:
The posterior limbs of the main lobe pass forward to form a stout lobe, the upmost lobe, which lies in the anteroposterior position beneath the gut. The upmost lobe is adequately stout and its inductive end is bent on itself like the handle of a walking stick. The cells of the upmost lobe are much larger than those of the initial lobe and are traversed past numerous regular intracellular canals.
(iv) Main Lobe:
The chief lobe, forming the horse-shoe proper, lies in a ventrolateral position between the adjacent diverticula of the ingather. It consists of two unequal limbs, one longer and inductive in position, and the other smaller and posterior. The cells of the main lobe are the largest in the nephridium and are polyhedral in shape.
(5) Inner Lobe:
The inner lobe is narrow and lies all forth the inner concavity of the main lobe and also runs frontward along the outer border of the upmost lobe for about half of its length. Its cells are long and tubular, the lumen in each cell is very large and makes a big excavation in the cell, cytoplasm contains a small nucleus.
(vi) Vesicle Duct and Vesicle:
From the lower end of the anterior limits of principal lobe arises a sparse vesicle duct which passes over and joins a large thin-walled oval bag called vesicle or bladder. Bhatia (1940) has described that the lining of bladder is ciliated merely a subsequently worker B. Dev is of the view that the so called cilia are nephridial micro-flora consisting of not-motile leaner ranging from two.eight µ to 7 µ in length.
From the vesicle emerges a curt excretory duct which opens externally by a rounded aperture, the nephridiopore in the last annulus of the segment in which the nephridium lies. A nephridium is fabricated of a string of cells, the initial lobe has no canal only an intercellular ciliated canal starts from the apical lobe, goes into the inner lobe, and then passes through the main lobe to enter the vesicle duct.
Pre-testicular Nephridia:
The beginning six pairs of nephridia, called pre-testicular nephridia, resemble the testicular nephridia in structure; but they lie in the segments from sixth to eleventh in which testis sacs, perinephrostomial ampullae, and ciliated organs are absent-minded. The initial lobes of these nephridia cease loosely in the general connective tissue on either side of the ventral nerve cord.
Central Culvert of Nephridium:
The cells of initial lobe, upmost lobe and inner lobe possess intracellular canals, all these open up into a central canal originating from the anterior part of apical lobe.
The central canal is, thus, a long continuous passageway traversing through the different lobes of nephridium and finally enters the vesicle duct most inductive limb of the main lobe. Thus, this canal carries the excretory products secreted by the glandular cell masses of the nephridium and finally discharges into the vesicle through vesicle duct.
Physiology of Excretion in Hirudinaria Granulosa :
The ciliated organ is completely separated from the nephridium in the adult. It has no excretory function but manufactures coelomic corpuscles of the haemocoelomic organisation. The nephridium proper is truly excretory in part and serves to eliminate excess of water and nitrogenous waste. Nitrogenous waste consists mainly of ammonia and minor quantities of urea, hence, leech is ammonotelic.
Nephridia deed as excretory as well as osmoregulatory organs. The nephridium is richly supplied with branches of haemocoelomic channels and the gland cells separate waste products from the haemocoelomic fluid. The excretory fluid is finally collected in the vesicle of nephridium to be discharged through the nephridiopore.
Every bit referred to, nephridium is also osmoregulatory in function because it is related to maintain water remainder in the body; the osmotic pressure level of body fluid is always higher than the surrounding water, hence, water enters its torso continuously. The nephridia, nonetheless, removes excess water.
The leeches are as well said to possess a special machinery in their epidermis for taking in Na and CI ions to compensate those lost in the metabolism. This helps in maintaining a continuance in the body fluid osmotic force per unit area. Several workers have also assigned an excretory function to the botryoidal tissue, the capillaries of which are in advice with the haemocoelomic fluid.
10. Nervous System of Hirudinaria Granulosa :
The nervous arrangement is of usual annelidan type except at that place is a fusion of ganglia at the anterior and posterior ends.
It consists of three parts:
(ane) Central nervous organization
(2) Peripheral nervous organization
(three) Sympathetic nervous organization
1. Central Nervous System:
The central nervous system consists of v parts, viz.,:
(i) A pair of cerebral ganglia,
(ii) A pair of peripharyngeal connectives,
(iii) A sub-pharyngeal ganglionic mass,
(iv) A ventral nerve cord, and
(five) Terminal ganglionic mass. The entire central nervous system is enclosed inside the ventral haemocoelomic aqueduct.
