Dissection of Different Contents under Microscope | Zoology

In this article we will discuss about the dissection of different contents for vertebrates and invertebrates under microscope.

I. Gut Contents:

Preparation:

Cut a small portion of the gut, contents of which is to be studied. Put it in a watch glass. Open it giving a longitudinal incision with a pair of fine scissors. Add a small amount of physiological saline solution. The concentration of the solution is 0.7% NaCl for invertebrates; 0.6% for fishes, amphibian, reptiles; 0.9% for birds and mammals. Wash the contents of the gut in a watch glass.

Macroscopic Objects:

Transfer the macroscopic objects from the watch glass to a glass slide containing a drop of normal saline, with the help of a brush or a pair of fine forceps. Spread those on the slide with needles and examine under a powerful dissecting binocular or low power of a microscope. Temporary or permanent preparation may be made in the usual way.

Microscopic Objects:

Put a drop of the washing on a slide. Spread it to a thin film and examine under the low power of a microscope. Wait till the water almost evaporates or semidry. Fix the objects with Schaudinn’s fluid for 10-15 minutes and make stained, temporary or permanent prepa­ration.

Gut Parasites:

Cockroach:

The most common parasites are Nyctotherus sp., Balantidium sp. (Ciliaphora); Gregarina sp. (Apicomplexa); Entamoeba sp. (Sarcomastigophora); Leidynema sp. (Ascaridida), etc. (Fig. 30.1).

II. Rectal Contents (Toad):

Preparation:

To study the rectal contents inject about 0.5 ml physiological solution into the rectum of the specimen with a pipette. Wait for about a minute. Draw out a small amount of the fluid from the rectum with a pipette by suction. Put a drop of the fluid on a slide. Examine under the low power of a microscope.

Fix with Schaudinn’s fluid. Make a temporary or permanent stained preparation. The most common parasites are Sicuophora sp., Balantidium sp.; Opalina sp. (Ciliaphora); Entamoeba sp. (Sarcomastigophora); nematodes, etc. (Fig. 30.2).

III. Faecal Contents: Fowl, Cattle:

Technique:

A. Smear preparation:

Put a small quantity of fresh droppings (Fowl)/dung of cattle in a watch glass. Put a few drops of normal saline solution and mix thoroughly with a narrow sterilized stick.

a. Put one drop of the mixture at the centre of a glass slide, spread over to form a thin smear.

b. Add a drop of Lugol’s iodine over the smear and cover with a cover slip.

c. Examine under a microscope.

B. Concentration method (Willis technique):

a. Mix about 1gm of faecal matter with 25 ml. saturated NaCl solution in a measuring cylinder.

b. Fill a test tube up to the brim with the mixture.

c. Put a Mayer’s albumen coated square cover slip on the mouth of the test tube, taking care that no air bubbles are locked between the albumen coated cover slip and the mixture. Wait for 30 minutes.

d. Remove the cover slip with a forceps, put it face down (albumented surface on the slide) on a glass slide.

e. Examine immediately under a microscope.

C. Centrifugal floatation method:

a. Mix about 5gm of faecal matter with 50 ml. distilled water in a measuring cylinder.

b. Strain the faecal suspension through 1 mm diameter pore sieve to remove coarse materials.

c. Centrifuge the mixture at 2000 r.p.m. for 2-3 minutes. Most of the contents settle at the bottom of the centrifuge tubes, but encysted protozoa and helminth eggs being lighter float on the surface.

d. Decant the supernatant from centri­fuge tubes, fill a test tube up to the brim with the fluid.

e. Put a Mayer’s albumen coated square cover slip on the mouth of the test tube, taking care that no air bubbles are locked between the cover slip and the fluid. Wait for 30 minutes.

f. Remove the cover slip, put it face down on a glass slide and examine immediately under a microscope.

1. Fowl: Egg or Cysts:

a. Protozoa—Eimeria sp., Trichomonas sp.,

b. Nematode—Ascaridia sp., Heterakis sp., Gongylonema sp., etc.

c. Cestoda—Raillietina sp., Davainea sp., Amoebotaenia sp., etc.

2. Cattle:

a. Protozoa—Eimeria sp.

b. Cestoda—Avitellina sp., Moniezia sp., etc.

c. Trematoda—Cotylophoron sp., Paramphistomum sp., etc.

d. Nematoda—Capillaria sp., Toxocara sp., Haemonchus sp., Gongylonema sp., Nematodirus sp., Chaberia sp., etc..