It is well known that the gonadotropic hormone secreted by the pituitary gland play an important role in the maturation of the gonads and spawning of fishes. The Brazilians were the first to succeed in inducing spawning by injecting fish with pituitary extract.
Several corps labeo rohita, L.bata, cirrhino mrigala, C.reba etc. were successfully breed by injecting pituitary extract. Now this technique is very popular in obtaining fish seed fro commercial purpose.
In fishes pituitary gland lies in a well protected depression the myodome, as the floor of the skull. For getting the pituitary the upper part of the skull is removed by a knife or bone cutter. The brain is lifted to reach the gland, which is preserved for future use in one of the following method.
Absolute alcohol in sealed tube in a dessicator at room temperature.
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Acetone, which dehydrates and hardens the gland. After 36 hours the gland is dried on a filter paper and stored in sealed phials in a refrigerator.
Just before injected these glands are taken out and harmogenized in distilled water or 0.3% saline. The suspension is then centrifused and supernatant fluid is taken in a syringe and injected intramusculary as the back or base of the caudal fin.