A pair of fused cerebral ganglia or supra-pharyngeal ganglia form a pocket-sized brain above the pharynx in the 5th segment. The brain has shifted back due to a reduction in size of prostomium.
From the brain, peri-pharyngeal connectives (one on either side of the pharynx) arise and join a sub-pharyngeal ganglionic mass lying beneath the pharynx in the fifth segment, this is formed past fusion of 4 pairs of ganglia. Thus, the cerebral ganglia and sub-pharyngeal ganglionic mass stand for the ganglia of first 5 segments of the body.
A double ventral nervus cord, existence covered in a protective sheath chosen neurilemma, runs forth the mid-ventral line, from the sub-pharyngeal ganglionic mass to the terminal ganglionic mass lying inside the posterior sucker. Information technology has 20-one double ganglia, each lying within the first annulus of its own somite, from the sixth to the 20-sixth segment.
The last ganglionic mass is a big ovoid torso composed of seven pairs of ganglia fused together, each pair belonging to a segment of, the sucker.
ii. Peripheral Nervous System:
Information technology consists of paired nerves given off from the diverse ganglia of the central nervous system, which innervate all parts of the body.
A pair of stout fretfulness arises from the brain which runs forward to supply the first pair of optics, the prostomium and the roof of the buccal sleeping accommodation.
The subpharyngeal ganglionic mass gives out iv pairs of nerves which become to the second, third, fourth and fifth pairs of optics and also to segmental receptors of the get-go v segments, roof of the buccal cavity and the muscles of body wall. From each ganglion of ventral nerve cord arise ii pairs of stout fretfulness, the anterior laterals and posterior laterals.
The anterior laterals arise from the anterior role of the ganglion, branch and innervate the vas deferens, nephridium, the nephridial vesicle, muscles of trunk wall, ventral nervus receptors and two outer dorsal receptors of their own side. The posterior laterals arise from the posterior role of the ganglion merely behind the inductive laterals.
The posterior laterals co-operative and innervate the viscera, median dorsal region of torso wall and the key pair of the dorsal segmental receptors. The concluding ganglionic mass sends off several nerves supplying the receptor organs and other structures found within the posterior sucker.
3. Sympathetic Nervous System:
It forms extensive nerve plexuses below the epidermis, within the muscle layers of body wall and on the wall of the alimentary culvert. It is continued, on the one hand, with certain cells on both sides of the peripharyngeal connectives and, on the other, with multipolar ganglion cells, irregularly distributed over the entire alimentary nerve plexus.
11. Sense Organs of Hirudinaria Granulosa :
The sense organs or receptors of leech consist of particularly modified epidermal cells.
At that place are four types of receptors:
(i) Gratuitous nerve endings
(ii) Annular receptors
(iii) Segmental receptors
(iv) Eyes
(i) Costless Nerve Endings:
The free nervus endings are establish all over the trunk, between the epidermal cells, with their ganglion cells lying below the epidermis. They are probably chemoreceptors.
(ii) Annular Receptors:
These are arranged in a line across the center of each annulus of a segment. Each annulus of the body bears 36 very minute annular receptors, 18 on the dorsal side and 18 on the ventral side. Each receptor projects as a small papilla and consists of many flat overlapping cells which receive nerve fibres from the lateral branches. Annular receptors are tactile organs or tango receptors.
(iii) Segmental Receptors:
These are small whitish patches elevated on the elliptical papillae borne upon the first annulus of everybody segment. They prevarication in four pairs on the dorsal surface and three pairs on the ventral surface in each segment. Each receptor consists of a group of long slender cells, 10 to 15 in number which are separated from ane some other by articulate spaces.
There are 5 to 10 long, slender tactile cells, separated from one some other and provided with v hair-similar processes at their outer free ends.
The photoreceptor or lite perceiving cells, found just in the dorsal receptors, contain a crescentic hyaline substance, the optic organelle or lens, in their cytoplasm. Each receptor receives a nerve branch from one of the lateral nerves and functions as tango receptors and photoreceptors.
(iv) Eyes:
In that location are five pairs of eyes lying in a semicircle of blackness spots on the dorsal surface of the anterior sucker, ane pair in the showtime annulus of each of the first five segments.
Each center is cylindrical or cup-like in shape with its long centrality perpendicular to the body surface. Each eye consists of a long pigmented loving cup covered externally by transparent epidermis and cuticle forming a cornea. Inside the loving cup are refractive cells arranged in several longitudinal rows.
