Structure of Leech (With Diagram) | Zoology

In this article we will discuss about:- 1. T.S. Leech through Crop Regions 2. T.S. Leech through Rectum and Post. Sucker.

T.S. Leech through Crop Regions:

1. It is the slide of T.S. of Leech through crop region.

2. It shows following characters:

(a) Body-wall is triploblastic and is comprised of a thin cuticle, an epidermis of columnar cells with modified epidermal glands and a thick dermis of connective tissue with interspersed blood capillaries and pigment cells etc.

(b) Below the dermis lies a circular muscle layer followed with a longitudinal muscle layer and ultimately the layer of botryoidal tissue.

(c) The coelom and coelomic epithelium are absent, instead there is present a haemocoel.

(d) In the centre lies a rounded and hollow crop.

(e) The inner surface of crop is projected into small villi.

(f) On either side of crop is present an oblique muscle band.

(g) Above the crop is present a hollow and thin walled dorsal haemocoelomic channel and below it the ventral sinus.

(h) The ventral sinus encloses the double nerve cord.

(i) On the outer side of oblique muscle band is present the lateral haemocoelomic channel and the nephridium, which appears as group of small and large irregular structures.

(j) The diverticula, wherever present, are having the same structure as the crop.

Note:

If the section is passing through anterior part of crop there will be single structure in centre; but if it is passing through posterior part there mill be three separate structures and if it is passing through the middle part of crop there will be three structures communicating with each other.

T.S. Leech through Rectum and Post. Sucker:

The slide is of T.S. leech through rectum and posterior sucker.

2. It shows following characters:

(a) Body wall is triploblastic and is comprised of a thin cuticle and epidermis of columnar cells with modified epidermal glands and a thick dermis of connective tissue with intersperced blood capillaries and pigment cells etc.

(b) Below the dermis lies a circular muscle layer, then a longitudinal muscle layer and ultimately the botryoidal tissue.

(c) The coelom is absent. Instead, there is present a haemocoel.

(d) In the centre lies a round and hollow rectum.

(e) The inner surface of rectum is beset with small cilia.

(f) On either side of crop lies an oblique muscle band.

(g) Above the rectum are present 2 hollow and thin walled dorsal channels and below it lies the ventral sinus.

(h) The ventral sinus encloses the double nerve cord.

(i) On the outer side of oblique muscle band there is present a small, hollow and round crop diverticulum.

(j) The internal lining of the diverticulum is folded into villi.

(k) On the outerside of crop diverticulum is present the lateral sinus as a small, thin walled and hollow structure.

(l) The nephridia are absent.

3. Below the large oval section lies an alliptical and almost solid structure the posterior sucker, which is lined with a thin epidermis, circular and longitudinal muscles and is filled with numerous round and irregular sucker glands.

4. The botroidal tissue and dermal layers are absent in posterior sucker.