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Feeding Annelids can be filter feeders or predators. From dorsal and dorso-lateral body wall haemocoelomic fluid goes direct to the lateral channel through latero-dorsals. Cells are large and radially arranged round the central canal. Annelids are found worldwide from the deepest. In the mean-time the glands of the clitellar segments secrete a snow-white foamy girdle around the clitellum. For their part, leeches have been used in medicine since 30 a. C., approximately. The inner walls of the vagina are thrown into folds.
Route of central canal inside the nephridium: The central canal follows a long and zigzag course throughout the body of the nephridium.
One branch runs vertically upward to innervate the viscera and mid-dorsal region of the body wall while the other branch runs posteriorly along the ventral body wall and supplies the testis sac, ventral part of the viscera and muscles. It is a compound structure made up of a central reservoir and ciliated funnels. Then it comes down the apical lobe to enter the inner lobe from where it goes of the posterior border of the anterior limb of the main lobe. There is only one pair of ovisacs situated in the 11th segment and very close to the ventral nerve cord. Respiratory System 8. In other species, the heart is at the rear end, where the upper and lower vessels converge. The phylum Annelida Is made up of about 22,000 species, including earthworms, sea worms and leeches. Circulatory System 9. 3-Present bilateral symmetry. The cells are hammer-shaped. The cells are elongated and tubular. The posterior sucker is much larger and more powerful than the anterior one. It is perforated by many pores. Habit and Habitat of Leech 2. Each cell is provided with hair-like processes at its outer free end (Fig. The cytoplasm is peripheral and the nucleus is round in these cells. The ventral nerve cord in reality is a double chain closely apposed to each other and bears 21 fused ganglia.
The broad outer surface of the eye is formed by a convex epidermal layer over which lies the cuticle (Fig. These are simplest of all receptors and consist of a tuft of delicate fibres scattered between the epidermal cells of the body wall. This is a question and answer forum for students, teachers and general visitors for exchanging articles, answers and notes. The crop and the diverticula are lined internally by endoderm which is projected towards the lumen of the alimentary canal. Some species of earthworms live under the soil. These multiple segments help in their movement. It makes one complete and another incomplete round of run inside the body of the nephridium. There are eleven pairs of vasa efferentia. In these species, two major blood vessels are present: the upper and the lower. 17.36 shows the disposition of haemocoelomic channels in transverse sections. The two oviducts join to form the, common oviduct in the 11th segment. There are 28 different species of lugworms with gills and bristles on different positions. The vesicle duct and the outgoing duct from the vesicle are both non- ciliated. The dorsal and ventral channels are distributary in function and the two lateral channels are both distributary and collecting in nature. The ventral nerve cord passes through the ventral haemocoelomic channel. After traversing the main lobe and forming many loops in it the canal emerges from the posterior lip of the anterior limb and continues into the vesicle as vesicle duct. The lateral sides are occupied by nephridia. It includes a long alimentary canal and digestive glands in the form of salivary glands (Fig. Hence they are considered as chemoreceptors.
Blood passes into the crop and caeca and is stored there. Posteriorly, it encloses the terminal ganglia. The cocoon may house one to two dozens of such ova. Consequently the penis of one gets into the female gonopore of the other, and vice versa. For example, earthworms open furrows on the ground, allowing oxygen and water to flow more easily.
They are reddish, greenish or black in color. Development and emergence of young leeches: Development is direct and occurs within the cocoon and the process is completed in about fifteen days. These muscles are arranged either singly or in bundles (Fig. Annelid, phylum name Annelida, also called segmented worm, any member of a phylum of invertebrate animals that are characterized by the possession of a body cavity (or coelom), movable bristles (or setae), and a body divided into segments by transverse rings, or annulations, from which they take their name. - Leeches are annelids of the family Hirudíneos. The inner end of the anterior limb of the main lobe gives rise to a vesicle duct. The basic form of annelid consists of multiple segments.
Embedded in the connective tissue are unicellular epidermal glands. What is the reserve food material in red algae? Annelids are segmented or ringed worms. What are the general characters of pteridophytes?
Proteolytic enzymes secreted by the stomach help in digestion. It is thin-walled and it opens to the outside through anus which is placed on the dorsal surface of the 26th segment. The coelom becomes restricted to four longitudinal channels, two of which are lateral, one dorsal and the remaining one is ventral in position. These seven segments constitute the posterior sucker. These species create furrows in the ground, which allows a better circulation of oxygen and water. 9-Most species are hermaphrodites. This stripe is either uniform or interrupted. (1) Four longitudinal channels (Fig. In some leeches as Branchellion, lateral outgrowths of the body wall serve as gills for respiration. A closed blood-vascular system like that of earthworm is absent in leeches. But fusion of several anterior and posterior ganglia due to abbreviation of segments to form the anterior and posterior suckers is a new feature.