Each refractive cell contains a crescentic hyaline substance, the optic organellae or lens surrounded by a very sparse peripheral layer of cytoplasm containing a small rounded nucleus. An optic nerve enters each centre basally and runs forth its median axis distributing branches to all photoreceptor cells.
All the eyes are not of equal size; the first and 2nd pairs are the largest, while the remaining pairs are insufficiently smaller in size, the fifth pair being the smallest.
The eyes are differently directed and each eye can receive the light simply from i direction. It is not known whether the eyes are able to form images of external objects; probably they can distinguish lite from darkness and enable the leech to locate the direction of the source of light.
On the basis of their metameric arrangement and histological structure, Whiteman regards the eyes to be serially homologous with the segmental receptors.
12. Reproductive System of Hirudinaria:
Leeches are hermaphrodite (monoecious), i.e., each individual possesses a complete ready of well differentiated male and female reproductive organs. Cocky-fecundation does non occur. Cantankerous- fertilisation, preceded past copulation, is existence effected.
Male Reproductive Organs of Hirudinaria :
The male reproductive organs consist of:
(i) Testis sacs
(ii) Vasa efferentia
(3) Vasa deferentia
(iv) Epididymis
(v) Ejaculatory ducts
(vi) Atrium
(i) Testis Sacs:
At that place are usually xi pairs of testis sacs in segment 12th to twenty- 2d, 1 pair in each segment, lying ventrally, one on either side of the ventral nerve cord. Each testis sac is modest spherical coelomic sac, from the walls of which spermatogonia or sperm-mother cells are budded off. The spermatogonia float in the coelomic fluid within each testis-sac and develop into spermatozoa.
(2) Vasa Efferentia:
From the posterior border of each testis-sac arises a curt sinuous duct, the vas efferens, through which the mature spermatozoa are passed into the vas deferens. All the vasa efferentia of one side open into the common vas deferens of that side.
(iii) Vasa Deferentia:
They are a pair of slender longitudinal ducts running forward, from twenty-second to the eleventh segment, lying along the ventral body wall on either side of nerve cord. Each vas deferens is enclosed within a tubular coelomic infinite which contains amoeboid corpuscles like to those of the haemocoelomic fluid.
(iv) Epididymis:
Each vas deferens, in the tenth segment, swells to form closely convoluted and compact mass, the epididymis or sperm-vesicle. The two epididymis serve to store the spermatozoa.
(v) Ejaculatory Ducts:
From the inner and inductive end of each epididymis arises a brusque narrow ejaculatory duct or ductus ejaculatorious.
(vi) Atrium:
It is a pyriform sac situated in the ninth and tenth segments, to which join the ejaculatory ducts of both the sides. The atrium is made of an anterior prostate chamber and a posterior penis sac. The prostate sleeping accommodation possesses thick muscular walls covered over with several layers of unicellular prostate glands.
The penis-sac is an elongated muscular chamber and contains a tubular coiled penis which tin can be everted and is often seen protruding out through the male genital aperture on the ventral side of the 2d annulus of tenth segment.
The spermatozoa produced in testis-sacs are stored in the epididymis. From the epididymis of each side the spermatozoa laissez passer into the prostatic chamber where they are glued together past a secretion of the prostate glands to form bundles called spermatophores. The spermatophores pass into the narrow canal of the penis, through which they are transferred into vagina of other leech during copulation.
Female Reproductive Organs of Hirudinaria Granulosa :
The female reproductive organs consist of:
(i) A pair of ovisacs
(two) A pair of oviducts
(iii) Common oviduct
(iv) Vagina
(i) Ovisacs:
There is a single pair of globular ovisacs enclosing coelomic spaces and an ovary in each, situated in the eleventh segment. Each ovary is a coiled nucleated string from which ova are budded off; information technology terminates in club-like ends. The coiled ovaries remain floating in the haemocoelomic fluid enclosed within the ovisacs.
(ii) Oviducts:
From the base of operations of each ovisac arises a brusque slender tube, the oviduct. The correct oviduct passes beneath the ventral nervus cord.
(iii) Common Oviduct:
The oviducts of 2 sides unite to class a mutual oviduct which is like an South. The common oviduct lies in the eleventh segment. At the junction of oviducts is a mass of unicellular albumen glands opening into the mutual oviduct. The common oviduct opens into a pear-shaped muscular vagina.