There are both aquatic and terrestrial species although only few species are commonly known. Receptor Organs 12. It is a member of the class Hirudinea. 17.37) consists of: It is a horse-shoe-shaped structure and ventro-lateral in position.
The intestine narrows down at the posterior end and enters into the rectum. That’s why they are active only at night and remains underground on the sunny part of day. several times their own weight at one stretch blowing up to huge size and can fast up to months together. Share Your PPT File. 17.34 shows the disposition of lateral channels and their tributaries in a segment of leech. Retrieved on August 23, 2017, from encyclopedia.org, Annelida. Mouth is a tri-radiate aperture situated in the middle of the anterior sucker and leads to a very small buccal chamber. Of these seventeen pairs, the anterior six pairs lie in the pre-testicular segments and are called pre-testicular nephridia and the remaining eleven pairs in the testicular segments, are called testicular nephridia. A sphincter muscle is present round the opening of the outgoing duct from the vesicle. In 6th to 22nd segments, the ventral channel gives in each segment a pair of nephridial branches. 17.30). Reproductive System. The sperms are carried to the epididymis through the two vasa deferentia and they remain stored there.
Each paired ganglion of the ventral nerve cord gives off two pairs of nerves, the anterolateral and postero-lateral. The commissures of successive segments are in communication with each other through three inter-segmental and longitudinal commissural branches.
Each sac is coelomic in origin and contains a filamentous ribbon- shaped organ called ovary. Annelids are segmented or ringed worms. The cells are heavily pigmented and appear black in colour. Digestive System 7. Body is elongated and vermiform (Fig. These are small non-articulated structures that facilitate movement in the annelids. These spots offer keys to taxonomy. The vesicle duct opens into the terminal vesicle.
The cocoon is filled with albumen in which float the fertilized ova.
Ultimately a tri-radiate wound is made and blood comes out.
There are seventeen such loops between 6th and 23rd segments. ADVERTISEMENTS: In this article we will discuss about Leech:- 1. It is subservient to haemocoelomic system and manufactures haemocoelomic corpuscles. Why does plant cell possess large sized vacuole? The different receptors found in leech are: There are five pairs of eyes— one pair in each of the first five anterior segments. Earthworm, belonging to the group of Clitellates.
Some species can be To reproduce asexually . Like the earthworms, they too feed on sand along with small particles of dead organic matter. Reproductive System. They also have a variety of sensory cells that are responsive to light or touch. Now contraction of longitudinal muscles and relaxation of circular muscle occur and the posterior sucker is released from the substratum. The wall consists of an outer spongy layer and a tough inner layer. These plexuses are connected to the peri-pharyngeal nerve ring through scattered multipolar ganglionic cells.
The albumen of the cocoon is used as food during development. The last pair of caeca extends as far as 22nd segment. Bilaterally symmetry, … 17.31). These are present -as elevated and elliptical papillae on the first annulus of each segment of the body.
The posterior part of the common oviduct takes a curved course and opens into the vagina. Each lateral channel distributes to the nephridia, genital organs, gut and ventral body wall through latero-ventrals and receives back from these regions through latero-laterals and latero-dorsals. Digestive System 7. The walls of the stomach are produced internally into transverse folds. From each epididymis sperms pass to the base of the atrium where they are bound together to form packets of spermatophores by the secretion of the prostate glands.
They also have a complete digestive system including mouth and anus. 17.35). The type which is discussed here is commonly called cattle leech and its scientific name is Hirudinaria granulosa. Annelids are found worldwide from the deepest marine sediments to the soils in our parks. The ‘head’ or flat surfaces of these cells are directed towards the cuticle while the ‘handle’ is directed inwards.
The secretion of the glands prevents the coagulation of blood of the prey during feeding. The digested food is absorbed in the intestine and the residue is thrown out as black mass through the anus.
Our mission is to provide an online platform to help students to share notes in Biology. All these segments bear a pair of nephridiopores on the ventral surface. 17.40). Body appears cylindrical in contracted state and dorso-ventrally flattened in extended condition. The spaces between the inner ends of the epidermal cells are occupied by fibrous connective tissues containing blood and capillaries.
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