(iv) Vagina:
The vagina is a large pear-shaped muscular pocketbook lying in the posterior role of the eleventh segment. It increases in size during the breeding flavour and likewise becomes internally thrown into a large number of longitudinal folds.
It opens to the exterior through a mid-ventral female person genital discontinuity in the 2d annulus of eleventh segment. The ova, budded off from the ovaries, pass through the oviducts into the vagina where they remain for some time.
thirteen. Copulation and Fecundation in Hirudinaria Granulosa :
Copulation takes place in the months of March and April; during copulation two leeches come together by their ventral surfaces pointing in opposite directions, so that the male person aperture of each is contrary the female aperture of the other. The penis of each is inserted into the vagina of the other and spermatophores are deposited, so that there is mutual insemination.
Copulation may occur on land or in h2o, it lasts for an hour subsequently which the 2 worms separate. Fertilisation occurs in vagina, i.due east., it is internal. The fertilised eggs are discharged through the female genital discontinuity into the cocoon (ootheca) where further development occurs.
14. Cocoon or Ootheca Formation in Hirudinaria Granulosa :
The cocoons (Fig. 67.32) of Hirudinaria are formed in Apr, May and June. The clitellum forms around segments nine to eleven during breeding season, its glands secrete a frothy girdle which hardens to form a cocoon, the clitellar glands secrete albumen into the cocoon used as nourishment past the developing embryo.
The fertilised eggs are extruded into the cocoon. The leech wriggles out backwards from the cocoon, the ii ends are closed by polar plugs secreted by the prostomial glands. The cocoon is an amber-coloured barrel 30 mm 10 fifteen mm in size. It has an outer spongy layer and an inner tough chitinous layer. The cocoons are ever laid in moist mud but never in h2o. Cocoon formation takes virtually six hours.
15. Evolution of Hirudinaria Granulosa :
Evolution of young proceeds within the cocoon. In each cocoon i to twenty-iv embryos develop and swim in the cocoon feeding on albumen, they finally escape from the cocoon. Development is direct, at that place is no larva, and information technology is completed in about fourteen days.
16. Parasitic Adaptations in Hirudinaria Granulosa:
Hirudinaria, the mutual Indian cattle leech, leads a parasitic life as it feeds on the claret of cattle and homo. For parasitic mode of life, at that place are a number of adaptive features in it.
However, some of these features are as under:
ane. Its long, flattened, limbless swift swimming nature and slimy body is well suited for its aquatic life.
ii. Its slimy body covering protects information technology from desiccation; reduces friction in water during locomotory activity and likewise facilitates respiration through the pare.
3. Its preference to live in shallow waters of the pond, tank, lake and stream ensures food every bit the catties and man frequently visit these water reservoirs for drinking or bathing. It also provides darkening under weeds, logs and stones lying at the banking company of these water reservoirs.
4. Inductive and posterior suckers are the organ of zipper; particularly posterior sucker is much more powerful and muscular.
5. Since it is sanguivorous in habit, hence, it must attach itself to the body of the host. So, its suckers help in doing so.
six. Information technology possesses denticulated jaws in the buccal cavity; the jaws make wounds on the body of victim so that victim's blood vessels are exposed and claret starts oozing out.
vii. It possesses a muscular suctorial pharynx; the oozing blood from the victim's trunk is sucked by the pumping activity of the throat.
eight. Its saliva contains hirudin, an anticoagulant, that prevents blood clotting then that the leech may suck the blood for longer duration, as getting a host is a hazard.
ix. Its 10 chambered ingather with caeca aid in storing the claret; it is believed that leech can suck blood several times more of its own weight in a single meal. Then, this blood is stored in crop and caeca.
10. Its one full meal is supposed to exist enough for many months and even for a twelvemonth because the process of digestion is very slow.
11. Since special respiratory organs are not found in leech, hence, its skin is richly supplied by haemocoelomic capillaries to ensure proper exchange of gases from the surroundings.
12. Its well developed receptors provide better chances of survival.
13. Its hermaphroditic sexuality has doubled the rate of reproduction as all individuals are capable of laying eggs in dissimilarity to only 50 per cent individuals of unisexual forms.
14. Development occurs in ootheca or cocoon; the cocoon provides protection to developing young ones.
15. A short span of developmental period, i.e., a fortnight, and formation of several (up to 24) individuals in a unmarried cocoon ensure to maintain its regular population.
Source: https://www.biologydiscussion.com/invertebrate-zoology/phylum-annelida/hirudinaria-habitat-locomotion-and-development/29455
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